Monkeymatic Hammond Stout

[billc]

No cab plan. Chassis is an odd duck, 12x10x2. And reverb tank is 17" wide. Got something in mind?

Nice job! FWIW I have three old Hammonds similar to yours and an going to try to recycle some of the original cabinet wood into head enclosures, maybe with biscuit joined corners...will post some photos if it works out, have the basic tools (table saw, etc.) but not so sure about the skills

[xtian]

Good luck. Both of the Hammond organs I got (L-100 series) were particle board with veneer. Not worth reusing. Though I did make a nice 2x12 conversion:

http://chico.craigslist.org/msg/4417289762.html

[xtian]

Speaking of really big logos...

I got this one all dressed up with faceplate and Hammond cage. Named her "Diablo", part of my CA mountain peak name series.

[sepulchre]

Wow! Great solution! That's bound to turn some heads.

[topbrent]

Looks like you added a tone stack (Treble-Bass). What did you use there?

[M Fowler]

That looks great

[xtian]

Thanks, guys!

@topbrent: I used a Princeton Reverb AA764 tone stack. Turns out I dislike the one-knob tone controls I've tried. The PR stack makes it sound much more Fendery--scoops the mids.

[Tubelube]

I am embarking on a mission to convert an AO-39 to a dedicated power amp for my rack mount tube amp, I didn't know this thread had been started and inadvertently started another one under technical amp discussions can someone help me out using a schematic Thanks!

[xtian]

See the power amp building blocks on ax84.com. Very well documented.

[Tubelube]

[ToneMerc]

I did as you suggested xtian; I did not find any info on EL84 push pull (assuming that is what an AO-39 is) stand alone power amps. which is a shame as there are many AO-39 power amps that would take a minimal amount of effort for to convert. One of the modifications that would have to be addressed is as follows:

• The "PI" is really just a two input dual phase driver. The actual dual phase signals are developed using a transformer located on the preamp chassis. The driver has a signal balance adjustment (left end of chassis).

• The output tubes have a HUM BAL adjustment in the cathode circuit that actually balances (matches) the idle current through each output tube.

• The two NFB loops are taken from the plates of the output tubes and loop back to the cathodes of the PI.

Due to the above mentioned circuits the process could require gutting everything up to the power tubes however minimal that is as we are just dealing with a simple power amp. The positive would be having plenty of room for the simple (minimal circuitry). The power and output of the output tubes and loop back to the cathodes of the PI.
Due to the above mentioned circuits the process could require gutting everything up to the power tubes however minimal that is as we are just dealing with a simple power amp. The positive would be having plenty of room for the simple (minimal circuitry). The power and output tranys could stay right where they are, the 5u4 tube rectifier could stay seated also to hold the volume down and create sag (Fat Fender sound).

It would be helpful if someone designed and tested a circuit for an AO-39 at some point. They could sell a circuit boards (populated and blank) for a business. The AO-39 is juicy, full and fat sounding through out its entire volume range, it was designed to be clean and full sounding for an organ sound. Where the AO-39 really shines is in lead work with a modern all tube preamp, the notes flow together like liquid. I guess no one is interested in a dedicated stand alone AO-39 power amp at this time, to bad as I have three of them I saved from the junk heap over the years. Know of any last ditch efforts I could focus on for info regarding my quest.

If it's so easy to do, then take the info that you have been directed too and run with it and build one.

Otherwise, it's really obvious now why you have been starting multiple threads on TAG about these amps, you are lookin for someone to do the grunt work so you can profit from it.



TM

[Tubelube]

I did as you suggested xtian; I did not find any info on dedicated EL84 stand alone power amps from the Building Blocks thread of the site you mentioned, which is shame as the AO-39 power amp would take a minimal amount of effort to convert. Some of the modifications that would have to be addressed are as follows:
• The "PI" is really just a two input dual phase driver. The actual dual phase signals are developed using a transformer located on the preamp chassis (which I don't have). The driver has a signal balance adjustment (left end of chassis).
• The output tubes have a HUM BAL adjustment in the cathode circuit that actually balances (matches) the idle current through each output tube.
• The two NFB loops are taken from the plates of the output tubes and loop back to the cathodes of the PI.
The power and output transformers could stay right where they are, the 5u4 rectifier tube could stay seated also to hold down the volume and create sag (Fat Fender sound).
It would be helpful if someone designed and tested a circuit for the AO-39 at some point. They could sell circuit boards (populated and blank) for a business. The AO-39 is juicy, full and fat sounding through out its entire volume range; it was designed for a clean, full frequency organ sound. Where the AO-39 really shines is in guitar lead work using a modern all tube guitar preamp, the notes flow together like drippy sweet liquid. A friend of mine's father who was a Ham Radio guy converted one of these for his son. The only thing I remember was he moved the 12AX7 closer to the output tubes and rewired it to become a mixer/driver, can't remember much else. I remember how alive the conversion sounded. His Dad passed away years ago, the secret on how to convert the AO-39 was lost with him.
I can't Blue Print the amp as it was stolen while my friend was on tour. I guess no one is interested in (dedicated stand alone) AO-39 power amps at this time, to bad as I have three of them I saved from the junk heap over the years hoping some one would discover how to convert them as they are. Know of any last ditch efforts I could focus on regarding my quest.

[Tubelube]

I can't seem to figure out this edit posting stuff

[xtian]

I wasn't suggesting that AX84 had plans for converting Hammond amps, just that they had plans for push-pull power amps.

Yes, you should start by stripping all the old circuit out of that chassis, then build what you want, using a known, well documented design. Then the kind folks all all these forums will be able to help you.

[Tubelube]

I am not going to profit from anything. I am a guitar player new to the site expressing the value of these amps as I have heard them and they are beyond words. I would attempt to build however I found no schematic at the sites where I was directed that use an EL-84 push pull dedicated power amp setup. There is one build that uses EL-34's as I stated, however it uses a solid state rectifier which is not acceptable for this amps unique sound not to mention different tubes. Why is it o.k. for others to ask questions about builds? They profit in that they are able to accomplish a build that would take years in just a few days. In your philosophy every one should just stick with it and learn the hard way and take years to accomplish a build. That would render a site like this ethically unusable, not helpful and obsolete. Maybe everyone should just bug out of your click, you really didn't have to respond to my post then I wouldn't have had to waste my time writing this.