Good PT for 5E3 type build with 5881?

[Muttleyboy]

Hi,

I have some extra parts, and I'm thinking of putting a 5E3 build in a Valve Junior boxand chassis. I have a vibrolux OT and a 4 ohm cabinet.

I'm not really looking for it to be much louder than a stock 5E3, but I'm thinking that with a 6L6/5881 (or possibly EL34) type tube the amp may have a bit more extended highs and lows. I'm looking for a PT that would be 350V to 370V in the circuit, and be able to handle the higher current of the larger tubes.

[tubeswell]

Hi,

I have some extra parts, and I'm thinking of putting a 5E3 build in a Valve Junior boxand chassis. I have a vibrolux OT and a 4 ohm cabinet.

I'm not really looking for it to be much louder than a stock 5E3, but I'm thinking that with a 6L6/5881 (or possibly EL34) type tube the amp may have a bit more extended highs and lows. I'm looking for a PT that would be 350V to 370V in the circuit, and be able to handle the higher current of the larger tubes.

For cathode biased 5881s in a 5E3 type amp, to get about 360-380 volts on the plate, I would guess you'd want about 270-0-270 to 280-0-280 @150mA-180mA with SS rectification or around about 325-0-325 @150mA-180mA with a 5U4G for some sag. I'd suggest that the heater winding be rated about 4A (and a 3A rectifier winding for the 5U4). These are all fairly crude guesses and JM2CW

[10thTx]

I agree with Tubeswell. Look at a Hammond 270FX or 270HX power trannie. I use a 270FX with a cathode biased amp using 5881's.

With respect, 10thtx

[Lonely Raven]

I agree with Tubeswell. Look at a Hammond 270FX or 270HX power trannie. I use a 270FX with a cathode biased amp using 5881's.

With respect, 10thtx

I think I might have one of those in storage I'd let go inexpensively. I don't have as much time or money to build the amps I bought transformers for. I'd rather finish the work I have now.

If this is the power transformers you decide on, PM me and I'll see if I still have it tucked away somewhere.

[Muttleyboy]

Hi Tubeswell, Hi 10thtx,

Thanks for the replies... Yeah I forgot to say that I'm going to want some tube rectifier sag, and that I'm hoping to get around 350V with a 5Y3 and then experiment with other rectifiers for some higher voltages (under 400v).

I saw on the allen amps site that they have a PT for the Brown Sugar model which they rate as 320V and 180mA. The description goes on to say that in the circuit, it should be 410V with a gz34. I'm thinking that may be too much.

10thtx, with that hammond 270fx, are you using a tube rectifier and what is the B+ voltage in the circuit?

Thanks again,
-Chris.

[10thTx]

275vac X 1.2 (5V4 recitifier) = 325v estimated

275vac X 1.3 (GZ34 rectifier) = 350v estimated

275vac X 1.4 (solid state rectification) = 375v estimated


You can step up to a 272HX trannie for 300-0-300 & use a GZ34 for around 390v.


While Silvertone did it, you probably do not want to use a 5Y3 with 5881 or 6L6 tubes that are push/pull cathode biased.

With respect, 10thtx

[Muttleyboy]

Hey Thanks 10thTx,

That sounds like it should be the one.