Valve amplifiers

[suri]

George - I greatly enjoyed this particular post from the link you provided. Made sense to me. Or so I think

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1st and foremost a tube (the triode) is the most linear amplifying device invented by man.

All else follows from that.
A typical SS Amp (order of magnitude figures) will have an open loop gain of 100,000 with a feedback factor of 5,000 giving a closed loop gain of 20.
A typical tube amp will have an open loop gain of 50 with a feedback factor of 2.5 giving a closed loop gain of 20.

I'm talking about a combination of local and global feedback here.

Any feedback signal is time delayed and smears time coherency. The more stages the feedback is applied over the worse that problem.

Tube amps therefore tend to sound more "correct" in terms of pace rhythm and attack, they are just (for want of a better adjective) more fluid and "breathe" with the music.

This tends to influence things like stereo imaging or "sound stage" and ambience.

Higher amounts of feedback tend to counter soft compression effects and make clipping harder and more abrupt. In engineering terms we say the transfer function graph (signal voltage out vs signal voltage in) is less smooth with more abrupt corners near the limits. The more abrupt a change in the transfer function the more higher order harmonics are generated. Anyone who has studied musical theory will know that the second harmonic of (for example) a C note is a C one octave above and 3rd harmonic is still musically related BUT by the time you get to 7th, 9th , 11th harmonic the "note" produced is musically unrelated to the fundamental, we call this musically "quint". While 1% 2nd harmonic distortion is "euphonic", about 0.01% of 7th harmonic is seriously objectionable and just grates like fingernails on the blackboard.

The more feedback, the more harmonic multiplication, that is the harmonic distortion products which are in the feedback signal are subject to further harmonic distortions which are then fed back to produce even more.

There are other things at work as well BUT I believe that the level of feedback is the major difference in the sound between SS and tube amps and that teh time coherency is at least or more important than the harmonic distortion profiles.

I design tube amps with local feedback around each tube stage, seldom over 2 or more stages, never over 3 or more stages, and in particular don't use "global" (from output back to input stage) feedback at all.

Just one mans opinion, but an opinion based upon designing and building both SS and tube amps over many years (I've given up the SS Amps now).

Does that mean I don't use SS at all - NO, my tube amp designs use transistor current sources in the "tail" of triode tube differential amplifiers on the input, I often use MOSFET Source Followers with transistor current source loads to drive the output tubes etc. BUT all of the gain stages are tubes. Also I borrow ideas from modern SS amp design to implement things like balanced shunt feedback loops (local feedback around only 2 stages).
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man speaks with forked tongue- witch doctor - shaman

 

[thevortex]

Whether an explanation exists or not for the distortion or the dissonance or whatever it is , that makes tubes sound 'different' from solid state amps, I know that my ears liked them over more than 3 hours.

Even this particular sub-field in the world of Hifi could be a lifetime's worth of learning - that is what I see.

 

[gobble]

I have a very simple theory for the appeal of tube amps, that people (sometimes, including me) actually prefer distortion to real music. A live instrument is sometimes brash and edgy, that is its nature. A tube amp tends to (due to its distortion profile) soften these edges and present things more casually, and that is their appeal..

Therefore since these distortions in a tube setup generate 2nd order harmonics I guess the human ear loves them ...? Will a low slew rate in a tube amp also cause more of these pleasant harmonics giving the "euphonic" tube sound we love?

I have experienced music with its rough edges on the setup I grew up with and I certainly agree. In fact it is only last month that I realized that the smooth sound of my amp is not a faithful true to life repro but is glossing over the natural edges of the sound. The only plus is fatuige free listening for long hours

Regards

 

[Asit]

Cranky, that thread is filled with posts like this. Whatever little I have managed to learn listening to music all these years and from people like you and just by reading from articles by people like NP (of course I have not understood or misunderstood many parts for sure), I felt I was very confused after reading 2 pages of that thread, no offense to anybody, definitely my own limitation. Thanks for explaining and sharing your thoughts on the above.

Vortex, please bear in mind you have not heard all tube amps. Arj in our forum, for example, finds his Sugden (SS) more 'tubey' than his Leben (tube) and he says (in other forums as well) Leben was the best upgrade he ever had, and I can understand where he is coming from.

As I said many times, just get whatever you really like and your budget allows and can drive your speakers well (unless you are upgrading your speakers as well, in that case it's an all new ball game). This is the best from an illiterate like me.

Regards.

 

[thevortex]

Cranky, that thread is filled with posts like this. Whatever little I have managed to learn listening to music all these years and from people like you and just by reading from articles by people like NP (of course I have not understood or misunderstood many parts for sure), I felt I was very confused after reading 2 pages of that thread, no offense to anybody, definitely my own limitation. Thanks for explaining and sharing your thoughts on the above.

Vortex, please bear in mind you have not heard all tube amps. Arj in our forum, for example, finds his Sugden (SS) more 'tubey' than his Leben (tube) and he says (in other forums as well) Leben was the best upgrade he ever had, and I can understand where he is coming from.

As I said many times, just get whatever you really like and your budget allows and can drive your speakers well (unless you are upgrading your speakers as well, in that case it's an all new ball game). This is the best from an illiterate like me.

Regards.

Point duly noted, Asit. Unless I can plan a trip to Calcutta it is quite possible that Viren's 2A3 amp is the only one I am going to have listened to. I know there is no substitute for the real thing, but everything I have read on the internet seems to point to the excellence and mellowness of the 2A3 tubes. And there is quite a bit of information praising SETs over PP's - although I suspect with the right implementations both can be very good.

At the moment, I am crossing fingers and waiting...

 

[stevieboy]

Welcome. Here is one more ...

World's oldest working computer to be rebooted - The Inquirer

Uses vacum tubes to store digits ...

Cheers

if you read that the museum has been broken into you know whodunit

the other tube rolling job is heaven! now just where do i apply for it? monster? timesjobs?

 

[gobble]

Soon we are gonna have a "mad scientist" in Bangalore folks!! One who mods his SET amp, hooks it up to a dish antennae and tell his incredulous neighbors he's waiting for a signal from outer space ...

Start growing your hair and beard my man .. you need to have the look when the media outlets start invading your house :lol:

I will donate the white labcoat ..

Cheers

 

[Asit]

Hi Vortex,

I am not saying 2A3 SET's are not good. If experienced people are saying it, it got to be good. All I am saying is: I cannot find too much of a difference between a good valve amp and a good SS amp. If you read the last part of Venkat's review of the Lyrita system, he also has said a similar thing there.

Frankly I have not heard too many tube amps in India (just 4 I think: Cayin A-88T, Cayin A-50T, Cadence VA-1 and the Leben CS300). As you may know I lived abroad for nearly a decade and a half, and there I did hear a lot of tube gear, but none of that stuff were low priced ones. From all that, I find it difficult to distinguish the sound signatures and all these acclaimed differences between good implementations of SET, PP etc. I do not think I'll ever buy an amp just because it is tube, or SET, or PP. But I also must say at the same time that this is strictly my observation, and is likely to be resulting from my lack of depth in these fields.

As I have said before, even when a vocalist is at a standing note, say the tonic, for the length of his breadth (as very often happens in Indian classical music) there are certain things an amp has to do to bring out the tonal quality, effect of the amount of air being let out at a contolled fashion, fading etc. Not all amps can convey the message, only some can. Based on what you have written about your experience at Rajiv's place (BTW, I am yet to read that fully, hence did not respond in that thread), it seems to me, Rajiv's amp is able to do that.

I will read that review of yours (and also contribution from Ramanujam) fully. Particularly I am interested in finding out the speed aspects, especially in the lows.

Regards.

 

[gobble]

Particularly I am interested in finding out the speed aspects, especially in the lows.

Regards.

Is it true that tubes can be sluggish on this front?

Regards

 

[thevortex]

I understand where you are coming from, Asit. Personally speaking I experienced the difference in tone, texture, speed and presentation when I heard the amp at Rajiv's place. If you read that review I would have observed that I had transported my speakers and source (HTPC) there to try and narrow down the variables. The listening area is the only aspect over which we had no control. Considering that there was a fair bit of difference.

I have nowhere near your knowledge in and of classical music. But I do appreciate classical music insofar as I know how to. And yes, sometimes, the ability of a system to produce silence in contrast to dynamic music is endearing.

I do see specific differences between my NAD C372 and the Lyrita amp. It would be very simplistic to say one is better than the other. There are specific things that I enjoy in both. I think I have mentioned a few aspects in the review itself - let me not repeat it here as well. Look forward to your thoughts and comments in the review thread.

If you had heard the Lyrita amp, I would have been most interested in reading your thoughts on the differences and/or similarities between that and your amp. Is there a chance of you hearing that amp?

 

[thevortex]

Is it true that tubes can be sluggish on this front?

Regards

Gobble - the amp that I heard had a bit of looseness in the bass department. I dont know how much the listening area contributed to this. However, I have it from Viren that tightness and crispness of bass is something in which the Solid State amps hold an upper hand.

 

[Asit]

Is it true that tubes can be sluggish on this front?

Regards

Well, again, let me just say that any of these weaknesses can be there in an SS amp too.

Regards.

 

[Asit]

If you had heard the Lyrita amp, I would have been most interested in reading your thoughts on the differences and/or similarities between that and your amp. Is there a chance of you hearing that amp?

I think Mahiruha will be getting his before the Pujas (later this month). I think I'll wait for a few weeks for his amp, speaker and cables to break in (or burn in?) and then would have a chance to hear his system. I would schedule my audition (of course Mahiruha permitting) following the break-in recommendations by Viren (some people as you well know do not believe in break-in even for speakers, as AS of Harbeth has promised to eat an entire Harbeth speaker if anybody can prove that those speakers break-in or burn in. That will be a sight, someone eating a speaker . People like Gobble or Unleash should actually draw a sketch of that and post, if they have any drawing skills).

From my reading about the Lyrita SET amps, I am expecting to hear a lush sound. Actually if you ask me, this is where I find the usual tube implementations very attractive (as I have already mentioned this in my first post of this thread and my initial impressions of my Leben in my amp thread)

 

[gobble]

I think Mahiruha will be getting his before the Pujas (later this month). I think I'll wait for a few weeks for his amp, speaker and cables to break in (or burn in?) and then would have a chance to hear his system. I would schedule my audition (of course Mahiruha permitting) following the break-in recommendations by Viren (some people as you well know do not believe in break-in even for speakers, as AS of Harbeth has promised to eat an entire Harbeth speaker if anybody can prove that those speakers break-in or burn in. That will be a sight, someone eating a speaker . People like Gobble or Unleash should actually draw a sketch of that and post, if they have any drawing skills).

From my reading about the Lyrita SET amps, I am expecting to hear a lush sound. Actually if you ask me, this is where I find the usual tube implementations very attractive (as I have already mentioned this in my first post of this thread and my initial impressions of my Leben in my amp thread)

Well I certainly believe in speaker and amp break-in. And I've heard cables sound better after a while - whether this was subjective adaptation and mere mental perception or not can be debated. But for the speaker I was very much involved in listening when the breakthrough moment arrived. And my amp lost its grain after the first 12 - 15 hours of play for sure.

The trick is in convincing somebody who is confronted with the prospect of eating a speaker, that too one that cost him $$$$

Edit: Perhaps more than proving speaker break-in, it will be a bigger challenge to break down his (Mr. Habreths) mental resistance to eating his own speakers

Cheers

 

[gobble]

Gobble - the amp that I heard had a bit of looseness in the bass department. I dont know how much the listening area contributed to this. However, I have it from Viren that tightness and crispness of bass is something in which the Solid State amps hold an upper hand.

Can it be the lower damping factor of tube amps contributing to this?

Regards

 

[stevieboy]

Can it be the lower damping factor of tube amps contributing to this?

Regards

yes. lower damping factor. there's no 'general sluggishness'. unless you ask the tubes to work early in the morning before they've woken up properly. they do tend to yawn broadly then. that's when you get the widest soundstage.

regards

 

[gobble]

yes. lower damping factor. there's no 'general sluggishness'. unless you ask the tubes to work early in the morning before they've woken up properly. they do tend to yawn broadly then. that's when you get the widest soundstage.

regards

I guess one needs to sprinkle cold water and use a toot brush on them every morning

Thanks
Cheers

 

[anm]

and serve them a good coffee - do you know what is more famous about Viren than his amps? His coffee!

 

[gobble]

and serve them a good coffee - do you know what is more famous about Viren than his amps? His coffee!

My best listening sessions are accompanied by a cup of organic arabica coffee, not scotch whisky. Because I go into meditative states, alcohol doesnt work in this case. Coffee and great listening - they go hand in hand.

Cheers

 

[gobble]

A popular article about tube sound is Joes Tube lore:

AudioAsylum.com -- Joe's Tube Lore

FYI

Cheers