Just finished up a build that I'd been thinking about doing for a month or two. A single EL84 being driven by an ODS type pre, minus tone controls. I really dug Mat's SE EL84 amp, the "Revenge of the miniHRM!!", and drew inspiration from there. I wanted to simplify my design and since I'm using a Bud chassis with what I consider limited space, I wanted it to be simple and not employ tone controls, save for a NF pot. Other than that, nothing but volumes. I also included a manual toggle switch that removes the second and third stages as well as the final volume control so the amp can get as open of a clean sound as possible. Just fired her up yesterday and after a couple of touchups, I have to say I'm very pleased. I was going for more of a classic ODS (70s) tone and wanted the drive to be more raw, which this most certainly is! I also included a passive loop. Tube rectified with a TAD GZ34 right now. Two TAD 7025s and a JJ EL84 were also used for start up. Hope you guys dig!
DK
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I would love for you to play it! Just a quick couple thousand miles.
The hum's very reasonable for what's going on in there when playing in high gain mode. It gets pretty nasty when the volumes before the master get way up there, but that doesn't sound very good anyway IMO. The settings I've come to really dig have pretty low hum.
Well, I used the tube rect to employ the 5v winding on the PT and avoid using another board in there for diodes. I also like tube rects. As they say, smoke em if you got em.
Didn't use a hum balance pot. Excess noise isn't an issue in this amp.
eniam rognab wrote:you stole my idea for a keyed switch!!
what happens if you lose the key? jumper with a screwdriver?
Didn't steal shit!
If you lose the key, you simply play Stairway To Heaven and the amp will light.
Here's a pic of the amp re tubed as I was playing earlier...
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Nice build!
I always raise the heater reference on my SE builds to the cathode voltage of the output tube. That usually helps alot with hum and is very easy to do.
Planning to do any soundclips?
Thanks guys. Interesting ideas for the heaters. I did a clip yesterday and had the overall volume at a good level and the hum was negligible. I was fooling around with one of the echo units I just posted in FS, so please forgive the pauses while I noodle with it. I think the likeness of the amp was captured very nicely and accurate to what I hear in person, even though I just used my phone. I need to do a clean and mean recording next. Hope you get through it all.
To kill the hum I add an extra filter stage at the front end of the power supply and run the output stage through it. So a 33uf, 100R 33uf use this point as your B+ and then in to the rest of your PSU.
This way the output tx will see little ripple and the amp will be quite. I guess your amp pull's about 65mA so a 2w 100R resistor will handle the power.
Nice looking and sounding build. Congrats! I got very good results with a tube reverb unit on the passive loop. I think it will sound eaven better with a dumbleator I'm building right now.
If You want to smoothen the drive maybe a 390p or 470p snubbers from plate to cathode on V2 might do the job.
I also included a manual toggle switch that removes the second and third stages as well as the final volume control so the amp can get as open of a clean sound as possible. Just fired her up yesterday and after a couple of touchups, I have to say I'm very pleased. I was going for more of a classic ODS (70s) tone and wanted the drive to be more raw, which this most certainly is! I also included a passive loop. Tube rectified with a TAD GZ34 right now. Two TAD 7025s and a JJ EL84 were also used for start up. Hope you guys dig! 
