Ultimate Hammond Conversions thread

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sluckey
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Re: Ultimate Hammond Conversions thread

Post by sluckey »

I just completed a conversion of an AO-63. I kept the 7591 main power amp stock but replaced the organ preamp with an Ampeg Gemini II preamp, modified the reverb amp to mix the wet signal back into the main amp, and added a 6G16 Vibroverb tremolo circuit. It reminds me of my old Gemini II amp back in the '60s. It's the heaviest Hammond I've worked on. I call it "Hampeg GemiVibe". Here's the schematic and a couple pics...
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xtian
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Re: Ultimate Hammond Conversions thread

Post by xtian »

Wow, Steve, unique cabinet, and nice P-to-P. Very very.
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sluckey
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Re: Ultimate Hammond Conversions thread

Post by sluckey »

Thanks! The cab is just a dressed up chassis stand with a little lipstick. I was gonna leave it with my crappy looking chassis stand but got shamed into dressing it up a little.

Clearing out the original circuitry that I didn't need was the hardest part. It was quite a job to remove all those components without damaging sockets and terminal strips. Took waaaay longer to do that than it did to rebuild my circuits. The control side of the chassis was heavily modified.

It's a very warm, clean sounding amp. The reverb goes up to Dick Dale! But it's very controllable with the dwell and reverb level controls. And the bias vary trem is strong and smooth with those 7591s. I added a flashy LED to the trem just for eye candy.

Her are a couple more pics. One is the original gut shot so you can see what I had to remove. The other is my crappy looking but functional amp stand before the facelift...
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dragonbat13
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Re: Ultimate Hammond Conversions thread

Post by dragonbat13 »

I have an AO-14 chassis I had originally bought for a hammonator build. But have changed my mind. Was thinking about something along the lines of an octal express or some sort of octal preamp/6v6 build.

Any ideas on other builds that would be simple and use the iron out of this chassis. Not too interested in using the hammond chassis. Been wanting to build a 5e3 for years, dont know if this chassis is a good candidate for that or if it could be used for something more unique seeing where it has all the octal stuff.
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donzoid
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Re: Ultimate Hammond Conversions thread

Post by donzoid »

1. Really cool build Steve....curious what that chassis came out of, B-1 or 2? Pretty resourceful using a cradle as the case. I have found the same thing through 3 builds it takes a lotta time to clean 'em out vs. building 'em back up.

2. Dragon, I also have one of these chassis but have not yet done any measurements of the iron etc., so whatever you decide to build please do share with us...I was also thinking a 5e3 style with octal pre would be a good candidate.
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Re: Ultimate Hammond Conversions thread

Post by sluckey »

donzoid, the AO-63 comes from an E-100 organ.
PhilRob
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Re: Ultimate Hammond Conversions thread

Post by PhilRob »

Hey guys. This is an AO-68 amp that I converted into a combo a while back. I didn't have to do much to it, I just added a parallel 12AX7 input stage feeding a FMV tonestack. I tweaked the reverb stage to reduce the gain somewhat as I was suffering from resonant feedback from the cab, and added some switching options on the negative feedback. Turned out really great. Simple but with the right pedals it can do a lot.
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sluckey
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Re: Ultimate Hammond Conversions thread

Post by sluckey »

This project is an AO-43 conversion to Supro S6424. It's not strictly a conversion, more like I used the PT and OT from the AO-43. But this Supro would easily fit inside the AO-43 chassis and the board could be modified for the Supro circuit. Since I had a blank chassis I decided to go for a clean new look.

The AO-43 iron is well suited for the Supro circuit. The voltages all worked out very near the voltages listed on the original schematic. The tremolo circuit sounds very good. The amp has plenty of grit and has a nice distortion at high volume. Easy to clean up the sound just with the guitar volume.

Here's the link to the project. Short sound clip and all documents at the bottom of the page...

http://sluckeyamps.com/supro/supro.htm

PS... I've also built a Plexi 6V6 amp using AO-43 iron. And I've seen several AB763 Deluxe Reverb conversions. The AO-43 seems to be a great platform for a variety of 20 watt amps.
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chopstuck
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Re: Ultimate Hammond Conversions thread

Post by chopstuck »

I love those little AO-44 amps. I lose the EZ 81 recto which frees up 0.9 amps heater current, then you have capacity for a few preamp tubes. I move things around but leave the can cap and iron alone. I will post a " before" picture soon . These are two builds about 3 years apart. I'm liking the turret strips.

The strip version is a Tweed Champ into a Little Wing power amp with VVR.
The Yellow board version is a 6AU6 into a Z28 style preamp into a Tweed Deluxe PI and 6BM8 outputs.
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andresound
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Re: Ultimate Hammond Conversions thread

Post by andresound »

I believe this the correct thread for my latest with the help of members of TAG. Old 50’s (?) Siemens projector type speaker cabinet with a converted Hammond AO-66 reverb amp
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darefugee
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Re: Ultimate Hammond Conversions thread

Post by darefugee »

I think you guys might get a kick out of this.

A friend at work, an amateur musician, sent me a link to an ad for a Hammond L-100, $45 on Craigslist. He asked if it’s the same as mine. I told him no, but it’s a good source for parts and I offered to go with him to pick it up so we could strip it and use the parts to build him a cool amp. His response was - “No I’m good thanks. Remember I have a Variax Guitar and Bass. So close enough is good enough for me.“ He’s right of course.

But lost in that is the fun of finding the vintage organ, arranging to pick it up, the trip and conversation to and from, finding and arriving at a new place, meeting new folks and hearing the organ’s story, and surprises found while stripping the organ down. I guess that sounds mundane, but I think it’s fun. I can't imagine the fun I'd missed if I'd have turned down all the salvage trips on account of “well, my sampler is good enough”.

And building the new amp with vintage parts is the coup d'gras.
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Re: Ultimate Hammond Conversions thread

Post by andresound »

2D15A969-A8F7-48AD-A3DA-8348056CE44C.jpeg
andresound wrote: Tue Jan 08, 2019 8:43 am I believe this the correct thread for my latest with the help of members of TAG. Old 50’s (?) Siemens projector type speaker cabinet with a converted Hammond AO-66 reverb amp
Quick update. Changed the baffle and mounted a more efficient EV 12” driver. Had to relocate v1 due to space. Besides a small amount of hum at full volume, i am called this done. Sounds awesome. Yes.. I WILL put in the remaining speaker fastening bolts 😂
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andresound
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Re: Ultimate Hammond Conversions thread

Post by andresound »

Anyone done anything with the AO-71 stereo amp?
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Stevem
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Re: Ultimate Hammond Conversions thread

Post by Stevem »

Nice conversion!
I love that old speaker cab also!

I would suggest to you that to kill off a good chunk of that cranked hum level that you have you should replace that red and white wire off of the input jack with a shielded cable that is only grounded at the end on the input jack.

Also if you sit the chassis on a sheet of bare steel when it's bolted in the cabinet and make sure that it's grounded to the chassis that will kill off any , or most of the hum level you might be having from the rectified voltage in the amp.
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thetragichero
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Re: Ultimate Hammond Conversions thread

Post by thetragichero »

hello it seems that i have found my people!
I've made a hobby of picking up old solid state organs (for free from Craigslist), stripping them for amp/effects parts, and selling the speakers for guitar use
so when i saw a Hammond l112 pop up i offered $100 to the guy (he had it listed for $200)
ao-43 chassis and a gibbs reverb tank i figured would make for a great first build

gut shot

Image

and schematic (redrawn, slightly less messy than what was in my notebook):
Image

that schematic has the values i used... some slightly different from what i had planned as in a lot of cases the capacitor i have makes a lot better sound than the one i have to wait to come in the mail. I'm happy with all of my substitutions besides using 22k instead of 47k or 68k (which i had but not in 1watt or larger sizes) across the standby switch contacts, in between the rectifier and first filter cap (i think this idea came from merlinb's site).... so instead of a standby switch i have a low power switch... yeah that's it! v1 pins 1 and 6 labeled backwards... electrically both triodes are in parallel so let's pretend it's correct. inspiration for this build was a vox top boost channel but without their funky tone control... i don't like the little sliver of mid scoop so i played around with values in a James tone stack in tsc. reverb was a one tube reverb circuit i found somewhere that used the 12dw7 that was in i think the vibrato chassis. power amp (including pi) stolen from orange ad15. power supply close to what was in the original Hammond but i moved the choke tho after the first filter cap. ran it all through psud and that's where the B+ rail voltages i listed are from. temporary placement of output jack and ht fuse until i have some aluminum plates made for the front and the back

quick demo video in low power mode (because the ones i recorded full up into my kustom 2x15 destroyed the mic on my spacephone). i have to make a head shell which i will be covering on purple tolex. once it's all together I'll make real demos recorded with my daw but for now i am quite pleased

quick demo video on 'low power mode'

currently working on a sunn beta bass/lead on a lowrey chassis with a transformer from i think a baldwin? but that's solid state so I'll leave that for elsewhere ;-)
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