5E3 based amp

[stephenhartley]

Just finished my first ever amp build - in fact my first go at proper electronics of any kind. The circuit is largely 5E3 with a few tweaks and Bruce Collins' tone mod. I've built the cab using 2 old Wharfedale 6" alnicos and 2 Jensen 8" alnicos - I'm working towards a scaled down Bassman type idea.

I've had quite a bit of tweaking to do to get it working (rerouting mains cable, replacing a couple of resistors and a cap) and now it sounds great - no hum.

Thanks for all the help and advice on here - particularly from Bruce Collins.

Just one question - before I found the faulty cap, I had to use a 500 ohm cathode resistor to get 42 mA on the output tubes.

With the cap replaced, the amp sounded loud clean and bright, but was only giving 22mA at the output tubes - I rebiased it to give 32 mA using 220R (Gerald Weber recommends 30 to 40 mA in his book) and now it's quieter with earlier breakup. I actually prefer the louder cleaner sound. Will I damage the output tubes running them at 22mA? (they're a matched pair of Russian military grade 6V6s)

[loudthud]

No problem running at 22mA if you like that sound.

[stephenhartley]

5E3

Thanks for that - I've just been reading about using 6L6s in a 5E3. I'll stick with 6v6s for now and maybe try a 5v4 rectifier.

[Bruce / Mission Amps]

Thanks for that - I've just been reading about using 6L6s in a 5E3. I'll stick with 6v6s for now and maybe try a 5v4 rectifier.

I've had a few player customers that liked their 5E3 amps with 6V6s and cooler cathode biasing. What ever sounds good to you IS GOOD.
I ran one for myself for months with a 390 ohm 10 watt cathode biasing resistor, a GZ30/(Russian 5Y3GT) and a 2k2@2 watt screen node resistor... it still was a little hotter then I expected, but sounded great into a reissue P12Q.

[Chuck H]

Fixed bias at 22mA should be even more of what you like about the cooler bias. Not too hard to build a bias supply.

[pdf64]

I rebiased it to give 32 mA using 220R (Gerald Weber recommends 30 to 40 mA in his book) and now it's quieter with earlier breakup

It's unlikely to be louder and cleaner with a 500ohm cathode resistor; are you sure something else hasn't changed, eg cathode bypass cap bad or dry jointed, etc?

[stephenhartley]

5e3 build

I've just put the cathode resister back to 500R and it sounds wonderful - clean shimmering Fendery sound with lots of headroom with lovely response to my distortion and delay pedals and nice break-up at louder values - am I likely to do any damage if the cathode bypass cap isn't working?

I will check the cathode bybass cap - I've been puzzled why it's needing such a big value cathode resistor when the stock circuit one is only 250R.

I'm going to stick with the cathode biasing for now - I like the idea of a bit of sag.

Thanks for the helpful suggestions