converting Hammond reverb to guitar

[shovel]

I have an old Hammond organ reverb I want to use as a stand alone reverb unit and need to know where to start.Can it be done with what I have here?It uses 2 ECL86s and 1 EZ81.Thanks for ane help.

[Sweetfinger]

Years ago...

I had that same chassis, but with 2 EL84's. I ended up using the OP transformer in a rebuilt Harmony amp that had a tweed pro power section and a blackface pre-amp. sounded awesome! That should make a great little 12 to 20 watt amp, but you'll have to add a pre-amp tube and socket, or ditch the recto tube. Dig the little light bulbs used for current limiters.

[Arthur B.]

I have an old Hammond organ reverb I want to use as a stand alone reverb unit and need to know where to start.Can it be done with what I have here?It uses 2 ECL86s and 1 EZ81.Thanks for ane help.

Assuming that you've gone over the amp and checked that it's operatiing correctly, add a reverb tank to the output since I don't see one.You may have to rebias it into Class A to reduce power and improve linearity.

[shovel]

reverb

Assuming that you've gone over the amp and checked that it's operatiing correctly, add a reverb tank to the output since I don't see one.You may have to rebias it into Class A to reduce power and improve linearity.

I have the origonal tank and the amp worked when I took it out of the organ.I just need to know where to start as far as an input jack and a way to adjust the amount of reverb going to my Bassman Ten.

[john82]

hey what a great idea, i hope you can do it.
sorry i can't help i don't know much about electronics but please update if it works, i'd like to know... I also have an organ with a built-in reverb box, maybe i can make into a stand alone too.

_______
Johnny
http://www.guitars101.com

[Steve Conner]

AFAIK, that little amp drives the speakers inside the bottom of the Hammond organ itself, and the reverb tank was also driven off its output. But I think the exact wiring depends on the Hammond model.

The amp is total overkill for driving a reverb tank, way more power than you need, and would probably be unhappy without its speakers.

I know a guy who has a Hammond, and I know he disabled the speakers inside the organ itself because he plays through a Leslie, but I'm not sure what he did with his reverb tank.

[smothaudio]

conversion to stand alone reverb

Funny to stumble on this thread, I happen to be doing the same thing! Here?s what I did:

Basically I separated the verb recovery amp (the first stage with the transistor) from the rest of the circuit. I feed my signal into the tube part and into the verb tank from the output transformer, from there I took the output of the tank and fed that into the transistor recovery circuit and then to my amp.

I know the output of the amp is meant to drive a speaker, so I used a 20 watt 8 ohm adjustable ceramic wire wound resistor from the output to ground to take the weight, then I fed the adjustable tap from the resistor into the reverb tank so as not to over load it. I'm not sure how much signal the tank can take, so I just adjusted it up until I couldn't hear a difference and then backed it off a bit. I'm getting no clipping and it sounds clean enough. I put a 1M resistor to ground on the grid of the first preamp tube and a 1M pot from the grid to ground on the second for a drive control, plenty of unused gain, but I don't mind... I also got rid of the current limiting lights, and the feedback wire.

It's a crude dirty Frankenstein job, but it works-though has a few minor bugs to iron out. I have plans to replace the rectifier tube with diodes, then use the empty socket for a 12ax7 stage to replace the transistor circuit and enable a wet/dry mix and a tone control (like the fender 6G15). I currently use a 2 channel fender bassman amp. I split my guitar signal and feed one into the modified reverb unit with its output going into channel one and take the dry branch into channel two. Then I can make a nice wet dry mix with independent tone controls. It's interesting but still requires some more tweaking. I think once I put the tube in, get all my levels right and make the wet dry control, I?ll be a lot happier.

Best of luck!

[imo]

these are great guts for an AC15 style amp. I made one out of a similar part, used the El84's, used the 12AX7, subbed in a Ef86, and used an EZ81 rectifier.
Thing sounds awesome, and took only a few hours to put together
Ian

[olddawg]

The reverb unit seems to be a separate chassis from the main amplifier in these units. Everyone is suggesting to convert the reverb unit to a stand alone amp. It was not used as such in the original organ. It was used with another amp chassis and a small internal speaker. There should be a way to convert the reverb unit to instrument level signal and add some controls (intensity, dwell, etc). Here is something similar on eBay with all of the parts: http://search.ebay.com/_W0QQsassZshortsets

Also with the repro Fender stand alone reverb units being inferior and rather pricey and with the originals being virtually gold plated, it would be a great project to pick up one of these Hammons for $50 or so and convert it to an approximation of the Fender. I have not compared the schematics. I was going to build a Fender Reverb from scratch once and found it would be cheaper and easier to buy a new repro and convert it to original specs. It seems that if you get a usable chassis, the right transformers, and a good tank with these Hammons it might be a much cheaper and not too dificult way to do it. Then again, if it was tht easy, everyone would be doing it.

[Marc]

I'll second Ians' post. I've used these amps several times for very nice AC-15 / Spitfire clones.

Marc

[H20rider]

Conversion

I have a Hammond Reverb unit with tank. How would I go about converting to a small guitar amp? I'm an electronic illiterate, so I'll need a site for dimwits.
Thanks

[cminor9]

I have a Hammond Reverb unit with tank. How would I go about converting to a small guitar amp? I'm an electronic illiterate, so I'll need a site for dimwits.
Thanks

Don't take this the wrong way, but if you are an electronics illiterate, the only thing you'll turn that into is a fried transformer, some toasted el84s, and maybe you'll even get electrocuted out of the deal. Don't go cracking that amp open, either, until you've learned how to discharge filter caps That is, if you'd like to retain your bilateral symmetry and a pulse.

Now, if you are willing to spend some time learning about electronics and tube amps, you'll turn that into a burner of a guitar amp. Hammond made a few reverb amps, but the one in my M3 has a couple of transformers and an el84 push-pull power stage. That'd make a nice little 8-15w amp, which is exactly what you want if you love the tried-and-true sound of a little amp getting the snot beat out of it (and who doesn't love that?) I am actually trying to get my hands on old Hammond stuff, because you can make a nice guitar amp from that stuff. Often, people have old organs that have broken, but the circuitry is still salvagable.

Anyway, if you really want to learn, first thing to do is learn about electrical circuits. http://www.allaboutcircuits.com/ and http://www.angelfire.com/electronic/funwithtubes/ You don't need to become an engineer, but you do need to know the basics. At least know how AC and DC behave, how to read a schematic, and what transformers, capacitors, resistors, and vacuum tubes do. Learn how to solder. Learn how to be safe when dealing with electricity.

Then learn about tube amps. This is a very simple read, and will teach you what you need to know if you want to fix or build (not design, build!) a tube circuit. http://www.pacificrecone.com/JackDarrBook.html

Then, study guitar amp schematics. Best to start studying Fender schematics, since that is pretty much the starting point for serious guitar amps. http://ampedia.redbeartrading.com

Also, check out a schematic for the Hammond amp you want to convert.. There are a lot of Hammond schematics here: http://www.captain-foldback.com/Hamm...schematics.htm

If that sounds like a lot, it is. But if you are willing to put forth some effort and want to learn, then you might be rewarded with a nice little guitar amp, and enough knowledge to build many more. It's a very rewarding hobby. If you don't want to put forth the requisite effort and aren't interested in electronics, save yourself some headache and sell it and just go buy an amp.

[H20rider]

I appreciate the warnings, encouragement, and caveats. They all make sense. I suppose I'm actually electronically semi-literate. I've recapped a couple of amps and made basic repairs, but will use the advice provided. This is exactly what I was looking for. Thanks