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  #1   Report Post  
roger
 
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Default Which 6550 for SVT reissue?

Hi all,

I'm intending to retube my ampeg svt classic (reissue) with either
sovtek 6550we's or the electro harmonix 6550's. They're both priced
about the same, which would be the better choice? Thanks.
  #2   Report Post  
J. Vincent Collins
 
Posts: n/a
Default

Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
only tube for that amp is the GE 6550A,, Jim McShane has a fine stash.

In ADVANCE

**** THE POLISHED TURD
Yup,, that's you FAT WILLIE


VIN COLLINS




"roger" wrote in message
om...
Hi all,

I'm intending to retube my ampeg svt classic (reissue) with either
sovtek 6550we's or the electro harmonix 6550's. They're both priced
about the same, which would be the better choice? Thanks.



  #3   Report Post  
Jim Anable
 
Posts: n/a
Default

"J. Vincent Collins" wrote:

Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
only tube for that amp is the GE 6550A


BIG second on the above ^^^

  #4   Report Post  
Rich Koerner
 
Posts: n/a
Default



roger wrote:

Hi all,

I'm intending to retube my ampeg svt classic (reissue) with either
sovtek 6550we's or the electro harmonix 6550's. They're both priced
about the same, which would be the better choice? Thanks.


It was not uncommon for a set of GE-6550A's to last over five years of heavy full time
professional use during the Magnavox years of SVT.

The best tubes ever made for an SVT or 400-PS.

FYI, http://timeelect.com/6550a-ex.htm


Regards,

Rich Koerner,
Time Electronics.
http://www.timeelect.com

Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
  #5   Report Post  
Lord Valve
 
Posts: n/a
Default



J. Vincent Collins wrote:

Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
only tube for that amp is the GE 6550A,, Jim McShane has a fine stash.

In ADVANCE

**** THE POLISHED TURD
Yup,, that's you FAT WILLIE

VIN COLLINS


I also have a fine stash of NOS GE 6550A. Excellent tube.

Sometimes, however, folks are short on cash and can't
spring for NOS. The Sovtek 6550WE is a good choice;
in fact, there are people who prefer the tone of the Sovtek
over the GE. (Horrors!) One of those people is Tod Smallie,
bassist for the DTB (and the Yonrico Scott Band, which just
released their first CD) who is now going on three years
of 200+ dates per year with the same set of Sovtek 6550WE
I installed when I rebuilt/tweaked his 1973 SVT head (and sold
it to him).

It's all a matter of taste. Mine, in fact, runs to the Tung-Sol;
as far as I'm concerned, in my bi-amped 122 Leslies there
is Tung-Sol and then there's everything else. No tellin'
what folks might like.

Have a nice day, son.

Lord Valve
Tone Chaperone

VISIT MY WEBSITE: http://www.nebsnow.com/LordValve
I specialize in top quality HAND SELECTED NOS and
current-production vacuum tubes for guitar and
bass amps. Good prices, fast service.
QSC amps, RNC compressors, lots of other good stuff!

Partial Client List: * Derek Trucks/Allman Brothers Band *
* Meatloaf * Catherine Wheel * Yo La Tengo * Let's Go Bowling *
* John Hall * Tyrin Benoit * Eugene Fodor * Dale Bruning *
* Komet Amplification * Dr. Z * Maven Peal * Blockhead Amps *
* Jim Kelley * Balls Amplification * Roccaforte Amplifiers *
* Gerhart Amplification * The Right Half of AGA * Lots More *

NBS Electronics, 230 South Broadway, Denver, CO 80209-1510
Phone orders/tech support after 1:30 PM Denver time at 303-778-1156

- Our 23rd Year -

VISA - MASTERCARD - PAYPAL

Philo T. Farnsworth sez, "Vacuum tubes kick major ass.
Be a MAN...and buy some TODAY!"



  #6   Report Post  
Who's Drivin?
 
Posts: n/a
Default


"roger" wrote in message
om...
Hi all,

I'm intending to retube my ampeg svt classic (reissue) with either
sovtek 6550we's or the electro harmonix 6550's. They're both priced
about the same, which would be the better choice? Thanks.


I also had 6 GE 6550's in my old Fender 400 PS. They will last a long, long
time.

Dave


  #8   Report Post  
Naked Clarke
 
Posts: n/a
Default

Willie,

What period do your GE 6550's date from? Are they all stamped Rivera?
Were they assembled in the USA?

Clarke


wrote in message ...

I also have a fine stash of NOS GE 6550A. Excellent tube.

Sometimes, however, folks are short on cash and can't
spring for NOS. The Sovtek 6550WE is a good choice;
in fact, there are people who prefer the tone of the Sovtek
over the GE. (Horrors!) One of those people is Tod Smallie,
bassist for the DTB (and the Yonrico Scott Band, which just
released their first CD) who is now going on three years
of 200+ dates per year with the same set of Sovtek 6550WE
I installed when I rebuilt/tweaked his 1973 SVT head (and sold
it to him).

It's all a matter of taste. Mine, in fact, runs to the Tung-Sol;
as far as I'm concerned, in my bi-amped 122 Leslies there
is Tung-Sol and then there's everything else. No tellin'
what folks might like.

Have a nice day, son.

Lord Valve
Tone Chaperone

  #10   Report Post  
Rich Koerner
 
Posts: n/a
Default



wrote:

(roger) wrote in message . com...
Hi all,

I'm intending to retube my ampeg svt classic (reissue) with either
sovtek 6550we's or the electro harmonix 6550's. They're both priced
about the same, which would be the better choice? Thanks.


You are fortunate: the 6550 is a very rugged tube and any brand that
is not poorly made in China etc. is about equally good, it's a hard
tube to screw up & still meet spec. Take LV's suggestion, ignore the
snobs & try the Sovteks from him, you'll be happy and not broke.


EXCUSE ME!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


Are you in some way trying to say service life, and sustained high performance level IS,
or is NOT reflected in that cheaper price!!!!!!

The 6550WE in a Twin Reverb is one thing!!!!

In an SVT or 400-PS, it is totally an other world.

The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.

For the bass player who has that, I'm going to push this amp till it blows attitude, where
the amp has to fill the club, the GE-6550A is the only tube to use.

BUT, if you are one of those bass players who plays before that threshold, and have a DI
and mic on the speaker cab, feeding a concert level house sound system, 6550WE's work ok.

It depends on if the bass player shakes the house with HIS Bass amp, or the sound system
shakes the house for him from the DI, then his amp really becomes HIS bass stage
monitor,...

which tube is better for the application!!!!!!!!!




Regards,

Rich Koerner,
Time Electronics.
http://www.timeelect.com

Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers


  #11   Report Post  
Fred Nachbaur
 
Posts: n/a
Default



J. Vincent Collins wrote:

Snob?

SNOB!!!

This sonofabitch calls US a snob!!!

YOURE GODDAMN RIGHT!

Take those turds and put em in the friggin TERLET where they belong!! :-)
LOL

Just felt the need to poke a stick into the cage of the Turd Mongers.


Vin Collins
The Anti-Turd
[...]


To paraphrase an old saying, "One man's turd is another man's treasure."

It's all so subjective. Haven't you ever met a guitarist who treasured
nasty old 12AX7's with gain out the bottom and just the barest breath of
emission, because they sound so (choose your description) cool and
crunchy -- ballsy -- just like hendrix, man.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

  #12   Report Post  
RonSonic
 
Posts: n/a
Default

On Fri, 20 Feb 2004 06:50:00 GMT, Lord Valve wrote:



J. Vincent Collins wrote:

Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
only tube for that amp is the GE 6550A,, Jim McShane has a fine stash.

In ADVANCE

**** THE POLISHED TURD
Yup,, that's you FAT WILLIE

VIN COLLINS


I also have a fine stash of NOS GE 6550A. Excellent tube.

Sometimes, however, folks are short on cash and can't
spring for NOS. The Sovtek 6550WE is a good choice;
in fact, there are people who prefer the tone of the Sovtek
over the GE. (Horrors!) One of those people is Tod Smallie,
bassist for the DTB (and the Yonrico Scott Band, which just
released their first CD) who is now going on three years
of 200+ dates per year with the same set of Sovtek 6550WE
I installed when I rebuilt/tweaked his 1973 SVT head (and sold
it to him).

It's all a matter of taste. Mine, in fact, runs to the Tung-Sol;
as far as I'm concerned, in my bi-amped 122 Leslies there
is Tung-Sol and then there's everything else. No tellin'
what folks might like.


I am amazed at how old those amps get before I see them needing tubes. Those
ancient Tung-Sol kick ass. I haven't seen NOS on them, is there any supply these
days?

Ron

  #13   Report Post  
claudel
 
Posts: n/a
Default

In article ,
RonSonic wrote:
On Fri, 20 Feb 2004 06:50:00 GMT, Lord Valve wrote:



J. Vincent Collins wrote:

Put some real tubes in that prick,, Don't listen to the Turd Mongers,, the
only tube for that amp is the GE 6550A,, Jim McShane has a fine stash.

In ADVANCE

**** THE POLISHED TURD
Yup,, that's you FAT WILLIE

VIN COLLINS


I also have a fine stash of NOS GE 6550A. Excellent tube.

Sometimes, however, folks are short on cash and can't
spring for NOS. The Sovtek 6550WE is a good choice;
in fact, there are people who prefer the tone of the Sovtek
over the GE. (Horrors!) One of those people is Tod Smallie,
bassist for the DTB (and the Yonrico Scott Band, which just
released their first CD) who is now going on three years
of 200+ dates per year with the same set of Sovtek 6550WE
I installed when I rebuilt/tweaked his 1973 SVT head (and sold
it to him).

It's all a matter of taste. Mine, in fact, runs to the Tung-Sol;
as far as I'm concerned, in my bi-amped 122 Leslies there
is Tung-Sol and then there's everything else. No tellin'
what folks might like.


I am amazed at how old those amps get before I see them needing tubes. Those
ancient Tung-Sol kick ass. I haven't seen NOS on them, is there any supply these
days?

Ron


I have 3.

:^)


Claude, who one day will finish the set
and install them in his SUNN 2000S.
  #14   Report Post  
WakyAmps
 
Posts: n/a
Default

Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to back
that one up?

Mind you, you have my utmost respect, but I think you're being a
bit of a zealot here. Ferinstance, when I push the (also very
expensive) 7581As for old Fender 6L6 setups, they're different
and you can tell, but it'd be a helluva stretch to say "not even
close".

Fer me anyway, sonically and _electrically_ not even close for a
6550 (but still keeping among power tubes) would be an EL84.
Maybe an EL34?


  #15   Report Post  
Lord Valve
 
Posts: n/a
Default



Naked Clarke wrote:

Willie,

What period do your GE 6550's date from? Are they all stamped Rivera?


I have some stamped Rivera, some with regular GE print.

Were they assembled in the USA?


Sure. I didn't know there were any that *weren't.*Where would they make 'em besides
the USA?

LV





Clarke

wrote in message ...

I also have a fine stash of NOS GE 6550A. Excellent tube.

Sometimes, however, folks are short on cash and can't
spring for NOS. The Sovtek 6550WE is a good choice;
in fact, there are people who prefer the tone of the Sovtek
over the GE. (Horrors!) One of those people is Tod Smallie,
bassist for the DTB (and the Yonrico Scott Band, which just
released their first CD) who is now going on three years
of 200+ dates per year with the same set of Sovtek 6550WE
I installed when I rebuilt/tweaked his 1973 SVT head (and sold
it to him).

It's all a matter of taste. Mine, in fact, runs to the Tung-Sol;
as far as I'm concerned, in my bi-amped 122 Leslies there
is Tung-Sol and then there's everything else. No tellin'
what folks might like.

Have a nice day, son.

Lord Valve
Tone Chaperone






  #16   Report Post  
Rich Koerner
 
Posts: n/a
Default



WakyAmps wrote:

Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to back
that one up?


Don't NEED to. Any one standing in the room listening to the sound of the bass coming off
the stage will tell you the difference. Just put them up there side by side.

Not to mention the test bench tells the story.

With a stock 400-PS, I have to mod the damn thing to keep it from smoking the
6650-WE's!!!!

And, after that is done, they can't even get the output of the 400-PS to stock rated 435
watts output on the three loads required!!!!!!!

Then, after used in for a few months of gig playing on it as a hard ass POWER PLAYER, put
it back on the bench, and see where things sit on the test loads again.

BTW, that spec is 435 watts R.M.S. at *50* Hz. Clean sine wave before clip!!!

That sine wave looks a little squirrelly down there with those WE's.

What does an SVT do at that 50 Hz with 6550-WE's after the same
treatment!!!!!!!!!!!!!!!!!!!!!


Mind you, you have my utmost respect, but I think you're being a
bit of a zealot here.


No, I'm none of that.

I'll tell you what I am though.

I'm a kick your ass bass player ALL my life. There is nothing timid of shy when it comes
to my bass providing the horsepower in the songs to ROCK the HOUSE, when I'm on stage in a
formal band!!!!!!!!!!!!!!!!!

I played the Big amps and the Stacks, when they were in fashion. And, the SS crap bass
players use today, with that freaking in your face EQ'd sound, is NOT my idea of what bass
is all about!!!!

I'm old school, and not about to change any time soon!!!!!!!

Big fat gut bottom that rumbles through the club's walls into the parking lot, without
getting in the way of the band in the house, is what I'm all about.

But, that is not what today's bass player is all about, with his in your face bass rig
that falls on it face when I hit my neck pickup on my 66 bass, and the amp hits clip
trying to get down below the low end roll off.

That place below the roll off, IS where the freaking BASS belongs in the MUSIC.

Even Willie knows what FAT BOTTOM from a B3 is all about.

Ask him if He'd like to slap a 10" power piston in a 122, and not find the low end
fundamental rolling around the room on the floor soft as a pillow. But NOW, it's IN YOUR
FACE, where you HEAR it, and DON'T *FEEL* IT!!!!

400-PS amps present the bass like I like it. And, it takes TWO, not one, but TWO killer
setup SVT's with GE's and FOUR 8x10" cabs to equal tricked up 400-PS.

And THAT, is FACT. Rich gray's band opened for Black Oak Arkansas using one of my tricked
up 400's and four custom cabs. Black Oak had the Ampeg endorsement, and the bass player
had the SVT's.

But, after the first show, their bass player comes up to Richie, and asks if he could use
the 400-PS for the rest of the tour. I know its fact, because Richie called me for my
opinion. I said, let him do it. What the hell, have fun.

Later, that same 400-PS got people sick in the Filmore East from the low end of an ARP
synth.

If there is one thing I know, and have experienced, is the power of the Big Bass Tube
Rigs.

I've lived it, when most you guys were either doing something else, or weren't on the
planet then.

I had my vision blurred standing in from of a dual SVT stack playing Sunshine of your
love, when the record broke. BTW, that's two SVT heads, and four 8x10 cabs.

So, till you been there and done it, what are you going to tell me about it!!!!!!!!

I can't wait for things to come together where Kent and I can have some fun doing a stack
gig, doing it ALL exactly the way Jimi did it, so some of you all can *EXPERIENCE* the
Experience, as people did when a lot of you all MISSED it!!!!!!!!!!!!!!!!!!!!


Ferinstance, when I push the (also very
expensive) 7581As for old Fender 6L6 setups, they're different
and you can tell, but it'd be a helluva stretch to say "not even
close".


I ain't talking 6L6's, you are.

When it comes to 6L6's, My purple monster blows away 900's and 2000's in front of their
owners, when comparisons are done.

Then, you should SEE the look on their faces, when I pull the purple monster stack away
from the wall and turn it around, and all they SEE sitting the sockets are a PAIR of OLD
GE-6L6GC's!!!!!!!!

Yeah, NO ****!!!!!!!!!!!!!!!!!!!!!

Now, that is no brag, fantasy, or drugs talking.

It's just MY reality!!!!!!!!!!!!!

And, anyone is free to stop in the shop, step into my reality, and EXPERIENCE It, for
themselves!!!!!!!

Look, I've heard people talking their ****, and it comes off like they are on the same
page as I am.

BUT, when you are in the room with me and my gear, it's a whole different
world!!!!!!!!!!!!!!!!!!!!

And then, you will know, I'm in whole different place that really exists, where the music
becomes a whole different kind of spirit, which moves people, because they can *feel* it.

Yeah, the clubs are smaller, and the sound man tells ya to TURN IT DOWN, for that 5000
watt house system.

Yeah, you weak back guys want your air boxes with all that gain, so you can get a piece of
what I'm talking about. But that's all you're EVER going to get. Is just a freaking
SMALL piece.

You ain't going to FEEL it. Or what it FEELS like to SMOKE the SET, and SMOKE the crowd,
as the Music Takes You, and THEM Higher!!!!

Those are not just lyrics to a song, they're REAL!!!!!

The MUSIC, alone, really DID, take YOU, HIGHER!!!!!!

Not like today's music tries to, with the sound of PROCESSED Guitar sounds.

THAT'S, freaking Bull ****!!!!!!!!!!!!!!!!!!!!!!!!


Fer me anyway, sonically and _electrically_ not even close for a
6550 (but still keeping among power tubes) would be an EL84.
Maybe an EL34?


That's so small a piece, you can't even get an idea of what I've experienced on the stage
from the music.

Most importantly, there ain't enough in the written or performed MUSIC, to take even a
garden slug higher with that on the stage, for today's reality.

After thought

There is one man *out there* more than me.

Bootsy uses 15 KW Crown power on stage when he plays. No Less!!!!!!!!!!!!!!!!

How do I know this,...... look.

http://timeelect.com/Book22.htm

There you go.

GE-6550A's, ain't got no equal with the numbers 6550 on the glass!!!!

The 400-PS, is the test bed for that ****!!!!

It was designed for it!!!!!

http://timeelect.com/6550a-ex.htm


CASE CLOSED!!!!!!!!!!!!!!!!!!!



Regards,

Rich Koerner,
Time Electronics.
http://www.timeelect.com

Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
  #17   Report Post  
Patrick Turner
 
Posts: n/a
Default



Rich Koerner wrote:

WakyAmps wrote:

Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to back
that one up?


Don't NEED to. Any one standing in the room listening to the sound of the bass coming off
the stage will tell you the difference. Just put them up there side by side.

Not to mention the test bench tells the story.

With a stock 400-PS, I have to mod the damn thing to keep it from smoking the
6650-WE's!!!!

And, after that is done, they can't even get the output of the 400-PS to stock rated 435
watts output on the three loads required!!!!!!!

Then, after used in for a few months of gig playing on it as a hard ass POWER PLAYER, put
it back on the bench, and see where things sit on the test loads again.

BTW, that spec is 435 watts R.M.S. at *50* Hz. Clean sine wave before clip!!!

That sine wave looks a little squirrelly down there with those WE's.

What does an SVT do at that 50 Hz with 6550-WE's after the same
treatment!!!!!!!!!!!!!!!!!!!!!


Mind you, you have my utmost respect, but I think you're being a
bit of a zealot here.


No, I'm none of that.

I'll tell you what I am though.

I'm a kick your ass bass player ALL my life. There is nothing timid of shy when it comes
to my bass providing the horsepower in the songs to ROCK the HOUSE, when I'm on stage in a
formal band!!!!!!!!!!!!!!!!!

I played the Big amps and the Stacks, when they were in fashion. And, the SS crap bass
players use today, with that freaking in your face EQ'd sound, is NOT my idea of what bass
is all about!!!!

I'm old school, and not about to change any time soon!!!!!!!

Big fat gut bottom that rumbles through the club's walls into the parking lot, without
getting in the way of the band in the house, is what I'm all about.

But, that is not what today's bass player is all about, with his in your face bass rig
that falls on it face when I hit my neck pickup on my 66 bass, and the amp hits clip
trying to get down below the low end roll off.

That place below the roll off, IS where the freaking BASS belongs in the MUSIC.

Even Willie knows what FAT BOTTOM from a B3 is all about.

Ask him if He'd like to slap a 10" power piston in a 122, and not find the low end
fundamental rolling around the room on the floor soft as a pillow. But NOW, it's IN YOUR
FACE, where you HEAR it, and DON'T *FEEL* IT!!!!

400-PS amps present the bass like I like it. And, it takes TWO, not one, but TWO killer
setup SVT's with GE's and FOUR 8x10" cabs to equal tricked up 400-PS.

And THAT, is FACT. Rich gray's band opened for Black Oak Arkansas using one of my tricked
up 400's and four custom cabs. Black Oak had the Ampeg endorsement, and the bass player
had the SVT's.

But, after the first show, their bass player comes up to Richie, and asks if he could use
the 400-PS for the rest of the tour. I know its fact, because Richie called me for my
opinion. I said, let him do it. What the hell, have fun.

Later, that same 400-PS got people sick in the Filmore East from the low end of an ARP
synth.

If there is one thing I know, and have experienced, is the power of the Big Bass Tube
Rigs.

I've lived it, when most you guys were either doing something else, or weren't on the
planet then.

I had my vision blurred standing in from of a dual SVT stack playing Sunshine of your
love, when the record broke. BTW, that's two SVT heads, and four 8x10 cabs.

So, till you been there and done it, what are you going to tell me about it!!!!!!!!

I can't wait for things to come together where Kent and I can have some fun doing a stack
gig, doing it ALL exactly the way Jimi did it, so some of you all can *EXPERIENCE* the
Experience, as people did when a lot of you all MISSED it!!!!!!!!!!!!!!!!!!!!

Ferinstance, when I push the (also very
expensive) 7581As for old Fender 6L6 setups, they're different
and you can tell, but it'd be a helluva stretch to say "not even
close".


I ain't talking 6L6's, you are.

When it comes to 6L6's, My purple monster blows away 900's and 2000's in front of their
owners, when comparisons are done.

Then, you should SEE the look on their faces, when I pull the purple monster stack away
from the wall and turn it around, and all they SEE sitting the sockets are a PAIR of OLD
GE-6L6GC's!!!!!!!!

Yeah, NO ****!!!!!!!!!!!!!!!!!!!!!

Now, that is no brag, fantasy, or drugs talking.

It's just MY reality!!!!!!!!!!!!!

And, anyone is free to stop in the shop, step into my reality, and EXPERIENCE It, for
themselves!!!!!!!

Look, I've heard people talking their ****, and it comes off like they are on the same
page as I am.

BUT, when you are in the room with me and my gear, it's a whole different
world!!!!!!!!!!!!!!!!!!!!

And then, you will know, I'm in whole different place that really exists, where the music
becomes a whole different kind of spirit, which moves people, because they can *feel* it.

Yeah, the clubs are smaller, and the sound man tells ya to TURN IT DOWN, for that 5000
watt house system.

Yeah, you weak back guys want your air boxes with all that gain, so you can get a piece of
what I'm talking about. But that's all you're EVER going to get. Is just a freaking
SMALL piece.

You ain't going to FEEL it. Or what it FEELS like to SMOKE the SET, and SMOKE the crowd,
as the Music Takes You, and THEM Higher!!!!

Those are not just lyrics to a song, they're REAL!!!!!

The MUSIC, alone, really DID, take YOU, HIGHER!!!!!!

Not like today's music tries to, with the sound of PROCESSED Guitar sounds.

THAT'S, freaking Bull ****!!!!!!!!!!!!!!!!!!!!!!!!

Fer me anyway, sonically and _electrically_ not even close for a
6550 (but still keeping among power tubes) would be an EL84.
Maybe an EL34?


That's so small a piece, you can't even get an idea of what I've experienced on the stage
from the music.

Most importantly, there ain't enough in the written or performed MUSIC, to take even a
garden slug higher with that on the stage, for today's reality.

After thought

There is one man *out there* more than me.

Bootsy uses 15 KW Crown power on stage when he plays. No Less!!!!!!!!!!!!!!!!

How do I know this,...... look.

http://timeelect.com/Book22.htm

There you go.

GE-6550A's, ain't got no equal with the numbers 6550 on the glass!!!!

The 400-PS, is the test bed for that ****!!!!

It was designed for it!!!!!

http://timeelect.com/6550a-ex.htm

CASE CLOSED!!!!!!!!!!!!!!!!!!!

Regards,

Rich Koerner,
Time Electronics.
http://www.timeelect.com

Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers


It is with interest I read your ideas about providing music
with feeling, rather than with false edgy sounding fake bass.

I also see the Fender 400 watt amp you refer to has only 6 x 6550
tubes to make the 400 watts, which means 133 watts per pair of 6550,
which is rather a lot of stress on the tubes, regardless of the brand of tubes used.
When such an amp is is pushed into over drive one would think
that screen currents and grid currents could be rather high,
and the danger of tube damage would be ever present,
especially if someone connects too many speakers accidentally.

Ever thought of using a dozen 6550 to do the job?
This reduces the power per pair to a more survivable 66 watt.
Audio Research use 16 x 6550 for their Reference 600,
and that 75 watts per pair, same as a humble McIntosh.

See http://www.turneraudio.com.au/htmlwe...00monobloc.htm
to see a sample.

My amps make about 200 watts of class A, and its all very relaxed
and the idea is to have limitless headroom for a hifi situation,
where effortless and distortion free sound is sought.

In one of my 8585 hifi amps, I used 8 x jan GE6550, nos, green lettering.
They were about twice the price I pay now for EH6550.
I don't know wherther there was anything really special about them.
After 7 years of on -off use in a hifi situation, they all became prone to
grid current even at idle, and some of the grids going a volt or two positive.
Then I reduced the bias resistors to 100k, and they held their bias better.


The client had me replace all the tubes with EH 6550,
and he said there was a big improvement in the soundstage,
which seemed to have depth, not only width, as before with GE,
then he said the dynamics and detail were improved.

Hifi amps are never subject to severe signal overloads and gross clipping
with rock musician amps.
But they are left running for hours on end, day after day,
with a substantial bias current to allow lots of class A.
I guess the tubes wear out for different reasons in the
music amp versus the hi-fi amp.

One of the sweetest music amps I heard was 6V6 PP,
about 80% UL taps, nearly triode, in class A.
Another 6V6 in triode drove the output stage via a transformer.
This amp was one of the few which seemed to have sweetness
and a sort of natural reverb, but without a reverb unit used.
The owner-builder was a physics lecturer, whose interest off campus was guitar,
and rocket engines.

Another client uses Sovtek 6550 in triode in a Marshall head for use
in his "dark metal" band, and the sound is basically like a continual stream
of jumbo jets crashing on the pavement in front of you.
Not my cuppa tea, but some folks think its very cool!
The tubes are either off, or 40 dB over clipping.
After 4 years, I think he's on his second pair......
The first pair expired after using too low a load impedance
when swithed to the 16 ohm setting.
So when I hear about tubes failing, I wonder first
about the human element.

Unlike Fender, I fit individual cathode current sensors
to each output tube so that if any one tube out of so many
misbehaves, and goes red with too much cathode current,
the amp is turned off.
That mightn't suit a muso, who might prefer to blow a few tubes rather than stop
to change to a spare amp between songs, if the fuse hasn't blown.

Patrick Turner







  #18   Report Post  
Patrick Turner
 
Posts: n/a
Default



WakyAmps wrote:

Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to back
that one up?

Mind you, you have my utmost respect, but I think you're being a
bit of a zealot here. Ferinstance, when I push the (also very
expensive) 7581As for old Fender 6L6 setups, they're different
and you can tell, but it'd be a helluva stretch to say "not even
close".

Fer me anyway, sonically and _electrically_ not even close for a
6550 (but still keeping among power tubes) would be an EL84.
Maybe an EL34?


Doesn't the way the tubes are set up affect the sound?
EL84 in a Vox AC30 sound sweet as, and smooth tubey over drive,
because its real class A.
In some other amp with higher B+, and lower idle current
for near class B, they ain't so good.

I some how think it ain't what you got that is everything,
but the way you use it!

Patrick Turner.


  #19   Report Post  
WakyAmps
 
Posts: n/a
Default

Patrick Turner wrote in
:



WakyAmps wrote:

Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to
back that one up?

Mind you, you have my utmost respect, but I think you're
being a bit of a zealot here. Ferinstance, when I push the
(also very expensive) 7581As for old Fender 6L6 setups,
they're different and you can tell, but it'd be a helluva
stretch to say "not even close".

Fer me anyway, sonically and _electrically_ not even close
for a 6550 (but still keeping among power tubes) would be
an EL84. Maybe an EL34?


Doesn't the way the tubes are set up affect the sound?
EL84 in a Vox AC30 sound sweet as, and smooth tubey over
drive, because its real class A.
In some other amp with higher B+, and lower idle current
for near class B, they ain't so good.

I some how think it ain't what you got that is everything,
but the way you use it!

Patrick Turner.




Yes, how it is set up makes a huge difference, no a Vox AC-30
isn't really class A.

My point was (and continues to be) that Rich is describing
GE6550s vs Sovs as if they came from a different planet. I'm
guessing further (though Rich hasn't explicitly said so) that
he'd classify the Sovs as polished turds. I'm merely suggesting
that, while for Rich there's no other tube than the GE and no
other amp than the PS400, the OP is looking to retube a reissue
SVT and the OP may be quite satisfied with the Sovs (at half
the price no less). And it is the OP's needs we're trying to
address here, right?

The 6L6 comparison wasn't meant as a comparison of 6L6 vs 6550,
but to serve as an example of gradation between similar tubes.
Remember, Rich claims that the GE and Sov "aren't even close"
sonically or electrically. Maybe so in his tweaked 400PS and to
his ears and playing style; there may not be as strong a case
in the OP's RI-SVT and to the OP's ears and style.


  #20   Report Post  
TD Madden
 
Posts: n/a
Default

Patrick Turner wrote:


WakyAmps wrote:


Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to back
that one up?

Mind you, you have my utmost respect, but I think you're being a
bit of a zealot here. Ferinstance, when I push the (also very
expensive) 7581As for old Fender 6L6 setups, they're different
and you can tell, but it'd be a helluva stretch to say "not even
close".

Fer me anyway, sonically and _electrically_ not even close for a
6550 (but still keeping among power tubes) would be an EL84.
Maybe an EL34?



Doesn't the way the tubes are set up affect the sound?
EL84 in a Vox AC30 sound sweet as, and smooth tubey over drive,
because its real class A.
In some other amp with higher B+, and lower idle current
for near class B, they ain't so good.

I some how think it ain't what you got that is everything,
but the way you use it!

Patrick Turner.


Seems I read some where that AC-30s aren't "really" Class-A....anyone
have the scoop?


  #22   Report Post  
 
Posts: n/a
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I notice nobody uttered as much as a word about the (formerly Svetlana) now
Winged C 6550C How come?. We use plenty of these in repairs and lot's in
SVT's with very good results. They aren't GE's or Tung Sol's either but they
hold up well over time and sound pretty damn good. My 2c

Todd


  #23   Report Post  
TubeGarden
 
Posts: n/a
Default

Hi RATs!

Winked =C= 6550WC are great wired triode in my SE amp, but, that wasn't the
application in question.

VTV said the 6550WC tested stronger than the KT88, or something like that. I
run mine happily at 330V and 80mA, nowhere near what manly musicians crave

They do sound good

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead
  #24   Report Post  
Patrick Turner
 
Posts: n/a
Default



WakyAmps wrote:

Patrick Turner wrote in
:



WakyAmps wrote:

Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to
back that one up?

Mind you, you have my utmost respect, but I think you're
being a bit of a zealot here. Ferinstance, when I push the
(also very expensive) 7581As for old Fender 6L6 setups,
they're different and you can tell, but it'd be a helluva
stretch to say "not even close".

Fer me anyway, sonically and _electrically_ not even close
for a 6550 (but still keeping among power tubes) would be
an EL84. Maybe an EL34?


Doesn't the way the tubes are set up affect the sound?
EL84 in a Vox AC30 sound sweet as, and smooth tubey over
drive, because its real class A.
In some other amp with higher B+, and lower idle current
for near class B, they ain't so good.

I some how think it ain't what you got that is everything,
but the way you use it!

Patrick Turner.




Yes, how it is set up makes a huge difference, no a Vox AC-30
isn't really class A.


The ones I have serviced were class A,
with absolutely no feedback.
They had a high bias current, and each of the 4 EL84 draws about 12
watts
at least at idle.


My point was (and continues to be) that Rich is describing
GE6550s vs Sovs as if they came from a different planet. I'm
guessing further (though Rich hasn't explicitly said so) that
he'd classify the Sovs as polished turds.


I have not used enough 6550 in guitar amps to know
who is right here.

The 6550 and KT88 are capable of 140 watts per pair,
and to me that's a recipe for unreliability.
From what I have seen the russian 6550 from EH
is exactly the same internally as the EH KT88 or smaller bottle sovtek
KT88. It seems as though EH have rationalised the construction of
these two tube types, and the only thing different is the packaging,
ie, the glass bottle and lettering is nicer on the more expensive 6550
and KT88.
I don't care that they seem to have done this, as I quite like the
6550/KT88
being currently made.
As I see it, all the 6550 from yesteryear about which ppl rave as being
just so superior to
anything else are all actullay prone to failure from hard use,
unfortunate
events with the wrong speaker impedance, etc, since all the ratings
indicate that they are what they are, mortal tubes, and like us mortal
human beings,
they are gonna die one day.

I'm merely suggesting
that, while for Rich there's no other tube than the GE and no
other amp than the PS400, the OP is looking to retube a reissue
SVT and the OP may be quite satisfied with the Sovs (at half
the price no less). And it is the OP's needs we're trying to
address here, right?


I assure you that other folks make big tube amps.
As new old stocks of favourite old tubes dry up, all we are gonna have
is sovtek, EH, Svetlana etc.
But asking more than 75 watts per pair of bottles is asking for trouble.



The 6L6 comparison wasn't meant as a comparison of 6L6 vs 6550,
but to serve as an example of gradation between similar tubes.


Indeed.
Some 6L6 were far better than others, and I forget now who
used multi layer material in the anodes to prevent red hot spots,
which meant that the whole anode ran at much closer to the same temp,
which meant an effective 30 watt diss rating, instead of only 22 watts.
In the wrong circumstance, the screens would still melt anyways.....


Remember, Rich claims that the GE and Sov "aren't even close"
sonically or electrically. Maybe so in his tweaked 400PS and to
his ears and playing style; there may not be as strong a case
in the OP's RI-SVT and to the OP's ears and style.


How anyone can tell much difference between the sound of
tubes when the thd is at around 25%, and IMD at around 50%
is beyond me.
I once repaired a Lennard aus made 400 watt PA amp with inputs
for 4 performers. It ran on a 900 volt supply, 450volt screen supply,
with 8 x EL34,
so the power per pair was 100 watts.
But it kept spitting smoke and tubes out.
I then examined the dude's speakers.
He had two bins each with 6 x 12" speakers, which he said were 8 ohms,
but he hadn't said he'd re-wired them all together in parallel some
years before!
He'd been sending more power into the cables than to the speakers,
and had been labouring on for years with only 50 watts from the amp
with a load of about 3/4 of an ohm.
But when he went to do open air gigs, he needed more volume,
and poof went these tubes.
He had 4 different brands plugged in when I first saw the amp,
Mullard, Telsla, chinese, and Miniwatt.
I rewired his speakers so that they all were series/parallel for 8 ohms,

and rewired the amp B+ to an available lower HT tap on the PT,
and placed a separate bias pot for each output tube,
replaced all the tubes for sovteks,
and revised the FB for a useful 12 dB, and placed RC snubber
networks across the 1/2 primaries of the OPT,
and thus made it impossible for RF to start when tubes glowed red,
and burning out quickly.
Power is now limited to 250 watts, and I have not heard from this guy in
4 years,
so I guess the amp is going OK.
Such an amp runs nearly all in class B, with a low bias current, so idle

diss for each tube is about only 16 watts, but at
about 2/3 max po the diss goes beyond the rated 28 watt max,
but because the duty cycle is low, ie, the signal isn't a continuous
sine wave,
the tubes survive, providing there is nothing wrong with the load value.

In this case, its better to err on the load value by choosing a value
too
high, rather than too low!

Most of my experience is with hi-fi usage, when thd is only 0.02%.
Even then you *can* here a difference between tubes despite very
similar measurements of thd/imd, etc.
The change of brands of tubes in preamps makes just as big a difference.

I know there are times when "kick ass bass" is a must, and the sound
system
at the film club I go to provides this when you hear a train going past
nearby.
Not a tube amp to be seen. Its all SS behemoths, perhaps several 1,000
watters,
but sure, you feel the sound, as well as hear it, and ear plugs are
required
by folks such as I with such movies made deliberately to be sonically
provocative,
because the technology is the focus, to disguise the attrocious acting,
gadgets used to prop up otherwise failure prone humans,
with special effects every minute, and even with sharks growling
underwater.
I am appalled at such idiotic stories about tomb raiding, and all the
sound engineering
is in vain, as its an attempt to deafen me, ie, injure my hearing.
I have visited very briefly some indoor venues in university canteens
where they had several
thousand watts of amplification. Even with ear plugs, it was quite
impossible for me
to enjoy anything I saw, heard, or smelt, and my chest heaved with the
bass,
and at every amplified drum beat.
I have to agree that some SS set ups *do* sound quite loud.
I don't like it that loud, and never have, but to some folks whose ears
are not yet
"matured", such excess sound is somehow cool.
I often wonder if the use of tube amps in theatres would soften the
often
appallingly harsh sound tracks, where the cowboy alteration of recorded
sound has routinely
been compressed, noise filtered, de-essed, eq'd unaturally, etc.

I quite like classical music which is 200 years old, and my local town's

orchestra has about 40 players, and the bass from the two, perhaps
three
entirely unamplified acoustic bass violins plus a couple of various
drums
is entirely adequate to form a foundation for the music.

The levels attained are entirely sufficient to fill my senses, and
transport
my mind away where the composer wants to take it.
The use of electricity over the last 50 years, by a handful
of groovy, cool, awesome, whatever types on a stage who obviously
have never been to music college has not made concert going
any better for me. Rolling Stones concerts with 140,000 watts
and 250,000 people are to me quite boring/irritating events I wouldn't
be seen dead at.
I probably wouldn't have turned up at the Colleseum in Rome
in AD 100, to watch and hear christians being fed to lions,
and to witness the mayhem of the chariot races, and the fight to the
death
gladiator battles. All too gross.
Another 1,500 years had to pass before music evolved which
I could really be entranced by, because of its lack of repetition,
complex music structure, and complete absense of peurile wailings
about "lerve" et all.
Its hard to get much volume from a hard bodied electric guitar,
so an amp is essential, but if anything in this electronic age
is used so often to excess, apart from drugs and grog, it has to be the
sound amp.

I am quite happy with someone sitting 30 feet away, using about 2 watts,

and who really knows how to play some real blues, and whose amp
sounds inviting, warm, musical.

Patrick Turner.


  #25   Report Post  
roger
 
Posts: n/a
Default

Thank you to those few who provided some relevant information amongst
this torrent of bull****. Has anyone anctually used the EH 6550s in an
SVT? I've seen some good reports from the hi-fi guys.

ps I run an ampeg 410hlf most of the time and mic/di the amp when the
gig requires it.


  #26   Report Post  
dw
 
Posts: n/a
Default

Patrick Turner wrote:


WakyAmps wrote:


Patrick Turner wrote in
:



WakyAmps wrote:


Rich Koerner wrote in
:


The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Not even close Rich? Got sounds samples or RTA traces to
back that one up?

Mind you, you have my utmost respect, but I think you're
being a bit of a zealot here. Ferinstance, when I push the
(also very expensive) 7581As for old Fender 6L6 setups,
they're different and you can tell, but it'd be a helluva
stretch to say "not even close".

Fer me anyway, sonically and _electrically_ not even close
for a 6550 (but still keeping among power tubes) would be
an EL84. Maybe an EL34?

Doesn't the way the tubes are set up affect the sound?
EL84 in a Vox AC30 sound sweet as, and smooth tubey over
drive, because its real class A.
In some other amp with higher B+, and lower idle current
for near class B, they ain't so good.

I some how think it ain't what you got that is everything,
but the way you use it!

Patrick Turner.




Yes, how it is set up makes a huge difference, no a Vox AC-30
isn't really class A.



The ones I have serviced were class A,
with absolutely no feedback.
They had a high bias current, and each of the 4 EL84 draws about 12
watts
at least at idle.


My point was (and continues to be) that Rich is describing
GE6550s vs Sovs as if they came from a different planet. I'm
guessing further (though Rich hasn't explicitly said so) that
he'd classify the Sovs as polished turds.



I have not used enough 6550 in guitar amps to know
who is right here.

The 6550 and KT88 are capable of 140 watts per pair,
and to me that's a recipe for unreliability.
From what I have seen the russian 6550 from EH
is exactly the same internally as the EH KT88 or smaller bottle sovtek
KT88. It seems as though EH have rationalised the construction of
these two tube types, and the only thing different is the packaging,
ie, the glass bottle and lettering is nicer on the more expensive 6550
and KT88.
I don't care that they seem to have done this, as I quite like the
6550/KT88
being currently made.
As I see it, all the 6550 from yesteryear about which ppl rave as being
just so superior to
anything else are all actullay prone to failure from hard use,
unfortunate
events with the wrong speaker impedance, etc, since all the ratings
indicate that they are what they are, mortal tubes, and like us mortal
human beings,
they are gonna die one day.


I'm merely suggesting
that, while for Rich there's no other tube than the GE and no
other amp than the PS400, the OP is looking to retube a reissue
SVT and the OP may be quite satisfied with the Sovs (at half
the price no less). And it is the OP's needs we're trying to
address here, right?



I assure you that other folks make big tube amps.
As new old stocks of favourite old tubes dry up, all we are gonna have
is sovtek, EH, Svetlana etc.
But asking more than 75 watts per pair of bottles is asking for trouble.



The 6L6 comparison wasn't meant as a comparison of 6L6 vs 6550,
but to serve as an example of gradation between similar tubes.



Indeed.
Some 6L6 were far better than others, and I forget now who
used multi layer material in the anodes to prevent red hot spots,
which meant that the whole anode ran at much closer to the same temp,
which meant an effective 30 watt diss rating, instead of only 22 watts.
In the wrong circumstance, the screens would still melt anyways.....


Remember, Rich claims that the GE and Sov "aren't even close"
sonically or electrically. Maybe so in his tweaked 400PS and to
his ears and playing style; there may not be as strong a case
in the OP's RI-SVT and to the OP's ears and style.



How anyone can tell much difference between the sound of
tubes when the thd is at around 25%, and IMD at around 50%
is beyond me.
I once repaired a Lennard aus made 400 watt PA amp with inputs
for 4 performers. It ran on a 900 volt supply, 450volt screen supply,
with 8 x EL34,
so the power per pair was 100 watts.
But it kept spitting smoke and tubes out.
I then examined the dude's speakers.
He had two bins each with 6 x 12" speakers, which he said were 8 ohms,
but he hadn't said he'd re-wired them all together in parallel some
years before!
He'd been sending more power into the cables than to the speakers,
and had been labouring on for years with only 50 watts from the amp
with a load of about 3/4 of an ohm.
But when he went to do open air gigs, he needed more volume,
and poof went these tubes.
He had 4 different brands plugged in when I first saw the amp,
Mullard, Telsla, chinese, and Miniwatt.
I rewired his speakers so that they all were series/parallel for 8 ohms,

and rewired the amp B+ to an available lower HT tap on the PT,
and placed a separate bias pot for each output tube,
replaced all the tubes for sovteks,
and revised the FB for a useful 12 dB, and placed RC snubber
networks across the 1/2 primaries of the OPT,
and thus made it impossible for RF to start when tubes glowed red,
and burning out quickly.
Power is now limited to 250 watts, and I have not heard from this guy in
4 years,
so I guess the amp is going OK.
Such an amp runs nearly all in class B, with a low bias current, so idle

diss for each tube is about only 16 watts, but at
about 2/3 max po the diss goes beyond the rated 28 watt max,
but because the duty cycle is low, ie, the signal isn't a continuous
sine wave,
the tubes survive, providing there is nothing wrong with the load value.

In this case, its better to err on the load value by choosing a value
too
high, rather than too low!

Most of my experience is with hi-fi usage, when thd is only 0.02%.
Even then you *can* here a difference between tubes despite very
similar measurements of thd/imd, etc.
The change of brands of tubes in preamps makes just as big a difference.

I know there are times when "kick ass bass" is a must, and the sound
system
at the film club I go to provides this when you hear a train going past
nearby.
Not a tube amp to be seen. Its all SS behemoths, perhaps several 1,000
watters,
but sure, you feel the sound, as well as hear it, and ear plugs are
required
by folks such as I with such movies made deliberately to be sonically
provocative,
because the technology is the focus, to disguise the attrocious acting,
gadgets used to prop up otherwise failure prone humans,
with special effects every minute, and even with sharks growling
underwater.
I am appalled at such idiotic stories about tomb raiding, and all the
sound engineering
is in vain, as its an attempt to deafen me, ie, injure my hearing.
I have visited very briefly some indoor venues in university canteens
where they had several
thousand watts of amplification. Even with ear plugs, it was quite
impossible for me
to enjoy anything I saw, heard, or smelt, and my chest heaved with the
bass,
and at every amplified drum beat.
I have to agree that some SS set ups *do* sound quite loud.
I don't like it that loud, and never have, but to some folks whose ears
are not yet
"matured", such excess sound is somehow cool.
I often wonder if the use of tube amps in theatres would soften the
often
appallingly harsh sound tracks, where the cowboy alteration of recorded
sound has routinely
been compressed, noise filtered, de-essed, eq'd unaturally, etc.

I quite like classical music which is 200 years old, and my local town's

orchestra has about 40 players, and the bass from the two, perhaps
three
entirely unamplified acoustic bass violins plus a couple of various
drums
is entirely adequate to form a foundation for the music.

The levels attained are entirely sufficient to fill my senses, and
transport
my mind away where the composer wants to take it.
The use of electricity over the last 50 years, by a handful
of groovy, cool, awesome, whatever types on a stage who obviously
have never been to music college has not made concert going
any better for me. Rolling Stones concerts with 140,000 watts
and 250,000 people are to me quite boring/irritating events I wouldn't
be seen dead at.
I probably wouldn't have turned up at the Colleseum in Rome
in AD 100, to watch and hear christians being fed to lions,
and to witness the mayhem of the chariot races, and the fight to the
death
gladiator battles. All too gross.
Another 1,500 years had to pass before music evolved which
I could really be entranced by, because of its lack of repetition,
complex music structure, and complete absense of peurile wailings
about "lerve" et all.
Its hard to get much volume from a hard bodied electric guitar,
so an amp is essential, but if anything in this electronic age
is used so often to excess, apart from drugs and grog, it has to be the
sound amp.

I am quite happy with someone sitting 30 feet away, using about 2 watts,

and who really knows how to play some real blues, and whose amp
sounds inviting, warm, musical.

Patrick Turner.


Great post, Patrick.

thanks,

dw

  #27   Report Post  
Miles O'Neal
 
Posts: n/a
Default

Patrick Turner responded to WakyAmps, who said:

Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
really class A.


The ones I have serviced were class A, with absolutely no feedback.
They had a high bias current, and each of the 4 EL84 draws about 12 watts
at least at idle.


Now this doesn't make any sense at all.
In Class A, full tilt isn't different
enough from idle to make any difference.

So, just curious - why do you say they
were Class A? What do you think that
means?

....
As I see it, all the 6550 from yesteryear about which ppl rave as being
just so superior to
anything else are all actullay prone to failure from hard use, unfortunate
events with the wrong speaker impedance, etc, since all the ratings
indicate that they are what they are, mortal tubes, and like us mortal
human beings,
they are gonna die one day.


While this is true, some of the tubes made back
in the far exceeded their published specs, and
hence are worth far more than the common tubes
of today, to some people. If it'll last five
times as long when being punished, it's worth at
least five times the price - more if you calculate
the lower likelihood of failure during a gig.

I'm merely suggesting
that, while for Rich there's no other tube than the GE and no other amp
than the PS400, the OP is looking to retube a reissue SVT and the OP may
be quite satisfied with the Sovs (at half the price no less). And it is
the OP's needs we're trying to address here, right?


Sure. I agree with you here. At the same time
I understand where Rich is coming from. He's a
firm believer in the value of the old tubes over
anything built today (so far), and wants to help
others understand that.

In some case I agree with him on the state of the
art and the value; in others I don't. Most of the
time we're in different threads, because I mostly
deal with 6BQ5s and 6V6s, which he dismisses as
"radio tubes". 8^)


I assure you that other folks make big tube amps. As new old stocks of
favourite old tubes dry up, all we are gonna have is sovtek, EH, Svetlana
etc.
But asking more than 75 watts per pair of bottles is asking for trouble.


With the new tubes this may be so - I don't know.
But I have known lots of folks getting 100W or more
per pair (think SVT!) with no problem.

....
Remember, Rich claims that the GE and Sov "aren't even close" sonically
or electrically. Maybe so in his tweaked 400PS and to his ears and
playing style; there may not be as strong a case in the OP's RI-SVT and
to the OP's ears and style.


How anyone can tell much difference between the sound of tubes when the
thd is at around 25%, and IMD at around 50% is beyond me.


Just curios - are you a musician? Do you care about
tone? Do you consider your ears good? Because the
sonic differences in tubes are ell documented. My
wife and kids, none of whom play guitar (Josiah keeps
saying he wants to, but never practices much) can hear
these differences, and they aren't tube freaks by any
stretch of the imagination!

[Story of 0 ohm tube PA into 1 ohm bins snipped]

In this case, its better to err on the load value by choosing a value too
high, rather than too low!


Why not try your friend's PA head into, say, 64
ohms at full blast and let us know how that goes?

-Miles


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  #28   Report Post  
Don
 
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I know there are times when "kick ass bass" is a must, and the sound
system
at the film club I go to provides this when you hear a train going past
nearby.
Not a tube amp to be seen. Its all SS behemoths, perhaps several 1,000
watters,
but sure, you feel the sound, as well as hear it, and ear plugs are
required
by folks such as I with such movies made deliberately to be sonically
provocative,
because the technology is the focus, to disguise the attrocious acting,
gadgets used to prop up otherwise failure prone humans,
with special effects every minute, and even with sharks growling
underwater.
I am appalled at such idiotic stories about tomb raiding, and all the
sound engineering
is in vain, as its an attempt to deafen me, ie, injure my hearing.


I suggest you see "Cold Mountain" an American Civil War movie, with folk
music.

Mystic River and Lost in Translation are two good adult films, no tomb raiding
involved.

  #29   Report Post  
JTM50
 
Posts: n/a
Default

in article , Miles O'Neal at
wrote on 2/21/04 7:58 PM:

Patrick Turner responded to WakyAmps, who said:

Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
really class A.


The ones I have serviced were class A, with absolutely no feedback.
They had a high bias current, and each of the 4 EL84 draws about 12 watts
at least at idle.


Now this doesn't make any sense at all.
In Class A, full tilt isn't different
enough from idle to make any difference.

So, just curious - why do you say they
were Class A? What do you think that
means?

Yeah, and 12 watts on an EL84 is almost Ice cold!
My Guytron runs em at 17-18 watts static (45-50ma)!

Lloyd




...
As I see it, all the 6550 from yesteryear about which ppl rave as being
just so superior to
anything else are all actullay prone to failure from hard use, unfortunate
events with the wrong speaker impedance, etc, since all the ratings
indicate that they are what they are, mortal tubes, and like us mortal
human beings,
they are gonna die one day.


While this is true, some of the tubes made back
in the far exceeded their published specs, and
hence are worth far more than the common tubes
of today, to some people. If it'll last five
times as long when being punished, it's worth at
least five times the price - more if you calculate
the lower likelihood of failure during a gig.

I'm merely suggesting
that, while for Rich there's no other tube than the GE and no other amp
than the PS400, the OP is looking to retube a reissue SVT and the OP may
be quite satisfied with the Sovs (at half the price no less). And it is
the OP's needs we're trying to address here, right?


Sure. I agree with you here. At the same time
I understand where Rich is coming from. He's a
firm believer in the value of the old tubes over
anything built today (so far), and wants to help
others understand that.

In some case I agree with him on the state of the
art and the value; in others I don't. Most of the
time we're in different threads, because I mostly
deal with 6BQ5s and 6V6s, which he dismisses as
"radio tubes". 8^)


I assure you that other folks make big tube amps. As new old stocks of
favourite old tubes dry up, all we are gonna have is sovtek, EH, Svetlana
etc.
But asking more than 75 watts per pair of bottles is asking for trouble.


With the new tubes this may be so - I don't know.
But I have known lots of folks getting 100W or more
per pair (think SVT!) with no problem.

...
Remember, Rich claims that the GE and Sov "aren't even close" sonically
or electrically. Maybe so in his tweaked 400PS and to his ears and
playing style; there may not be as strong a case in the OP's RI-SVT and
to the OP's ears and style.


How anyone can tell much difference between the sound of tubes when the
thd is at around 25%, and IMD at around 50% is beyond me.


Just curios - are you a musician? Do you care about
tone? Do you consider your ears good? Because the
sonic differences in tubes are ell documented. My
wife and kids, none of whom play guitar (Josiah keeps
saying he wants to, but never practices much) can hear
these differences, and they aren't tube freaks by any
stretch of the imagination!

[Story of 0 ohm tube PA into 1 ohm bins snipped]

In this case, its better to err on the load value by choosing a value too
high, rather than too low!


Why not try your friend's PA head into, say, 64
ohms at full blast and let us know how that goes?

-Miles


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  #30   Report Post  
WakyAmps
 
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JTM50 wrote in
:

Yeah, and 12 watts on an EL84 is almost Ice cold!
My Guytron runs em at 17-18 watts static (45-50ma)!

Lloyd


Since max rated dissipation for an EL84 is 12 watts, I
wouldn't call it ice cold. I'd call 17-18 running the
bejeezus out of 'em[1]

However, static dissipation equal to max dissipation does not
necessarily mean class A.



[1] though 17-18 is a nice static point for class ab1 el-34s


  #32   Report Post  
 
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The application in question was about soliciting opinion on what type 6550
works best in an Ampeg SVT wasn't it?
Todd
"TubeGarden" wrote in message
...
Hi RATs!

Winked =C= 6550WC are great wired triode in my SE amp, but, that wasn't

the
application in question.

VTV said the 6550WC tested stronger than the KT88, or something like that.

I
run mine happily at 330V and 80mA, nowhere near what manly musicians crave



They do sound good

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead



  #33   Report Post  
James Angelo Ruggieri, P.E.
 
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I would guess any tube whose structural elements are rigid enough to
maintain spacing and does not readily "short" when subject to
shock/vibration. This can be easily determined by energizing the amp with a
100 Watt clear light bulb in series with the line, and with all the tubes
installed, tapping on the tubes with a rubber handled screwdriver - while
observing the series line light for changes in luminance. Changes in the
light would indicate structurally unstable tube elements - meaning it is
likely the amp/tubes will short during service. Otherwise, I doubt you would
be able to discern any quality difference. The SVT is also tough to
balance - from what I recall, and can be very touchy.

Jim



--
JAMES RUGGIERI
"roger" wrote in message
om...
Hi all,

I'm intending to retube my ampeg svt classic (reissue) with either
sovtek 6550we's or the electro harmonix 6550's. They're both priced
about the same, which would be the better choice? Thanks.



  #34   Report Post  
 
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Rich Koerner wrote in message ...

The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Pls clarify, Rich - R U saying that it doesn't dissipate well enough
under full load?

If so, what specific failures have you noted or had reported - i.e.
screen toasted or etc.? This wld be valuable to know, as well as the
conditions under which there was a failure, if available.

Yes we know the amp.

Electrically, it would be a stretch to make a distinction; unless the
mfgr is fraudulent or really lax, a spec is a spec..."not even close"
would seem to be a rash statement unless some mfgr's version sucketh
in specific, doccumented ways.

But it was/is not uncommon for some to run them above their 35w plate
dis at full power, which our old GE's sometimes tolerate somewhat (and
sometimes didn't or won't, as well).

None of us hv seen it all, in my case hv yet to see a crappy 6550 that
wasn't oriental.
  #35   Report Post  
Patrick Turner
 
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Miles O'Neal wrote:

Patrick Turner responded to WakyAmps, who said:

Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
really class A.


The ones I have serviced were class A, with absolutely no feedback.
They had a high bias current, and each of the 4 EL84 draws about 12 watts
at least at idle.


Now this doesn't make any sense at all.
In Class A, full tilt isn't different
enough from idle to make any difference.


The input power to the 4 x EL84 is around 48 watts.
In an ideal class A amp, a max of 24 watts in class A is available.
But usually, class A max efficiency is about 40%, so
expect about 20 watts of class A from 4 x EL84,
with a few extra AB watts to make it to about 30 at onset of clipping.
Such operation is substantially class A.
In a Musical Reference hi-fi amp made in the US, Ea = 700v, Eg2 = 350v,
and power output at clip from a pair is 36 watts, but its very definately
mainly class B, with only a couple of class A watts.
Idle power is about 5 watts per tube. During low level operation,
there is much more thd than for amps with gobs of class A power..
But nevertheless, the use of a high value RL seen by the tubes of 14k,
and 5% of CFB from a winding on the opt, and global FB, the amp
measures ok.

Many EL84 amps are less ambitious about power,
with a quite a few good for 21 watts, such as Mesa Boogie,
some Fenders with 6V6, where the B+ is high enough, as well as
the load value, to get such power, which is well in excess of what you'd get
if every watt was class A.
The Fender I fixed last week got 21 watts AB1 from 6V6, with 450v supply.
BIG voltage swing, low current swing, and mainly class B operation.
The cut off behaviour of tubes is such that the crossover distortion
of such amps is not entirely awful, certainly not in a guitar amp,
where distortions are prized, and there is no such thing as really
clean operation, because it sounds so plain dull and boring.

One is forced to allow some harmonic distortions, principally 3H,
and then boost the hell out of all the treble, add some reverb,
and maybe it sounds well.
Most guitar amps are PP mainly class B in their output stages.
Very few *pure* class A PP output stages are ever used, and
*extremely* few single ended class A output stages.
But all the input stages are nearly all SE stages using 12AX7,
so much of the warmth comes from the SE triode input stages which
are over driven a bit, and the distortion happens to be musically appealing,
( with a high level of 2H and 4H ), even to old smoothies, like George Benson.
But don't ask me what Mark Knoffler uses in his amp circuit to give him his
trademark sound.



So, just curious - why do you say they
were Class A? What do you think that
means?


because they are substantially class A.
Not totally class A, but more class A than nearly all other amps
in the output stages.



...
As I see it, all the 6550 from yesteryear about which ppl rave as being
just so superior to
anything else are all actullay prone to failure from hard use, unfortunate
events with the wrong speaker impedance, etc, since all the ratings
indicate that they are what they are, mortal tubes, and like us mortal
human beings,
they are gonna die one day.


While this is true, some of the tubes made back
in the far exceeded their published specs, and
hence are worth far more than the common tubes
of today, to some people. If it'll last five
times as long when being punished, it's worth at
least five times the price - more if you calculate
the lower likelihood of failure during a gig.


But none of the tubes I have seen will take 5 times the
power dissipation of an average spec tube.
There is *no* 6550 with an anode diss rating of 200 watts,
and nealry all turn red at just over 45 watts, and then its time for
prayer, or to reach for the off switch.

I actually like NOS US made tubes.
I have a pair of ancient 40 yr old Sylvania 6CA7,
which in UL still pump out 28 watts of class AB at
0.125% thd with 17 dB of NFB in an ancient ex school PA
amp which I use regurlarly in my shed to test speakers etc.
It withstands the occasional red plate session, when left running into
a load which is too low. Done that a few times.
Accidently had the leads come together for awhile with a signal,
and sure, it got hot, but good as new after being turned off for
5 minutes.
These tubes were old and tired when I bought 7 years ago sh for $3 each,
but they keep truckin. I know I ain't likely to
ever blow up a nice pair of customers speakers I happen to be testing,
simply because I'm usin a transformer coupled amp, and there is no nasty
DC to come a leapin outa the box to fry a driver.

I see no reason why today's tubes won't survive the "industrial use".

I have had one sovtek KT88 get a broken heater connection on a tube pin,
and this made the other in the PP circuit do all the work, and it went red
for quite some time before the customer noticed, ( customers are
non techs, and notoriously slow to realize something is wrong ),
but after a resolder, the overheated tube seemed undamaged.



I'm merely suggesting
that, while for Rich there's no other tube than the GE and no other amp
than the PS400, the OP is looking to retube a reissue SVT and the OP may
be quite satisfied with the Sovs (at half the price no less). And it is
the OP's needs we're trying to address here, right?


Sure. I agree with you here. At the same time
I understand where Rich is coming from. He's a
firm believer in the value of the old tubes over
anything built today (so far), and wants to help
others understand that.

In some case I agree with him on the state of the
art and the value; in others I don't. Most of the
time we're in different threads, because I mostly
deal with 6BQ5s and 6V6s, which he dismisses as
"radio tubes". 8^)


The littlies have a very nice sound though, and its why dudes use them.
For a small venue for a jazz scene, maybe its all that's needed.




I assure you that other folks make big tube amps. As new old stocks of
favourite old tubes dry up, all we are gonna have is sovtek, EH, Svetlana
etc.
But asking more than 75 watts per pair of bottles is asking for trouble.


With the new tubes this may be so - I don't know.
But I have known lots of folks getting 100W or more
per pair (think SVT!) with no problem.


Back in the 1960's, quite a few amps using EL34 with
800 volt B+ supplies were used, mainly for PA, because
100 watts was available, and low THD wasn't a priority.
I probably sat thru many a sermon ( boring ) at the church
where I was taken each sunday as a kid with such amps.
Where are all those amps? all gone to the Yonder!
And these were all mainly used for just a bit of pious speach,
not kickass bass with serious overdrive.
Tube and socket replacements due to arcing were common,
so one reason they all were replaced was the spectacular
failures, costs of maintenance, and anyone selling the then very
new, and even rather expensive solid state amps had little trouble.
I don't believe they sounded all that much worse in the PA field.
Most of those have all expired and been thrown out.
Nothing is forever.

...
Remember, Rich claims that the GE and Sov "aren't even close" sonically
or electrically. Maybe so in his tweaked 400PS and to his ears and
playing style; there may not be as strong a case in the OP's RI-SVT and
to the OP's ears and style.


How anyone can tell much difference between the sound of tubes when the
thd is at around 25%, and IMD at around 50% is beyond me.


Just curios - are you a musician?


Not now; I was in a band many years ago,
and played acoustic 12 string. I did some time in coffee lounges
with folk music; I can stil play, but I have little time.
I often have to fix guitar amps, and I hear the musician's problems
and the sound, during testing....

Do you care about
tone?


Yes, and mainly at low levels, because at gross overload levels,
the waveform is mainly a square wave, and the difference in tube brands
does not make an enormous difference to the sound
of such energy being supplied to a speaker.

Do you consider your ears good?


Good enough.

Because the
sonic differences in tubes are ell documented. My
wife and kids, none of whom play guitar (Josiah keeps
saying he wants to, but never practices much) can hear
these differences, and they aren't tube freaks by any
stretch of the imagination!


I hear differences, sure, but mainly at low levels.
The "dark metal" guy who likes his 6550 in triode runs them at
gross overload all night. I don't believe the sound would change
if he changed from Sovtek to GE.
To me it would still sound like a continuous aeroplane crash
happening right in front of me.



[Story of 0 ohm tube PA into 1 ohm bins snipped]

In this case, its better to err on the load value by choosing a value too
high, rather than too low!


Why not try your friend's PA head into, say, 64
ohms at full blast and let us know how that goes?


If you have a 400 watt amp capable of 400 watts into 64 ohms,
then using 64 ohms would give only a fraction of the power,
and the sound level, because the voltage swing from the tubes is
nearly maximum even with 8 ohms, at 56 vrms, and
with 64 ohms, only 20 more swing is available, ie 67 volts,
so one gets only 70 watts. But the class A % would be quite high.
Pentode/tetrode operation is almost universally used for output stages
in the music industry in tube amps.
Distortion in such amps with a high RL is not necessarily
all that much lower than some lower value RL which is the optimal for
low thd. But high value RLs mean the output stage has much higher gain.
If there is a feedback loop, then there is effectively much more applied FB
with a high value RL.
The gain of a 6550 in class A with a 2 kohm plate load is about 19.
But with 16k its about 80+, or five times the gain, which is + 14 dB.
If there was 12 dB of FB applied with 2k, then there is about
5 times the feedback applied when the load is changed to eight times the load
value.
Thus with 16k, there is an effective 26 dB of FB applied.
One has to be careful about stability if using a high value load, lest the amp
begin to oscillate at some LF or HF.
In practice, since most amps operate mainly in class B,
the open loop gain is about 1/2 what I have described, so the max amount of
FB with a 64 ohm load would be 20 dB at high power.
But at low power, the gain is higher, since it is class A.
This explains why some poorly stabilised amps oscillate just a little
and no more, because they do so only in the operating region where the tube gain
is high.

Speaker impedances rise to high values at HF, because of their
inductive character.

So, I would never recommend that anyone use a 64 ohm load with
a pentode/tetrode amp which was designed for 8 ohms.
16 ohms would be OK though, but 4 ohms could be deadly.
To ensure stability, even with no load at all, when the output tube
gain is perhaps 150+ then the feedback loop has to be carefully
considered, and some way of damping, ie, loading the output stage
at F above 20 kHz should be employed,
say by having an RC network with HV rated C and large wattage R
strapped across each 1/2 primary.
Some ancient amps using V1505 power triodes with 2 kV B+,
good for 1,100 watts class AB2 used adjustable spark
gaps to allow arcs to occur if the anode to anode signal voltage exceeded a
certain
level. Little FB was used. That was the primitive approach.
But with pentodes or tetrodes, unlike triodes, the gain changes with load,
and often some FB is used. Well concieved RC gain limiting networks are
good practice.

The idea of using multiple parallel KT88 or 6550
isn't new for high power.
There was a design described in full in a 1957 edition of Wireless
World, which easily tested at 400 watts with 10 x KT88.
All the parts were mounted on a piece of 3/4" plywood,
about 24" x 9", breadboard style. Class A % of the power was
substantial.
Probable use was for a stadium, theatre PA.
Poor struggling musos could never afford such gear, and all the speakers
that went with the amp, and the van to carry it all.
There were 10 ohm resistors to each cathode of the KT88, with a meter which
could be switched
to each 10 ohms to check the bias currents.
The tube idle power dissipation was kept low, and to allow for
uneven bias drift; such amps often have only one fixed bias voltage,
and one has to allow for one or more tube's idle current to
mysteriously escalate during its life.
Nevertheless, the tests of the 1957 amp showed it could sustain
the use of lower load values briefly, and that it was capable of
well over 500 watts.

I believe the prudent designers then would never have considered the use of only

6 x 6550 to do the job.

It'd be like flogging good men to death.

Patrick Turner.



-Miles

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  #36   Report Post  
Rich Koerner
 
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wrote:

Rich Koerner wrote in message ...

The 6550WE is NO GE-6550A. It's not even close!!!!!!!!

Sonically, or electrically.


Pls clarify, Rich - R U saying that it doesn't dissipate well enough
under full load?


They don't give high output yield no the loads.

At low frequency, a sine wave is not a good looking sine wave, when the GE yields one.

The screens are not as hardy as the GE's.

Their service life for high power yields is short when compared to the GE.



If so, what specific failures have you noted or had reported - i.e.
screen toasted or etc.?


You can't stick a 6550 that is from off shore into everything you can stick a GE 6550A.

You will have to make changes so you don't toast the screens.

In low demanding unit they are OK.

A Leslie amp will not hurt them.

They may live in an SVT for a long period of time, all the while the power output is
slowly going down.

The low end punch on the B and E strings of the bass is getting flabby sounding, and you
may think you have a speaker problem going on.

It's one thing for the tubes to LIVE through the task, and another to HOLD UP high
performance yield, in performing the task.

GE's, hold a high level of performance for a LONG time.

I've NEVER had an imported 6550's give the 435 watts out from a 400-PS.

I slap in a set of GE's, and it's there at 50 Hz.

What does that tell you!!!!!!!!!!!!!!!!!!!!

Simple, ain't it.



This wld be valuable to know, as well as the
conditions under which there was a failure, if available.


Look, when someone comes in with an SVT or a 400-PS in the shop, there is a reason WHY,
they own them in the first place.

Magnavox SVT's with GE's do what they do. And, the owner WANTS that at all cost!!!!!

So, I slap in a set of say WE's. I get a call a few months later from the owner, and he
says, I think there is something going on with the amp, it seems to be getting weaker.
The punch in the low end is soft now.

Like the speakers are getting loose.

I slap the thing on the bench, and the output is now lower than were we started, and the
sine wave at low freq. is not so good looking.

Slap in a set of GE's, and the smile on his face says it all!!!!!!!!!!!!!!!!!!!

So, the WE's still work!!!!!!

They don't blow up the amp!!!!!!

So, I guess you can say there is no failure, except..... they just don't live up to the
performance characteristics, and give the service life of the GE-6550A!!!!!!!!!!!!!!!

THAT, is their failure!!!!!!!!




Yes we know the amp.

Electrically, it would be a stretch to make a distinction; unless the
mfgr is fraudulent or really lax, a spec is a spec..."not even close"
would seem to be a rash statement unless some mfgr's version sucketh
in specific, doccumented ways.

But it was/is not uncommon for some to run them above their 35w plate
dis at full power, which our old GE's sometimes tolerate somewhat (and
sometimes didn't or won't, as well).


Well, I've run GE-6550A's at way more than 35w.

More than 50w with out protest.





None of us hv seen it all, in my case hv yet to see a crappy 6550 that
wasn't oriental.


My standard for a yardstick IS the 400-PS. Because, the yardstick for the GE-6550A, was
the 400-PS.

That is how the history went.

So, re-writing history to favor the imports, is what is going on here!!!!!!


Regards,

Rich Koerner,
Time Electronics.
http://www.timeelect.com

Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
  #37   Report Post  
Patrick Turner
 
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Don wrote:

I know there are times when "kick ass bass" is a must, and the sound
system
at the film club I go to provides this when you hear a train going past
nearby.
Not a tube amp to be seen. Its all SS behemoths, perhaps several 1,000
watters,
but sure, you feel the sound, as well as hear it, and ear plugs are
required
by folks such as I with such movies made deliberately to be sonically
provocative,
because the technology is the focus, to disguise the attrocious acting,
gadgets used to prop up otherwise failure prone humans,
with special effects every minute, and even with sharks growling
underwater.
I am appalled at such idiotic stories about tomb raiding, and all the
sound engineering
is in vain, as its an attempt to deafen me, ie, injure my hearing.


I suggest you see "Cold Mountain" an American Civil War movie, with folk
music.

Mystic River and Lost in Translation are two good adult films, no tomb raiding
involved.


I enjoyed Cold Mountain, and Lost in Translation, although in the latter case
it was entirely improbable in real life that the younger female lead wouldn't have
bonked
the older lead man, instead of him bonking the singer in the bar closer to his own
age.
America does try to be responsible about where it leads its folks on morals,
and fornication, but there is much hypocrisy......
But nearly all young sheilas of 20 something think its entirely
repugnant to bonk someone twice their age, unless he's stinking rich or famous,
when indeed there are all manner of younger cool dudes,
dateless and desperate to plug in and discard
when the itch needs a scratch.
They never spell it out like this.....
If I walk into a bar, I am Mr Invisible, and I know who the sheilas are watching,
and it ain't me. Used to be me, but not any more.....
And if I started singing folks songs they'd call the police.....


Patrick Turner.




  #38   Report Post  
JTM50
 
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From Patrick Turner below: "because they are substantially class A. Not
totally class A, but more class A than nearly all other amps in the output
stages."

This is called Class A/B1.
Just cause a tube conducts for 360 degrees when it's delivering some amount
less than full power (below the onset of clipping) doesn't mean that it's
operating as Class A at that point.

Lloyd


in article , Patrick Turner at
wrote on 2/22/04 3:31 PM:



Miles O'Neal wrote:

Patrick Turner responded to WakyAmps, who said:

Yes, how it is set up makes a huge difference, no a Vox AC-30 isn't
really class A.

The ones I have serviced were class A, with absolutely no feedback.
They had a high bias current, and each of the 4 EL84 draws about 12 watts
at least at idle.


Now this doesn't make any sense at all.
In Class A, full tilt isn't different
enough from idle to make any difference.


The input power to the 4 x EL84 is around 48 watts.
In an ideal class A amp, a max of 24 watts in class A is available.
But usually, class A max efficiency is about 40%, so
expect about 20 watts of class A from 4 x EL84,
with a few extra AB watts to make it to about 30 at onset of clipping.
Such operation is substantially class A.
In a Musical Reference hi-fi amp made in the US, Ea = 700v, Eg2 = 350v,
and power output at clip from a pair is 36 watts, but its very definately
mainly class B, with only a couple of class A watts.
Idle power is about 5 watts per tube. During low level operation,
there is much more thd than for amps with gobs of class A power..
But nevertheless, the use of a high value RL seen by the tubes of 14k,
and 5% of CFB from a winding on the opt, and global FB, the amp
measures ok.

Many EL84 amps are less ambitious about power,
with a quite a few good for 21 watts, such as Mesa Boogie,
some Fenders with 6V6, where the B+ is high enough, as well as
the load value, to get such power, which is well in excess of what you'd get
if every watt was class A.
The Fender I fixed last week got 21 watts AB1 from 6V6, with 450v supply.
BIG voltage swing, low current swing, and mainly class B operation.
The cut off behaviour of tubes is such that the crossover distortion
of such amps is not entirely awful, certainly not in a guitar amp,
where distortions are prized, and there is no such thing as really
clean operation, because it sounds so plain dull and boring.

One is forced to allow some harmonic distortions, principally 3H,
and then boost the hell out of all the treble, add some reverb,
and maybe it sounds well.
Most guitar amps are PP mainly class B in their output stages.
Very few *pure* class A PP output stages are ever used, and
*extremely* few single ended class A output stages.
But all the input stages are nearly all SE stages using 12AX7,
so much of the warmth comes from the SE triode input stages which
are over driven a bit, and the distortion happens to be musically appealing,
( with a high level of 2H and 4H ), even to old smoothies, like George Benson.
But don't ask me what Mark Knoffler uses in his amp circuit to give him his
trademark sound.



So, just curious - why do you say they
were Class A? What do you think that
means?


because they are substantially class A.
Not totally class A, but more class A than nearly all other amps
in the output stages.



...
As I see it, all the 6550 from yesteryear about which ppl rave as being
just so superior to
anything else are all actullay prone to failure from hard use, unfortunate
events with the wrong speaker impedance, etc, since all the ratings
indicate that they are what they are, mortal tubes, and like us mortal
human beings,
they are gonna die one day.


While this is true, some of the tubes made back
in the far exceeded their published specs, and
hence are worth far more than the common tubes
of today, to some people. If it'll last five
times as long when being punished, it's worth at
least five times the price - more if you calculate
the lower likelihood of failure during a gig.


But none of the tubes I have seen will take 5 times the
power dissipation of an average spec tube.
There is *no* 6550 with an anode diss rating of 200 watts,
and nealry all turn red at just over 45 watts, and then its time for
prayer, or to reach for the off switch.

I actually like NOS US made tubes.
I have a pair of ancient 40 yr old Sylvania 6CA7,
which in UL still pump out 28 watts of class AB at
0.125% thd with 17 dB of NFB in an ancient ex school PA
amp which I use regurlarly in my shed to test speakers etc.
It withstands the occasional red plate session, when left running into
a load which is too low. Done that a few times.
Accidently had the leads come together for awhile with a signal,
and sure, it got hot, but good as new after being turned off for
5 minutes.
These tubes were old and tired when I bought 7 years ago sh for $3 each,
but they keep truckin. I know I ain't likely to
ever blow up a nice pair of customers speakers I happen to be testing,
simply because I'm usin a transformer coupled amp, and there is no nasty
DC to come a leapin outa the box to fry a driver.

I see no reason why today's tubes won't survive the "industrial use".

I have had one sovtek KT88 get a broken heater connection on a tube pin,
and this made the other in the PP circuit do all the work, and it went red
for quite some time before the customer noticed, ( customers are
non techs, and notoriously slow to realize something is wrong ),
but after a resolder, the overheated tube seemed undamaged.



I'm merely suggesting
that, while for Rich there's no other tube than the GE and no other amp
than the PS400, the OP is looking to retube a reissue SVT and the OP may
be quite satisfied with the Sovs (at half the price no less). And it is
the OP's needs we're trying to address here, right?


Sure. I agree with you here. At the same time
I understand where Rich is coming from. He's a
firm believer in the value of the old tubes over
anything built today (so far), and wants to help
others understand that.

In some case I agree with him on the state of the
art and the value; in others I don't. Most of the
time we're in different threads, because I mostly
deal with 6BQ5s and 6V6s, which he dismisses as
"radio tubes". 8^)


The littlies have a very nice sound though, and its why dudes use them.
For a small venue for a jazz scene, maybe its all that's needed.




I assure you that other folks make big tube amps. As new old stocks of
favourite old tubes dry up, all we are gonna have is sovtek, EH, Svetlana
etc.
But asking more than 75 watts per pair of bottles is asking for trouble.


With the new tubes this may be so - I don't know.
But I have known lots of folks getting 100W or more
per pair (think SVT!) with no problem.


Back in the 1960's, quite a few amps using EL34 with
800 volt B+ supplies were used, mainly for PA, because
100 watts was available, and low THD wasn't a priority.
I probably sat thru many a sermon ( boring ) at the church
where I was taken each sunday as a kid with such amps.
Where are all those amps? all gone to the Yonder!
And these were all mainly used for just a bit of pious speach,
not kickass bass with serious overdrive.
Tube and socket replacements due to arcing were common,
so one reason they all were replaced was the spectacular
failures, costs of maintenance, and anyone selling the then very
new, and even rather expensive solid state amps had little trouble.
I don't believe they sounded all that much worse in the PA field.
Most of those have all expired and been thrown out.
Nothing is forever.

...
Remember, Rich claims that the GE and Sov "aren't even close" sonically
or electrically. Maybe so in his tweaked 400PS and to his ears and
playing style; there may not be as strong a case in the OP's RI-SVT and
to the OP's ears and style.

How anyone can tell much difference between the sound of tubes when the
thd is at around 25%, and IMD at around 50% is beyond me.


Just curios - are you a musician?


Not now; I was in a band many years ago,
and played acoustic 12 string. I did some time in coffee lounges
with folk music; I can stil play, but I have little time.
I often have to fix guitar amps, and I hear the musician's problems
and the sound, during testing....

Do you care about
tone?


Yes, and mainly at low levels, because at gross overload levels,
the waveform is mainly a square wave, and the difference in tube brands
does not make an enormous difference to the sound
of such energy being supplied to a speaker.

Do you consider your ears good?


Good enough.

Because the
sonic differences in tubes are ell documented. My
wife and kids, none of whom play guitar (Josiah keeps
saying he wants to, but never practices much) can hear
these differences, and they aren't tube freaks by any
stretch of the imagination!


I hear differences, sure, but mainly at low levels.
The "dark metal" guy who likes his 6550 in triode runs them at
gross overload all night. I don't believe the sound would change
if he changed from Sovtek to GE.
To me it would still sound like a continuous aeroplane crash
happening right in front of me.



[Story of 0 ohm tube PA into 1 ohm bins snipped]

In this case, its better to err on the load value by choosing a value too
high, rather than too low!


Why not try your friend's PA head into, say, 64
ohms at full blast and let us know how that goes?


If you have a 400 watt amp capable of 400 watts into 64 ohms,
then using 64 ohms would give only a fraction of the power,
and the sound level, because the voltage swing from the tubes is
nearly maximum even with 8 ohms, at 56 vrms, and
with 64 ohms, only 20 more swing is available, ie 67 volts,
so one gets only 70 watts. But the class A % would be quite high.
Pentode/tetrode operation is almost universally used for output stages
in the music industry in tube amps.
Distortion in such amps with a high RL is not necessarily
all that much lower than some lower value RL which is the optimal for
low thd. But high value RLs mean the output stage has much higher gain.
If there is a feedback loop, then there is effectively much more applied FB
with a high value RL.
The gain of a 6550 in class A with a 2 kohm plate load is about 19.
But with 16k its about 80+, or five times the gain, which is + 14 dB.
If there was 12 dB of FB applied with 2k, then there is about
5 times the feedback applied when the load is changed to eight times the load
value.
Thus with 16k, there is an effective 26 dB of FB applied.
One has to be careful about stability if using a high value load, lest the amp
begin to oscillate at some LF or HF.
In practice, since most amps operate mainly in class B,
the open loop gain is about 1/2 what I have described, so the max amount of
FB with a 64 ohm load would be 20 dB at high power.
But at low power, the gain is higher, since it is class A.
This explains why some poorly stabilised amps oscillate just a little
and no more, because they do so only in the operating region where the tube
gain
is high.

Speaker impedances rise to high values at HF, because of their
inductive character.

So, I would never recommend that anyone use a 64 ohm load with
a pentode/tetrode amp which was designed for 8 ohms.
16 ohms would be OK though, but 4 ohms could be deadly.
To ensure stability, even with no load at all, when the output tube
gain is perhaps 150+ then the feedback loop has to be carefully
considered, and some way of damping, ie, loading the output stage
at F above 20 kHz should be employed,
say by having an RC network with HV rated C and large wattage R
strapped across each 1/2 primary.
Some ancient amps using V1505 power triodes with 2 kV B+,
good for 1,100 watts class AB2 used adjustable spark
gaps to allow arcs to occur if the anode to anode signal voltage exceeded a
certain
level. Little FB was used. That was the primitive approach.
But with pentodes or tetrodes, unlike triodes, the gain changes with load,
and often some FB is used. Well concieved RC gain limiting networks are
good practice.

The idea of using multiple parallel KT88 or 6550
isn't new for high power.
There was a design described in full in a 1957 edition of Wireless
World, which easily tested at 400 watts with 10 x KT88.
All the parts were mounted on a piece of 3/4" plywood,
about 24" x 9", breadboard style. Class A % of the power was
substantial.
Probable use was for a stadium, theatre PA.
Poor struggling musos could never afford such gear, and all the speakers
that went with the amp, and the van to carry it all.
There were 10 ohm resistors to each cathode of the KT88, with a meter which
could be switched
to each 10 ohms to check the bias currents.
The tube idle power dissipation was kept low, and to allow for
uneven bias drift; such amps often have only one fixed bias voltage,
and one has to allow for one or more tube's idle current to
mysteriously escalate during its life.
Nevertheless, the tests of the 1957 amp showed it could sustain
the use of lower load values briefly, and that it was capable of
well over 500 watts.

I believe the prudent designers then would never have considered the use of
only

6 x 6550 to do the job.

It'd be like flogging good men to death.

Patrick Turner.



-Miles

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  #39   Report Post  
WakyAmps
 
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Patrick Turner wrote in
:



Miles O'Neal wrote:

Patrick Turner responded to WakyAmps, who said:


Actually, it was Miles who said... but I've a few questions of
my own.

[humongous snip]

Not sure we're all speaking the same language here ('least I'm
sure as hell not...)

In my dictionary[1], a push-pull amp biased class B has one
output tube in cutoff when the other is conducting. Class A has
both tubes conducting for the entire waveform. Class AB1 has
each tube conducting for somewhat more than half of each cycle,
though the outputs still alternate between cutoff[2].

I think we'll all agree that an AC-30 runs the bejeezus out of
its outputs. However, please explain to me, for a P-P AB1
biased amp, the difference between the "Class A watts" and the
"Class B watts". I don't think I've ever seen those terms used
in that context before.

Are you saying that an AB1 amp where the outputs conduct for,
say, 80% of the signal has more "class A watts" than an amp
where the outputs conduct for 70% of the signal? The latter, of
course, having more "class B watts"?

Just tryin' to understand yer post.


[1] Which I understand may only apply to my very skewed view of
the world, hence the question

[2] and, to be anal, with no grid current -- otherwise it'd be
AB2.
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