Turtlerock Forum

Hi all,

I'm in the planning stages of building a tube amp PP 6V6. At this stage the plan is to not use a tube rectifier (although I am still open to this).

But, assuming I do not use a tube rectifier, do I need to use a choke if I have a solid state (bridge) rectifier?

Thanks

Gian, is this for a guitar amp? ... if so then no you do not need a choke, the choke resists change in current and effectively acts as a filter to the power supply ripple. With a full wave bridge rectifier and a largish cap, say 470uF, this should work well in a guitar amp.

Hi Michael, yeah, its for a guitar amp. My thinking is that I don't need one if I have a large-ish cap and solid state bridge rectifier.

Gian, you don't have to use a choke but it has advantages over a resistor. It gives better power supply filtering. But the inductance and DC resistance value of the choke is important. The DC R becomes important as far as the valve screens are concerned.
You don't want to exceed the 6V6's max screen voltage rating and I don't think its a good idea to have the screen voltage higher than the anode voltage. The choke DC R needs to be large enough to get the required voltage drop across it.
And if it isn't, its better to use a resistor. I recently re built a Ceriatone Matchless spitfire clone. The original used a choke but the HT volts were so high that choke wouldn't drop enough volts for reasonable safe operation of the EL84's, so I had to use a resistor.
In some Fender 2 x 6V6 amps 4.7k was used, but in even earlier versions it was much higher and in others it was 1k
I recommend you try btwn 4.7k & 1k 2W, taking into account screen volts as per above. The second resistor in the HT power supply chain being typically 22k.
Also if your HT volts are on the high side it is a good idea to include the two separate resistors that directly feed the screens (see Deluxe AB763 schematic.) The earlier 5E3 didn't.

Hey Ross, thanks. I appreciate that info. I always find I have to tinker with the screen resistor, as you say, so screen voltage is lower than anode voltage.