baldwin amp conversion

[Ran Randle]

baldwin tube amp guitar conversion

This thing is a beast, uses 4-6L6, 2-5u4, 1-12ax7 tubes and guessing it would put out around 100 watts? No luck finding a schematic or model number even but it looks pretty clean, fairly straight forward. Wondering how it will sound with simple mods like a gain, master volume, input / output, and maybe a tone control. Appears to be a two channel amp?

I'll post better pics soon.

[JHow]

Wondering how it will sound with simple mods like ...input / output....

I strongly support the idea of including input and output on your amp.

[Ran Randle]

I strongly support the idea of including input and output on your amp.

Indeed, captain obvious here.

[Ran Randle]

Hi all,

I could use some help on this if anyone would be so kind.

I received this Baldwin amp yesterday and the only identifying model number is a stamp "B35".

2-5U4G rectifiers, 4-6L6G, 1-12AX7

Is this a good prospect for a two channel guitar/bass amp? Would more preamp sockets need to be added to make that possible or is just one workable? If anyone has some suggestions for possible modifications, that would be helpful.

Thanks for any advice.

[JHow]

One dual-triode seems like a stretch to make two channels out of. I think you would want another stage in there and something in the way of a phase inverter, no?

[Ran Randle]

yes, adding the driver tube like a 12Au7 will be the next step but not looking forward to drilling for the new socket, hard work.

[JHow]

To make a really professional hole, you can use a "chassis punch". They are made by greenlee in the US and are current production, you can find them used on fleabay, also look for punches by walsco, pioneer, or olson. They operate by first drilling a small pilot hole and then screwing the punch to cut a plug - very clean, very round, not a lot of deburring to make a nice hole. They come in all sizes.

Next step down, in my view is step-drill.

[Cygnus X1]

Hey Ran...what are the chances?
I have almost the same Baldwin, same setup.
As well as that Conn we were talking about!

The Baldwin is waiting for a plan, looks like it already has a driver tube and this is indeed strictly
a power amp.
I was thinking of making an entire single channel preamp section...there should be plenty of juice
in the PT to handle it.
Not much room to work with though.

Let me know how it goes!

[Ran Randle]

Thanks JHow, appreciate the information. It's a tricky process and will be looking into a chassis punch. I'll have a fair amount of fabricating ahead of me. The hand drilling with oil and deburring method has worked ok for smaller holes.

[Ran Randle]

Wow....go figure! I'm working up a plan for that one too, I'll keep you posted on the progress, thanks.

[Cygnus X1]

I cleaned up my Baldwin, hooked up two speakers and fired it up yesterday.
Mine is a little different, it has two phase inverters and the 6L6's are split.
One set drives a small output transformer for I guess..a high frequency driver, and the other is likely
a 30 watt output that sounds OK.

It is indeed purely a power amp.

Are you guys converting these cathode-biased power tubes or do you just let them be?
I'm wondering about the safety factor of running without screen grids.

I'm thinking about just what I am going to do with this amp.
I've seen them converted to stereo power amps but not real sure about the sound quality.
Might just make a split personality guitar amp out of it!

[Ran Randle]

I assume mine is just a power amp with dual OTs for running separate cabs but with only a single 12ax7 which I guess each side of the preamp tube drives each set of 6L6s each with a 5U4 rectifier. I haven't fired it up or done anything to it yet and just got a set of tubes for it recently. I have to figure out the PT hot and neutral windings to wire in a power switch.



I was leaning towards leaving it alone as much as possible. Included some (crude) schematics for fixed and cathode bias set-ups. I’m not sure about which to use yet.
There is much for me to learn still, yeesh. I have to think about what I'm going to do with mine as well but its tough with no schematic to go from. The split personality guitar amp idea is what I was thinking too. Let me know how it goes.

[loudthud]

Note that the chassis is stamped 6L6G. This is the old low power version of the 6L6 that was only good for about 25W per pair. It shouldn't be that hard to trace the exsisting circuit and create a schematic. What kind of bias did Baldwin use? Follow the connections to pin 8 of the 6L6s.

[Cygnus X1]

I'm the thread hijacker, but mine is 6L6GC with a cathode bias on each 6L6.
200 ohm on pin 8 of each.

I asked somewhere just how safe this setup is, with no grid stoppers.
Fender uses a 1500 ohm from 5 to 6 on the Deluxe running 6V6's...I was wondering if I should
do the same.

[loudthud]

Grid stoppers are like insurance. You never know when you're going to need it (them). If you don't have a scope, your amp might have a problem that you can never find, but it never really sounds quite right. You might be able to fix it with lead dress or just the right set of output tubes. So it's up to you. Play it safe or fly blind. Myself, I always install them.