K&K Audio / Lundahl Transformers

AC/DC heating with series feed

24.106.50.158

Thought a new thread might be recommended at this point.

6n6p series feed with LL1689AM/PP. Heaters are currently using regulated DC voltage from a home brew choke input supply to LM1086 regulators.

Also working on a second project, a 5V DC supply to feed 300B filaments. Very future project, likely a Karna amp. Got the prototype completed last night, and started poking around with the scope, to make sure my supply is quiet. Found significant RF hash on the output due to rectifier switching/choke ringing, exactly like what is described in Morgan Jones' book. I'll be posting at DIY for some assistance on this front.

However, this made me poke around a little bit in the series feed amp, in which I discovered the same problem. RF has always been my enemy, and I'm not very good at taming it. If I get any success with the 5V 300B supply, I'll use the same solution here, but for now, I'm considering the possibility of just going with AC heating on the series feed.

So my question is, what do you use, AC or DC for the 6n6p? Being this is my first stage past the RAKK DAC, I want to ensure hum-free operation. I would use shielded twisted pair for the heater lines, of course, and elevate them by 30V.

Thanks.

Follow Ups:

RE: AC/DC heating with series feed - KevinC 07:45:25 10/10/07 (1)
- RE: AC/DC heating with series feed - KurtP 10:15:59 10/10/07 (0)
RE: AC/DC heating with series feed - AndyN 06:08:02 10/10/07 (1)
- RE: AC/DC heating with series feed - KurtP 07:14:46 10/10/07 (0)

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