Tube Rolling: Does it Make a Difference?

[watchnerd]

And some legitimately suffer.
Good strawman tho...

I measure my cognition in specific gravity.

 

[pseudoid]

@mhardy6647
Are you sure it was Abraham Lincoln who said that?
Are you sure that it was NOT "William Bruce Cameron"?

View attachment 169989

William Bruce Cameron – Quote Investigator®

quoteinvestigator.com

1963, Informal Sociology, a casual introduction to sociological thinking by William Bruce Cameron, Page 13, Random House, New York. (Google Books snippet view) (Checked on paper: Fifth printing, January 1967; Copyright 1963)

"Not Every Count [e.g. Dracula] that knew how to count counted" << Yes, you could quote me on that!

 

[TCD333]

I recently reviewed the Mhdt Pagoda tube DAC. Owner was kind enough to send me three other tubes to test with it. Here are the set of tubes I received:

View attachment 168967

Let's start again with the tube supplied with the unit (GE 5670)

View attachment 168968

Now let's switch to Tesla 6CC42 (GA):

View attachment 168969

Other than slightly more mains hum at 60 Hz, I see no other difference. Gain is reduced negligible amount.

Next up is the Western Electric JW2C51:

View attachment 168970

Distortion is 0.7 dB lower. So nothing significant there.

Finally I tested the Western Electric 396A tube which produced a surprising result:

View attachment 168971

Channel 1 is the same but channel 2 has 6 dB lower distortion. Is half the tube better or is there some asymmetry in the design?

That's all I have for you.

Conclusions
It is clear that by far the source of distortion is the design and not choice of tube. In three cases the difference is negligible and inaudible. In the forth example, the WE 396A, there is reduction of distortion in one channel. In the larger picture, there is so much distortion here that reducing it with this tube is not going to make a difference one way or the other.

Notice the level of instrumentation it takes to see the impact of the tube. You need to measure to see if there is a difference and not just assume there is.

Personally even if I signed up for a tube product, I would not waste time "rolling tubes." You are likely to suffer more from "rolling placebo" by your brain than any variation in such tubes.

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Amir, sometimes you leave me scratching my head... I guess you are not a designer so don't always have a deep insight into what you are measuring. In this case the DAC design is likely using what is referred to as a resistive I-V and as such will have significant voltage swing on the DAC's OP which is then amplified by the tube stage. This DAC chip (1704) is quite sensitive to voltage swing on it's OP and will produce significant distortion with too much. In traditional (ie: data sheet) designs the 1704 would be fed into a 'virtual ground' type opamp I-V with zero voltage swing at DAC OP. A lot of the distortion you are measuring could in fact be coming from the DAC chip and not the tube stage. You would really need to measure the DAC OP dist and so on down the chain to isolate which is adding what. Some circuits are sensitive to tube changes others are not. Some tube types have a higher variance in parameters than others, for eg high gm frame grid tubes come to mind. It's a deep subject and just grabbing a 1kHz spectrum from one product is not going to prove much.

 

[mhardy6647]

View attachment 169989

William Bruce Cameron – Quote Investigator®

quoteinvestigator.com

"Not Every Count [e.g. Dracula] that knew how to count counted" << Yes, you could quote me on that!

Of course! The Count!

 

[amirm]

Amir, sometimes you leave me scratching my head... I guess you are not a designer so don't always have a deep insight into what you are measuring. In this case the DAC design is likely using what is referred to as a resistive I-V and as such will have significant voltage swing on the DAC's OP which is then amplified by the tube stage. This DAC chip (1704) is quite sensitive to voltage swing on it's OP and will produce significant distortion with too much. In traditional (ie: data sheet) designs the 1704 would be fed into a 'virtual ground' type opamp I-V with zero voltage swing at DAC OP. A lot of the distortion you are measuring could in fact be coming from the DAC chip and not the tube stage. You would really need to measure the DAC OP dist and so on down the chain to isolate which is adding what. Some circuits are sensitive to tube changes others are not. Some tube types have a higher variance in parameters than others, for eg high gm frame grid tubes come to mind. It's a deep subject and just grabbing a 1kHz spectrum from one product is not going to prove much.

I am not engaging in science projects. I don't have the luxury of time or frankly interest to analyze subystems in products I test. This project was about rolling tubes and that is what I did.

As to your guess of what "a lot of the distortion" is coming from, is just that: a guess. It is not like you have this unit or have its schematic to know any better. Keep in mind that with one tube swap, distortion did go down 7 dB in one channel:

So unless you have some hard data, I suggest you lay low in the insult department and random guessing.

 

[pseudoid]

... This project was about rolling tubes and that is what I did...

How rude of me! I would like to thank you @amirm for turning this stone over or rolling it or whatever.
It has been most educational and your time and efforts have not gone to waste.

 

[watchnerd]

Keep in mind that with one tube swap, distortion did go down 7 dB in one channel:

Interestingly, I could stick a JW2C51 in my 6922-based headphone amp if I used an adapter.

I've certainly seen pricier, but it ain't cheap:

Western Electric JW2C51 and 5670 to 6922 Adapter Combo

Have you ever dreamed of a Western Electric 6922, but know that's just not possible? Well, now it is. Take a Western Electric JW2C51 / 396A, add one of our 5670 to 6922 adapters, and you have a long-lasting & great-sounding Western Electric made 6922 / E88CC preamp tube. We just received a healthy

tubedepot.com

$150 for 1 tube plus adapter.

Although I'm not sure there is any advantage to doing so.

 

[DanielT]

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.

Maybe it was a little off topic for the thread. What I'm really curious about when you hear the difference. If the tubes wear out gradually and the sound gradually gets worse or if they work until they do not do so anymore. Either or that is, works or or does not work, or gradual deterioration.

By the way, this was the case with the Norwegian (we are joking with our neighbors) when he tested his turn signal on his car: Works, does not work ...

 

[0bs3rv3r]

You should understand that tubes were not made to the same specification, even the same tube types. And there was no STANDARD for frequency response (not to mention many tubes used in audio amplifiers were not designed for audio) back in the post WW II period that I am aware of. Are you? I've not seen references to 20 hz - 20 khz until like the 1970s.

SO:

would it not be stranger for the tubes to sound alike than it would be for them to sound different?

I have no idea what that is. But were tubes designed for flat frequency response in the audio band to the same spec? Military tubes were made to tighter tolerances but what does that mean? +/- 3 db? 10? 1?

Tubes are not "designed for a flat frequency response in the audio band". It's the circuits that you put them in that largely determines that. The tubes will amplify signals WAY in excess of the audio upper limit. Heck, many being used in audio today were designed and used in radio frequency circuits.

As for 20 Hz to 20kHz, there was a period before that where it tended to be more conservative for "full fidelity", say 25 Hz to 15 kHz, before that, there were specs for telephony, much reduced again.

 

[solderdude]

Maybe it was a little off topic for the thread. What I'm really curious about when you hear the difference. If the tubes wear out gradually and the sound gradually gets worse or if they work until they do not do so anymore. Either or that is, works or or does not work, or gradual deterioration.

When it is gradual it may be more difficult to detect. Of course this too depends on the circuit design (feedback can correct it up to a point) and what the actual effect is.

 

[JackStraw5877]

I am not engaging in science projects. I don't have the luxury of time or frankly interest to analyze subystems in products I test. This project was about rolling tubes and that is what I did.

As to your guess of what "a lot of the distortion" is coming from, is just that: a guess. It is not like you have this unit or have its schematic to know any better. Keep in mind that with one tube swap, distortion did go down 7 dB in one channel:

So unless you have some hard data, I suggest you lay low in the insult department and random guessing.

Ok I am supremely grateful to you, Amir, and to many others for the participation and education. This is the last time I can stand you responding this way to a decent objection to your analysis. This isn't how science works. It's just plain awful. Sorry man, it's awful.

Mods, somebody, please (this is my second request) get me off the ride. I can't support this by association anymore. It is with regret that I request my account deletion.

Thank you to all. Really.

 

[pseudoid]

This is the last time I can stand you responding this way to a decent objection to your analysis.

I did not know it was addictive...

 

[Deleted member 27254]

I never understand why it's called "rolling tubes" as opposed to "changing tubes". It seems to imply some inherent skill involved in the process.

I believe it's called tube rolling because of the gentle circular motion your hand and wrist make when you remove the tube from its socket. Pulling straight up tends to not work so well as the socket usually grips the tube pins very tightly, and you don't want to exercise so much pulling force that you could theoretically shatter the glass housing.

Installing the tube goes more or less the same way, but with more of a slight rocking motion.

At least that's how I do it.

Hope this helps!

 

[Snafu]

Interestingly, I could stick a JW2C51 in my 6922-based headphone amp if I used an adapter.

i replaced my pre amps 6922/E88CC's and power amps 12AU7's tubes with adapters and.... CV-181's...

 

[PeteL]

I am not engaging in science projects. I don't have the luxury of time or frankly interest to analyze subystems in products I test. This project was about rolling tubes and that is what I did.

As to your guess of what "a lot of the distortion" is coming from, is just that: a guess. It is not like you have this unit or have its schematic to know any better. Keep in mind that with one tube swap, distortion did go down 7 dB in one channel:

So unless you have some hard data, I suggest you lay low in the insult department and random guessing.

Personally I see nothing wrong with these sorts of experiments, as long as it is clearly stated that the conclusions of the experiment don't extend past the scope of what is being demonstrated, or at least not imply that it would be.

 

[musicforcities]

Tubes are another form of tone control, with added euphonics…aka distortion. That’s all.

I have to admit I do enjoy my Sunfire Vacuum tube preamp. It sounds great. Is it neutral? No way. But it’s actually pretty good measurement wise for a tube amp. Carver managed to even get the output imprudences very low.

I don’t use it often anymore but it’s fun to take for a spin. Like a convertible that you drive on a weekend but is terrible for everyday driving.

Only complaints I have are:
1) it is single ended and while it does have balanced out, the balanced output is noticeably worse sounding somehow (I guess the conversion circuit is not great).

2) it has an apparently rare mm/Mc phono preamp stage that was an option. The phono stage is on a separate board and is also tube based with a separate power supply stage. It’s great as far as tube phono stages go I gather. But it has FIVE tubes itself. Two for MM, two for MC, and one for a subsonic filter / RIAA eq circuit. All are always on whenever the preamp is on. Combined these create lots of heat inside the unit and cooked the capacitors used for the phono power supply, causing three out of 9 to leak and eat through the board. When I repaired and replaced I mounted the new caps underneath the board and thus away from the tube heat. And added a switch to turn off power to the board when it’s not needed.

The preamp stage itself has a tube just for the tone / contour controls, which are themselves very nice: they are switches to select different discrete components to change freq. response. But if that tube’s sides is not very well matched, it’s a mess cause eq will be slightly different for the channels. Same for the two preamp tubes for the channel signals itself. Those two have to be well matched. But it has a balance control — imao tube preamps/amps MUST have a very good balance control in the chain; tubes age differently and even well matched as new can begin to drift with age.

I did add a remote controlled relay based stepped attenuator to replace the volume pot. Big improvement in convenience and sound, in part I suspect by shortening/ improving the signal path.


seems like it would be relatively easy to make software/dsp based tube simulator. Just imagine. Sell it to audiophiles for $2000 for instant rolling. Of course, it would also need to have tubes itself. But they could just power the whole Oled display so, you know, so that the display would have greater lifelike presence and “air” in its presentation of information.

 

[PeteL]

Never got in tube rolling but I do own a Schiit Freya+. It measures good and I purchased it knowing it also has a solid state stage as an alternative.
In the end it's on tube all the time, mainly because it offers a bit more gain which comes useful in my use case. The difference in sound is subtle (if audible since it has more gain and didn't try DBT). Wondering if when you have something that measure good to start with tube rolling makes more significant differences, or on the contrary, it means the way the tubes have been integrated in the design their contribution is minimal so any tube difference would be inaudible. For topology it's semi cyclotron but I didn't dig deep to understand it. Should I try other tubes for fun?

 

[pseudoid]

I believe it's called tube rolling because

That word has become an "earbug" for me and I have to stop reading this posts.
In the 1969 movie "EasyRider", The Fraternity of Man sang the song "Don't Bogart That xxxxx"
The earbug part is this:

Don't bogart that TUBE, my friend

Pass it over to me.

Ro-o-o-o-o-o-o-o-o-o-o-o-o-o-o-oll another one

Just like the other one.

This one's burnt to the end

Come on and be a friend.

 

[Poultrygeist]

William Bruce Cameron – Quote Investigator®

quoteinvestigator.com

1963, Informal Sociology, a casual introduction to sociological thinking by William Bruce Cameron, Page 13, Random House, New York. (Google Books snippet view) (Checked on paper: Fifth printing, January 1967; Copyright 1963)

Can you find him on a poster with the quote? If so no one would buy it or care.

 

[amirm]

Personally I see nothing wrong with these sorts of experiments, as long as it is clearly stated that the conclusions of the experiment don't extend past the scope of what is being demonstrated, or at least not imply that it would be.

You realize what he asked for? That I open, reverse engineering the unit, find out the proper DAC output prior to buffer and measure that. No way I can sign up for this, nor defend any such results. If a product has external outputs for such, sure, I measure that as I do for AVRs and such. But without, and based on some guess, on a product no one cares about, it has no justification.