No I don't ask for this, the previous contributor asked for this not me.
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Tube Rolling: Does it Make a Difference?
- Thread starter amirm
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DanielT
Major Contributor
Although I think tubes are interesting, purely in terms of sound history in any case, I would not be particularly interested in you spending time engineering different tube amps and performing various tests on them. As you said, you are neither interested in it nor consider yourself to have the time for it. I think it sounds good that you are not interested. There is MUCH MORE interesting things you can measure and investigate. And also do not forget to have fun. Without it, the motivation disappears.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.
You have previously mentioned the time:
I love the simplicity of tube amps like this. There is just so little to them. If I were less busy, I would not mind playing with one to get it to optimal performance.
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I think you should start relaxing now instead. Fix an eggnog, or whatever you drink in the US at Christmas time.
You've done a great job with everything this year.
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On the Prima Luna there is a noticeable difference between Ultra Linear and Triode mode.
How is that happening?
I think that the the KT120s may have more output than the EL34s, but I have not put them in yet.
How is that happening?
I think that the the KT120s may have more output than the EL34s, but I have not put them in yet.
Gain, power, source impedance.
They’ll be different, but that makes less audible difference than impedance and power.
If @Holmz is using Vandersteen2C (per his avatar); then, the load impedance should not greatly impact his subjective results while "rollingcomparing" tubes.
(from https://www.stereophile.com/content/vandersteen-2c-loudspeaker-measurements)
Sure looks like it will. And he was talking about comparing ultralinear to triode, where source impedance will absolutely change.
All things considered, AND per stereophile review by A.H.Cordesman statement: "The Vandersteen 2C has a very flat impedance curve for so sophisticated a design. It should be an easy speaker to drive..."
[see Revel F228 floor-standing ASR review specifically for comparitive impedance... all things considered.]
Change source impedance and you'll change the frequency response. Cordesman was way out of his element when he tried to talk technical in audio. Should have stuck to his main specialty, advising the government on how to kill people in faraway lands.
watchnerd
Grand Contributor
I think we can largely discount the massive 30 Hz bump as there was not a lot of musical content there.
And even less using the Vandy powered sub and the crossover.
But back to the point… There mention of source and load impedance.
And
What is happening that makes the ”Ultra Linear” mode more “meaty” sounding in the midrange?
With vocals in the 200-2k range it has a distant, more airy and hollow sound in Triode, and the in UL is has a more richer/fuller sound.
They both sound good, and the amp looks nice.
sitting there all a glow.The impedance is between 8 and 9 ohms between 200 Hz and 4 kHz.
Maybe I need a link to explain the impedance effects?
Do you know how to do a basic voltage divider model?
Where do you get "constant 8-9 ohms"? The impedance plots show exactly the opposite.
Caffeine and alcohol.
It's not constant there, either. Humans are far more sensitive to frequency response than to normal distortion profiles, so (assuming the described differences are real and not effects of peeking and level-matching) look there first.
57gold
Active Member
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Finally something I have decades of experience with, "tube rolling". To conclude with a couple of distortion measurement tests that different tubes can't impact sonics is pretty weak.
I have spent many hours selecting between various Amperex, Mullard, RCA, Telefunken...tubes for my several guitar amps and know that they have dramatic and repeatable impacts on an amp's sonic performance. Not surprisingly, the tube with the most "tube rolling" sensitivity is the first tube in the circuit that sees the instrument signal. And, the simpler the circuit, the more the tube selection matters (a three preamp tube circuit like a 1959 Fender Tweed Deluxe is very revealing of tube choice versus a seven preamp tube Mesa Boogie, which is less sensitive, but the first tube is still very significant).
If tests do not measure these sonic realities, then the tests aren't measuring the right performance aspects of the circuits.
I have spent many hours selecting between various Amperex, Mullard, RCA, Telefunken...tubes for my several guitar amps and know that they have dramatic and repeatable impacts on an amp's sonic performance. Not surprisingly, the tube with the most "tube rolling" sensitivity is the first tube in the circuit that sees the instrument signal. And, the simpler the circuit, the more the tube selection matters (a three preamp tube circuit like a 1959 Fender Tweed Deluxe is very revealing of tube choice versus a seven preamp tube Mesa Boogie, which is less sensitive, but the first tube is still very significant).
If tests do not measure these sonic realities, then the tests aren't measuring the right performance aspects of the circuits.
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