Tube amps - what 3 things…

Hi @ideal8592 ,

In my case 100uf/16v were Black Gate CE W (M).

10000 were the same Black Gate  + Nichicon Muze 10000uf/16v.

100000 were the same Black Gate, Nichicon Muze + Nichicon KA 9x10000uf/16v + Elna 3300uF/10v

It wasn't my "invention". At least dozen DIY people tried it many years before me. You can try yourself and it works!

Hi @atmasphere ,

In my case cathode resistor was 820 Ohm, so:

with 100uF  - f = 2Hz,

10000uF - f = 0.02Hz

100000uF - f=0.002Hz

In theory, even 100uF is good enough. But in the real life the difference between 10000uF and 100000uF is very clear and significant.

Thanks very much for your input Ralph. The designer/builder of our custom amps told me that fixed bias provides more "snot" than cathode bias. He meant power by snot. I know you’ve stated in this thread that there is no power difference between these two biasing configurations. Can you please discuss the bias configuration elements related to power magnitude?

I’m very confused as I view both he and you as extremely well on informed on this subject so am quite puzzled at how such diametrically opposed assertions could come from you and he.

Thank you.

The designer/builder of our custom amps told me that fixed bias provides more "snot" than cathode bias. He meant power by snot. I know you’ve stated in this thread that there is no power difference between these two biasing configurations. Can you please discuss the bias configuration elements related to power magnitude?

@xenolith 

Fixed bias does have that reputation (and FWIW, we use it in our amps as well).

The power output is the same for a given bias point, but for cathode bias you need a higher power supply voltage since a voltage is dropped across the cathode resistor and that might have to be 30 or 40 Volts in a lot of cases.

The cathode resistor has the additional issue, if its unbypassed, of creating degenerative feedback. This makes it harder to drive. The feedback means it will be lower distortion, but that might not mean much if the driver circuit makes more in order to drive it.

So there are a lot of variables and each has to be managed properly to pull it off. I would expect it to be pretty difficult to do a side by side audition if that were the only variable, on account of all the secondary variables involved.

@alexberger 

The ESR would be quite different with parallel caps... and topology counts