Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on September 26, 2023, 04:42:25 pm
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my plan is to convert it to a spitfire. The OT looks undersized. What can i swap it with?
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The OT is the perfect size for a pair of 6BQ5s (EL84s). The PT is way oversize because it had to power many other tubes in addition to the AO-35.
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Lots of amps built with that iron - commercially the Dr Z Carmen Ghia and the Goodsell Super 17. Eventually they both used other iron as they ran out of Hammond organ stock, but both sold a lot of those A0-35 based amps. I'm sure many Spitfire clones have been built on those. I built one using Trace Elliot iron - was too bright for me, but a good amp with pedals.
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I agree with Sluckey and bmccowan. I've built/converted plenty of these amps and never felt like the OT was lacking. I currently have 3 sitting on the shelf collecting dust. At the point you replace the OT with a new one the convenience and savings of the AO35 is now gone. Not sure what you paid, but the average price (shipped) for the AO35 is $150 without tubes and $200 with, now add a new OT.
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should the cap can be replaced? it looks clean but it is like 60 years old
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should the cap can be replaced? it looks clean but it is like 60 years old
Try it and see. My AO-63 still has the original cap cans.
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I came across a 1959 Hammond M-1 after playing with it a few minutes with a variac and dim bulb I saw that the amplifier passed signal so I bought it for $100 a couple of years ago. I bought it thinking I would strip the AO-29 from it to build something fun. Once I got it home I dicked with it for an hour or so I got it fully working, cleaned all of the switches etc. So now I have a great sounding organ I can't play but I don't have the heart to part it out since it is all original and works perfectly, no filter him or anything.
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Albatross - I am glad you saved it. I have bought the amps from deconstructed Hammonds, but also have not had the heart to tear a good instrument apart. I saw a working M-1 in a thrift shop last year - $50 - so tempting. Figured I could use it to tune my guitar.
For the Mallory cans in these Hammond amps - I have built a few amps from AO-39s and 35s. Those old cans seem to always be good. The reason I can think of defies common wisdom. Those amps likely were not pushed hard by family singalongs and such, and many sat idle. Common wisdom says that E caps dry up if not used and need to be reformed or tossed. So I question common wisdom on that.