1937 Gibson guitar amp

[Joel]

I finally did a much needed rebuild of my old Gibson guitar amp - and since I had no luck finding an accurate schematic of this model, I reverse engineered the whole thing. I thought others might find it useful.

This is the same model used by the famous jazzer Charlie Christian. One 12" field coil speaker, about 15 watts output.


http://members.aol.com/Junip/images/gibsoneh-150.jpg

[dwjj]

When was the first Gibson amp? '35?

Have any idea of the number of amps produced the first few years?

[Joel]

I think it was the smaller EH-100. In '36 or so.

[James D.]

Hi Joel,

That's a really nice looking amplifier...parafeed interstage no less!!!

What is the speaker tone like?

Have you tried a more modern guitar speaker with it?

Is your Les Paul to hot for it?

ciao

James

[Joel]

Originally posted by James D.
That's a really nice looking amplifier...parafeed interstage no less!!!

I thought you guys would like that.

What is the speaker tone like?

Quite nice. Has a very woody tone to it.

Have you tried a more modern guitar speaker with it?

Blasphemy! Certainly not.

Is your Les Paul to hot for it?

No, it's fine - my "antiquity" humbuckers are only 7.5k ohms each - not very hot.

[Brett]

Very interesting circuit Joel. Thanks for posting it. If I ever find a suitable field coil speaker here, it would be a fun project.

[SHiFTY]

Can you post a pic of it?

[James D.]

Hi Joel

James said:

"Have you tried a more modern guitar speaker with it?"

Joel replied

"Blasphemy! Certainly not."

I wouldn't suggest that you replace the origonal speaker....Never


But it might be an interesting data point to try the amp into, say, a Vintage Blue and hear the tone...

My experience with early speakers are that they don't have as much bite as 60's and later speakers... "woody" indeed! But that the amps can be very, very good and it makes an interesting contrast to the origional tone. I have modified a couple of late 40s combos with a speaker out jack and so can plug them into a cab for a different tone palete...

I really like early guitar amps (pre marshalls) into their own speakers and into modern speakers... depends whether my boys are playing delta blues or 'clapton'!

It doesn't make my bass sound like a double bass though...

No, it's fine - my "antiquity" humbuckers are only 7.5k ohms each - not very hot.

Nice touch!

ciao

James

[cavalino]

Hey Joel,

I realize this thread is pretty old, but if you're still out there, thanks a million for posting your EH-150 amp schematic.

I was just about to embark on the same reverse-engineering project for my 1937 EH-150 after coming up empty handed when searching the web. You've saved me a tremendous amount of time.

Now I can get the electronic restoration done and start playing that little tweed, round-shouldered cutie.

By the way, the only difference I noticed in my amp is a center-tapped secondary on the output transformer for the "echo" speaker jack. Also, to anyone trying a later PM speaker in place of the field-coil speaker (if you really insist on doing this), just remember to leave the field wires connected to the old speaker. It does double-duty as a filter choke in the power supply.

Thanks again Joel....

[Trout]

Originally posted by cavalino
Hey Joel,

I realize this thread is pretty old, but if you're still out there, thanks a million for posting your EH-150 amp schematic.

I was just about to embark on the same reverse-engineering project for my 1937 EH-150 after coming up empty handed when searching the web. You've saved me a tremendous amount of time.

Now I can get the electronic restoration done and start playing that little tweed, round-shouldered cutie.

By the way, the only difference I noticed in my amp is a center-tapped secondary on the output transformer for the "echo" speaker jack. Also, to anyone trying a later PM speaker in place of the field-coil speaker (if you really insist on doing this), just remember to leave the field wires connected to the old speaker. It does double-duty as a filter choke in the power supply.

Thanks again Joel....

Interesting, I looked at the Gibson service manual thats downloadable

Click Here Adobe Needed
And there are 2 entirely different schematics for that model.
The one posted in the original thread here is Similar but not exact. Possibly a 3rd Version of the EH150?

I have a really nice field coil speaker from a Vintage Stromberg Carlson Unit I had planned on using to build one of Gibsons early amps as a winter project. So I had downloaded the entire manual. 128 or so megs!!!
Gene