Fixed bias/battery bias question

[6A3sUMMER]

Chris Hornbeck,

Either way to float it is OK, as long as an unintentionally placed ground does not short out the battery.

I like your idea, but I do not plan on building a phono preamp now.
I am relatively happy with the one I have.

 

[Chris Hornbeck]

Yeah, I've got 50 feet of records - no lie - but rarely play one. I'm old enough that CDs sound just fine to me. They probably always did, and that's my story and I'm sticking to it.


Phono equalizers are fun challenges though, so a certain tingle remains. Fun to look at these little hot spit Russian pentodes with 15mA/V and very low 1/f and think about punching some holes in chassis'.


All good fortune,
Chris

 

[Magz]

One more variant, which I'm using in my 26/01A preamp/DAC. Similar to variant C but with an input transformer so no blocking cap is needed. The two caps shown in the schematic are an RC snubber across the transformer and an optional 10nF across the battery for ultra high frequencies to bypass the battery to ground if you're concerned about that.

 

[Hificat]

Interesting idea, what if use here Sowter 9335 attenuator?

 

[kevinkr]

I use battery bias extensively in my phono stages, but I also use CCS on the stages that are fixed biased so I have some idea of the actual operating point in that stage.. Anyone else?

It is certainly a better option than cathode bias and large el caps with high transconductance triodes and pentodes. (even without CCS loading)

Another option is infra-red LEDs for cathode bias. (devices with a Vf of 1.2V can be found.)

 

[kodabmx]

I did that with a power amplifier. The result was disgusting. A crossover notch that was almost 50% of the music cycle. Apparently, they played off of each other.

 

[Hificat]

Kevinkr, From my experience leds and diodes on cathode have their flavor to the sound, very dynamic though. I do try battery on gridleak its unlike diodes very neutral