Cavalli OCL Buffer

[Dxvideo]

Hi all,

As a group of Turkish DIY ers, we started a common project that a clone of Cavalli OCL Buffer with DC servo;
http://www.cavalliaudio.com/oclbuffer/main.php?page=diy
With my PSU design, the total application schematic will be like that;

And the PCB design I made;

Now I am waiting for your precious comments on this..
Thanks a lot for your advices in advance..

PS: Were using Russian 6N6P instead of ECC99 tube.

[Zen Mod]

not as complain but more as reminding - draw on schematic grid to gnd resistor , to prevent possible confuse .

beside that - having grid resistor is always good , in case that anything goes wrong with pot contact ; not of much importance here , where triode is biased with CCS , but anyway ....

also - grid stopper is good thing to have

on link you gave - bootstrapped (cascoded) version is certainly better ( not just in test , but soundwise too) ; then it's real SLCF , as Alan Wright like to call it , and you squeeze all quality possible in that stage .

[Dxvideo]

Actually I was thinking about to put a grid resistor too! Thanks for reminding.
And concerning the bootstrapping issue;
I have tried a bootstrap like in this application with Pedja Rogic's famous JFET buffer stage however I found its sound a bit dull. Then I've removed the bootstrap and connect the input JFET directly to the Vcc (like this application) then the trebles came back again. May be the bootstraped version was more musical and the non-bootstraped was more boring...
Anyway, I can add a space for bootstrap to the PCB, who wants to add bootstrap just solder a MOSFET to here..
Thanks for your comments again.
More?

[Gordy]

An interesting project for you. However my guess is that your power supply with just CRC will give too much ripple. I suggest more RCRC, or even better to use a TL783 for a regulator.

[Gordy]

C14 and C15 are close to V1, so will they get too hot?

[Shoog]

Allan Wright claims that every mosfet replaced by a valve brings sonic benefits. My experience says I am inclined to agree with him. Unfortunately it makes the voltages a lot higher and the need for two twin triodes for a full SLCF.

Its possible to achieve a decent CCS in the tail by using a voltage divider from +B down to about 20V and then referencing a triodes grid to that. This then allows you to include a much bigger cathode resistor. This impedance is multiplied by the triodes mu and you have a decent and adequate impedance CCS. I did the same thing but with a pentode as the CCS element for a much higher output impedance. I used a simple mosfet regulator for the screen and the same resistive reference chain raised the grid to 30V. Works a treat.

This is not meant as criticism of your circuit, just passing on my experience

Shoog

[Dxvideo]

Thanks a lot for your comments.

Dear Gordy,
- I will move C14 and C15 more distance place against the tubes heat.
- About the CRC filter for B+.... I am confused about that because in the simulation I saw -40dB @100Hz. Isn't it enough you think?

And Dear Shoog,
I think I am not good at tube designing. And this is not my design. So I think I cannot make a critical modification the on design.

[Gordy]

Originally posted by Dxvideo


- About the CRC filter for B+.... I am confused about that because in the simulation I saw -40dB @100Hz. Isn't it enough you think?

Perhaps reality will match the simulation.
In my own Cathode Follower I used a regulator (TL783) and it was fine. Maybe I worry too much? Maybe your CRC will be enough when combined with the PSRR of the CF.

[Karsten Sømand]

Maybe I´m missing something here, but wouldn´t it be very beneficial replacing the CRC with Salas´ very exciting regulator?

Karsten

[Dxvideo]

What benefits should we expect with adding a regulator to B+ , do you think?
And whats "Salas' very exciting regulator", is it a special thing?