[Patrick Turner]

Lord Valve wrote:

Despite what you may have seen from a couple of
the know-it-alls on this NG, don't do it. Audiophools
rarely stress their gear, and consequently rarely
consider what may happen to it when it is operated
beyond design parameters - as guitar amplifiers
*routinely* are. You risk a condition known as high-
tension flyback if you run a tube guitar amp into a higher
than rated impedance; this will fry your power tube
socket, along with the tube in it. Lower-powered
amps are certainly not immune to this, judging by
the number of tube sockets I've replaced in Fender
Champs and small Gibsons over the years. Get
the correct impedance speaker.

Lord Valve
Expert


Yes, we hear what you are saying and without any load on the amp
the anode to anode signal voltage can be maybe 2,000Vrms instead of a
maximum
of say 500Vrms with a load of below 20 ohms is at the output.

The majority of guitar amps are set up for maximum power into a load
which is slightly less than what SHOULD be used anyway
so that the typical operation is to have a small amount of class A%
power
in the total class AB power.

So changing from say 4 ohms to 8 ohms is never going to cause a problem
of overloading.

However, the speaker will have a resonant frequency where the Z of the
speaker is very high
at some bass F, and 50+ ohms would not be uncommon, so regardless of
what sort
of speaker is fitted there will be an impedance at bass which is way
above the rated Z
of 4 or 8 ohms which is only valid for the mid F, say at 400Hz.
The inductive nature of the voice coil will have the Z rising at
6dB/octave above a pole
at say 500Hz, so by 5kHz, the speaker Z has gone very high, and as you
know
ppl run their amps with treble and brightness turned right up, so that
the amp is overloaded by HF
before the bass F cause overloading. The resulting distortions are much
favoured by rock'n'rollers,
and when the wave forms become clipped the HF content is even greater,
and there is even more risk of arcing.

So regardless of what you say Lord V, there is always a risk of arcing
at the tube sockets
because there is so little ever done to prevent it, like say
having diodes connected from each anode to ground, to prevent the Vswing
ever moving negative with respect to 0V, and thus prevent Eamax ever
swinging more than twice
the supply voltage.
There is never ever any Zobel network connected across the output so
there is a HF load on the amp.

Guitar amp makers rarely ever do anything to prevent over voltaging the
tube sockets and OPT
insulation because they don't give a **** if an amp blows up because its
going to then need replacing,
and they like the new business, any way they can get it.

So after considering what LV has siad, and has NOT said, and what I have
brought to folk's attention,
I would maintain that changing from a 4 ohm speaker to 8 ohms is OK.
The amount of class A power is increased, although maybe the overall
power is reduced,
which won't alter percieved volume levels much.
The tubes won't be subject to such high peak currents and should perhaps
last a few gigs longer.

Patrick Turner.

[Patrick Turner]

Ian Iveson wrote:

zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

SS amps have a load of NFB and there is a Zobel network which loads the
output,
and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,
so risk of arcing in SS amps is not a problem. Sensible SS guitar amps
have diodes from the output to
the rails to prevent swings on the output ever going more than the rail
voltage peak value,
since this can occur with the inductive load of a speaker, and cause
instant death to the output
bjts with reverse flow currents.

Tube guitar amps under discussion don't have any precautions to limit
anode voltage swings way above what happens with 4,8, or 16 ohms.


Low value loads on tube guitar amps means much earlier death for the
tubes,
as evidenced in amps used for heavy metal / grunge band use where the
guitar sound
is a continuous stream of square waves during gross output tube
saturation.


NEVER use a lower than recommended load on a tube amp.
If you do, send the bill for new tubes to Ian who will pay because he
advises its OK.

Patrick Turner.

cheers, Ian

[Phil Allison]

"Eeysore the ****WIT POMMY **** "

"Arny Krueger"

Ironically, if one takes Phil's advice and searches alt.guitar.amps for
posts about flyback spikes, you find him dodging the same basic
question
you asked about generating 5 Kv spikes around 2/25/2003, for example.

** Massive, silly LIE.

There are no relevant posts there from me around that date.

UTTER ******** !

http://groups.google.com/group/alt.g...2b685575212897


** Shame how the date is the 19th, not the 25th as stated.

Shame how the issue is not the same one alluded to by Arny.


**** the HELL OFF & DIE you POMMY ASS !!




......... Phil

[Patrick Turner]

Eeyore wrote:

Ian Iveson wrote:

zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

Oh puhleeze ! Is that nonsense or what ?

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will
drive a 1 - 2 ohms load very well, yet many SS amps do it admirably.

Graham

Tube amps can be load matched to allow any low value load to be
connected since there is an OPT which may have adjustable configurations
of windings.
Even many crummy old tube amps had matching for 4 or 16 ohms by
paralleling or seriesing
the two secondary OPT windings. This allowed a range of anything above 2
ohms, because the
4 ohm load may have given a match for class A, and the 2 ohm would be
tolerated
since the load is still an OK class AB load.

The typical low levels used with hi-fi permit some load mismatch, but
not in guitar amp world,
a world of plectrum demons.

SS amps have no such matching OPT or other device, and need current /
voltage limiting.
What is NEVER fitted to an SS amp is an intelligent circuit that detects
if the load
is below 2 ohms and TURNS THE AMP OFF even if it is used at low level.
This safety option would save all the amps who expire when connected to
shorted speaker cables
or to fried/faulty speakers/crossovers.

The makers of SS amps have had 40 years to fit decent active protection
but they
prefer you buy a ****ing new amp, rather than have the old one continue
for too long.

Tubes will also glow red and thermal out if the load is too low, but it
just takes longer for it to happen.
If an OPT is destroyed in the process, it can be very expensive!


Patrick Turner.

[Phil Allison]

"Eeysore the Raving CRIMINAL LUNATIC" "


" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.


But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.



** Err - what about inductive loads ??

Like guitar speaker cabs ??



Finally did a little Googling - did we ?

No need.


** But I bet you did so anyhow - LIAR !!



Now, how did *YOU* get 5kV flyback spikes.

What was the load ?


** A quad box, 4 x Celestion 12 inch, wired series /parallel.

An 8 or 16 ohm dummy load with series inductor of a few mH simulates the
above.


How hard was the amp being driven ?


** Full overdrive / clipping.

Just like most guitarist play their Marshalls for hours on end.



What was the input signal ?


** A slide guitarist with his Gibson SG demonstrated in one case.

A sine wave bench gen does nicely too.


BTW :

I don't expect a VILE CRIMINAL LUNATIC

like Graham Stevenson to accept a single word of this.

He did not ask me in order to find out the facts.

Having done NO such tests himself - he has not the SLIGHTEST clue about
it.

He will never do any either.




........ Phil

[Eeyore]

Patrick Turner wrote:

Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

SS amps have a load of NFB and there is a Zobel network which loads the
output, and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.

Graham

[Eeyore]

Phil Allison wrote:

"Eeysore the ****WIT POMMY **** "

"Arny Krueger"

Ironically, if one takes Phil's advice and searches alt.guitar.amps for
posts about flyback spikes, you find him dodging the same basic
question
you asked about generating 5 Kv spikes around 2/25/2003, for example.

** Massive, silly LIE.

There are no relevant posts there from me around that date.

UTTER ******** !

http://groups.google.com/group/alt.g...2b685575212897

** Shame how the date is the 19th, not the 25th as stated.

You said " around that date.". Which it is.

15
From: Phil Allison - view profile
Date: Tues, Feb 18 2003 10:08 pm


Shame how the issue is not the same one alluded to by Arny.

It is exactly......

" ** There are often MAJOR inductive spikes with a nominally **correctly
loaded** amp when run very hard into real speakers or simulated reactive
loads - I have measured up to 5 kV peaks on the tube plates with a 100 W
Marshall with 8 ohms plus 5 mH. "


Graham

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:
Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

Oh puhleeze ! Is that nonsense or what ?

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will
drive a 1 - 2 ohms load very well, yet many SS amps do it admirably.

Graham

Tube amps can be load matched to allow any low value load to be
connected since there is an OPT which may have adjustable configurations
of windings.

I had in mind the 'typical' 4, 8 and 16 ohm taps on most power amplifiers.

Have you ever seen a 2 ohm tap btw ?

Graham

[Phil Allison]

"Eeysore the ****ing Pommy ****head "

Patrick Turner wrote:

SS amps have a load of NFB and there is a Zobel network which loads the
output, and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.



** Ahhh - the diodes are to catch those pesky flyback spikes, yet again.

The ones this ASININE POMMY ****HEAD denies exist.

ROTFLMAO !!!


What an absolute hoot this Stevenson Criminal Nutter is !!




........ Phil

[Patrick Turner]

Eeyore wrote:

Phil Allison wrote:

"Eeysore the Raving LUNATIC" "

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

You don't know do you ?

Graham

I suggest that where you have an OPT which has a large amount of
inductance
in its primary, that where the anode current is sharply cut off, as is
the case in an unloaded
pentode amp which is over driven, then there are huge emfs produced
unless these are shunted somehow.
The simplest way to avoid the phenomenon that Phil Allison and myself
and LV say occurs,
is to connect 3 x IN4007 in series from each anode to 0V so that the
diode cathodes are at the tube anodes,
and diode anodes are at 0V.
Under normal use there s no flow in the diodes to 0V, but should a large
back emf
occur, it will try to one end of the OPT primary very +ve while sending
the other end
very -ve, and THEN THE DIODES CONDUCT and this loads the OPT and shunts
the back emf,
thus limiting, or clamping the output T primary voltage.
I have never seen 5,000Vrms in a wayward unloaded OPT, but I can't say
it wouldn't occur.
I have seen many amps suffer from arcing because of the rather highish
ordinary working voltages
including those with B+ rail = 350V and with EL84 etc, but this usually
occurs
because the sockets/underchassis area is polluted, or damp, or the OPT
is dmap after storage
in a damp place for 20 years.

Amps using EL34 with B+ = 900V and Eg2 = 450V are VERY PRONE TO ARCING
between the anode pin 3 and the earthy
heater pin 2 on the octal socket.

807 amps with 600V at the anode top cap and only 300V at Eg2 are less
prone to socket worries
but the OPT is still very prone to arcing if not well insulated or
varnished.

Patrick Turner

[Phil Allison]

Eeysore the ****WIT POMMY **** "


"Arny Krueger"

Ironically, if one takes Phil's advice and searches alt.guitar.amps
for
posts about flyback spikes, you find him dodging the same basic
question
you asked about generating 5 Kv spikes around 2/25/2003, for
example.

** Massive, silly LIE.

There are no relevant posts there from me around that date.

UTTER ******** !

http://groups.google.com/group/alt.g...2b685575212897

** Shame how the date is the 19th, not the 25th as stated.

You said " around that date." Which it is.


** No - it is 6 days earlier & cannot be in the same thread as Arny is
saying.



Shame how the issue is not the same one alluded to by Arny.

It is exactly......



** The post is NOT relevant to the claim Arny's made above.


YOU ASININE, ASD ****ED IDIOT !!.




......... Phil

[Phil Allison]

"Patrick Turner"


The simplest way to avoid the phenomenon that Phil Allison and myself
and LV say occurs,


** Just wanna make sure this does not go unnoticed.



is to connect 3 x IN4007 in series from each anode to 0V so that the
diode cathodes are at the tube anodes,


** Best use high speed diodes.

Watch out for the traps in doing this too.

The exact position of fuses or standby switches in an amp's circuit can make
this idea very un-safe.




............ Phil

[Eeyore]

Phil Allison wrote:

"Eeysore the Raving CRIMINAL LUNATIC" "

" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.


But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.


** Err - what about inductive loads ??

Like guitar speaker cabs ??

Finally did a little Googling - did we ?

No need.

** But I bet you did so anyhow - LIAR !!

I didn't. As I said - simply no need.


Now, how did *YOU* get 5kV flyback spikes.

What was the load ?

** A quad box, 4 x Celestion 12 inch, wired series /parallel.

An 8 or 16 ohm dummy load with series inductor of a few mH simulates the
above.

How hard was the amp being driven ?

** Full overdrive / clipping.

Just like most guitarist play their Marshalls for hours on end.

What was the input signal ?

** A slide guitarist with his Gibson SG demonstrated in one case.

A sine wave bench gen does nicely too.

So why didn't you just say this when I originally asked ?


BTW :

I don't expect a VILE CRIMINAL LUNATIC

like Graham Stevenson to accept a single word of this.

He did not ask me in order to find out the facts.

Having done NO such tests himself - he has not the SLIGHTEST clue about
it.

He will never do any either.

I do accept it. In fact I accepted it when you first posted it if you bother to
check.

What I said in fact was that if you can create 5kV spikes with the *correct*
load, then changing it from 4 to 8 ohms isn't going to change that.

Graham

[Eeyore]

Patrick Turner wrote:

What is NEVER fitted to an SS amp is an intelligent circuit that detects
if the load
is below 2 ohms and TURNS THE AMP OFF even if it is used at low level.
This safety option would save all the amps who expire when connected to
shorted speaker cables
or to fried/faulty speakers/crossovers.

Actually QSC have a very crude system that does do this.
http://www.freepatentsonline.com/4321554.html

It's an area I've been looking into myself actually as it can hugely benefit
amplifier design by eliminating 'hard' current limiting.

Graham

[Arny Krueger]

"Phil Allison" wrote in message

Eeysore the ****WIT POMMY **** "


"Arny Krueger"

Ironically, if one takes Phil's advice and searches
alt.guitar.amps for
posts about flyback spikes, you find him dodging the
same basic question
you asked about generating 5 Kv spikes around
2/25/2003, for example.

** Massive, silly LIE.

There are no relevant posts there from me around that
date.

UTTER ******** !

http://groups.google.com/group/alt.g...2b685575212897

** Shame how the date is the 19th, not the 25th as
stated.

You said " around that date." Which it is.


** No - it is 6 days earlier & cannot be in the same
thread as Arny is saying.


I specified no particular thread, Phil. Time to admit that Graham is right
and you were wrong.

[Eeyore]

Phil Allison wrote:

"Eeysore the ****ing Pommy ****head "
Patrick Turner wrote:

SS amps have a load of NFB and there is a Zobel network which loads the
output, and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.


** Ahhh - the diodes are to catch those pesky flyback spikes, yet again.

The ones this ASININE POMMY ****HEAD denies exist.

ROTFLMAO !!!

What an absolute hoot this Stevenson Criminal Nutter is !!

None of which has anything to do with loading a 4 ohm tap with 8 ohms.

Graham

[Phil Allison]

"Eeysore the Raving CRIMINAL LUNATIC" "


" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of
"flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain
it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.


But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.


** Err - what about inductive loads ??

Like guitar speaker cabs ??

Finally did a little Googling - did we ?

No need.

** But I bet you did so anyhow - LIAR !!

I didn't. As I said - simply no need.


** Blatant LIE !!




Now, how did *YOU* get 5kV flyback spikes.

What was the load ?

** A quad box, 4 x Celestion 12 inch, wired series /parallel.

An 8 or 16 ohm dummy load with series inductor of a few mH simulates the
above.

How hard was the amp being driven ?

** Full overdrive / clipping.

Just like most guitarist play their Marshalls for hours on end.

What was the input signal ?

** A slide guitarist with his Gibson SG demonstrated in one case.

A sine wave bench gen does nicely too.

So why didn't you just say this when I originally asked ?



** I did say, over and over, it was with a speaker cab and normal guitar amp
use.

You never asked specific, defined questions previously.

Only ones full of ambiguity and smartarse.





BTW :

I don't expect a VILE CRIMINAL LUNATIC

like Graham Stevenson to accept a single word of this.

He did not ask me in order to find out the facts.

Having done NO such tests himself - he has not the SLIGHTEST clue about
it.

He will never do any either.

I do accept it. In fact I accepted it when you first posted it if you
bother to
check.


** Then decided to contradict it like all hell - eg:


" But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure. "



What I said in fact was that if you can create 5kV spikes with the
*correct*
load, then changing it from 4 to 8 ohms isn't going to change that.


** Which is WRONG.

It *does* change things and often for the worse.

Depends on specific and individual cases whether a failure will occur.

I have already answered you on this.

The POINT is that ALL guitar amps that suffer from large voltage " flyback
spikes" are an accident just waiting to happen.




........ Phil

[Eeyore]

Phil Allison wrote:

Eeysore the ****WIT POMMY **** "

"Arny Krueger"

Ironically, if one takes Phil's advice and searches alt.guitar.amps
for posts about flyback spikes, you find him dodging the same basic
question you asked about generating 5 Kv spikes around 2/25/2003,
for example.

** Massive, silly LIE.

There are no relevant posts there from me around that date.

UTTER ******** !
http://groups.google.com/group/alt.g...2b685575212897

** Shame how the date is the 19th, not the 25th as stated.

You said " around that date." Which it is.

** No - it is 6 days earlier & cannot be in the same thread as Arny is
saying.

The date is close enough for me and the thread was about exactly the same topic we're discussing here !

Why on earth would you want to deny it ?

Graham

[Phil Allison]

"Arny Krueger"


" Ironically, if one takes Phil's advice and searches alt.guitar.amps for
posts about flyback spikes, you find him dodging the same basic question you
asked about generating 5 Kv spikes around 2/25/2003, for example. "


** No - it is 6 days earlier & cannot be in the same
thread as Arny is saying.


I specified no particular thread, Phil.


** You specified a date and a * particular * line of content.

Both are missing in that link.

Where the **** is it ??

Were you LYING or just totally WRONG as USUAL ???



Time to admit that Graham is right and you were wrong.


** Go get totally ****ED

you MONSTROUSLY EVIL HYPOCRITE





......... Phil

[Phil Allison]

"Eeysore the ****ing Pommy ****head "

Patrick Turner wrote:

SS amps have a load of NFB and there is a Zobel network which loads
the
output, and there is no OPT, so no high voltages with no load, and
supply
voltages are lower anyway,

Not to mention diodes fron output to supply rails too.


** Ahhh - the diodes are to catch those pesky flyback spikes, yet
again.

The ones this ASININE POMMY ****HEAD denies exist.

ROTFLMAO !!!

What an absolute hoot this Stevenson Criminal Nutter is !!

None of which has anything to do with loading a 4 ohm tap with 8 ohms.



** Not the claim of yours at issue.

As you very well know.



......... Phil

[Eeyore]

Phil Allison wrote:

"Eeysore the Raving CRIMINAL LUNATIC" "

So why didn't you just say this when I originally asked ?

** I did say, over and over, it was with a speaker cab and normal guitar amp
use.

Rubbish, you only just posted that answer once about half an hour ago.

Anyone looking at the time stamps on the posts can see that for themselves.


You never asked specific, defined questions previously.

They were perfectly clear !


Only ones full of ambiguity and smartarse.

And how exactly is that any different from you ? Weren't you smart enough to
understand my question ?

Graham

[Eeyore]

Phil Allison wrote:

"Eeysore the ****ing Pommy ****head "
Patrick Turner wrote:

SS amps have a load of NFB and there is a Zobel network which loads
the output, and there is no OPT, so no high voltages with no load, and
supply voltages are lower anyway,

Not to mention diodes fron output to supply rails too.


** Ahhh - the diodes are to catch those pesky flyback spikes, yet
again.

The ones this ASININE POMMY ****HEAD denies exist.

ROTFLMAO !!!

What an absolute hoot this Stevenson Criminal Nutter is !!

None of which has anything to do with loading a 4 ohm tap with 8 ohms.


** Not the claim of yours at issue.

Show where I claimed anything else.


As you very well know.

No. It was you who brought up the *off-topic* issue of 5kV spikes with *correct*
loading.

Graham

[Phil Allison]

"Eeysore the Raving CRIMINAL LUNATIC" "


So why didn't you just say this when I originally asked ?

** I did say, over and over, it was with a speaker cab and normal guitar
amp
use.

Rubbish, you only just posted that answer once about half an hour ago.


** INSANE CRAPOLOGY !

This post was 10.5 hours ago.

" Eg, any Marshall valve amp can easily be made to exhibit +/- 5 kV spikes
on the output plates when operating into a speaker cab. "


** This was only 44 mins later:

" Normal operation ( for a guitar amp) is the case. "


** Then, 7 hours ago, I combined them for you:

" Eg, any Marshall valve amp can easily be made to exhibit +/- 5 kV
spikes on the output plates when operating into a speaker cab.

LVs phrase " high tension flyback " is a very apt one - cos it don't
happen with a resistive load. "

" Normal operation ( for a guitar amp) is the case. "




Anyone looking at the time stamps on the posts can see that for
themselves.


** See CLEARLY what a damn INSANE LIAR you are !!!



........ Phil

[Phil Allison]

"Eeysore the ****ing Pommy ****head "


** Ahhh - the diodes are to catch those pesky flyback spikes, yet
again.

The ones this ASININE POMMY ****HEAD denies exist.

ROTFLMAO !!!

What an absolute hoot this Stevenson Criminal Nutter is !!

None of which has anything to do with loading a 4 ohm tap with 8 ohms.


** Not the claim of yours at issue.

Show where I claimed anything else.


** Here it is:

" Utter garbage. The voltage swings on the primary of the output transformer
are typically well *under* a thousand
volts. They cannot in any case exceed 2 x B+ in normal operation. "

Denies the existence of flyback spikes, even in guitar amps.



No. It was you who brought up the *off-topic* issue of 5kV spikes with
*correct*
loading.


** LV mentioned " high tension flyback" .

I quoted this remark in my first post.

Then gave some actual figures.

Not OT in the slightest.

You PITA ****ing Dim Wit.




......... Phil

[Sander deWaal]

Eeyore said:


There are only 2 professional designers here and they are Patrick Turmer and myself.


Oh? Just the 2 of you?

;-)


Lord Valve is a very experienced tube expert at the practical level but has no design experience AFAIK.


Repair experience is probably even more useful, one gets to see all
different kinds of amps, topologies and failures.

One can get a very good insight about the weak spots in designs by a
lifelong career in repairing various audio gear.
At least, that's where I came from.
And I still do repair every now and then, of MI and SR amps, domestic
audio and studio gear.

I would take LV's advice about tubes and guitar amps over anyone elses
every day, despite the fact that we're hardly friends.

--

- Maggies are an addiction for life. -

[Sander deWaal]

Eeyore said:


Have you ever seen a 2 ohm tap btw ?


Yes.
My own OPTs have 2.83 ohm taps, in fact.

I use them to drive 2 paralleled Magnepans per channel.

--

- Maggies are an addiction for life. -

[Lord Valve]

The RAT's ass mumbled:

Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will
drive a 1 - 2 ohms load very well, yet many SS amps do it admirably.

Graham

Tube amps can be load matched to allow any low value load to be
connected since there is an OPT which may have adjustable configurations
of windings.

I had in mind the 'typical' 4, 8 and 16 ohm taps on most power amplifiers.

Have you ever seen a 2 ohm tap btw ?

Where ya been, junior?

Two of the "Holy Grail of Tone" amps - the Fender '59
Tweed Bassman and the Fender '65 blackface Super
Reverb - have 2-ohm outputs. (So does the famous
Ampeg SVT, designed to drive one or two 4-ohm
cabinets containing eight 10" 32-ohm speakers
wired in parallel, with a switching jack for selecting
the 2-ohm tap when two cabinets are used. Try running
one of those into an upward mismatch - 8 ohm box
on the 4-ohm tap - and watch the fireworks.) Both of the
Fender amps drive four 10" 8-ohm speakers wired in parallel.
A few times a year - *every* year since I have been repairing
guitar amps, and that would be about 40 of 'em years)
I've had to fix several of these amps which had the
speaker wiring "corrected" to the much more common
series-parallel arrangement that produces an 8-ohm
load from four 8-ohm speakers. Said "correction"
usually performed by some audiophool "expert"
who "knew" that tube amps don't drive 2-ohm
loads. Of course, as soon as this "repair" was
accomplished, the poor *******'s amp started
blowing fuses. Seems the sockets were arced.

Imagine that.

Lord Valve
Expert

[John Byrns]

In article ,
Patrick Turner wrote:

SS amps have a load of NFB and there is a Zobel network which loads the
output,
and there is no OPT, so no high voltages with no load, and supply
voltages are lower anyway,
so risk of arcing in SS amps is not a problem. Sensible SS guitar amps
have diodes from the output to
the rails to prevent swings on the output ever going more than the rail
voltage peak value,
since this can occur with the inductive load of a speaker, and cause
instant death to the output
bjts with reverse flow currents.

I have had that happen in an amp without the diodes you mention. When
it went it made quite a show, the transistors were in TO-3 packages and
when it went one stated arcing between the emitter post inside and the
top of the package. The arc cut a hole through the top of the package
and started blasting out a jet of hot metal and flame sort of like some
sort of plasma torch, until I killed the power.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[John Byrns]

In article ,
Patrick Turner wrote:

So regardless of what you say Lord V, there is always a risk of arcing
at the tube sockets
because there is so little ever done to prevent it, like say
having diodes connected from each anode to ground, to prevent the Vswing
ever moving negative with respect to 0V, and thus prevent Eamax ever
swinging more than twice
the supply voltage.

You are assuming the transformer has no leakage inductance between
primary halves, is this a valid assumption for the typical guitar amp?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Iain Churches]

"Eeyore" wrote in message
...


Patrick Turner wrote:

Eeyore wrote:
Ian Iveson wrote:
zyx wrote

I have an epi valve jr combo with 8" speaker that is 4 ohms. I want
to try it on a 12" speaker which is 8 ohms.

Jam away?

A bit risky. Anode voltage may rise higher than some parts can cope
with reliably.

Oh puhleeze ! Is that nonsense or what ?

As a general rule, SS amps don't care too much about a higher load
impedance, and valves are tolerant of a lower one.

Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve
amps will
drive a 1 - 2 ohms load very well, yet many SS amps do it admirably.

Graham

Tube amps can be load matched to allow any low value load to be
connected since there is an OPT which may have adjustable configurations
of windings.

I had in mind the 'typical' 4, 8 and 16 ohm taps on most power amplifiers.

Have you ever seen a 2 ohm tap btw ?

Yep. I have an amp on my bench with a stock Sowter UK transformer.
The secondary windings can be connected in series and in parallel for
1,4,8, and 16 Ohms.

Iain


Graham

[zyx]

"Sander deWaal" wrote in message
...
Eeyore said:


There are only 2 professional designers here and they are Patrick Turmer
and myself.


Oh? Just the 2 of you?

;-)


Lord Valve is a very experienced tube expert at the practical level but
has no design experience AFAIK.


Repair experience is probably even more useful, one gets to see all
different kinds of amps, topologies and failures.

One can get a very good insight about the weak spots in designs by a
lifelong career in repairing various audio gear.
At least, that's where I came from.
And I still do repair every now and then, of MI and SR amps, domestic
audio and studio gear.

I would take LV's advice about tubes and guitar amps over anyone elses
every day, despite the fact that we're hardly friends.

--

- Maggies are an addiction for life. -

Thanks for your honesty and I think I'll trust LV's advices. I remember long
ago that the tubes have speakers rated at 3.2 ohms. 4 ohms sure ain't far
from that.

Now another question. Can this little 5 watt single ended class A amp (12ax7
and el84) drive a 2x12 speakers? I believe wiring two 8 ohm speakers in
parallel will give me 4 ohms?

[Eeyore]

zyx wrote:

"Sander deWaal" wrote in message
Eeyore said:

There are only 2 professional designers here and they are Patrick Turmer
and myself.

Oh? Just the 2 of you?

;-)

Lord Valve is a very experienced tube expert at the practical level but
has no design experience AFAIK.


Repair experience is probably even more useful, one gets to see all
different kinds of amps, topologies and failures.

One can get a very good insight about the weak spots in designs by a
lifelong career in repairing various audio gear.
At least, that's where I came from.
And I still do repair every now and then, of MI and SR amps, domestic
audio and studio gear.

I would take LV's advice about tubes and guitar amps over anyone elses
every day, despite the fact that we're hardly friends.


- Maggies are an addiction for life. -

Thanks for your honesty and I think I'll trust LV's advices. I remember long
ago that the tubes have speakers rated at 3.2 ohms. 4 ohms sure ain't far
from that.

Now another question. Can this little 5 watt single ended class A amp (12ax7
and el84) drive a 2x12 speakers?

Their physical size is unimportant from the perspective of whether the amp can
drive them.

You will however miss out on any colouration that you might typically associate
with such speakers though.

Guitar amplification often relies strongly on exploiting the technical
'shortcomings' of traditional amplification equipment in an 'artistic' way. The
speakers themselves play a part in this with their 'overdriven' sound. You won't
be overdriving a 12" speaker with 2-3 watts though.


I believe wiring two 8 ohm speakers in parallel will give me 4 ohms?

It will indeed.

Graham

[Phil Allison]

"Sander deWaal"


Repair experience is probably even more useful, one gets to see all
different kinds of amps, topologies and failures.

One can get a very good insight about the weak spots in designs by a
lifelong career in repairing various audio gear.


** But ONLY if that technician is * insatiably curious* about audio
electronics and puts in the time and considerable mental effort to analyse
nearly every circuit & component failure scenario they come across.

The vast majority of service techs are not allowed ( even if they wanted to)
to indulge in such time consuming, non profit making activity when there is
other work waiting to be done and a prowling boss to keep happy.

Only independent, self employed techs who are not too overworked might do as
you suggest, even then only if they have the required technical ability.

The typical product design engineer never gets involved with repairs, even
to his own designs, gets little or no feedback from the field unless a very
serious failure situation arises. They are normally quite unwilling to
accept any input or criticism from ANY folk involved in the repair business
and especially not from other designers.

This of course condemns them to repeating their dumbest mistakes - which
are then mass produced, sold to a gullible marketplace and ultimately left
to mere repair techs to eventually unravel & attempt to find fixes for.

I have many times wished I could deliver some expensive pile of audio
garbage back to the doorstep of the utter ass who is responsible for it and
say - " you designed this POS - so you bloody fix it " !!




........ Phil

[Chris Hornbeck]

On Thu, 18 Jan 2007 14:34:29 GMT, Lord Valve
wrote:

Despite what you may have seen from a loud-mouthed
know-it-all on this NG, don't worry.

Well, ****-fire and boy howdy, son...

First of all, let me apologize for what, last night,
seemed like a funny play on your larger-than-life
reputation, but today just reads as awful. You're
a real gentleman to have let it slide so easily.

You're wrong, but you can derive some small solace
from the fact that you're wrong for all the right reasons,
chief among them being ignorance regarding actual
field operating conditions for *guitar* amplifiers.

You've also never seen an Epiphone Valve Junior,
nor the schematic thereto. Right?

Spent more than three decades doing bench repairs, but
fortunately never met these Chinese Firecracker Champs.
That you're having to repair 'em at all makes me
wonder if the repairs are on your dime - my heart
goes out to ya either way. Lotta work for little return.

It's too late to fix their design issues, but it'd be
interesting to know how the external speakers connect.
Speaker cabs are wired several different ways. Do these
connect the external speakers in parallel with the internal
or do the jacks disconnect the internal speaker? Is
the jack make-before-break? They could even be connected
in series. God dwells in the details.


You're obviously seeing a real issue here, but I'll have
to stand by my statement that the nominal speaker impedance
is the wrong place to be looking. Uhh... I think.

Much thanks, as always,

Chris Hornbeck
"History consists of truths which in the end turn into lies,
while myth consists of lies which finally turn into truths."
- Jean Cocteau

[[email protected]]

On Fri, 19 Jan 2007 12:49:27 +1100, "Phil Allison"
wrote:


"Sander deWaal"


Repair experience is probably even more useful, one gets to see all
different kinds of amps, topologies and failures.

One can get a very good insight about the weak spots in designs by a
lifelong career in repairing various audio gear.


** But ONLY if that technician is * insatiably curious* about audio
electronics and puts in the time and considerable mental effort to analyse
nearly every circuit & component failure scenario they come across.

The vast majority of service techs are not allowed ( even if they wanted to)
to indulge in such time consuming, non profit making activity when there is
other work waiting to be done and a prowling boss to keep happy.

Only independent, self employed techs who are not too overworked might do as
you suggest, even then only if they have the required technical ability.

The typical product design engineer never gets involved with repairs, even
to his own designs, gets little or no feedback from the field unless a very
serious failure situation arises. They are normally quite unwilling to
accept any input or criticism from ANY folk involved in the repair business
and especially not from other designers.

This of course condemns them to repeating their dumbest mistakes - which
are then mass produced, sold to a gullible marketplace and ultimately left
to mere repair techs to eventually unravel & attempt to find fixes for.

I have many times wished I could deliver some expensive pile of audio
garbage back to the doorstep of the utter ass who is responsible for it and
say - " you designed this POS - so you bloody fix it " !!




....... Phil




Excellent post, Phil, I congratulate you.

As a "repair tech" I've always been amazed at the crap some engineers can come
up with... at the same time, impressed with the bullet proof designs of others.

And I've used my experience to design lots of equipment over the years - I use
the "empirical design and idea theft" methods, picking the best circuits I've
seen and modifying them to suit my needs.

I would sooner follow an experienced independent tech then an unknown engineer
any day.

[Ian Iveson]

Phil said:

The typical product design engineer never gets involved with
repairs, even to his own designs, gets little or no feedback from
the field unless a very serious failure situation arises. They are
normally quite unwilling to accept any input or criticism from ANY
folk involved in the repair business and especially not from other
designers.


Not typical in my experience.

Within the larger manufacturing companies, the relationships between
production engineering, research and development, and quality
assurance are pretty much standard and optimised. In general, you
won't find a problem that they don't already know about in minute
detail.

Unreliable or defective products are shipped for all sorts of
structural reasons: inertia, internal politics, cash flow
requirements, etc.

Also, for the general consumer market, most new products will be
sensibly designed to equal the accepted standards of reliability set
by producers as a whole. The higher cost of producing a more reliable
product can't be handed down to consumers who aren't willing to pay.

Nevertheless, modern mass-produced consumer products, particularly
electronics, have hugely reduced the cost of reliability.

cheers, Ian

[Phil Allison]

"Ian Iveson Colossal ****wit "

The typical product design engineer never gets involved with repairs,
even to his own designs, gets little or no feedback from the field
unless a very serious failure situation arises. They are normally quite
unwilling to accept any input or criticism from ANY folk involved in the
repair business and especially not from other designers.


Not typical in my experience.


** You do not have any - you stinking ASD ****ed LIAR.


Within the larger manufacturing companies, the relationships between
production engineering, research and development, and quality assurance
are pretty much standard and optimised.


** Completely and UTTERLY beside the point.

Iveson is totally illiterate.




........ Phil

[Ian Iveson]

Phil Allison wrote

The typical product design engineer never gets involved with
repairs, even to his own designs, gets little or no feedback from
the field unless a very serious failure situation arises. They are
normally quite unwilling to accept any input or criticism from ANY
folk involved in the repair business and especially not from other
designers.

Not typical in my experience.


** You do not have any - you stinking ASD ****ed LIAR.

ASD?

You know nothing about what I do, or what I have done, for a living.
I'm happy with your ignorance. I said "in my experience" in order to
qualify "typical".

Your idea of typical is only within your experience, too. You have
experience of grubby back-street tinkering. I can understand why you
feel bitter, but you are barking up the wrong tree.


Within the larger manufacturing companies, the relationships
between production engineering, research and development, and
quality assurance are pretty much standard and optimised.


** Completely and UTTERLY beside the point.

You missed the last sentence of the paragraph, which explained the
link, silly. And the other paragraphs which clarified it.

Let me make it a bit clearer. In my experience, and to my knowledge,
the typical designer doesn't need you. There is adequate provision
within the organisation to ensure that designers are aware of the
performance of their designs in the field.

Iveson is totally illiterate.

Not totally. Slightly, sometimes. Takes me a while to do the
crossword, but I get there in the end.

love and kisses, Ian

[Patrick Turner]

Lord Valve wrote:

Chris Hornbeck wrote:

Despite what you may have seen from a loud-mouthed
know-it-all on this NG, don't worry.

Well, ****-fire and boy howdy, son...

You're wrong, but you can derive some small solace
from the fact that you're wrong for all the right reasons,
chief among them being ignorance regarding actual
field operating conditions for *guitar* amplifiers.

You've also never seen an Epiphone Valve Junior,
nor the schematic thereto. Right?

So - this amp runs a single EL84, giving an output
of around 4 watts RMS. One 12AX7. SS bridge
rectifier for the HV, as well as one for the heaters.
No screen resistor. The entire shebang - including
the speaker - *retails* for $139, and can often be
had for less than $100, brand new in the box. In
short, it's a cheap-ass piece of Chinese ****,
a bare-bones minimum design intended to sell
for the lowest price possible - less, in fact, than
most audiophools spend on a couple of snob-glass
preamp tubes.

Think any corners were cut?

I've had around a half-dozen of these across my
bench in the last year. All but one had the same
problem: fried socket. Cause: "I hooked it up
to my (brand XYZ) speaker cabinet cuz it wasn't
loud enough for me to play with a drummer."
Said speaker cabinet, of course, was nearly
always an 8-ohm box. One was 16.

This is a 4-watt amp commonly purchased by
the worst gear abusers on the planet: guitar
pickers. Since it's only 4 watts, it is *always*
played at full-bore output clipping, for max
distortion and "blues tone." Its (often short)
life is one of maximum stress, placed upon
the sleaziest components imaginable.

Now, son - you may know what you may
know, and it may well be at odds with what
I've said, but I have hands-on time with this
particular gizmo, and I know for certain it
eats tube sockets when operated into a
higher than spec load. If you want to show
me the math which proves that a bumblebee
can't fly, be my guest. I've seen 'em fly, so
I'll take your "knowledge" with a grain of salt,
if that's OK with you. You don't catch my ass
on this NG telling the audiophools about their
SET 300B snob designs for a fairly good
reason: I know jack **** about 'em. The
difference between me and the audio******s
is that I can admit it.

Lord Valve
Expert Guitar Amp Dude


Lordy Lord. I agree mostly.

But the failures when speakers are changed from 8 to 16 ohms isn't
why it fails; failures due to arcing is gonna happen anyway
since a speaker presents a high Z at each siode of its power range, and
chinese crapologists dunno how to make good ****.

And the chinese dunno what they are doing except they try to copy ****
and
finish up with ****tier **** that you can poke a stick at.....

They make 'Goochi' handbags for sheilas, 'Rolecks' watches for the
un-wary,
and any ****en thing goes as long as some poor ******* buys it.

Patrick Turner.

[Patrick Turner]

Eeyore wrote:

Phil Allison wrote:

"Eeysore the Raving CRIMINAL LUNATIC" "

" Normal operation ( for a guitar amp) is the case. "

Ok - so *how easily* ?

** The question has been answered.

Do your own tests if you want proof.

Do a GG search on " alt .guitar.amps" on the topic of "flyback
spikes
"
for confirmation the phenomenon is well known.


So you're just making it up ( you can't or refuse to explain it ).

** What an UTTER non sequitur !!!!!!!!

So go-on, what causes the 5kV ?

** So you have no idea what the term " flyback spikes" refers to ?

I know exactly.

But you do now accept that they really exist in valve amps ???

If the load's disconnected for sure.

Finally did a little Googling - did we ?

No need.

Now, how did *YOU* get 5kV flyback spikes.

What was the load ?

How hard was the amp being driven ?

What was the input signal ?

Graham

Graham, no need to react against Allison's poor manners which are a
response to your
inability to understand that perhaps 5,000V is possible in a guitar amp
without a load.

Try measuring one, and you will find out all about.

Very much higher signal voltages anode to anode ARE generated by an
unloaded pentode/beam tetrode
output stage than the normal working loaded voltages.

Patrick Turner.