Has anyone measured the effect (if any) of tube rolling?

[solderdude]

What about the differences between the tubes that we see on the graphs, anything potentially audible?

Are the white FFT peaks the same amplitude as the green ones or are the green ones substantially higher and masking the white peaks ?
There appears to be no reason based on the 1kHz tone and FR to suspect anything would be audibly different.

 

[watchnerd]

Yes, measure the electrical signal. Your comparing the tubes, not the speakers and room. If the electrical signal is flat with freq. for different tubes ( it should be close ) why would you have freq. variations in the room unless it was caused by the room. And do it with the load connected some tube circuits will change freq. response with load.

What about microphonic effects of tubes used in a low signal phono stage being affected by acoustic feedback / vibration from speakers in the room?

Is that possible?

 

[Cbdb2]

Possible but unlikely. Lots of talk by the audiophools on the web but no measurements, which are dead easy to do. Not even by people trying to sell cures, which is always a red flag. And you can always move your tubes into another room and try them.

 

[watchnerd]

Possible but unlikely. Lots of talk by the audiophools on the web but no measurements, which are dead easy to do. Not even by people trying to sell cures, which is always a red flag. And you can always move your tubes into another room and try them.

It's a phono stage....I don't see how I could easily move it to another room away from the turntable without doing something nutty involving 50' of RCA cables and the problems that come with that and mV level signals.

I could do vinyl rips with and without speakers on, but then you're also getting the effect of the TT/cart reacting to sounds, which definitely happens.

 

[Cbdb2]

Actually all you have to do is the above electrical testing, once with no sound out of the speakers and again with your speakers loud. I would really like to see those results.

 

[Cbdb2]

Did you test with soundcard out into the pre?

 

[watchnerd]

Actually all you have to do is the above electrical testing, once with no sound out of the speakers and again with your speakers loud. I would really like to see those results.

I don't have a scope.

Did you test with soundcard out into the pre?

When I do vinyl rips with the tube stage, the chain is:

TT -> SUT -> tube phono -> line in on Devialet (which does ADC) -> USB out on Devialet -> MacBook

 

[Cbdb2]

It's a phono stage....I don't see how I could easily move it to another room away from the turntable without doing something nutty involving 50' of RCA cables and the problems that come with that and mV level signals.

I could do vinyl rips with and without speakers on, but then you're also getting the effect of the TT/cart reacting to sounds, which definitely happens.

Agree moving is a pain, easieast to just run speaker wire room to room. Yes, the TT microphonics are real and orders of magnitude higher than the pre.

 

[Cbdb2]

I don't have a scope.



When I do vinyl rips with the tube stage, the chain is:

TT -> SUT -> tube phono -> line in on Devialet (which does ADC) -> USB out on Devialet -> MacBook

Iwas talking about the freq sweeps and distortion measurements of the 2 tubes you showed earlier. Can repeat those, once with and once without the speakers loud. This would isolate the tubes.

 

[watchnerd]

Iwas talking about the freq sweeps and distortion measurements of the 2 tubes you showed earlier. Can repeat those, once with and once without the speakers loud. This would isolate the tubes.

That wasn't me.

 

[pozz]

There's this review:

• (31 January 2019) Schiit Saga & (31 January 2019) Tube Rolling

And for good measure, op-amp rolling:

• (26 April 2019) Gustard H20 & (26 April 2019) Op-Amp Rolling
• (19 March 2018) Topping D10 & (15 September 2018) Op-Amp Rolling

 

[zalan.reilly]

I’m very much enjoying my new DarkVoice 336se tube headphone amp, and part of the fun is rolling in different 6SN7s I have on hand with my Sennheiser Nox Vidmate VLC 6xx cans. Perhaps it’s folly, but I do think I detect differences in sound depending on the tube. Ken-Rads tend to have deeper bass, RCAs are darker, Sylvanias as brighter. I’m talking different 6SN7s, not substitutes. So, in Objective Land, has anyone measured the effect of tube rolling? Do measurable difference show up when it’s looked at?

I particularly like the idea of "brand sound," considering that "brand" correlates to the shape of the printed ink on the box and tube envelope- and nothing else. I posted pix a few years back of some ECC83/12AX7 which all clearly came from the same factory. They were branded Amperex, Radio Shack, Mullard, RSI, and one or two others I don't recall at the moment.

 

[GXAlan]

Switching from KT88 to GE JAN 6550A definitely had a difference in sound on my MC2102 (which is up for sale). The Mc2102 has no transistors in its entire signal chain which may account for the difference.

Ken Rockwell has a review showing a wide range of differences between new and old tubes for one of his tune amps.

 

[solderdude]

The thread is not about hearing differences, it is easy to hear differences, even when there are are none, not saying there are none, there could be.
This thread is about measurements showing differences.
Has anyone measured the effect (if any) of tube rolling?

So we want: amplitude, distortion (spectrum), noise, phase measurements and amplitude dependent distortion measurements not 'measurements' (anecdotal reports) done with a very poor measurement device such as ears + brain in sighted conditions.

And even then those measurements are most likely tube amp dependent so what is measured in tube-amp A may have different measured results in tube-amp B, C or whatever other model.

And as stated before... it all depends on the tube circuit and perhaps also condition of the tube more so than anything else.

 

[Wombat]

In a decent circuit, that's not as hard as you'd think. New tubes stabilize with 30 minutes or so after their first use, and it takes a while before the deterioration with age is apparent. I had no problem getting comparable results to Morgan's 6SN7 measurements with a similar test setup.

Agree.

This is one area of audio where bias matters. Even when replacing a tube with one ostensibly 'identical', re-biasing can be essential for designed performance due to mfg tolerances or tube age - circuit related of course.

Most tube-rollers don't understand tube biasing, let alone have gear that allows it or the ability to do it.

I cringe when I see 'audiophiles' using-up scarce vintage tube stocks for their ham-fisted tinkering. Similarly, rock bands chewing up vintage output tubes running at voltages/currents well above spec.

This high value demand has set up an active market for fakes. Many who slip a 'special' tube into their gear and espouse the improvement have been suckered.

 

[rebbiputzmaker]

Agree.

This is one area of audio where bias matters. Even when replacing a tube with one ostensibly 'identical', re-biasing can be essential for designed performance due to mfg tolerances or tube age - circuit related of course.

Most tube-rollers don't understand tube biasing, let alone have gear that allows it or ability to do it.

I cringe when I see 'audiophiles' using-up scarce vintage tube stocks for their ham-fisted tinkering.

Biasing only applies usually to power amplifiers. You bias output tubes, output stages, And sometimes these can be self bias, as in the case of most single ended amplifiers. You don’t get to bias, preamps, inputs or Driver stages usually. If tubes do sound different, it can be measured. One easy test is microphonic‘s. Depending if you isolate your equipment from the listening area or not, microphonics can really drive one crazy.

 

[GXAlan]

Has anyone measured the effect (if any) of tube rolling?

https://kenrockwell.com/audio/mcintosh/mc240.htm#measurements

 

[solderdude]

yes... but as mentioned, the same effect/measurements won't necessarily apply to other amplifiers.
Also it is tube quality dependent, not all tubes are working equally well so one might own a dodgy tube, not like it and then dismiss the brand/type based on that while another sample may work great.

 

[Wombat]

Biasing only applies usually to power amplifiers. You bias output tubes, output stages, And sometimes these can be self bias, as in the case of most single ended amplifiers. You don’t get to bias, preamps, inputs or Driver stages usually. If tubes do sound different, it can be measured. One easy test is microphonic‘s. Depending if you isolate your equipment from the listening area or not, microphonics can really drive one crazy.

All tubes are biased. The bias on low signal level stages is not usually user adjustable, usually because feedback circuitry does this well. In Hifi amps power tube bias adjustment is usually ranged to set a new specified tube to the recommended bias-point setting and adjust as the tube ages(how many users do this?).

Tube characteristics determine design bias choice. Good design allows some latitude in this regard, within reason, for a given tube-type normal spec. variation. All bets are off when substituting different tube types in circuits that were not designed for them, e.g. the various 12--7 types or tubes with marginal(for type) specs. Even with SE circuits the performance can be optimised with bias adjustment.

Microphonics is another issue. Unless the tube is faulty or unsuited to the application, microphonics can be addressed at the design and construction stage.

 

[watchnerd]

Agree.

I cringe when I see 'audiophiles' using-up scarce vintage tube stocks for their ham-fisted tinkering.

I've got, I dunno, 12-14 pairs of 6922/6DJ8/7DJ8/etc tubes for my Fi Yph tube-based RIAA stage.

Maybe 10 of those pairs are NOS, ranging from 1960s to 1980s.

Use life in this application is thousands of hours, so I have enough tubes to last decades until I'm senile.

Other than using them in microphones, what's the other use case you're concerned will be impacted by "using-up scarce vintage tube stocks"?

And it's not like people can't buy modern 6922 issues instead of NOS...