5E5 power supply mod

[stephenhartley]

Hi - a couple of questions re 5E5.

I bought a set of Hammond transformers including a choke when I was deciding whether to build a 5E5 or 5E5A. I've decided on a 5E5 with switchable fixed/cathode bias. Can I safely use the choke in the 5E5 by copying the power supply in the 5E5-A and similar amps such as the Super 5E4-A? i.e the choke between the first 2 power caps and 10k resistors between the 2nd & 3rd and the 4th & 5th? Also what's the spec of the diode in the fixed bias circuit then I can order one.

So far, I've built the chassis and made the eyelet board

Thanks

Stephen Hartley

[Jazz P Bass]

1N4007 will work fine for the negative bias voltage.

[frus]

What's the max current rating for your choke? 5e5-a, 5f4, 5e7 have the plates connected after the choke, so it has to be able to withstand the plate current (plus screens + preamp currents). I think the spec is 200mA (not 100% sure?)

You can always connect the plates before the choke (like swapping the 2500 resistor in 5E5 with choke) if its rating is lower. All the later amps (5F6A, blackface etc) had them connected like that. I've built a 5F4 and like it better that way (less sag) but that's individual preference of course

[stephenhartley]

Thanks - the choke is a Hammond 194A - 4H @ 50mA DC so I'll use it in place of the 2500 resistor as you suggest - I'll order a diode.

[isaac]

Stephen you are probably much better off to order 100 or so diodes, because they can be used in any rectifier pretty much, lots of pedals, tons of things, and they aren't expensive. Just a tip. Also you might find it worth buying an original style choke so you can put it in front of plates. The sag is part of the tone for sure. It all depends. I built a 5e7 bandmaster, but I don't have the choke, and while it sounds great, it almost loses the tweedish tones because its so crisp and good, I was hoping for a little more sag, but it sounds great. I also used a solid state rectifier, so that probably didn't help too much, but it sounds great.

[stephenhartley]

Thanks - I'm making it with switched fixed/cathode bias for a bit more clean headroom to use with bass. I found a couple of schematics for the switch after advice on here - it took me a couple of hours to suss out how to physically wire it up - there are a coupe of variations out there which confused me - I've made it to fit the 4x8 cab of my first build.