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Author Topic: Hammond AO-35 conversion tone stacks  (Read 17727 times)

Mike Sokol

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Hammond AO-35 conversion tone stacks
« on: March 05, 2015, 02:19:00 PM »

So I found a Hammond AO-35 Reverberation amp in my pile of old tube things, and see that it can be made into a really nice 18-watt guitar amp. I powered it up and the old amp works perfectly, no hum or unwanted distortion, and the power supply transformer has less than 50 micro-amp leakage to ground. It just needs a tone-stack and a case to become a playable stage amp. Have any of you guys done this sort of conversion? If so, what did you like for a tone-stack? I'm leaning towards a single knob tone control such as the Moonlight circuit shown here: http://amps.zugster.net/articles/tone-stacks and Dr. Z has a similar circuit for his Carmen Ghia amps.

BTW: My 1954 Danelectro Tweed still sounds fantastic after a few weeks of breaking in, and I'm amazed at how great a simple one-knob tone control can sound. So I'm looking for something similar for the AO-35 conversion.  Ideas?  ;D

David Morison

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Re: Hammond AO-35 conversion tone stacks
« Reply #1 on: March 05, 2015, 02:23:42 PM »

So I found a Hammond AO-35 Reverberation amp in my pile of old tube things, and see that it can be made into a really nice 18-watt guitar amp. I powered it up and the old amp works perfectly, no hum or unwanted distortion, and the power supply transformer has less than 50 micro-amp leakage to ground. It just needs a tone-stack and a case to become a playable stage amp. Have any of you guys done this sort of conversion? If so, what did you like for a tone-stack? I'm leaning towards a single knob tone control such as the Moonlight circuit shown here: http://amps.zugster.net/articles/tone-stacks and Dr. Z has a similar circuit for his Carmen Ghia amps.

BTW: My 1954 Danelectro Tweed still sounds fantastic after a few weeks of breaking in, and I'm amazed at how great a simple one-knob tone control can sound. So I'm looking for something similar for the AO-35 conversion.  Ideas?  ;D

If you're not already familiar with a variety of types, there's a cool little simulator that allows you to model a few pretty simple circuits at Duncan Amps.

Sorry if this is old hat to you,
David.
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Scott Holtzman

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Re: Hammond AO-35 conversion tone stacks
« Reply #2 on: March 05, 2015, 03:06:53 PM »

So I found a Hammond AO-35 Reverberation amp in my pile of old tube things, and see that it can be made into a really nice 18-watt guitar amp. I powered it up and the old amp works perfectly, no hum or unwanted distortion, and the power supply transformer has less than 50 micro-amp leakage to ground. It just needs a tone-stack and a case to become a playable stage amp. Have any of you guys done this sort of conversion? If so, what did you like for a tone-stack? I'm leaning towards a single knob tone control such as the Moonlight circuit shown here: http://amps.zugster.net/articles/tone-stacks and Dr. Z has a similar circuit for his Carmen Ghia amps.

BTW: My 1954 Danelectro Tweed still sounds fantastic after a few weeks of breaking in, and I'm amazed at how great a simple one-knob tone control can sound. So I'm looking for something similar for the AO-35 conversion.  Ideas?  ;D

Dr. Z is right here in CLE, always a fun place to stop in.

If you have too many toys on your plate I would not mind playing with it.  PM me with a number if you want to sell.

Thanks
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Scott AKA "Skyking" Holtzman

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Mike Sokol

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Re: Hammond AO-35 conversion tone stacks
« Reply #3 on: March 05, 2015, 03:11:12 PM »

If you're not already familiar with a variety of types, there's a cool little simulator that allows you to model a few pretty simple circuits at Duncan Amps.

Sorry if this is old hat to you,
David.

Definitely NOT old hat to me. I've seen this modeling program mentioned on a few DIY guitar amp sites, but I've not downloaded it until now. Really great interactive interface with a bunch of suggested tone circuits to try. I'm going to make the tone stack removable with RCA connectors so I can plug in a new circuit anytime without butchering everything. Thanks very much for the link.

Ned Ward

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Re: Hammond AO-35 conversion tone stacks
« Reply #4 on: March 05, 2015, 03:36:31 PM »

Mike - this is how Richard Goodsell at Goodsell amps got his start - turning old Hammond amps into guitar amps. He's a great guy and very reachable - may be worth talking to him!

I second Scott on Dr. Z's being a fun place to stop in - tiny, but wall to wall quality. Plus seeing stacks of Schumacher and Triad transformers, all hand soldering, amazing how many great amps they put out of that place. I visited in 2011 and am hankering to go back!
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Mike Sokol

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Re: Hammond AO-35 conversion tone stacks
« Reply #5 on: March 05, 2015, 03:44:30 PM »

Dr. Z is right here in CLE, always a fun place to stop in.

If you have too many toys on your plate I would not mind playing with it.  PM me with a number if you want to sell.

Thanks

I DO have too many toys (just ask my wife) but I'm not ready to give them up just yet. Once the AO-35 conversion is done I may modify a HeathKit W7-A to be a cool bass amp. I've had that one on my back shelf for 35 years and never fired it up. Guess it's time to kick the tires and light the fires.

Scott Holtzman

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Re: Hammond AO-35 conversion tone stacks
« Reply #6 on: March 05, 2015, 04:45:55 PM »

I DO have too many toys (just ask my wife) but I'm not ready to give them up just yet. Once the AO-35 conversion is done I may modify a HeathKit W7-A to be a cool bass amp. I've had that one on my back shelf for 35 years and never fired it up. Guess it's time to kick the tires and light the fires.

To me, that's far more valuable than the Hammond amp.  That's a real slice.  Too bad you don't have two of them.  Would may a great stereo.  Powdercoat the bases, new caps and tubes and a general cleanup.

Anyway.
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Scott AKA "Skyking" Holtzman

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Mike Sokol

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Re: Hammond AO-35 conversion tone stacks
« Reply #7 on: March 05, 2015, 05:00:44 PM »

To me, that's far more valuable than the Hammond amp.  That's a real slice.  Too bad you don't have two of them.  Would may a great stereo.  Powdercoat the bases, new caps and tubes and a general cleanup.

Anyway.

I also have a matched pair of Dynaco MKIII tube hi-fi amps that were factory built and in beautiful condition. I plan to restore those to factory specs without any crazy mods. I used to use them in my studio, but one power supply cap went a little nuts so I put them on the shelf. I won't get to them until next year at this rate, but that would be another fun restoration project.

Mike Sokol

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Re: Hammond AO-35 conversion tone stacks
« Reply #8 on: March 05, 2015, 05:24:13 PM »

I also have a matched pair of Dynaco MKIII tube hi-fi amps that were factory built and in beautiful condition.
8)

Ummmmm..... Maybe I do have too many toys.

Josh Millward

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Re: Hammond AO-35 conversion tone stacks
« Reply #9 on: March 05, 2015, 06:10:57 PM »

8)

Ummmmm..... Maybe I do have too many toys.
No.

Stop thinking that.

You can never have too many toys.

Now, the real question is how often you play with them...
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Josh Millward
Danley Sound Labs

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Re: Hammond AO-35 conversion tone stacks
« Reply #9 on: March 05, 2015, 06:10:57 PM »


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