Sonic signatures of KT88, 300B, 805, 845 in SET & PP Configurations - diyAudio
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Old 20th October 2009, 01:32 AM   #1
88man is offline 88man  United States
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Default Sonic signatures of KT88, 300B, 805, 845 in SET & PP Configurations

Can someone explain general sonic differences between the EL34, KT88, 300B, 2A3, 805, 845 in SET and PP configurations in terms of bass, midrange, highs, tonality, sound stage, dynamics, resolution, imaging, harmonics, etc. I'd be curious if there are references for the various output tube types?

Perhaps, the perfect amp would be a cross between a PP KT88 and a 300B SET based on observations. It seems difficult to strike a balance between lush, detailed, silky smooth mids, and airy highs, with a solid bass punch. I've often wondered if I should build a 6SN7 based preamp mated with a 300B SET amp crossed over for the mid/highs, and use a solid state amp crossed over for the bass...

Thanks

Last edited by 88man; 20th October 2009 at 01:45 AM.
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Old 20th October 2009, 01:40 AM   #2
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Quote:
Originally Posted by 88man View Post
Can someone explain general sonic differences between the EL34, KT88, 300B, 805, 845 in SET and PP configurations in terms of bass, midrange, highs, tonality, sound stage, dynamics, resolution, imaging, harmonics, etc.

Yes, I'm, interested too. Please include the 45 and the 2A3 type tubes as well. Considerations for fixed bias vs. auto or cathode bias strategies would be appreciated. In the interest of fairness, please only compare designs with similar front end topolgies. Oh, and try to keep the responses to 200 words or less - I'm only interested in the facts.
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Old 20th October 2009, 01:50 AM   #3
Gordy is offline Gordy  United Kingdom
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Quote:
Originally Posted by 88man View Post
Can someone explain general sonic differences between the EL34, KT88, 300B, 805, 845 in SET and PP configurations in terms of bass, midrange, highs, tonality, sound stage, dynamics, resolution, imaging, harmonics, etc.
[etc.]
Tubes themselves have no sound quality. Unfortunately the sentiment-driven audiofiles find this FACT difficult to grasp and hence continue to spread their ignorance-based nonsense.

Tubes actually have electrical characteristics, not sound quality. The characteristics must be manipulated by the designer to assemble an appropriate circuit. That circuit, when used in an appropriate system (including media, source, power supply, cables, amplification, transducers and listening environment), may be able to reproduce an encoded music signal such that the reproduction (by the SYSTEM) can be interpreted emotionally and hence (finally) subjectively labelled with a specific sound-quality.

So an inanimate tube (of whatever type) has no specific sound. Never has, and never will.
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Old 20th October 2009, 01:58 AM   #4
grufti is offline grufti  United States
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Thank you, Gordy. This is where the thread should end, but I have no doubt that it will get to more than 1000 replies in no time.
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Old 20th October 2009, 02:04 AM   #5
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I doubt you'll find anyone who has all 14 of the amplifiers you cite, yet alone exemplary examples of each. And then to develop a subjective assessment of each amp based on 9 or more parameters becomes more than a lifes work.

But to think that there would be any consensus on the results......

I understand the desire to know and heck, if the book existed I'd pay $150+ for it!! You've obviously read a lot of threads on the different amps and so probably have the basis of an opinion yourself. Can you be a bit more focused in your question?
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Old 20th October 2009, 02:36 AM   #6
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ffs, with what transformers, if any? Resistive, inductive or CCS loaded? Driven by what tube, or indeed by a tube at all? At what voltage/current? Into what speakers, if any? From what source, ideal or otherwise?

They are tubes. They are made of glass and wire and have no majical properties. They regulate the flow of electrons more or less precisely to allow more or less current to flow in some hopefully proportional relationship to a signal. The only sonic difference with any relationship to just the tube is the sound they make when dropped to a concrete floor from a height of, say, 1.5 metres. The bigger ones go "Boom", the midsize ones "pop" and the very little ones "tinck". Sonically, the bigger ones are more satisfying, but you get more for your dollar from a smaller one.

I'm with Gordon - the question is so steeped in mysticism, preposterously unfocused, ambiguous and loaded, it faces a noisey and short death or eternal bickering.

Is there a new issue of audiophool magazine out perchance?
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Old 20th October 2009, 05:01 PM   #7
kevinkr is offline kevinkr  United States
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Actually while "tubes have no sound of their own," they do have transfer functions, which differ substantially from one type to another, and therefore in any given topology can be expected to sound different. (Neglecting GFB which would tend to minimize these differences, however I don't use feedback in any of my current designs. My older designs used it including in some cases nested feedback.)

To be valid an experiment would have to be performed such that all the tubes to be compared would be tested under similar conditions and with the same driver circuitry and OPT. Obviously given the differing electrical parameters of power tubes like rp, transconductance, plate and screen dissipation making a fair comparison could be difficult.

The question itself is far too broad to be reasonably answered, and a meaningful comparison would be difficult to impossible to make.. (Being cognizant of the differing parametric limitations of each type and the impact they would normally have on the design. )

My experience is that it is possible to build excellent amplifiers with any of the types listed. The output tubes are not the only determinant of the end result, and it is not easy to separate them from the balance of the design.

I like GM70, 300B, 45 and the 6550/KT88. I have no idea what they sound like individually as I compare amplifiers I have designed to each other. Probably my best overall so far are all based on the 300B.. (SE and PP)
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Old 20th October 2009, 06:39 PM   #8
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Default The sound of tubes

Quote:
Originally Posted by aardvarkash10 View Post
... The only sonic difference with any relationship to just the tube is the sound they make when dropped to a concrete floor from a height of, say, 1.5 metres. The bigger ones go "Boom", the midsize ones "pop" and the very little ones "tinck". Sonically, the bigger ones are more satisfying, but you get more for your dollar from a smaller one...
Picture tubes sound pretty cool. Sort of a "Whump" with a tinkly tail. The way I used to hear them was: place picture tube at rear of a refrigerator shipping box on it's side, screen facing the opening. Hurl burnt-up power transformer into center of screen. Whump! Well, I was 9 or 10 years old at the time

Also, Eimac tubes make a sort of hollow clanky ringing sound due to the bell-like suspension of the anode.
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Old 20th October 2009, 07:16 PM   #9
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300B made a nice sound when I tried to use it as a 1500V rectifier. Sparkling treble but not too much bass, though.
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Old 20th October 2009, 07:54 PM   #10
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Originally Posted by kevinkr View Post
Actually while "tubes have no sound of their own," they do have transfer functions, which differ substantially from one type to another, and therefore in any given topology can be expected to sound different. (Neglecting GFB which would tend to minimize these differences, however I don't use feedback in any of my current designs. My older designs used it including in some cases nested feedback.)

To be valid an experiment would have to be performed such that all the tubes to be compared would be tested under similar conditions and with the same driver circuitry and OPT. Obviously given the differing electrical parameters of power tubes like rp, transconductance, plate and screen dissipation making a fair comparison could be difficult.

...
I did this experiment for a room full of people at the first VALVE conference, back in the 90's some time. I set up a driver stage and a SE output stage that could be configured to satisfy the needs of a variety of output tubes.
We worked up operating conditions that sounded best for each tube. I used a pair of Sowter 10K output transformers and ran them in parallel for the tubes that preferred a lower Z load. It worked out pretty well.

We compared a number to tubes from 45, 2a3, 300b, up to 211, 845 and some big Svetlanas. It was pretty easy to hear the difference. Sure, it wasn't a perfect comparison but I think a reasonable one.

We had some extra time at the end and compared different 211's and various operating points. It was fun. I let the audience make their own decisions about which tubes sounded best. In some cases the differences were fairly radical. Obviously this was with 1 driver stage, 1 output transformer and 1 speaker (Lowther). So that is both a plus and a minus. However, I think all the tubes we chose mated well to the environment.

I am not very good about verbally describing sounds (unless they are really bad!) so I will refrain from trying to differentiate your tubes. The best thing to do is try for yourself. It doesn't take much to lash up a prototyping board and some power supplies and swap the tubes around.
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