Favourite master for cathodyne PI's

[phsyconoodler]

What are the feelings about master volumes for the cathodyne PI?
  I'm putting one on my latest build but wanted to get some opinions on people's favourite ones.It's basically a Princeton Reverb with a couple of tweaks.
  Cheers.

[chocopower]

Hi!
I was thinking about the same.

Right now i´m using the Matchles way in my Green Bullet.

schem:
http://picasaweb.google.com/davidageitosfuentes/GreenBullet?authkey=Gv1sRgCN6Bwp3Ql576Lw#5531371600280562306

topic:
http://www.el34world.com/Forum/index.php?topic=8349.msg94519#msg94519

I don´t like it. Too thiny sound.

Maybe if i wire it before the two PI output caps (.022) and feed the pot with .220 pair it get a better sound...

just me and my imsonia.....

[Fresh_Start]

I tried a cross-line PPIMV in a Princeton Reverb circuit too and didn't like it.  By the time it made a noticeable difference in volume, the tone lost something.

Cheers,

Chip

[sluckey]

This just came up a few days ago...

[phsyconoodler]

It looks like you replace the 1meg with the 500k pot,change the 1k to 1.5k and splice the connection,then run the wiper to the grid.Correct?

[sluckey]

Yep. Except, don't bother changing the 1K to 1.5K. This drawing was specific to a 5E3.

[phsyconoodler]

Thanks Sluckey.That one works pretty good?

[LooseChange]

This just came up a few days ago...

I don't know about that one... DC on the pot... Gonna make some noise!

[sluckey]

DC on a pot is only an issue IF  it causes current to flow thru the pot.

[phsyconoodler]

What about this one;

[darryl]

This is an amplifier I described here a few months ago. It has the master volume arrangement I use in most of my designs.

[phsyconoodler]

Interesting.What are the 27v zeners for?

[sluckey]

What about this one;

YIKES!   

[phsyconoodler]

Ha Ha Ha! I suck at drawings.

[darryl]

Interesting.What are the 27v zeners for?

The 27 volt zeners have two purposes:

1. The zener voltage is set so with the master volume at max, the PI and output stages can be overdriven, but not to the point where the cathodyne is generating really harsh distortion.

2. As the master volume is turned down, the power output of the amplifier is steadily reduced by the symmetric clipping effect of the zeners. This clipping is easily achieved, without the additional gain stage which would otherwise be necessary to generate distortion, by overdriving the stage before the master volume.

The distortion generated by the zener clipper is not as smooth as genuine output stage overload, but still sounds acceptable ( to my old ears  :icon_smile: ).

[topbrent]

The ÷13 (Divided by 13) CJ-11 uses a Ken Fischer type II. Known these days as the LarMar type MV.  
On this drawing, conger calls it a cross-line, but I believe he is incorrect in his terminology.  


Very Cool little amp regardless.

[Fresh_Start]

The one chocopower linked to in the 2nd post is a crossline.  IIRC Ken Fisher called this one "type 2".

Cheers,

Chip

[Shrapnel]

This just came up a few days ago...

I don't know about that one... DC on the pot... Gonna make some noise!

Not really any different than the usual gain or volume pot that acts as a grid resistor as well. Only real difference is the "ground" potential is elevated to a more normal working bias voltage position.