My question regarding the airyness is because it is not always easy to find a compromise that doesn't... compromise the initial beauty of this amp (and that's the case for many units once you start tweaking).
I found that units often work around an optimal plateau, a king of short segment where things are equaly perfect and satisfying. So there isn't a sweet spot, a unique point where all parameters are right at a given level. More a segment where along its line you can find equaly satisfying "trade offs", all as nice sounding although sounding slightly different. The parameters to balance here are speed attack vs boomy, airynes vs nailed soundstage etc. And f course there are plateaus/ segments located at different "heights", reflecting in my view different overall levels.
IF you manage to make a big step, you can rise an entire plateau / segment and reach another level where all is better, along a new line of sweet spots / compromises.
I have the feeling I have now managed to raise the level to another plateau, higher, so everything is better. But where I am now is at the edge of such a plateau, where I would not want to sacrify more bass groove and airyness for anything else, whatever it is, FOR THIS AMP. I could do it, to gain elsewhere, but it would simply take out the magic of the amp and make it an ordinary amp similar to some Class D we have. Very good everywhere, excellent nowhere, little personality, little fascination.
So I won't. I have now enhenced up to a satisfying level the drive, dynamic and precision that I found somewhat perfectible initialy. I don't want or need more on these. I have gained maturity, wouldn't want more if it is at the cost of the joyfull kid. All coming tweaks are now towards the joyfull kid, that is here in this case IMO more groove and more airyness, or whatever defines the VFET...if it is possible. IF not, I am still on the narrow segment with an excellent, decently neutral but also very fine music representation. I still have at least 2 tweaks to try
Just all IMHO and IME, it is a balancing act and also a matter of taste of course, like cooking, fascinating... good we have a Chef and many cooks of various levels (mine being low) willing to learn cooking and shatre their experience.
As said, great community and fascinating...
Claude
I found that units often work around an optimal plateau, a king of short segment where things are equaly perfect and satisfying. So there isn't a sweet spot, a unique point where all parameters are right at a given level. More a segment where along its line you can find equaly satisfying "trade offs", all as nice sounding although sounding slightly different. The parameters to balance here are speed attack vs boomy, airynes vs nailed soundstage etc. And f course there are plateaus/ segments located at different "heights", reflecting in my view different overall levels.
IF you manage to make a big step, you can rise an entire plateau / segment and reach another level where all is better, along a new line of sweet spots / compromises.
I have the feeling I have now managed to raise the level to another plateau, higher, so everything is better. But where I am now is at the edge of such a plateau, where I would not want to sacrify more bass groove and airyness for anything else, whatever it is, FOR THIS AMP. I could do it, to gain elsewhere, but it would simply take out the magic of the amp and make it an ordinary amp similar to some Class D we have. Very good everywhere, excellent nowhere, little personality, little fascination.
So I won't. I have now enhenced up to a satisfying level the drive, dynamic and precision that I found somewhat perfectible initialy. I don't want or need more on these. I have gained maturity, wouldn't want more if it is at the cost of the joyfull kid. All coming tweaks are now towards the joyfull kid, that is here in this case IMO more groove and more airyness, or whatever defines the VFET...if it is possible. IF not, I am still on the narrow segment with an excellent, decently neutral but also very fine music representation. I still have at least 2 tweaks to try
Just all IMHO and IME, it is a balancing act and also a matter of taste of course, like cooking, fascinating... good we have a Chef and many cooks of various levels (mine being low) willing to learn cooking and shatre their experience.
As said, great community and fascinating...
Claude
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Yes, the delightful upper end is still there – airy, clear and easy to listen to. Maintaining this with the Dreadnought cards initially did require some perseverance. I knew the output stage needed to have R15 fully bypassed, and getting the rest of the sound to balance out required a few iterations of the key feedback capacitors. One of the variations simply didn't work, especially with one recording. I listened to that CD again this morning, and it sounded like I had a different amp. The right combination of tweaks on the Dreadnought cards plus the extra supply capacitance on the main power rails made a big difference.
This post is perhaps more directed to Papa (if OK), but of course anyone shoudl feel free to reply to it...
Mentioning the B1 Korg and remembering how the sound changed with bias, I am wondering about the effects the 20V bias can have on our VFET amps.
How does that work?
Does it make sense to play with this setting?
Is there some margin (eg between what safe values can we play)?
What can one expect going in one direction or in the other soundwise?
Also wondering if the setting is altered if I change slightly the PS voltage (say if due to additional filters I go from 35.8V to 35.6V at the OS boards, do I need to adjust the 20V again)?
Many thanks as ever, just trying to learn, not saying I will play the wizard apprentice, more for my understanding at this stage
Claude
Mentioning the B1 Korg and remembering how the sound changed with bias, I am wondering about the effects the 20V bias can have on our VFET amps.
How does that work?
Does it make sense to play with this setting?
Is there some margin (eg between what safe values can we play)?
What can one expect going in one direction or in the other soundwise?
Also wondering if the setting is altered if I change slightly the PS voltage (say if due to additional filters I go from 35.8V to 35.6V at the OS boards, do I need to adjust the 20V again)?
Many thanks as ever, just trying to learn, not saying I will play the wizard apprentice, more for my understanding at this stage
Claude
I'm currently running mine with 37.0V incoming from the external linear PSU, and Vds across the SITs is set at 20.25V. Probably fairly inconsequential differences, but the amp sounds very good this way.
I have taken the precaution of having one diode in series with the V+ power on my Dreadnought cards. This is to protect the opamp during the initial PSU voltage ramp up and hopefully to guard against accidentally wiring power backwards during the many times the boards have been in and out of the chassis.
I have taken the precaution of having one diode in series with the V+ power on my Dreadnought cards. This is to protect the opamp during the initial PSU voltage ramp up and hopefully to guard against accidentally wiring power backwards during the many times the boards have been in and out of the chassis.
During my original setup of the VFET amp I measured the 20V on the wrong Zener (stupid, I know!) and gave the amp a listen for about two hours. We LOVED the sound with my wife. Really it was something else to what we had been used to.
Later on, upon realizing my error, I went and measured what that 'meant' in terms of current, and the voltage on the 'right' Zener was around 18.6V.
I am not sure what that meant in terms of power, in terms of heat (it was REALLY hot!) or in terms of distortion. I think that with 20V the heat is a little less (not sure), cannot comment if the sound is better or worse.
I do know that we loved the sound when voltage was at 18.6V, whatever that means .
We also love the sound at 20V, not sure there is a difference. I just know that the sound with 18.6V was really nice, also!
Rafa.
Later on, upon realizing my error, I went and measured what that 'meant' in terms of current, and the voltage on the 'right' Zener was around 18.6V.
I am not sure what that meant in terms of power, in terms of heat (it was REALLY hot!) or in terms of distortion. I think that with 20V the heat is a little less (not sure), cannot comment if the sound is better or worse.
I do know that we loved the sound when voltage was at 18.6V, whatever that means
.We also love the sound at 20V, not sure there is a difference. I just know that the sound with 18.6V was really nice, also!
Rafa.
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