Hey guys,
Just scored on an old Allen Organ amp chassis that I will be using for bass guitar. It uses HUGE power/output transformers, 4x6l6, 2x5u4, 2x6sn7, and a 6au6. I haven't traced out the circuit yet but I'm planning on leaving everything except maybe the 6au6 input tube since my goal is to build in a B15 preamap and run it into the power section. Should be pretty doable, correct? I like the idea of the 4x6l6's as I could pull two of them and run it at half power most of the time.
I cannot find ANY information on this amp/schematic. I've wanted to build a bass amp and knew you needed a large output transformer but this is ridiculous! The pictures below are of one on ebay now, it's identical to mine and shows what I have to work with. I plan on replacing the electrolytics just in case they're on the their way out. I'm pretty damn excited to get going on this thing. I think running it through a couple 15's would be nice...
Just scored on an old Allen Organ amp chassis that I will be using for bass guitar. It uses HUGE power/output transformers, 4x6l6, 2x5u4, 2x6sn7, and a 6au6. I haven't traced out the circuit yet but I'm planning on leaving everything except maybe the 6au6 input tube since my goal is to build in a B15 preamap and run it into the power section. Should be pretty doable, correct? I like the idea of the 4x6l6's as I could pull two of them and run it at half power most of the time.
I cannot find ANY information on this amp/schematic. I've wanted to build a bass amp and knew you needed a large output transformer but this is ridiculous! The pictures below are of one on ebay now, it's identical to mine and shows what I have to work with. I plan on replacing the electrolytics just in case they're on the their way out. I'm pretty damn excited to get going on this thing. I think running it through a couple 15's would be nice...
Moving to the instrument & amps forum per forum policy. You'll get a lot more input for your design questions on I & A.
Congrats on your score! Based on your description, I think you have the guts from an Allen C-3 organ, the amp was rated for 60 Watts. I think it is safe to re-cap it to start with, then you probably want to get rid of the OC3 regulator and run the screen at a higher voltage to get the power up, then adjust the gains of the various stages, and play with the feedback a bit... Looks like a fun project.
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jazbo8: C-3, you nailed it! I've looked for such a schematic but turned up nothing! Thanks for this, it really gives me a starting point to understanding what's going on inside the amp. I've built a couple of guitar amps and repaired some as well but I'm still learning as I go. Think I could remove the first two tubes (6au6 and 6sn7) and slap in a B15 preamp section before the PI 6sn7? I'm really going for the old school soul tone so I think that Ampeg circuit is a decent goal.
This forum is wonderful!
This forum is wonderful!
No you read right, I wasn't clear. I don't have one but i wouldn't mind building a single tube b15 preamp and inserting into the chassis at a logical point before the power section. You're right, it won't really be a b15 but I think any decent preamp/tone stack with this amp would be just fine. I've never seen transformers so big! I think it'll stay in my practice space most of the time...
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