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Tube gear opinions

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DSJR

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#41
No mention of the very high output impedance of most tube amps equalising the speaker response as they 'track' the roller-coaster impedance curve that most speakers have and which most solid state amps all but ignore? Look at most recent Stereophile reviews of tube amps and ignore the verbal diarrhoea in the pages before the measurements... Even before low frequency transformer saturation is considered and the distortion (many valve/tube amps seem to have third harmonic leading the second), the altered response into a typical speaker is a huge no-no.

Apologies, I've been in this game far too long to be swayed by the looks of tube amps today and the big tubes lit like light bulbs scare me to death frankly when I think of the voltages involved and the heat of the glass casings (my Quad II's do this to me as well in terms of heat and they're tiny).
 

egellings

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#42
That's a major part of the mechanism by which the tube amps add their "seasoning" to the sound-voltage divider effect between amp Zo and speaker Zin. Some times it sounds right to the listener; other times, not, depending on the particular amp-speaker combination, their impedance characteristics and listener preference. As for appearances, it's in the eye of the beholder. Not everyone wants their living room to look like a radio transmitter shack. I myself, rather enjoy the look, and they can sound good without being overly euphonic. I don't like too much whipped cream on my pumpkin pie, so the single ended 300B sound is not for me. For the "one step nearer the reference" sort of listener, I recommend avoiding tubes altogether and going with a competent S.S. switchmode or AB design. To each his own. Tubes can work for music, but I would not want my life support machine populated with them. There, S.S. reliability, compactness and efficiency reign supreme.
 

MakeMineVinyl

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#43
No mention of the very high output impedance of most tube amps equalising the speaker response as they 'track' the roller-coaster impedance curve that most speakers have and which most solid state amps all but ignore? Look at most recent Stereophile reviews of tube amps and ignore the verbal diarrhoea in the pages before the measurements... Even before low frequency transformer saturation is considered and the distortion (many valve/tube amps seem to have third harmonic leading the second), the altered response into a typical speaker is a huge no-no.

Apologies, I've been in this game far too long to be swayed by the looks of tube amps today and the big tubes lit like light bulbs scare me to death frankly when I think of the voltages involved and the heat of the glass casings (my Quad II's do this to me as well in terms of heat and they're tiny).
Broad generalizations are not very constructive. There are significant graduations between 'very high output impedance' of some tube amps and the more typical output impedances of others. A damping factor of 20 has been accepted over the years as the threshold of acceptable, and a good tube amp can achieve that. The fact that some SS amps have damping factors in the hundreds does not alter that threshold.

The main problem is two trends: speakers which present far more difficult loads than in the past, and the trend to utilize less global negative feedback because its 'more audiophile', which increases the output impedance of any amp. Both of these trends are in my opinion crazy and unnecessary, but I don't have control over that. :confused:

Given the above, the main takeaway is that more consideration needs to be given to the speaker (the load it presents) matching the capability of the amplifier (topology, feedback) than in the past decades. In the 1960s this was never a concern because speakers were almost universally a much easier load, and amplifiers used more negative feedback which lowered the output (source) impedance.

In some ways, present day audio has twisted itself into contortions which confuse consumers, and serves as an enabler for those who market snake oil products and theories (and yes, generalizations and oversimplifications).
 

DSJR

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#44
The speakers available in the UK forty plus years ago had rollercoaster impedance curves, not just Spendor BC1's and valve amps generally will equalise the response. One or two models had ample impedance compensation but it's my experience this isn't and wasn't always the case. Maybe US models were different?

I wasn't going anywhere near 'damping factor' despite my beloved Crown amps making a huge thing about it back when I started. I'm talking about amp output impedance changing with frequency and the valve amp driving said load which in most cases will have a graphic equliser effect by a dB or two either way.

Apologies if I have it completely wrong here, but the above is measurable I believe and not a subjective thing.
 

mhardy6647

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#45
In some ways, present day audio has twisted itself into contortions which confuse consumers, and serves as an enabler for those who market snake oil products and theories (and yes, generalizations and oversimplifications).
You mean, like digital audio players and SMPS that produce all kinds of RFI hash, enabling the "high purity power center", "audiophile cabling", and "noise harvester" industries?
;)
 

MakeMineVinyl

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#46
The speakers available in the UK forty plus years ago had rollercoaster impedance curves, not just Spendor BC1's and valve amps generally will equalise the response. One or two models had ample impedance compensation but it's my experience this isn't and wasn't always the case. Maybe US models were different?

I wasn't going anywhere near 'damping factor' despite my beloved Crown amps making a huge thing about it back when I started. I'm talking about amp output impedance changing with frequency and the valve amp driving said load which in most cases will have a graphic equliser effect by a dB or two either way.

Apologies if I have it completely wrong here, but the above is measurable I believe and not a subjective thing.
You're right, its a measurable thing, but I was specifically pointing out the relative minefield vis a vis today's intentionally hard to drive speakers combined with the relative inadequacies of today's tube amps to deal with that.
 

MakeMineVinyl

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#47
You mean, like digital audio players and SMPS that produce all kinds of RFI hash, enabling the "high purity power center", "audiophile cabling", and "noise harvester" industries?
;)
Well, yes, sorta. Looking at the power coming in here at the factory, and the fact that there are nearby cell towers and heavy industrial users, the power looks like crap. I believe though that well designed gear can deal effectively with this. On the other hand, its a struggle sometimes when the 'crap in the air' gets out of hand and its effects can be clearly seen creeping into even the best designed audio path.

Of course audio marketers take advantage of customer ignorance and push all types of filtering/regeneration/voodoo in a blanket fashion, regardless of if there is a true need or not! :oops:
 

mhardy6647

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#48
You're right, its a measurable thing, but I was specifically pointing out the relative minefield vis a vis today's intentionally hard to drive speakers combined with the relative inadequacies of today's tube amps to deal with that.
Yeah, the "let's make the loudspeaker impedance curve as amplifier hostile as possible" school of engineering kind of baffles me (speaker pun not entirely unintended). :rolleyes:

I guess one might argue that the original Quad ESL ("ESL-57") started it... but I'd rather blame the Infinity IRS Beta, personally. :)

1620240873882.png

Fig.1 Infinity IRS Beta, impedance magnitude of woofer tower (top above 500Hz) and midrange/treble panel (2 ohms/vertical div.).
https://www.stereophile.com/content/infinity-irs-beta-loudspeaker-measurements
 

MakeMineVinyl

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#49
Yeah, the "let's make the loudspeaker impedance curve as amplifier hostile as possible" school of engineering kind of baffles me (speaker pun not entirely unintended). :rolleyes:

I guess one might argue that the original Quad ESL ("ESL-57") started it... but I'd rather blame the Infinity IRS Beta, personally. :)

View attachment 128111

https://www.stereophile.com/content/infinity-irs-beta-loudspeaker-measurements
Re. the ESL, I wonder too if the effects of frequency response modulation by the output impedance of the amplifier weren't considered as much in the past as they are now.

By the time the IRS came out, I think tubes were more or less out of fashion, and big amps like the Carvers, SAE, Crown etc were more the norm. A Dynaco ST-70 was a non-starter with those speakers!
 
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egellings

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#50
Tube power amp output impedance can be high or low, but I have to admit, on some it's ridiculously high, like on those feedback-less S.E. 300B amps. You really do want to operate a speaker with something resembling a voltage source, not a current source. My particular circlotron-style home brews measure at a Zo of about 0.23 ohm everywhere from 18Hz to about 30kHz, which is reasonable. Below about 18Hz, Zo on my amps rises, so I use a high pass filter to keep that garbage out of them, since I do not need subsonic performance at all. This is gotten by way of a bridge (circlotron style) design, paralleled output tubes, low turns ratio output transformers, and use of negative feedback. Of course then, if it's that close to S.S. performance, then why bother? Just go S.S. and get if over with. For me, it 'the little engine that could', plus the enjoyment of the glowing bulbs that motivate it, and importantly, they are my design & build. That's why I don't use them for background music; I have a nice Bryston 4Bst for that. The Bryston is a superb performer, but looking at those two little green eyes (LEDs) just doesn't cut it.
 

MakeMineVinyl

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#51
Tube power amp output impedance can be high or low, but I have to admit, on some it's ridiculously high, like on those feedback-less S.E. 300B amps.
The relatively high output impedance of my SET is the reason I only use it above 500Hz on compression drivers which have 16 Ohms impedance.

In the 1950s there was a fad of 'variable' damping, where the amplifier could be adjusted to 'match' the speaker by intentionally higher output impedance. o_O
 

egellings

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#52
I remember those variable damping amplifiers. I also remember ported speakers that had just a rectangular opening on the front of the box, below the driver, and this had a sliding door on it so that you could adjust the port opening area for what ever reason. This was before Thiele-Small came along and put that to rest.
 

MattHooper

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#53
I've already mentioned many times that I get a lot of satisfaction from the Conrad Johnson tube amps powering my speakers. To me they do have some classic "tube attributes" when I compare them directly to solid state amps (e.g. the Bryston 4B3 I had for a couple months) and I love what the tube amps bring to the sound.

Could it be pure subjective bias based on "tubes are supposed to sound this way?" Sure (though that wouldn't directly explain why I have rejected other tube amps that don't sound 'tubey' to me). Could it be that I'm actually hearing sonic differences? Plenty of people with knowledge of electronics say this is entirely plausible, that tube amps can depart from neutrality. That is one of the reasons "strict objectivist engineers" like Arny Kruger and the like decried the perseverance of tube amplification among audiophiles when truly neutral solid state was available. "Why color the sound?"

Could my impressions be due to a mix of hearing real differences AND bias? Sure.

All this is why I don't come on a board like this to make some objective claim that my tube amps Absolutely Do Sound Different than solid state.
But rather, I only present reasons why I continue to use them (which also includes that I think tube amps are charming and cool looking and I like seeing the music signal visibly passing through tubes).

I have both and while tube amps are fun they are lower power and generate a lot of heat and the tubes wear out. I went to a lot of trouble to set up a double blind ABX level matched test between a Dynaco ST 70 and a Neurochrome Mod 86 amp and could not tell them apart ... I would highly recomend you try this yourself as it will really open your eyes and set you free from a lot of BS surrounding the hobby.
Hi levimax,

I thoroughly enjoyed and appreciated your report of blind testing those amps.

Depending exactly on what you mean by your last sentence, I am of two minds about that.

If you mean that doing blind tests can really open one's eyes to the power of our bias, and help us take a position as to what claims are likely b.s. or not, I certainly agree. As I've mentioned I've done numerous blind tests with those results.

But if you mean that an individual doing a blind test of a tube amp at home will open his eyes to the B.S. idea that tube amps can sound different in a system, that would seem to be overreach (I'm betting you agree).

That would be evidence that the individual's tube amp in question doesn't sound different from the SS amp he has on hand. But it certainly doesn't establish that no tube amps alter the sound of any speaker system. So you wouldn't have established from that test "Tube Amps Sound Identical To Solid State." There are tons of different tube amp designs and speaker pairings, that make that inference problematic.

As to my own attitude towards the tube amp "sound:" As a "layman" in terms of not being an electrical engineer or amp designer, the best I can do is try to triangulate my own experience with observing what knowledgeable people have to say on the matter. While some will say that audible differences between tube amps and SS are simply a myth that seems to be a minority opinion. From what I've seen, most electronically knowledgeable folks acknowledge there are entirely technically feasible reasons for why tube amps can alter the sound of a system. They CAN be built to sound indistinguishable from solid state, but generally speaking "tube amps designed to sound exactly like solid state" isn't the market most tube manufacturers are designing for.

And I've noted that there is on almost any technical subject, whether it's tube amps or "the best speaker design" or anything else, there will be differences of opinion among experienced engineers, much of it ultimately born of their own experience.

It reminds me of my blind tests. I found some expensive AC cables indistinguishable in blind tests, which went against my sighted impressions.
That gave me personal/experiential reasons in support of being suspicious of claims about AC cable differences - which I triangulate with technical reasons to be suspect as well.

On the other hand, in the 90's I was told by a bunch of experienced audio engineer folks that the differences I percieved between some cd players and DACs were due to sighted bias. They "shouldn't sound different at all" if sighted bias is removed. So I tested that myself, did more than one series of blind tests, using the very recommendations of those engineers, level matching, randomized, in which I was able to easily identify between the CDPs and DAC. So what was I to do? Call 'em as I see 'em. They sounded different. I didn't expect the other folks to accept my test as overturning their own skepticism. They weren't there, couldn't see if I made any mistakes. But we individuals are going to be strongly influenced by our personal experience. I suspect that if any of those engineers had performed the test I did and were able to identify the devices just as easily, that experience would lead them to say "Well, yeah, it looks like in this case these ones do sound different."

So I understand why your test would heavily influence your view of tube vs ss amps. From my point of view, I take it as another data point to consider, a reminder of the power of subjective bias. Though, that was something I already accepted. It doesn't establish though that my tube amps don't sound different from the solid state amp I had. I just won't say definitively my tube amps sound different, because it could be subjective bias. But it could also be...they sound different in my system. My hunch is the latter. Either way the subjective effect is so strong I can't seem to shake it, I simply enjoy listening more with the tube amps in the system, so I'm going with it.
 
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MakeMineVinyl

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#54
In my own active crossover system, I have several passive filters and gain trims between the output of the HP and LP sections of the crossover and the respective inputs of the vacuum tube amplifiers which then connect directly to the drivers. Recording-to-recording and depending on the style of the music I'm playing, I find that I adjust these controls a lot in order to compensate for what I feel are inadequacies of particular recordings. I have a 'baseline setting' for what I consider good recordings.

I know I'm introducing orders of magnitude more obviously changed audio balance when I do this than any possible difference in any amplifiers could possibly have or coloration they may have. So for me at least, I choose the technology (tubes) on technical grounds to work with the high efficiency horns, knowing that what I'm doing upstream makes subtle amplifier differences essentially moot.
 

Sal1950

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#55
It's very hard to discuss "tube sound" since they run the gamut from very nearly, if not totally transparent, to very colored with high distortion. Much, if not all of it was intentionally voiced by the designer to fill the desire of buyers in that high end market segment..
OTOH modern SS amps are for the most part neutral and transparent with only a small market segment being intentionally voiced to again fill a market demand. But even then the differences in sound is subtle and quite depending on the speaker interface.
You buy your ticket and take your ride, my only objections to any non-transparent gear is you've then locked yourself into that sound with the only means of escaping is to sell the component for something different.
 

MattHooper

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#56
It's very hard to discuss "tube sound" since they run the gamut from very nearly, if not totally transparent, to very colored with high distortion. Much, if not all of it was intentionally voiced by the designer to fill the desire of buyers in that high end market segment..
OTOH modern SS amps are for the most part neutral and transparent with only a small market segment being intentionally voiced to again fill a market demand. But even then the differences in sound is subtle and quite depending on the speaker interface.
You buy your ticket and take your ride, my only objections to any non-transparent gear is you've then locked yourself into that sound with the only means of escaping is to sell the component for something different.
An eminently sensible post on the topic, to my ears!
 

H-713

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#57
Very likely the "tube sound" comes less from the tubes and more from the transformers in most well-designed amplifiers. It's fairly well-established that transformers aren't exactly the most transparent things in the world, and it's also pretty well established that those nonidealities can be an attribute in some circumstances- that's part of why a Neve 8038 or 8048, which are functionally very limited as far as mixing consoles go, are still worth more than a new Porsche 911.

Really good tube amps, including the ones I've built, tend to be pretty transparent. I've also seen a lot of tube amps with THD in the 1% range, and a lot of them sound bloody fantastic, especially on highs. This is why I maintain that an an amp that measures perfectly will almost certainly sound great, but one that measures poorly isn't necessarily a piece of crap, since what ultimately matters is the enjoyment the listener gets.
 

Phorize

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#58
I get a smug ‘I’m so SOTA’ feeling when I ‘listen’ to my hugely powerful, cool, efficient and utterly transparent purifi amps, yet I still look at tube kits on line and come far too close to pushing the button quite often. It’s pure nostalgia and probably the nice appearance of the gear.
 

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#59
It's very hard to discuss "tube sound" since they run the gamut from very nearly, if not totally transparent, to very colored with high distortion. Much, if not all of it was intentionally voiced by the designer to fill the desire of buyers in that high end market segment..
OTOH modern SS amps are for the most part neutral and transparent with only a small market segment being intentionally voiced to again fill a market demand. But even then the differences in sound is subtle and quite depending on the speaker interface.
You buy your ticket and take your ride, my only objections to any non-transparent gear is you've then locked yourself into that sound with the only means of escaping is to sell the component for something different.
That’s exactly it-class d modules guided me straight into safe waters, but I can still hear a distance voice through the fog beckoning me on to the jagged rocks!
 

Sal1950

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#60
but one that measures poorly isn't necessarily a piece of crap, since what ultimately matters is the enjoyment the listener gets.
Then not necessarily having anything to do with High Fidelity, some people like all sort of distorted messes.
 

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