Gibson EH 150

[aabbs20]

Great stuff guys!

Dave:

The LC feed goes: PT > 5AR4 Rectifier > Choke > Reservoir Cap?

Colossal:

I think I understand what you're saying, but I'm not positive. Do you have a photo or layout handy? I've looked for pictures of your finished build but haven't had any luck. I might be searching the wrong way again.

M Fowler:

You've got a much higher higher B+ than the original, does it have a lot more clean headroom or does it still break up early? There is no judgement here, just curiosity...does it sound like the original? Are you happy with the tone?

[RWood]

Search function takes a bit of learning.
Note that Mark used EH+150 in his search.
Use of the + sign is important.

How about someone putting up a sticky on this site's search engine.
I find it returns far too many results to be useful to anyone who doesn't know it's parameters. I made this request long ago without any responses.

[David Root]

Aaron, yes, I forgot the rectifier!

[Colossal]

Colossal:

I think I understand what you're saying, but I'm not positive. Do you have a photo or layout handy?

The field coil is about 750R, not 850R-1k as I said earlier. The choke between the plates and screens is about 5H. I've used a 7H JTM45 choke and that worked quite well.

[M Fowler]

I should recheck my voltages.

The expected voltages using the transformers specified by Tino Z are shown below. My transformers specs are what Tino suggested.

[aabbs20]

M Fowler:

Your voltages look right in line with Tino's. I have that book as well and I'm trying to decide if I want to build it to his specs or go with the original B+. Does yours still have the classic CC tone? What speaker did you use?

Colossal:

Thanks for that. I hadn't seen that version of the schematic yet, it seems like there are a bunch of different variations on the EH 150. If I was to leave out the field coil speaker in that design, would I use a second choke in its place?? Maybe a big dropping resistor? If I was to search for a field coil, is there a good source or do I just have to comb Ebay to find the right one?

Thanks for all your help guys, I'm getting really exciting about building this!

[David Root]

I would forget about a field coil speaker. They cannot handle being overdriven and you would very likely blow it up.

Just use a reasonably sized PT and a rectifier tube and choke that will get you to the plate voltage you want, and a decent alnico speaker. A 250-0-250 PT with 150mA should get you close to 280V or so with a 5U4 or 5R4 rectifier.

You might have trouble finding 150mA at that voltage, might have to go to a 275-0-275 eg a Hammond 270EX or FX and pick a choke or power resistor that will drop some of that overvoltage. Musical Power Supplies makes a 285-0-285 @ 150mA for a reasonable price. I used one in my Maggie 113 and it works fine.

[M Fowler]

M Fowler:

Your voltages look right in line with Tino's. I have that book as well and I'm trying to decide if I want to build it to his specs or go with the original B+. Does yours still have the classic CC tone? What speaker did you use?

I used a variety of speaker cabs but prefer Celestion Vin 30 or WGS for this dark of an amp.

This amp is loud, nice mellow octal preamp tone and also has high gain channel so a variety of sounds are possible. I don't play C.C. style.

[Colossal]

I used a variety of speaker cabs but prefer Celestion Vin 30 or WGS for this dark of an amp.

This amp is loud, nice mellow octal preamp tone and also has high gain channel so a variety of sounds are possible. I don't play C.C. style.

I too found a run-of-the-mill Vintage 30 to work REALLY well with this amp. Very full, warm, punchy, and balanced. Not bright or shrill at all. With an archtop, you hear the guitar very clearly. Smoky and jazzy, but not in a muffled way as if the tone were rolled all the way off. Comfortably loud.

Colossal:

Thanks for that. I hadn't seen that version of the schematic yet, it seems like there are a bunch of different variations on the EH 150. If I was to leave out the field coil speaker in that design, would I use a second choke in its place?? Maybe a big dropping resistor? If I was to search for a field coil, is there a good source or do I just have to comb Ebay to find the right one?

Thanks for all your help guys, I'm getting really exciting about building this!

Yes, use a choke in place of the field coil and add some series resistance to reach about 750R-1k total. You need to be dropping about 100VDC across that first Pi filter if you use a 390VAC transformer. The target plate voltage is 275-300VDC. You can go Class AB with a higher plate voltage however, like Tino's version, and it sounds quite similar to the real deal.

[aabbs20]

I too found a run-of-the-mill Vintage 30 to work REALLY well with this amp. Very full, warm, punchy, and balanced. Not bright or shrill at all. With an archtop, you hear the guitar very clearly. Smoky and jazzy, but not in a muffled way as if the tone were rolled all the way off. Comfortably loud.

This is exactly what I want to hear! Thanks.

Next step is ordering parts and building. I'll keep you guys posted.

[aabbs20]

Hey Guys.

I've been working hard on my build and finished up the wiring this morning. This is my first chassis punch and I changed my mind a few times...forgive me if its a bit messy. I followed Tino Z's schematic and layout with a few small changes. I plugged it in this morning and the pilot light came on with no smoke, which was a good start. I then plugged in the 5U4 rectifier and the filaments lit up, but when I flipped the standby switch I got a short laser light show in the tube and blew the fuse. I tried another tube and another fuse, same thing. I changed out the tube socket and fuse and tube and tried again...same thing! I have checked and rechecked my wiring and it looks fine. The pins on the rectifier socket read ok I think, 380AC on pins 4 and 6 and ~2AC on pins 8 and 2. What did I do wrong here????