I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam! Tubes should be usedin the power stage
in order to make a difference. What's the opinion on this?

Thanks.

razak & william wrote:

I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam! Tubes should be usedin the power stage
in order to make a difference. What's the opinion on this?

Thanks.

I'd cautiously agree - cautiously because there can always be
exceptions. But in general, I believe it's the output stages that
primarily determine the overall sound of an amplifier.

That's in the hi-fi world. In guitar and other musical instrument amps,
anything goes. I designed a simple high-gain tube preamp which has been
surprisingly successful (in terms of number of people who have built it
and like it). It very definitely adds a "tube sound" to any guitar amp,
even solid-state.

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

"razak & william" wrote in message
...
I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam!

.........

Tubes should be used in the power stage
in order to make a difference. What's the opinion on this?


** It sure makes a big difference to the price.



.......... Phil

My only listening experience was with a Moscode 600 that I fixed and owned
for awhile.

I didn't do anything as discriminating as a double-blind listening test.
But a MOSFET amp designer buddy of mine (Joe Berry - recently published in
audioXpress) thought it sounded a bit like a full tube effort yet definitely
had that "MOSFET sound" (which he imaginatively described as "pushing sound
through sand").

I'm about 70% through building a lower powered hybrid designed by Wim DeHaan
@ http://www.wdehaan.demon.nl/5687_1.html. Right now it sits abandoned on
one of my project racks in favor of some 100% tube builds. I've heard that
it sounds pretty good . . . the circuit is worth checking out, anyway.

Most amps sound different to me. My sample isn't satisfactory for me to
draw much of a conclusion. But I think Fred has the right idea.

- Jon



From: razak & william
Organization: TMnet Malaysia
Newsgroups: rec.audio.tubes
Date: Tue, 14 Oct 2003 11:32:11 +0800
Subject: hybrid amps

I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam! Tubes should be usedin the power stage
in order to make a difference. What's the opinion on this?

Thanks.

My experience with tube in, SS out was with high-power Carvin Bass-Head
equipment. The clean channel was the same as an all SS to me. I would
never spend money on it, that's for sure.

Now, as for SS in and tube out, I have built a phono stage using
complimentary 2N5087/5088 that was somewhat respectable, but sounded
"flat" and mike amps with a 5532/4 with the same response - flat. Might
be OK for a mixer or something you want "uber transparant", but meh, not
in the audio line for me :-p

I personally prefer the tubes in the signal line with the SS as slaves ;-)

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

razak & william wrote:

I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam! Tubes should be usedin the power stage
in order to make a difference. What's the opinion on this?

Thanks.

I have not heard a good hybrid, and I have heard a few.

Patrick Turner

Jon Yaeger wrote:

My only listening experience was with a Moscode 600 that I fixed and owned
for awhile.

I didn't do anything as discriminating as a double-blind listening test.
But a MOSFET amp designer buddy of mine (Joe Berry - recently published in
audioXpress) thought it sounded a bit like a full tube effort yet definitely
had that "MOSFET sound" (which he imaginatively described as "pushing sound
through sand").

I'm about 70% through building a lower powered hybrid designed by Wim DeHaan
@ http://www.wdehaan.demon.nl/5687_1.html.

This design is very simple, and could be improved by using a 6BQ5 in triode as
the driver,
which would ovecome the input capacitance of the Mosfets, probably around 400pF.

He gives 0.64% thd at 1 watt, which is quite high and indicates
that it isn't running in class A.
With two mosfets set up in source follower, like he shows them,
and operating in class A, to make say 25 watts into 10 ohms,
expect MUCH lower thd at a watt.

He says there is no NFB, but of course there is lots!
Source follower mode is like a cathode follower, and followers are examples of
heavy amounts
of series voltage negative FB, and in the case here, IF the circuit was class A,

the amount of FB used is around 20 dB, depending on load, since the internal
gain
of the mosfets varies with load, and to some extent the fet Gm,
which may be around 1 A/V.
Gain is vitually Gm x RL.
So with a follower, all gains are reduced to less than 1.0,
and if the load is say 3 ohms, then the gain reduction from the follower
is reduced from say 6 in a class A circuit to 0.86, which is about 14 dB of FB.


If class A is used, there isn't much need for anymore than 23 dB total FB,
regardless of whether the mosfets are set up as followers, ( common drain ),
or in common source.

The use of FOUR or SIX mosfets in class A vastly improves the
performance, allowing 40 watts class A even into 4 ohms.
But the capacitance rises a bit.

The use of source follower means the driver tube, which IS NOT
enclosed within a feedback loop, has to act all alone to be linear,
and should be able to make 20vrms at less than 1% thd,
so that at 2vrms, which is normal listening levels, the thd
might be 0.1% from the driver tube.
Probably a better driver can be made using a triode
with a CCS load, which will linearize the triode far better than just having a
resistive
load.
Also a Mu follower would be nice, and it will have greater
ability to drive the output stage to a higher F.

There will be some 2H generated, along with a lot more 3H,
in the output follower stage, because the mosfets are not
entirely matched since P and N devices are used.
Some 2H cancelation, or addition is then likely,
although the 3H cannot be got rid of since there is PP action.
Class A minimises the 3H.

Patrick Turner.




Right now it sits abandoned on
one of my project racks in favor of some 100% tube builds. I've heard that
it sounds pretty good . . . the circuit is worth checking out, anyway.

Most amps sound different to me. My sample isn't satisfactory for me to
draw much of a conclusion. But I think Fred has the right idea.

- Jon

From: razak & william
Organization: TMnet Malaysia
Newsgroups: rec.audio.tubes
Date: Tue, 14 Oct 2003 11:32:11 +0800
Subject: hybrid amps

I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam! Tubes should be usedin the power stage
in order to make a difference. What's the opinion on this?

Thanks.

I listened to a ARC classic 60 for a week (which has a solid state
front end and tube output), and thought my citation 2 blew it away.

Scott

Jon Yaeger wrote:

My only listening experience was with a Moscode 600 that I fixed and owned
for awhile.

I didn't do anything as discriminating as a double-blind listening test.
But a MOSFET amp designer buddy of mine (Joe Berry - recently published in
audioXpress) thought it sounded a bit like a full tube effort yet definitely
had that "MOSFET sound" (which he imaginatively described as "pushing sound
through sand").

I'm about 70% through building a lower powered hybrid designed by Wim DeHaan
@ http://www.wdehaan.demon.nl/5687_1.html. Right now it sits abandoned on
one of my project racks in favor of some 100% tube builds. I've heard that
it sounds pretty good . . . the circuit is worth checking out, anyway.

Most amps sound different to me. My sample isn't satisfactory for me to
draw much of a conclusion. But I think Fred has the right idea.

- Jon





From: razak & william
Organization: TMnet Malaysia
Newsgroups: rec.audio.tubes
Date: Tue, 14 Oct 2003 11:32:11 +0800
Subject: hybrid amps

I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam! Tubes should be usedin the power stage
in order to make a difference. What's the opinion on this?

Thanks.

Well, at the risk of blasphemy, I use a Rozenblit tube preamp driving a
John Linsley-Hood Class A solid state amp
(http://www.tcaas.btinternet.co.uk/). It is the best sound I've ever had.
Plus I have the satisfaction of having built both of the units.

Mike L.

razak & william wrote:

I've read somewhere that hybrid integrated amps which use vacuum tubes
in the preamp stage and transistors in the power stage sound no
different from transistor/solid state amps. I think the exact phrase he
used was that they were a scam! Tubes should be usedin the power stage
in order to make a difference. What's the opinion on this?

Thanks.

Well, at the risk of blasphemy, I use a Rozenblit tube preamp driving a
John Linsley-Hood Class A solid state amp
(http://www.tcaas.btinternet.co.uk/). It is the best sound I've ever had.
Plus I have the satisfaction of having built both of the units.


I thought as far as seperates go runnning a tube pre with ss power amp was
fairly common. I have a kit tube pre going into an old yamaha from the early
80s...

are mike and I better than individuals running tube front end (hybrid)
integrateds or should we all be burned @ the stake?

-will

nah.......just live your life-that's class A-what is important
)

"Will" wrote in message
...

are mike and I better than individuals running tube front end (hybrid)
integrateds or should we all be burned @ the stake?

-will



--
.................................................. ........................
Choky
Prodanovic Aleksandar
YU

"don't use force, "don't use force,
use a larger hammer" use a larger tube
- Choky and IST"
- ZM
.................................................. ...........................
...

Will wrote:

Well, at the risk of blasphemy, I use a Rozenblit tube preamp driving a
John Linsley-Hood Class A solid state amp
(http://www.tcaas.btinternet.co.uk/). It is the best sound I've ever had.
Plus I have the satisfaction of having built both of the units.


I thought as far as seperates go runnning a tube pre with ss power amp was
fairly common. I have a kit tube pre going into an old yamaha from the early
80s...

are mike and I better than individuals running tube front end (hybrid)
integrateds or should we all be burned @ the stake?

-will

An "audio heretic" might perhaps be a certain variety
of mythological audiophile, who challenges the norm,
and struts the world awide, trying things which no other are game
to try, towards the goal of audio nivirna, and ultimate enlightenment,
discarding the chains and straightjackets of the status quo,
and thus mixing the solid with the hollow, in a union quite blessed,
which to others may seem obscene.

The stake used for burnings should be reserved for all those who have this
horrid idea
that if it measures a certain way, its going to sound a certain way,
and those who cannot appreciate other folks dreams,
and especially those who have a solid mental block about SE amps,
and lump them all into a category of "not hi-fi", etc, etc, etc.

I myself have dabbled with solid state, and use solid state mosftet
amps that I built for the sake of the quest, and its enjoyments and
satisfactions.

I keep coming back to tube designs, and I do like them.
But just when I thought I'm done with SS, I think of an idea to try to
upgrade the last SS amp I have built, which is designed
for PP class A, with a transistor LTP driver, and 4 output N channel
mosfets with an OPT, JUST LIKE A TUBE AMP.
I now want to replace the 3 transistor front end with 3 x 2SK369
j-fets, so the whole circuit is a fet type, and fets probably
have a tube like sonic signature if anything does have a signature.
It now sounds OK to me, although I have been told by at least one dude
that its got that "mosftet mist" sound, but in all the AB switched tests
I have done with other listeners, using other 50 watt class A tube amps,
the guys cannot tell the difference.
What is it that my hard to please dude hears that is wrong?
Is it the transistor front end? I'd like to think it is.
Is it the old Hitachi mosfets I am using, instead of the
more audiologically correct newer Exicon mosfets,
which are slightly more current able, but which cost
as much as a KT88? I used the Hitachis because a bloke gave me a bag full
for some transformer design work, so I thought waste not, want not,
and used them.
One could say using bjts and mosfets in the same circuit is a case of
hybridisation.

I have learned to ignore the braying mob, unless I think
their criticism is on the mark, and worthy, or if they bring around a creation
of their
own which makes me seem to have been wasting my time up to the present.
It ain't happened yet.

Just today I had a guy listen to the renovated tube amp
I just did for him and he had a go at my speakers, so I surrepticiously switched

the signal to mono, and acted like nothing was different, and we had this chat
about
imaging, and he reckoned the image was not bad, and that my speakers were
very accurate and neutral, and finally I said, gee, I better switch it back to
stereo, eh,
and that shut him up for a few minutes..........
Then he found it was surprising what dynamics were heard in a ****ant
little amp with 4 x 6BM8 tubes.
We kept smilin......
Anyway, this bloke, a very nice man, presented me with
a look at an AMC hybrid integrated amp which has 2 x EL34 PP output tubes
and OPT, but all the rest of the circuit was literally dozens of transistors
for the input stages of the tube power stage and the preamp sections.
Maybe there was the odd opamp or two stashed in there.
Two too many, imho.

Anyway, this amp has horizontally mounted EL34, and fans mounted beneath them
to keep it all cool, and the tubes are soldered directly to the PCBs,
and they don't have easy access, like all the other parts.
The OPTs are toys compared to what I would make, and no bigger than
what's on a Leak Stereo 20, which has 2 x EL84 per channel.
Its not the way I would build an amp, that's for sure.
The owner says it sounds hard and solid like, and he loathes it.
I suggested he remove all the transformers, and mount them on a new chassis,
as a dedicated full tube power amp, then gut out the $2 board full
of preamp bjts in the existing box,
and make a tube preamp; there is plenty of room for
a pair of phono amps, tone control stage, and line stage,
and some quality pots and switches, with easy to service/modify
point to point wiring.

Then the top cover could be changed to a fine mesh type,
to make the whole lot LOOK right at night, since part of the appeal of tubes is
to
make a visual statement, not just an audio one.

With imagination, its not hard to beat the amp stylists based in HK,
or some other place where they greyly think in terms of boring black
boxes full of ticky tacky junk!

At least with DIY, we can thumb our noses to the outside world,
and to all its marketting ploys, and if we use half decent parts,
we get sound equal the most expensive high end gear.

Patrick Turner.