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    The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

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    Bob Latino
    Admin

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    Join date : 2008-11-26
    Location : Massachusetts

    The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by Bob Latino on Tue May 26, 2015 7:33 pm

    A little known Dynaco ST-70 type amp was the Hammond AO-58-1 amp. This was a hard wired clone of a Dynaco ST-70 amp and was used in the 1960's in a number of Hammond Organs. The circuitry was licensed to Hammond by Dynaco but the amp had a number of differences.

    1. There was no driver board - all the circuitry was hard wired
    2. The chassis was not nickel plated
    3. The power transformer was not "sunk in" like on the Dynaco ST-70
    4. The three transformers used were not Dynaco transformers
    5. No front tube sockets to measure bias. You had to take the bottom cover off and adjust the two bias pots from inside the amp. The bias pots were between the two output tubes and were attached to the inside of the amp with twist tabs in slots on the top of the amp.
    6. There was only a single 8 ohm tap to go to your speakers
    7. There appears to be a diode for the negative DC bias circuit. Dynaco always used a selenium rectifier here.

    Photos below ...

    Bob







    Blitzen

    Posts : 47
    Join date : 2009-07-10

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by Blitzen on Tue May 26, 2015 9:54 pm

    Neat! Hammond, of course, made its own transformers, so no need to use Dynaco's (even if they might be better!)
    I'm not sure why they wouldn't go the circuit board route, though. Point-to-point would mean more labor, but then they might have had to work up their own board.
    Do you know what this was used for/in?

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by sKiZo on Tue May 26, 2015 10:29 pm

    I suppose the first thing you'd want to do if you were to find one of these would be to modify it to use cheaper drivers. Those 7199s are getting expensive ...


    audiobill

    Posts : 271
    Join date : 2014-03-13
    Location : Philadelphia

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by audiobill on Wed May 27, 2015 5:08 am

    Very interesting!

    wildiowa

    Posts : 120
    Join date : 2012-03-19

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by wildiowa on Wed May 27, 2015 8:24 am

    Unfortunately, the Hammonds are the only vintage organ worth anything intact and still used by rock and rollers and others across the globe. Any tone wheel organ, including the M's, L's and especially the C-3 and B-3 are highly sought after and worth much $$ (no power amp in the B or I think the C, as it required a separate tone cabinet.) ....I have been grabbing old organs from churches here in rural Iowa and have quite a few Hammonds and it is soooo tempting to grab those old tube amps...they even used a separate tube amp to drive the reverb tank so there are two power amps in many models. But it is an act of heresy to trash them for the amps. I had an old Gulbransen with an excellent tube amp hand wired in Chicago, it was worth about $30 so I took a chain saw to it and got the Leslie and tube stuff out, but the Gulbransen, Thomas, etc. are worth nothing so might as well grab the goodies out of them. I put the tube amp (2-6L6) in a guitar rig and wow!! I did get gobs of great old tubes out of the Hammonds, especially the 6V6 which I put in my old vintage guitar amps. Recall also that the first Sunn bass amps used a stock Mark III with a preamp slapped in a cabinet. If you have a Hammond tone wheel organ of any type I say sell it and use the $$ buy one of Bob's amps....do not trash them out for the amps!!! But this is another fascinating piece of Dyna history.

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by Bob Latino on Wed May 27, 2015 10:53 am

    sKiZo wrote:I suppose the first thing you'd want to do if you were to find one of these would be to modify it to use cheaper drivers. Those 7199s are getting expensive ...


    Yes - 7199's are getting expensive, since Sovtek stopped making them sometime around 2006 or 2007. The cheapest thing to do if you have one of these amps would be to get 7199 to 6GH8A socket converter. A 6GH8A is the same as a 7199 but has a different pin out. The converter allows the use of 6GH8A tubes in a 7199 tube socket. Dynakitparts sells these at the link below ..

    7199 to 6GH8A socket converter at Dynakitparts

    Bob

    singNdrink

    Posts : 5
    Join date : 2012-10-27

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by singNdrink on Wed May 27, 2015 8:44 pm

    Is this MK 3 homebrew or ........?

    http://i46.photobucket.com/albums/f114/alice4u2e/misc/02_zpsmo2ml4rq.jpg

    http://i46.photobucket.com/albums/f114/alice4u2e/misc/06_zpsfvguges2.jpg

    http://i46.photobucket.com/albums/f114/alice4u2e/misc/01_zpsjr7vhfci.jpg

    http://i46.photobucket.com/albums/f114/alice4u2e/misc/04_zpszyvb7ikj.jpg

    http://i46.photobucket.com/albums/f114/alice4u2e/misc/07_zpsyyineklu.jpg

    singNdrink

    Posts : 5
    Join date : 2012-10-27

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by singNdrink on Wed May 27, 2015 8:51 pm

    Is this MK 3 homebrew or ........?

    singNdrink

    Posts : 5
    Join date : 2012-10-27

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by singNdrink on Sat May 30, 2015 5:42 am

    Hammond made Mark III?



    singNdrink

    Posts : 5
    Join date : 2012-10-27

    Re: The Hammond AO-58-1 > A hard wired Dynaco ST-70 clone from the 1960's

    Post by singNdrink on Sat May 30, 2015 6:27 am

    Bigg made MK 2

    This is a rare Bigg of California tube Amplifier. It is model BP-40-K.




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