6v6 plexi from AO43 questions

[lovecoffee01]

Hello everyone. I'm new to the forum, and new to playing with amps. I just picked up a chassis out of a hammond L100. The chassis is a AO43. I've read the transformers are suitable for various amp builds. I've always wanted to build a little marshall style amp like a 18w or a JTM45. I had originally planned on building a kit but never have the money to invest and just stumbled on these parts so figured I'd try to scratch build one. I found the schematic for sluckley's 6V6 and it seems to be suitable for what I have but have a few questions if anyone can help.
1) there's 2 25uf @150v caps in the bias circuit. Can these be a different value? I'm having trouble sourcing that value. Would 33uf @ 160v work? From what I've read, if I understand correctly, I could go up to 100uf as long as I stay at or above 150v.

2) The output transformer primary impedance is around 7200k with an 8 ohm secondary. . A 6v6 effective load resistance is 8000k according to the chart. Will this work? Also plate voltage is 400v give or take. Tube chart says 350v although I've read they can go higher. I'm just learning so thought I should ask.

3) resistors. Are half watts suitable for everything that doesn't call for anything higher?

4) the 2 470pf caps are mica. Can I use a different kind of cap? All I can seem to find is 500pf in mica. Would 500pf work?

Thanks in advance for any help. Please remember I'm a newbie at all of this. I've tried to educate myself as much as possible but still have a lot to learn.

6v6plexi.pdf

[Colossal]

1) there's 2 25uf @150v caps in the bias circuit. Can these be a different value? I'm having trouble sourcing that value. Would 33uf @ 160v work? From what I've read, if I understand correctly, I could go up to 100uf as long as I stay at or above 150v.

Yes, the bias circuit caps can be a different value. 33uF 160VDC is fine.

2) The output transformer primary impedance is around 7200k with an 8 ohm secondary. . A 6v6 effective load resistance is 8000k according to the chart. Will this work? Also plate voltage is 400v give or take. Tube chart says 350v although I've read they can go higher. I'm just learning so thought I should ask.

Close enough for Rock and Roll. I've built that amp using JJ6V6S (they are more like small bottle 6L6s) and ran them at 440VDC on the plates into a 7k8 load (much lower screen voltage though!).

3) resistors. Are half watts suitable for everything that doesn't call for anything higher?

That is fine. You may want to go with 1-2W metal or carbon film for your plate resistors for lower noise/hiss.

4) the 2 470pf caps are mica. Can I use a different kind of cap? All I can seem to find is 500pf in mica. Would 500pf work?

500pF is fine. Avoid the cheap, imported mica caps. Cornell Dubilier 500V and 1kV are good.

Thanks in advance for any help. Please remember I'm a newbie at all of this. I've tried to educate myself as much as possible but still have a lot to learn.

Have fun. That is a loud 22W amp.

[lovecoffee01]

Thanks so much Colossal. I've got to collect some parts together. For the mica caps it says generic but they are 500v. The it's the only generic cap they sell. Everything else is like F&T or sprague so I'm assuming it must be decent quality. My neighbor is going to give me his h100 organ so I'll have some 60s vintage gz34 tubes. Sadly there's no vintage 6v6's in there, but there's a bunch of other good stuff. I was going to use all metal film or wire wound resistors also. Thanks again and I'm sure I'll have a million other questions.

[sluckey]

There may be some useful info here...

http://sluckeyamps.com/6v6plexi/6v6plexi.htm

[lovecoffee01]

Yes Sluckley, I've seen all that. Just being new at this and all of the reading I've done, and parts availability locally, I just wanted to verify those things. Did you use 6v6s tubes? They look like them but I can't tell from the pics.thanks

[sluckey]

Did you use 6v6s tubes?

Yes. And the only thing I used from the AO-43 was the transformers and choke.

[lovecoffee01]

That's good to know. I was planning on using the transformers and choke also. I was also going to use some of the 12ax7 tubes. They're all 1963 rca's so they might or might not be good. Thinking they probably had a pretty easy life in an organ.

[lovecoffee01]

One more question.... the Mallory caps in the circuit, I can only find 630v even for the ones rated for 100v and 250v. Are these the same as electrolytic caps where as long as the voltage is rated higher, you're good? Thanks in advance.

[sluckey]

630V is fine but is way over-rated. And the .68µF will be quite large. May I suggest some Panasonic Polyester film capacitors from Hoffman (or similar)? Scroll way down the page. Very affordable.

[lovecoffee01]

Okay I can look into those. I did find the .68uf@100v locally from a different supplier. I was trying to keep them all mallory 150s but I did find this vishay for the .1uf cap. Would it be fine? If I order from 10 different suppliers I'm going to get killed on shipping and I'd prefer to keep everything I do ship in Canada. For pots, there is no need to use cts is there? Would alpha pots suffice?

[lovecoffee01]

Damn, I was looking at the tube compliment the h100 organ comes with and got thinking this would almost work with 7591 tubes. But on second thought, I should just stick to the schematic that I have because it's been built and tested. I think they'd likely melt the output transformer. Wait until I get a bit more knowledge I think.

[drew]

Okay I can look into those. I did find the .68uf@100v locally from a different supplier. I was trying to keep them all mallory 150s but I did find this vishay for the .1uf cap. Would it be fine? If I order from 10 different suppliers I'm going to get killed on shipping and I'd prefer to keep everything I do ship in Canada. For pots, there is no need to use cts is there? Would alpha pots suffice?

No need to get too hung up on brands, particularly for a first amp build. Get the right value parts and go to work.

You might want to check out justradios.com, if you haven’t already. I believe they’re Canadian.

[lovecoffee01]

I'll check them out. The only thing I was trying to do is either get everything from one place online or in town here. Saves shipping. Going to have to wait for a bit to get funding anyway. I appreciate all the info and help. Just going to stick to the Sluckley plan instead of trying to do anything crazy like putting 7591tubes in it until I learn more. I'd rather just make a proven design to get my feet wet. Thanks again