DAC - tube gain stage w/ AC heaters

[regal]

Building a 6N6P tube gain stage which takes a 200 mV p-p input signal. CCs plate load gain =22.

I had planned on using AC for the heater but am having second thoughts, should I place a Digikey order to build this as DC heated?

[dsavitsk]

Give it a try and see what happens, but I generally use DC in this position. Note that if all you have is a 6.3VAC winding, unless it is way overspec'd in terms of current, you will have trouble getting 6.3VDC.

[poynton]

My tube output stage for the Marantz CD63 used AC heaters with no hum noticed.

Andy

[Tweeker]

Float the heaters +30VDC from a voltage divider from B+ and use AC (or DC, either way floating the heater reduces noise coupling to cathode).

[regal]

Yes a planned on floating the AC heater, the transformer doesn't have a heater CT but I will just tie one end to the B+ voltage divider.

With amplifiers I have built in the past even when floating the AC heater, I still measure a -60db bump around 60 hz. I can't hear it but only measure it. My concern is feeding the amp with a tube DAC that also has this bump, the 60 hz hum may be multiplied.

[zigzagflux]

I use that exact tube in a differential pair immediately following the I/V resistor (RAKK DAC II).

Originally used DC, elevated 35V. To conserve space and eliminate harmonics and heat dissipation, I converted over to AC. Absolutely zero hum.