Prepping for first build...

[sonofdavid]

Hey guys, I'm really excited to be prepping for my first build, but I could use some advice. I'm new to this, so naturally there are going to be holes in my research that only experience can fill, so here I am.

I'm looking to start with a lower wattage, cathode biased build. I'm thinking somewhere along the lines of a Nighthawk and Z-28. I really want an EF86 up front, I'd like to have the Matchless-like oversized tranny ballsy-headroom-thing going on, and an effects loop is a must. No need for reverb. I'm severely limited on funding, so I'm considering using transformers I already have, or starting from an AO-43.

So the question is, would the Hammond transformers perform well in this application? I also have a Jet City JCA20H that I might gut if you guys think those transformers would cut it, and I already have it sitting around mostly unused, which is a big plus.

Thanks in advance for the input!

[gui_tarzan]

I'll let the builders answer those questions, let's start with safety and tools. What do you have for equipment? At a minimum you'll need a good volt/ohm meter, soldering iron, various pliers, cutters, screwdrivers, etc. and it would help if you have an oscilloscope and know how to use it.

Most important of all, are you aware of the voltages in the HT section? Do you know how to drain capacitors? Do you know to keep one hand out of the chassis when you're testing? Do you have a clean workspace that is organized so you're not pushing stuff all over the place? Oh wait, that's my bench.

Have you read the various sites online or books that explain how the circuits work and how not to kill yourself working on it? What is your electronic experience level? We all started from the beginning, but you're working with power that will stop your heart if you touch the wrong thing at the wrong time.

[xtian]

Your goals "low wattage" and "ballsy headroom" are contradictory.

Yes, you can use salvaged Hammond iron, but voltages are usually too high. I solved this problem in the past by using inefficient tube rectifiers (like 5U4 or 5Y3), or just having blisteringly high voltage (JJ tubes are usually OK with that).

[armillary]

To be fair, it's not possible that a beginner could expect to hack out anything remotely comparable to the legendary Mike Soldano designed Jet City JCA20H. Give the guy his creds. Gutting this amp would be a waste. Respect it for what it is. There are mods to this amp that can make the tone more your signature sound. Get your hands dirty on these. That's how you learn.
http://www.harmonycentral.com/forum/for ... 8/1376468-

[matt h]

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[Firestorm]

Building an amp and being severely limited on funding are not things that go together. You can cobble something together that sounds okay (if you're lucky), but it's ultimately more satisfying to build something with the proper components, even if that means saving your money and buying a kit.

[matt h]

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[M Fowler]

Nothing cheap about building your own amp.

Must decide EL84 power section or 6V6 power section.

The latter would be okay with the Hammond organ donor transformers.

The Hammond AO-35 reverb amp is a pair of EL84's and great platform.

[Firestorm]

Building an amp and being severely limited on funding are not things that go together. You can cobble something together that sounds okay (if you're lucky), but it's ultimately more satisfying to build something with the proper components, even if that means saving your money and buying a kit.

Eh... gotta disagree there. If you've already got the chassis, pots, knobs, jacks, switches, sockets, and most of the glass in a donor amp, to build something like a nighthawk (minus effects loop craziness that'd be required) would probably cost about 20 bucks plus shipping in R, C, and wire.

And there's a good chance that'll sound as good, or better, than another bloody champ kit clone.

You're not wrong. You could do that, I could do that, a lot of folks here could. I don't know if the OP is there yet (maybe).

[sonofdavid]

Thanks for all the replies, guys. I would have checked back sooner but I thought I'd get an email if there was a reply, like I do on other forums, and I didn't. I'll have to check my settings...

Anyway, I have a Hammond AO-35 chassis on the way, with just the transformers and tube sockets left. Should be here within a week. I scored it pretty cheap on Reverb.

Not only will that get me more in the direction I'm looking for, but it will keep the Jet City intact. I meant no disrespect to Soldano in my consideration of using that amp to strip down, but it's just not what I'm looking for, and frankly is not even in the same league as something like a Matchless or Z, imo. It's a great amp for the money, and is great at what it does, but it's not my flavor. Not to mention I've had the itch to start building for a while now, but haven't had the means to venture into the waters. There are just some things about everything that you don't really learn without experience. That being said, thanks again for sharing your experience. I'm excited to dive in.

I really dig the tones from just about any EL84 based amp with an EF86 front end, so I'm pretty set on going that direction for number one. I don't think it's such a good idea for me to try to get way too creative on my first build, so I'm thinking I'd like to basically put a Nighthawk in this chassis if possible. I do have some experience modding and repairing amps, I've taken my Fluke and soldering iron to several of them (successfully). I've built and modded several pedals as well, and have started to make them more my own as I've gotten more comfortable doing that. I'm excited to make some amps, though; that's what really gets me going...

Does anyone know what the specs of the transformers in the AO-35 are? The Creme Brulee layout specs are 290v on the PT secondary, but it doesn't give specs for the OT or choke. I've read that Matchless used a 4k OT, so would it be accurate that I would have the best results with that as well? Thanks for the support, and for your patience with the long-winded noob.

[sonofdavid]

btw I forgot to mention that I already have a pair of good RCA black plate 6BQ5's that I pulled from an old RCA radio. They both tested strong and close to one another on my tester. Pretty stoked about those...

[M Fowler]

AO-35 Hammond PT is 290-0-290 and not sure about the OT I think it is 8k primary.

Mark

[sonofdavid]

Sweet. Sounds like the PT will be perfect for what I want to do with it. If I'm not mistaken, 8k primary is spec for an AC15 OT, so that should be good too. If I'm off on that, somebody please chime in. Thanks

[sonofdavid]

As for the effects loop, I was planning on adding the same effects loop that is depicted on the DC-30 schematic that is floating around here on the net. Are there better options? I'm open to suggestions, but I don't see how it could be too detrimental to the overall tone if they were in the original Matchless amps; they are called Matchless for a very good reason. An effects loop is pretty vital to my rig if I'm going to use any of amp's gain, I use some really thick reverb and delay about half the time. Again, if anyone knows of a better solution, I'm all ears, but I think I'll need the loop. Thanks again

[matt h]

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