gofar99 wrote:
For all you folks who abstain from DC heaters these amps use AC.
HT Performance wrote:
I´m also using AC heaters on my EL34 Oddwatt. It´s amazing how it sounds. There is absolutely no hum at all!
HI.
I agree provided the AC supply is done
properly.Like my
Dynaco ST-70 also used AC heaters supply. Twisting pairs of wires to the tube heaters go without saying.
What I installed addtionally something crucial is a common mode AC noise filter to heater group of EACH channel. The AC noise filtler comprised 1
bifilar handwound coil on a small wooden form & an
AC film filter bridging the O/P leads of the coil. Bifilar winding is a must for any common mode noise filter.
Since the AC current is pretty large to go thru the coil, so the magnet wire used to wind the coil should not be too small. I used AWG #18, something I got in my part bin. The 2 small wooden forms were I DIY 'handcrafted' to size to fit the already very conjected space available underneath the metal chassis of the power amp.
Length of the manget wire is custom cut to provide only a small faction of a volt in order not to offset the required 6.3V heater voltage.
I need to install such RFI noise filter as the tube heaters in my phonostages are DC cells powered rechargeable by a SMPS which may emit RFI noises to the power amps. Besides common mode helps to cut down hum noise going thru the heaters.
c-J