Does tube-rolling actually make a difference in sound?

[Willakan]

Bleh, tube amp signatures, whilst probably exaggerated, are fine compared with the utter confusion that is the world of opamp sound signatures. Incredibly, discrete opamps always sound better, even if they measure terribly! (cough AudioGd). IC opamp opinions seem to vary - on some boards people suggest that X rolls off the treble, and all the new people who try X find themselves in agreement, whilst on another board X boosts the treble, which of course everyone end up agreeing with. A cynic might ponder the effects of expectation bias.
 
Tube amp changes, which do at least make sense, are probably mainly frequency response variation, unless one set of tubes has stupidly high distortion I suppose...

 

[Shike]

It depends on the design.  An OTL will vary in output impedance based on the tube which in fact does change the sound.  A properly done transformer coupled design should sound close if not indistinguishable from an also properly designed solid state design.
 
Effectively, one can make it so tubes do or do not make a large impact.  The problem is sifting through marketing BS claims and the objective results.
 
Quote:

Bleh, tube amp signatures, whilst probably exaggerated, are fine compared with the utter confusion that is the world of opamp sound signatures. Incredibly, discrete opamps always sound better, even if they measure terribly! (cough AudioGd). IC opamp opinions seem to vary - on some boards people suggest that X rolls off the treble, and all the new people who try X find themselves in agreement, whilst on another board X boosts the treble, which of course everyone end up agreeing with. A cynic might ponder the effects of expectation bias.
 
Tube amp changes, which do at least make sense, are probably mainly frequency response variation, unless one set of tubes has stupidly high distortion I suppose...

 
To feed the paranoia of opamps, the Benchmark DAC1 uses the NE5322.  They found "audiophile" approved opamps caused lots of issues and that upgrades performed using them ruined performance.  Even better, look-up the history of the Gain Card which was widely applauded by the audiophile community . . . till they found out that it only had a ~$15 opamp in a minimal circuit.
 
Also, another issue with opamps rolling: oscillations.  Not all opamps will work like they should in all circuits . . . some circuits if not done with care will ultimately kill the opamp.
 
 
Consider me part of the cynic group: I definitely expect placebo in lots of cases.  Especially seeing things like the Carver Challenge a while back.

 

[nanaholic]

Quote:

We could settle the question of whether different tubes sound different in a given amplifier by recording the output of the amplifier with a headphone plugged in, and then playing it back at a later date within seconds of each other!
 
Just saying. 
 
Considering the availability of good quality digital recording gear its neither difficult or expensive. 

It should be easier than that - connect the output of the tube amp to a line-in of a sound card and record the waveform, swap tubes and do it again.  Line up the waveforms and do a waveform subtraction and if the outcome is not a completely flat line at 0 amplitude, then there is a difference, if it is flat, then there isn't.  

 

[nikongod]

 
Quote:

It should be easier than that - connect the output of the tube amp to a line-in of a sound card and record the waveform, swap tubes and do it again.  Line up the waveforms and do a waveform subtraction and if the outcome is not a completely flat line at 0 amplitude, then there is a difference, if it is flat, then there isn't.  

That does not take into account the limits of hearing, which is kind of an ironic point of this whole section. Very few people ever consider this. 
 
Differences in the sound of an amp/source are totally audible when using devices that are themselves imperfect. You have to try reallllllly hard to buy a source or amp (including tubes!) that measures as poorly as a really good headphone or speaker. 
 
Edited:
I took this out because Im not sure its correct.
 

Im not sure that recording the voltages (as I suggested too) would work thinking about it some more. The voltages would not necessarily line up with the sound - in the case of an amp with a fairly high output impedance they would be opposite (An audible increase of volume in a given frequency range would be a dip!) but I think it would still work to prove there are audible differences between at least some tubes. 
 
Mount headphones on a dummy head, play a song or 2 and record. switch tubes repeat.