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Tube Rolling: Does it Make a Difference?

DanielT

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It will be used to replace microphone parts, is there a vacuum tube with good specifications for low distortion? The existing vacuum tube is 6AU6.
It's not me who designed that tube pre amplifier. I can not construct such so unfortunately I can not help you since am not a DIY "tube guy".I'm mostly in this thread because tubes fascinate me, mainly from a sound historical perspective.:)
 

DanielT

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The effect is design dependent. So the topology and circuit around them determines the 'sound' of the amplifier as a whole.

One can design a tube amplifier with just 1 tube, say a simple triode that has to do all of it. That tube is very flawed in specific ways and alters the signal. One can build an amplifier that has properties that change depending on the inserted tube.
Frequency response, distortion, gain, noise will all be different.
The fact that the gain can differ (even between channels) is often the culprit of someone perceiving the tubes to be different sounding.
Also frequency response and noise levels can be a reason to perceive them to have a different sound.

The problem is to determine if the change in sound you hear is real (and not caused by say the gain or expectation) is that to determine that there really is an audible difference you would have to test this in a scientific way.
This means: having 2 identical amplifiers, The ability to adjust the gain/volume of each channel, using 2 different tubes in each amp, let both amps warm up say. 5mins, and then switch (blind) between the 2 amps. Only then you can truly determine IF the tubes sound different or that it is 'something else' causing the perceived differences.

I am quite certain you have never done that. You can be quite certain I have with a bunch of tubes in 2 equal amps in such a setup because I have a few of those amps (proto's, pre-prod and 1 prod unit) and I can tell you that my non audiophile ears (no idea what Harman level I am :)) can't hear differences with quite a few tubes that are well suited but there are also a bunch of tubes that roll-off in the audible band or have a lot of hiss in that circuit and can easily distinguish them.
I don't see that as a having a sound but rather these tubes being faulty or not really usable in that particular design. Of course there are owners who love those tubes (rolled-off or a low added noise level)

You call it 'tubes having a sound' and I call it tubes altering the signal in specific ways determined by the used topology, schematic and tube.

One can also design an amplifier using a bunch of tubes but uses overall feedback. In that case the sound you hear with specific tubes in the simple design will not be there any more. Same tubes being swapped no change in sound. So the same tubes that have a 'sound' in circuit A may not have 'a sound' in circuit B.

It's not the tubes that have 'a sound' it is the circuit and topology combined with specific tubes that can change the response in specific ways (and thus the sound). The fact that you may prefer certain alterations in sound in a certain way is another matter.
But if you change the tubes and the old tubes approached their lifespan, do not you think you can then hear the difference between the old (soon used tubes) vs new healthy tubes? In the same amplifier, the same type of model of tubes. Power tubes that is.
 

JBNY

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Where is the evidence of this ?
I mean have the perceived differences between tubes been objectively verified ?
Also do not confuse rolling power tubes or not really suited tubes or tubes with substantially different gain and or transformers / loads (in non- or low-feedback designs) with a simple gain stage.
I mean, have you never listened to tubes in anything? Change the tubes and change the sound, the fact that you are asking where is the evidence just shows how little experience must you have.
 

Spkrdctr

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Butt he wasn't expecting to hear a difference. why is this deception happening to him to you suppose? Is he lying when he says he was not expecting a difference?

Actually I think these are more powerful tubes. He hears correctly. It's more powerful also they're new.
That is the issue with your brain/ear function. You can't outguess it. It is what it is, a trickster . I'm talking about the "concept" of the brain tricking what we call our hearing. It is all over the map. Plus, many have added that there are fairly large differences between tubes. I wonder what a very worn out tube vs a brand new one might do in a blind test. I don't have anything for a tube test. Since they are really such a small part of audio I have never messed with them. But the #1 issue is you cant A/B anything except speakers (or tubes?). The mind gets in the way. Measurements are important as they will get you most of the way there to good sound. If we want to tweak that with an EQ, that is ok too. People in general enjoy low quality music like old transistor radios from the 70's. Audio is a "wild west" market place. Amir is trying to bring some order to it as best he can. Wait, does that make Amir the new sheriff in town? :) But, it is still very wild and crazy out there in audio land!
 
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Leiker535

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I mean, have you never listened to tubes in anything? Change the tubes and change the sound, the fact that you are asking where is the evidence just shows how little experience must you have.

He asks for evidence precisely because anedoctical experience amounts to very little on the audio world, unless, of course, you are willing to factor in your own biases as fact.

Tube rolling, IMHO, is the epitome of bias allowance. We have inherent short memory for "microdetail" and nuances, so sightly swapping tubes and having to wait about 10 mins between each listen will give you ample amounts of time to fool yourself by either forgetting what you just heard or by paying new attention to things you didn't before.

When I was younger (literally 14) and with no before knowledge of what placebo was, I got my first tube amp (LD MK III) and tried swapping the original chinese EF95s for the premium voshkod EF95s. I immediately perceived everything I had read on them, bigger soundstage, detail, etc. I tried to replicate the same experiment this year, much more skeptical, and I got nada but a worse channel imbalance. Factor in that I know was biased AGAINST tube rolling, and was skeptically not waiting for a change; so that can be a bias in it of itself too.


This vid for example, I don't hear absolutely nothing when he swaps the tubes; but the people on the comments swear the change is dramatic, what gives? And no, I'm not implying I'm golden eared or that they're and I'm not. Just that we have biases and so, therefore, you can't use the argument you used as if amounted to anything.
 
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watchnerd

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He asks for evidence precisely because anedoctical experience amounts to very little on the audio world, unless, of course, you are willing to factor in your own biases as fact.

Tube rolling, IMHO, is the epitome of bias allowance. We have inherent short memory for "microdetail" and nuances, so sightly swapping tubes and having to wait about 10 mins between each listen will give you ample amounts of time to fool yourself by either forgetting what you just heard or by paying new attention to things you didn't before.

When I was younger (literally 14) and with no before knowledge of what placebo was, I got my first tube amp (LD MK III) and tried swapping the original chinese EF95s for the premium voshkod EF95s. I immediately perceived everything I had read on them, bigger soundstage, detail, etc. I tried to replicate the same experiment this year, much more skeptical, and I got nada but a worse channel imbalance. Factor in that I know was biased AGAINST tube rolling, and was skeptically not waiting for a change; so that can be a bias in it of itself too.


This vid for example, I don't hear absolutely nothing when he swaps the tubes; but the people on the comments swear the change is dramatic, what gives? And no, I'm not implying I'm golden eared or that they're and I'm not. Just that we have biases and so, therefore, you can't use the argument you used as if amounted to anything.

Now I know how to monetize the 16 pairs of NOS tubes I have!

Sweet click revenue, here I come.
 

BDWoody

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Leiker535

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Well, the nice thing was going to be the Focal Stellia, but so much for that!

I offered to pay Schiit extra for a silver Magnius, but they're not biting.
You can follow up on your channel with sound demos of said headphones! You just need a 40 thousand dollar couple with a dummy head, and an infinite supply of gear!


This guy also did a comparison between all his TOTL euphonic amps, showing the clear and contrasting euphonic difference source has on tonality:

 

mhardy6647

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so -- at the risk of changing the subject ;) -- what the fug is "microdetail" and how is it measured (quantified)?

I am actually pretty tolerant of much audiophile wordsmithing -- but that one is one of my hot buttons.
 

MattHooper

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When you swapped the KT 120's for the 6550's - did you readjust the bias? So, whether you optimized the bias or not - you heard a difference. To verify we could measure a couple of things. First, you could test for output impedance changes - affects damping factor. Being a tube amp we need to be careful - no open circuit voltage measurements! I would try a 100 ohm load and consider that "open circuit" to get the reference voltage at a given driven frequency. Being a tube amp we can short circuit the output with no fear as we lower the load until the output voltage is half the reference voltage. That load resistance is the output impedance at the driving frequency. Best to do sweeps with fancy test gear to plot this by frequency. Another way is to sweep your system with a measurement microphone and plot spl versus frequency. Compare the plots for between output tube plots for measured differences.

If your perceptions are real it should show a measurable difference. Some tube amp OEM's publish specs showing expected output power with different power tubes. KT120's always seem to glean a few extra watts versus 6550/KT88's. Five extra watts is not much loudness wise but might get you a bit more undistorted headroom.

All very reasonable and absolutely if there is a difference to be heard it should be measurable. As I mentioned before, though, I don't have the gear or the aptitude to measure it. I'm more of a "consumer" rather than a "techie" in this respect. (Just like I buy my computers and just use them, I don't get off on building them, where some people more technically inclined do like to get in to engineering/technical stuff, sleeves rolled up, measuring etc).

I do re-bias each time I change tubes, FWIW...
 

Bob from Florida

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All very reasonable and absolutely if there is a difference to be heard it should be measurable. As I mentioned before, though, I don't have the gear or the aptitude to measure it. I'm more of a "consumer" rather than a "techie" in this respect. (Just like I buy my computers and just use them, I don't get off on building them, where some people more technically inclined do like to get in to engineering/technical stuff, sleeves rolled up, measuring etc).

I do re-bias each time I change tubes, FWIW...
Just making an obvervation.

I don't measure anything unless I need to for a reason. I have a laptop that has not been turned on for years that has a RTA program on it and I had a calibrated microphone as well. Used it for in room testing of a crossover for some open baffle speakers I had built. I think stuff like that can be done on smart phones now.
 

watchnerd

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You can follow up on your channel with sound demos of said headphones! You just need a 40 thousand dollar couple with a dummy head, and an infinite supply of gear!


This guy also did a comparison between all his TOTL euphonic amps, showing the clear and contrasting euphonic difference source has on tonality:


Ugh I already have a day job
 

dfuller

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It will be used to replace microphone parts, is there a vacuum tube with good specifications for low distortion? The existing vacuum tube is 6AU6.
You'd want to use a 6AU6.
 

solderdude

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But if you change the tubes and the old tubes approached their lifespan, do not you think you can then hear the difference between the old (soon used tubes) vs new healthy tubes? In the same amplifier, the same type of model of tubes. Power tubes that is.

The subject was the tubes in this particular application, the DAC, as a line output stage that has a deliberate high distortion.
The tubes used by Amir do not show very different and audible differences.

That doesn't mean that tubes in power amps etc. that go bad and are replaced by new ones (which one has to do certainly with power amps) or that at least idle currents have to be adjusted.
 

solderdude

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I mean, have you never listened to tubes in anything? Change the tubes and change the sound, the fact that you are asking where is the evidence just shows how little experience must you have.

The fact that you wrote this reply tells me you have not read post #260
 

DualTriode

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so -- at the risk of changing the subject ;) -- what the fug is "microdetail" and how is it measured (quantified)?

I am actually pretty tolerant of much audiophile wordsmithing -- but that one is one of my hot buttons.

Hello,

Some people feign cognitive density for affect.

Let’s look at the first definition of micro detail that pops into mind. When a perfectly transparent playback system plays something just above the threshold of human audibility that very well could be micro-detail.

Say that tones that are being played are just barely above human audibility are lost in system hiss, much of the resonate quality (micro-detail) of a piano or violin string is lost in the noise.

How would you measure that? That is your homework exercise.

Hint: https://audioxpress.com/article/Test-and-Measurement-I-Can-Hear-It-Why-Can-t-I-Measure-It-

In this case, I can’t hear it why can I measure it?

Do not look so much like a lost puppy, it does not suit you.

Thanks DT
 

Spkrdctr

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Hello,

Some people feign cognitive density for affect.

Let’s look at the first definition of micro detail that pops into mind. When a perfectly transparent playback system plays something just above the threshold of human audibility that very well could be micro-detail.

Say that tones that are being played are just barely above human audibility are lost in system hiss, much of the resonate quality (micro-detail) of a piano or violin string is lost in the noise.

How would you measure that? That is your homework exercise.

Hint: https://audioxpress.com/article/Test-and-Measurement-I-Can-Hear-It-Why-Can-t-I-Measure-It-

In this case, I can’t hear it why can I measure it?

Do not look so much like a lost puppy, it does not suit you.

Thanks DT
My microdetail beats yours! Pyle full range 4 inch speaker. Nothing better than that.
 
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