any happy cathode biased d-style ampusers?

[Baltar]

Hi!

Anyone ever try this and kept it that way?
Just curious. due to i have the idea to build some d-style cleans amp,
but somehow can't let go the 4x6v6 cathode biased idea.

Cheers
Martin

[10thTx]

I think Physconoodler built several staying true to the Dumble designs with the exception of making them cathode biased?

Here are several amps that are based around Dumble designs but are cathode biased. Here is one:

https://tubeamparchive.com/viewtopic.php?t=13487

http://www.el34world.com/Forum/index.php?topic=10719.0

Some schematics and layout here:
http://www.el34world.com/Forum/index.php?topic=9498.0

And something loosely based on the D-style amps but with a 5879 in the second gain stage of the overdrive is this Tweed Overdrive Special:

https://tubeamparchive.com/viewtopic.php?t=12107

http://www.el34world.com/Forum/index.php?topic=9638.0

Some schematic and layouts here:
http://www.el34world.com/Forum/index.php?topic=9636.0

With respect, 10thtx

[Baltar]

thanks 10thTx

[Chris333]

Not a build, but the Fuchs ODS 30 is cathode biased. Nice squishy feel without being slow, if that makes any sense...

[Dr d]

Hi, I have a 4x6v6 Bluesmaster cathode biased. True to recent scheme/layout, only cathode biased. Sounds gorgeous to my ears and less strain on the JJs.

[pullshocks]

2x7591 cathode biased. Sounds fine to me, but we will see how it stacks up at the Portland d-fest against more "authentic" amps

[Baltar]

Not a build, but the Fuchs ODS 30 is cathode biased. Nice squishy feel without being slow, if that makes any sense...

cool, i didn't know that

Hi, I have a 4x6v6 Bluesmaster cathode biased. True to recent scheme/layout, only cathode biased. Sounds gorgeous to my ears and less strain on the JJs.

how would you judge your loud cleans and semicleans? do they stay crisp?
i tried to cathode bias a ab763 based 6v6 for testing and found the output to be way too undefined

2x7591 cathode biased. Sounds fine to me, but we will see how it stacks up at the Portland d-fest against more "authentic" amps

interesting choice.

cheers, Martin

[Dr d]

Hi Baltar, I am really happy with the cleans on my amp. They are beautifully balanced and "crisp" enough for my ears !!! Responds well to pedal effects also. Chorus and wah sound spectacular.

[pullshocks]

The cathode bias 7591 was dictated by use of an Eico Stereo 40 as a donor amp. I just hooked the stock Eico PA circuit to the d-style phase inverter. Possibly not the most optimized setup, but good enough.

It does provide a good measure of clean power, but I don't play out any more and don't know how it would stand up in a band setting

Eico info can be found here

http://w3.uniroma1.it/chemo/image/hifi/ ... e12-a3.png

[Baltar]

@Dr D, just curious how much B+ do you run your 6v6?
I've read once, that cathode biased shouldn go higher than b+ of 350v.

@pullshocks, sounds like a cool setup. any clips? never heard 7591 myself

cheers, martin

[da Geezer]

Here's a clip of my Tweed BluesMaster 50w, non-HRM, 5881's cathode biased. Kleinulator in the loop. OD only on this clip.

http://soundcloud.com/dageezer/tweedmas ... gain-floyd

[Dr d]

Hi Baltar, my B+ is @ 430v. I ground the JJ's in pairs, each pair via a 470 ohm resistor bypassed with a 22uf 100v cap. Everything looks good on the scope (according to my tech!) . Hope this helps.

[brewdude]

Hi Baltar, my B+ is @ 430v. I ground the JJ's in pairs, each pair via a 470 ohm resistor bypassed with a 22uf 100v cap. Everything looks good on the scope (according to my tech!) . Hope this helps.

Please excuse my ignorance, I don't have any experience in a 4x6V6 cathode bias push pull amp, but it seems to me that 470R per pair would bias the PA rather cold, wouldn't it.

I was under the impression that ~250R would be suitable per pair of 6V6's. Or, does the rather high B+ demand a higher cathode resistance. I apologize if I am of base, I have not looked at any data sheets or attempted any calculations.

[Dr d]

Hi Brewdude, By my calculations at 430v B+ and a cathode voltage of 30v, cathode current = 30/470R =0.063 amps. This is shared current so 0.063/2=0.031amps. 430-30 = 400v plate voltage. Therefore plate dissapation in watts equals 400v x 0.031amps =12.8watts. Max plate dissapation for JJ 6V6 =@14-16watts. This means they should be running at about 80% which some might argue is a touch on the hot side for a Dumble design. Hope this is accurate!!!

[Baltar]

Here's a clip of my Tweed BluesMaster 50w, non-HRM, 5881's cathode biased. Kleinulator in the loop. OD only on this clip.

amazing sweet singing!

Hi Baltar, my B+ is @ 430v. I ground the JJ's in pairs, each pair via a 470 ohm resistor bypassed with a 22uf 100v cap. Everything looks good on the scope (according to my tech!) . Hope this helps.

wow, 430 is a lot for 6v6. but the JJs should take it.
thanks for sharing.

cheers