Sorry, I didn't notice his join date or previous posts.. When I saw his question, I thought he was asking.. it's clear now he wasn't!
(sometimes sarcasm and other social attitudes don't travel through these copper wires so well)
(sometimes sarcasm and other social attitudes don't travel through these copper wires so well)
Interesting how this got off from frequency response to sounding different.
Differences in harmonic profile could well be the differentiator between how they sound, while the frequency response of all tubes in question would be orders of magnitude beyond the range of audio impact.
Differences in harmonic profile could well be the differentiator between how they sound, while the frequency response of all tubes in question would be orders of magnitude beyond the range of audio impact.
Even if "45" reacted in a inappropriate way, I agree with his statements a bit more than MerlinB's. (and Keit)
I had this case with a hifi amplifier with ECC81 driver tubes and EL34 power tubes. I tried all kind of tubes in it; but switching the ECC81 made the most difference in sound. I started with normal (old) Philips, and ordered some new Philips ECG ecc81/6201. With these the amp sounded overly brilliant; S and T sibilance was terrible. After switching to general electric 6201 everything was perfect, even better than the "old" ecc81.
These differences where not subtle and easily audible even for my wife. (she is not into hifi and even a little deaf😱)
After a little while I could get my hands on Philips E81CC/6201 SQ for cheap. These are the sought after Hamburg made Valvo's, rebranded for Philips. I swapped them expecting better sound🙂. Alas, same overly bright sound as the ECG's. At that time I didn't have my spectrum analyzer nearby, but made a promise to myself, that as soon as I got it back, I would measure all these variants and see what differences in harmonic spectrum and /or frequency response would be visible when swapping tubes.
After I measured all that, I was very surprised!
With all tubes the frequency response was absolutely flat!
There was difference in harmonic profile; but it was unrelated to the brilliant sound. If people are interested I have screenshots of the measurements.
There is definitely difference in sound between tubes made by different manufacturers of similar tubes.
I'm convinced there are some aspects to amplifiers wich we don't measure the right way, or we measure the wrong things.
Even With Guitar related/Circuits...set up everything be damn near as Flat and none coloring as you think you can....and say that EL34 vs 6L6 thing as well Set up Swapped attempting to run as close to similar condition's as you can, to not present more/different coloration's/distortion's with either one...I still hear the difference...It's just Plain as Day to Me....Its Obvious Beam vs Pentode Sounds....it cannot be entirely Circuit dependent...Not talking about Curves/Harmonic Characteristic's/Bandwidth whatever differences....Just overall sound how you/one initial response to how you would Perceive the Sound and all...
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Unsurprising, for a competent circuit.paul dune said:
I would suggest that it was very much related to the brilliant sound.
Unless you believe in little fairies carrying (and affecting) sound in ways not shown by the electrical characteristics of the circuit (and I assume this is not what you believe) then sound differences arise very much from boring engineering things like "Curves/Harmonic Characteristic's/Bandwidth whatever differences". The reason a beam tetrode may sound a little different from a similar pentode is that they have somewhat different characteristic curves, hence different distortion.AudioFreak88 said:
I never said it was Boring haha...I know that's different....Just saying some types don't sound all that much different while others really do...There is a damn big differences between Manufactures too for the most part imo...
Still No way I would say any of it is Identical..can set it up to sound pretty close/identical though haha
You are contradicting yourself here: first you say that the discussion is only about the power valves and then you introduce an even bigger context; musician, instrument, amp, speaker and even the room.
So the original question: do power valves differ in audio frequency response curves? Answer: no, they are capable of reproducing far beyond audio freqs.
When we rewrite the original question: 'What differences in frequency response curves (if any) can we expect when changing power valves in the same amp?', then we have something to talk about.
Most higher power guitar amps have some NFB in the power section. Changing to output valves with different gain changes the NFB and current drive capability.
As 45 showed with his speaker graphs, the frequency response is different between voltage drive and current drive. Therefore the response of the entire system changes when changing power valves.
In the early 70s the US importer of Marshall swapped the factory EL34s to 6550s. That can work: both types can handle similar voltages, use almost the same heater current, like to see a textbook 3k4 load per pair (pentode mode), giving similar power levels. However, they do have different gain and the NFB was not changed. Customers claimed the amps were not the same. Now I wonder why...
Can somebody here take some measurements of the frequency response of a system (including speakers) with different outputs?
I thought so too; but I wanted to know what was going on.
Much to my surprise it was completely unrelated.
Lets look at the Spectrum Analyzers output. I have five pictures of measurements.
The first is my favorite: General Electric 6201 (thanks Rudolf) 0.47% thd.
This valve sounds perfect! Sibilance is very natural, and sound is neutral.
Selected by ear, but after measurement the best of the tubes I tested.
The second is the Philips/Valvo 6201 SQ. This is the "brilliant" tube; Sibilance is horrible! Sound is overly bright. 0.52% thd. Spectrum identical to the General electric.
Third is a standard Philips ecc81. An old one. Sound is normal, sounds worse than GE 6201, but not bright, sibilance was ok. Spectrum is different from first two tubes. 4th harmonic is way higher, 1.25% thd.
Fourth is a DLG ecc81. 0.49% thd. Spectrum similar (unexpected) to first 2 tubes. Sounds OK; better than Philips ecc81, worse than GE 6201.
Fifth is an Adzam (Philips) ecc81. Construction similar to standard Philips ecc81. I threw this one in as extra reference. Spectrum similar to standard Philips ecc81. Didn't listen to this one. Although similar spectrum, even more thd; 2.9%.
All these measurement where done at speaker output of amplifier at approx 1 watt output power.
Most relevant to the discussion are the first two pictures. These valves sound very different, but have almost identical spectra.
Attachments
First and second tubed do NOT have identical spectrum. Second tube has higher upper order harmonics and noise floor. This can be seen by toggling between the two.
I said similar or almost identical. Differences are very small, almost all below -100db.
Your summation was that all were similar, however your statement at the end of the fifth paragraph was that the second tube had "Spectrum identical to the General electric."
I submit that the near 3db difference in 4th harmonic and difference in noise floor may be sufficient impact listening impressions.
I submit that the near 3db difference in 4th harmonic and difference in noise floor may be sufficient impact listening impressions.
I disagree. If this difference was responsible for the perceived sound, then tube 3 should be much worse. Here is a clear difference of much higher 4th and more higher harmonics. However tube 3 sounded just fine, worse than ge 6201, but without the sibilance problems.
But you agree with me that there is sonic difference between similar tubes? Because some people in this thread claimed there was no perceivable difference between similar tubes of different manufacterers. Hell they even claim there is no perceivable difference between totally different constructed powertubes, like el34 vs 6l6.
But you agree with me that there is sonic difference between similar tubes? Because some people in this thread claimed there was no perceivable difference between similar tubes of different manufacterers. Hell they even claim there is no perceivable difference between totally different constructed powertubes, like el34 vs 6l6.
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Looks to me as if this thread has seriously disappeared into the thicket.
That the various valve types mentioned in the OP have sufficient GBW to deliver identical frequency response over the audio band is certain, which settles the OP question. That harmonic distortion might vary significantly between device types is circuit specific, especially as to feedback and gain, is certain.
So everyone's a winner.........
That the various valve types mentioned in the OP have sufficient GBW to deliver identical frequency response over the audio band is certain, which settles the OP question. That harmonic distortion might vary significantly between device types is circuit specific, especially as to feedback and gain, is certain.
So everyone's a winner.........
Nice work Pauldune. I would be very interested in your set up
for measurement. Source, tone, preamp or amp, speaker, mic
etc.
It would be interesting for me to make some of my own measurements
and post them here. If I can get close it would be interesting to see what
plots of tubes I can come up with.
I also might note that musicians are not the best source to know
what's going on with their amps or gear.
For example, many of the guitarist that I've worked with told
me over and over they want their amps clean and didn't want
distortion. These were guys who used Fender amps.
I modded some of my own Fender amps to be able to go
cleaner than Fender clean tone to some nice Marshall
early distortion at the turn of a dial.
Virtually every guitarist who played through the amps
set up this way no one ever liked playing clean. NO one.
They all wanted more, a bit of crunch, a bit of drive,
a bit of distortion.
The better guitar players know how to dial in their tone
with an amp so that when they turn down the volume a
bit on the axe, it cleans up the tone. Turn up the volume
on the axe and it drives the amp into MORE distortion.
Even the squeeky clean guys typically want some distortion
in their guitar tone, they just don't identify it as such.
what's going on with their amps or gear.
For example, many of the guitarist that I've worked with told
me over and over they want their amps clean and didn't want
distortion. These were guys who used Fender amps.
I modded some of my own Fender amps to be able to go
cleaner than Fender clean tone to some nice Marshall
early distortion at the turn of a dial.
Virtually every guitarist who played through the amps
set up this way no one ever liked playing clean. NO one.
They all wanted more, a bit of crunch, a bit of drive,
a bit of distortion.
The better guitar players know how to dial in their tone
with an amp so that when they turn down the volume a
bit on the axe, it cleans up the tone. Turn up the volume
on the axe and it drives the amp into MORE distortion.
Even the squeeky clean guys typically want some distortion
in their guitar tone, they just don't identify it as such.
I have an older dual core windows XP laptop with an EMU 0202 USB soundcard. The EMU has class A inputs/outputs with very low (0.003%) distortion. In loopback mode I measure 0.003% so that seems accurate.
On this laptop I run Visual Analyzer: Visual Analyser
I made a simple attenuator (which i didnt use for these measurements) 1:1 1:10 1:100 1:1000.
VA has a build in signal generator, but for this measurements I used a 24bit/96 Khz wav (1 kHz) I mathematically generated with some software. (dont remember which)
Setup was Squeezebox touch -> Dac/Preamp -> poweramplifier -> speakers.
Measurement was directly connected to speaker outputs, so distortion measured is of all components combined.
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Relative to the pentodes of the OP, triodes such as Ecc81, 6201 etc lack GBW. So depending heavily on the external circuit and specific parameters of the valve, might exhibit valve specific hf roll-off in the audioband in principle. Hence the confusion, perhaps. Harmonic distortion performance is more obviously external circuit specific, of course.
'Brighter' means hf lift, no matter whether musician or engineer. So if not a trick of perception and rolling produces a brighter sound with triodes, this is probably what is going on.
'Brighter' means hf lift, no matter whether musician or engineer. So if not a trick of perception and rolling produces a brighter sound with triodes, this is probably what is going on.
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