Hammond Organ Amp to Guitar Amp Conversion Project

[Structo]

Hi, I won a Hammond organ amp the other day.
I don't have it yet but it's being shipped.
Got it for $58 + shipping.

Anyway the description said it was from a M3 organ.

In the Q & A section somebody asked the seller what was printed on the side of the amp and he replied AO 29.

I thought I had heard that was one that worked well for amps so I bid on it.
Hopefully Casey will chime in since he seems to know his way around these amps.
At first I thought since it was a 63 that it wouldn't have a field coil speaker but another guy told me it was older than that, then I looked more closely at a picture of it and it seems to have a FC speaker. Oh well, no biggy if I have to add an OT because I have one here that I think will work.

I'm thinking about making a Tweed Deluxe out of it and hopefully some of the tubes are good in it. Particularly the 12ax7's and the 6V6's.

This is what he said in the description:

Up for auction is an amp assembly from an old M3 Hammond organ serial # 105323. It was a console form A1. These are off an old organ from around 1963 give or take.

And some photos from the auction.

[chopstuck]

I think you stole that one. I just got one of those too for a good bit more but I haven't checked the voltages yet. We may have got them from the same guy in Moses Lake WA. I just snagged another AO-43 from him tonight that's going to pull mini plexi duty. I keep thinking about d-liting a Hammond but haven't done it yet.

[Structo]

If mine is indeed a AO 29 then it has a 320v secondary.

[CaseyJones]

Hopefully Casey will chime in since he seems to know his way around these amps.

Yeah, I've worked on a few of them.

At first I thought since it was a 63 that it wouldn't have a field coil speaker but another guy told me it was older than that, then I looked more closely at a picture of it and it seems to have a FC speaker. Oh well, no biggy if I have to add an OT because I have one here that I think will work.

There's an OT on it. The field coil is in the power supply, it acts as both a field coil and a choke.

Here's the lowdown: Most versions of the AO-29 use the same transformer set as the AO-35. So: Those of you who are unwilling to pay the current prices for AO-35s can just buy AO-29s instead. Hammond even used the same little phenolic barrier strip on the back of the two amps.

Everyone buys them for the transformers. Don't tell me you're going to use that goofy chassis, that shows zero class. I'd dump the transformers into something like a 5F6 or JTM45 chassis. At least use an aluminum chassis. The PT is larger than either a 5F6 or a JTM45 PT. Start with a blank box, saw a big hole in it for the PT and a smaller hole for the OT. It's won't look like a mutt if you start wif a fresh chassis. Don't make the same mistake some people do and assume that there's a whole lot of juice there, there's around 150ma om the high voltage. It will run 6L6s cathode-biased, it's not quite up to KT66s or EL34s. So cross those off yer list.

Near as I can tell these are the same transformers as early Matchless Spitfire. Too bad everyone lost interest in the Spitfire five or six years ago...

I'm thinking about making a Twee Deluxe out of it and hopefully some of the tubes are good in it. Particularly the 12ax7's and the 6V6's.

I'd expect there's a pair of nice Sylvania chrome top 6V6s in there, those are worth having. You get a couple 12AX7s and that 5U4.

[Cygnus X1]

I have an AO-14 I picked up for 50 dollars.
Field coil, I am not sure how it was set up.

The PT looks very beefy but I have not planned anything for this amp yet.

[Structo]

So Casey, you said the PT is a bit wimpy?
Geez I thought that it would be pretty beefy since it's powering 10 tubes.
Or are you saying that the HT winding doesn't have a lot of juice?

The heater winding must be pretty robust.

The seller mentions that the serial # is 105323. So that puts it eariler than the M3 schematics I have.

Are you saying that the OT which I guess is T3 is suitible for a push-pull Deluxe type amp?

[CaseyJones]

So Casey, you said the PT is a bit wimpy?
Geez I thought that it would be pretty beefy since it's powering 10 tubes.
Or are you saying that the HT winding doesn't have a lot of juice?

PT is wimpy. That's counterintuitive because it's rather large. HT winding is wimpy. I'm judging by what I've run on it and how hot it got. It will work fine for a Deluxe. Don't push yer luck, hot PTs ain't such a hot idea.

The heater winding must be pretty robust.

Yeah but most of those tubes are minis, not much filament there. I did the math at one point and figured I could run EL34s and maybe a couple preamp tubes. Wrong-o! I shoulda built the amp tubes-up wif a little "griddle" over my PT, that way I could fry my breakfast on it in the wee hours of the mornin' after the gig.

The seller mentions that the serial # is 105323. So that puts it eariler than the M3 schematics I have.

Are you saying that the OT which I guess is T3 is suitible for a push-pull Deluxe type amp?

Schematics? We don't need no stinkin' schematics!

I lump all the "M" models in to one pile although the M100 is a little different.

That's a great little OT in there, if it works for organ pedals you bet yer little guitar should sound o.k.. Field coil or no there's a single 8 ohm Jensen in those.

YOU'LL BE SORRY when the last "Baby B3" gets dismantled for parts and these things are worth some serious dough.

[skyboltone]

Man, I just hate to see all these destroyed for the freaking amps. Go to http://www.captain-foldback.com and look at the early AO-29 amp schematic. It shows the field coil on the center tap of the PT.

The PT is large, but it's really soft. It is different though than the AO-35. I've dealt with probably half a dozen of those two amps and the AO-35 is invariably 300-0-300 with a 250ohm DC resistance across the secondary. Usefull for it's intended 6BQ5 power tubes. The AO-29 , every one has 375-0-375 with about 160 ohms across the secondary. You cannot use this amp for anything larger than a pair of 6V6s. With 6CA7s and a capacitor input filter you'll have 475VDC with no load and 400VDC with the EL-34s biased at 70%. Hit a chord and the voltage almost goes away entirely. Laurens Hammond was a notorious cost cutter and the tone generator was so expensive to build that he didn't have one extra electron available in his power supply designs.

The Hammond conversion manuals suggested that a 700 ohm 10 watt resistor be substituted for the field coil when the owner wished to convert to a PM speaker.

The OT on the AO-35 is 8000:8 ohm with about 3/4" of iron. The AO-29 uses an OT with 10500:8 ohm ohm with about 1" of iron. I've used them both with success using EL-84 tubes. I gave one to a fellow on the board here, and he doesn't like it in his two hole rocket. Says it saturates too soon.

About Casey's final point. B3s, C3s and A100s are torn apart at a much slower rate than the M3s and others in the M series. This is really sad. I've got a minty '56 M3 that sounds just glorious. I'll be doing a complete overhaul in the coming year or so and intend to keep it forever. The photo of the back of that organ looks beautiful and some a**hole is murdering it. For shame. Go listen to some deep purple (jon lord) or some Santana, (joe coster?), Steve Winwood on his own or paired up with Jimi Hendrix or any of two dozen other artists. It's an irreplaceable sound. I know some guys are using clonewheels an likeing them but only because they have never played a real one. A clipped M3 weighs less than 200 pounds and when rebuilt with mylar or pvc caps is agressive and complete. Oh, and don't forget the Leslie. There are only about 200,000 122 leslies ever built and they are rare as hen's teeth because idiots tear out the amps for some kind of vintage sound horseshit. Think! It's like stripping your '59 paul and putting a glitter finish on it with deMarzio pups.

[skyboltone]

Oh, one last thing. The ideal use for an AO-29 other than in an M3 is to use the PT and the OT in a single ended design with the big tube of your choice and a 4 ohm cabinet.

If you want to murder something Hammond, find a tone cabinet amp. Nobody cares about the tone cabs anymore. Seek something with 7591As in it. It's a rightous OT and a honkin' PT too.

Here's one I picked up a couple of days ago. It has a pair of 7591s and a bonus OT for a pair of 6BQ5s. Not bad eh? You can build an amp with cathode biased 6CA7s and have a speaker driven reverb amp too.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0368626202

[Structo]

Here is a AO 29 with no bids so far $25.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... %26ps%3D33

[skyboltone]

Here is a AO 29 with no bids so far $25.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... %26ps%3D33

If somebody gets that; Pleeeeeeese, take the PT and the OT and the tubes and give me the rest untouched. Shipping of course on me. Pleeeese. I've already got the iron on hand from a previous murder. I need that as a back up for my M3.

[CaseyJones]

B3s, C3s and A100s are torn apart at a much slower rate than the M3s and others in the M series. This is really sad. I've got a minty '56 M3 that sounds just glorious. I'll be doing a complete overhaul in the coming year or so and intend to keep it forever. The photo of the back of that organ looks beautiful and some a**hole is murdering it. For shame. Go listen to some deep purple (jon lord) or some Santana, (joe coster?), Steve Winwood on his own or paired up with Jimi Hendrix or any of two dozen other artists. It's an irreplaceable sound. I know some guys are using clonewheels an likeing them but only because they have never played a real one. A clipped M3 weighs less than 200 pounds and when rebuilt with mylar or pvc caps is agressive and complete. Oh, and don't forget the Leslie. There are only about 200,000 122 leslies ever built and they are rare as hen's teeth because idiots tear out the amps for some kind of vintage sound horseshit. Think! It's like stripping your '59 paul and putting a glitter finish on it with deMarzio pups.

How 'bout Keith Emerson? Never mind we should all put together analog patchord Moogs fer the mental exercise and more to the point, to be able to play the synth solo in "Lucky Man" note fer note. Emerson would whip his M around on the stage, tip it on its back and hold notes down with daggers apparently.

Leslie 122s: Keep this under yer hat but the amp is oh-so-similar to the 147, the 147s amp was used in the 45, the 122 amp was used in a couple non-122 cabinets. All moot of course because if you had a "heads-up" Leslie built an amp that one-ups the 122. 'Nuff said, the "alternative" amp ain't worth squat on eBay 'cuz it ain't a 122.

Leslie and Hammond were two different companies. Hammond viewed Leslie as a competitor. Hammond went out of their way to offer products functionally dis-similar to Leslie. 'Course they're all under the same banner now as Hammond-Suzuki.

Vintage organ guys make vintage guitar guys look sane and rational by comparison.

If you want to murder something Hammond, find a tone cabinet amp. Nobody cares about the tone cabs anymore. Seek something with 7591As in it. It's a rightous OT and a honkin' PT too.

NOOOOooooo!!!

All this organ stuff is JUNK. No useful parts there at all for a guitar app. Save yer pennies and buy yer iron from Heyboer, it's shiny, new and built to yer app..

Here is a AO 29 with no bids so far $25.

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... %26ps%3D33

-Snurk-, snicker. "Ready to be updated" they say. Another one bites the dust...

Here's the way it goes, all those old "M"s weigh a ton, they don't have the goofy drum machine, auto-harmony and all the BS newer junk like Conn, Kimball, Yamaha, Roland etc. have. Effin' Citizens, they want all that bells and whistles crap. What they ("Ms") do have is tonewheel tone to da bone. But they're heavy, can't sell 'em on the 'net and ship 'em fer cheap so hack 'em up and make what ya can. Like Dan says, it's a cryin' shame...

I got a couple scruffy "M"s wif the desirable "waterfall" keys. I'm tempted to swap the generator and keyboards to an M100, the 100 gets the last version of the AO-29 and a couple other goodies. I can't save 'em all, might as well save one good one...

[xk49w]

A clipped M3 weighs less than 200 pounds and when rebuilt with mylar or pvc caps is agressive and complete.

But has no foldback, doesn't have 61 keys per manual, and is missing some drawbars and pedals. Still, A Whiter Shade of Pale was done on an M as the story goes.

Oh, and don't forget the Leslie. There are only about 200,000 122 leslies ever built and they are rare as hen's teeth because idiots tear out the amps for some kind of vintage sound horseshit.

Only cheap ones are rare. You can still buy a new 122A today with the 40 Watt tube amp. Expensive though ($2500?). The old ones are better. People don't tear the amp out for some kind of vintage sound horseshit, they tear them out because 40 Watts isn't enough power to compete on stage with any guitar amp driven into distortion. Serious power and upgraded drivers are the order of the day. The organ player I play with uses two 122s, 1200 Watts, active crossover, some kind of JBL (2225s?) and Altec 290 "Giant Voice" horn drivers. It sounds glorious.

How 'bout Keith Emerson? <snip> Emerson would whip his M around on the stage, tip it on its back and hold notes down with daggers apparently.

Keith used an L-100 for all that stuff.

Leslie 122s: Keep this under yer hat but the amp is oh-so-similar to the 147<snip>

Basically a balanced input and unbalanced input version of the same amp. Both 40 Watts, same transformers. 145/147 Leslies were unbalanced, 142/122 used the balanced input. It is common to convert the unbalanced to balanced style. Check out the feedback arrangement from the OPT secondary on the unbalanced version. It's kind of unique.

Leslie and Hammond were two different companies.

Hammond hated Don Leslie's guts. He wouldn't let a Leslie in any Hammond store, but all the Hammond salesmen supposedly owned Leslies. Hammond would change the interface to the tone cab to screw up Leslie. Then the next week Leslie would come out with another adapter kit.

Hammond invented a true pitch-shifting vibrato and chorus in response to the effect of the Leslie speaker. "You won't need a Leslie now because Hammonds have Electronic Vibrato." The Leslie still sounded better. Take a look at that chorus/vibrato circuit if you want to see something inspired.

[CaseyJones]

A clipped M3 weighs less than 200 pounds and when rebuilt with mylar or pvc caps is agressive and complete.

But has no foldback, doesn't have 61 keys per manual, and is missing some drawbars and pedals. Still, A Whiter Shade of Pale was done on an M as the story goes.

I can still get Ms free for the taking especially if they've been stored out on someone's porch and they look like ass. Good luck findin' a free B. (The original Freebie?! ) I have a couple well connected buddies who get 'em fer free once or twice a year, it's a matter of bein' in the loop and bein' there wif a truck at a moment's notice. Nuffin' illegal or underhanded, one just needs to recognize opportunity before the window of opportunity slams shut.

It's more common for old Ms to go out for a couple hundred bucks, Bs start at 2.5k and go outta sight from there. $5k is middlin' fer a B.

In terms of commitment it's easier to talk a guitar player into a low buck M instead of a high dollar B.

Oh, and don't forget the Leslie. There are only about 200,000 122 leslies ever built and they are rare as hen's teeth because idiots tear out the amps for some kind of vintage sound horseshit.

Only cheap ones are rare. You can still buy a new 122A today with the 40 Watt tube amp. Expensive though ($2500?). The old ones are better.

The old ones are better? Ya think?!!

It's the same old shit, we can go out and buy a "reissue Marshall" or a "reissue Fender", the punters lap 'em up and smile because they look like the real thing and they don't know any better. I know what the real thing looks like inside where it counts and more to the point I know what the real thing sounds like.

I'll bet part of the market for vintage Leslie amps is to retrofit "reissue" 122s.

"Expensive"?! Try to build one.

People don't tear the amp out for some kind of vintage sound horseshit, they tear them out because 40 Watts isn't enough power to compete on stage with any guitar amp driven into distortion. Serious power and upgraded drivers are the order of the day. The organ player I play with uses two 122s, 1200 Watts, active crossover, some kind of JBL (2225s?) and Altec 290 "Giant Voice" horn drivers. It sounds glorious.

Maybe I'm just a dumb-ass guitar player but that makes zero sense to me. Yeah, I get it. I get that organ players succomb to the "mine is bigger than yours is" thing and yeah, a gutted bi-amped Leslie is Viagra for keyboards. But you give up that nasty gnarly overdriven Leslie tone. This ain't no Church, this is Rock 'n' Roll. If it don't grind leave it on the truck. It's just a frickin' travesty to do that to a 122. Start wif a 770 and have yer way wif it.

Hammond invented a true pitch-shifting vibrato and chorus in response to the effect of the Leslie speaker. "You won't need a Leslie now because Hammonds have Electronic Vibrato." The Leslie still sounded better. Take a look at that chorus/vibrato circuit if you want to see something inspired.

Necessity is one muther of an invention!

I wish we'd all get with the program when it comes to conservin' rock 'n' roll. There are certain iconic tones that only happen one way in reality. Sure, we can sample 'em and model 'em all day and all night but the real thing is still th' real thing. Ya got yer Strats, yer Les Pauls, yer Marshalls and the like... then of course boutique rarities like Wrecks and Dumbles. Comes the day we're gonna feel as stupid about hackin' up tubes 'n' wheels as we do about '50s Strats wif big ol' splintery aftermarket routes and changed parts.

Save the baby seals! erm... Save the Baby wheels! umm... Save the Baby B's!

Now that I got a cause... do I get to bang hippy chicks?!

[skyboltone]

But (M3) has no foldback, doesn't have 61 keys per manual, and is missing some drawbars and pedals. Still, A Whiter Shade of Pale was done on an M as the story goes.

Of course all that you've written is true, and in the "Beauty and the B" book. But perhaps you aren't aware that foldback is easily added by anyone who can build a guitar amp.
http://www.sympac.com.au/~retrojet/foldback.htm

But more importantly all that wasn't my point. Many of us like the 44 key manuals and 12 pedals. If you want the chorus manual voiced differently it's not an impossible task to wire it differently. It's not a B, it's a full percussion tonewheel spinet that most ears can't tell from a B3, C3, or A100.

All the video's I've seen of Procul Harem show Matt Fisher playing a full size Hammond,
http://www.youtube.com/watch?v=wc0imHr5Mxc
I can't tell but probably a C3. An M3 in the studio? I dunno. I don't see why not, but someday I'm gonna go to a garage sale and find a B3 or one of it's equals with a 122/147 for $50. In Kansas maybe, or North Dakota. Maybe Detroit, where most folks would just shoot themselves if they could afford the bullets.