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 Post subject: Who made this amp
PostPosted: Nov Fri 25, 2022 4:01 pm 
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Joined: Jan Sun 31, 2016 8:49 pm
Posts: 70
Location: Hamilton, ON. Canada
Recently picked up this neat little amp. Looking to see who may have made it. Tube lineup is 6SC7, 6SC7, 6SJ7, 807, 807, 5X3

Someone has replaced the audio output transformer and I will need to find a suitable replacement

Thanks John


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first peek under the hood.JPG
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 Post subject: Re: Who made this amp
PostPosted: Nov Fri 25, 2022 4:24 pm 
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I'd say home-brew.


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 Post subject: Re: Who made this amp
PostPosted: Nov Fri 25, 2022 6:02 pm 
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Location: Macedon NY 14502
I would also say home-brew - since sockets are mounted with screws, and since controls are wired to cover. And the tiny output transformer - almost missed it!

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 Post subject: Re: Who made this amp
PostPosted: Nov Fri 25, 2022 10:00 pm 
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Location: Hamilton, ON. Canada
The person I bought it from thought it might be home brewed. Those metal chicken head knobs with engraved letters make me think military, some military equipment from WWII had similar letter markings. All those tube socket bolts, and the other mechanical parts have red paint applied after assembly, a form of early Locktite ? Something I've also seen on miliary equipment.

I've worked out the schematic, it's a fairly basic octal amp. with three inputs and a nice tone stack. The light patch under the Bass and Treble controls suggests to me it may have had a banner with a name etc. Wishful thinking?


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 Post subject: Re: Who made this amp
PostPosted: Nov Fri 25, 2022 10:25 pm 
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Location: Detroit, Michigan, USA
The wiring and overall assembly is way too sloppy to have been factory built, but as the others noted, the fact that it's assembled with screws and nuts is indicative of home brew.

Probably built from a generic schematic found in the back of tube manuals or a magazine article. Since 807's are electrically identical to older 6L6's, the builder may well have used what they had on hand.

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 Post subject: Re: Who made this amp
PostPosted: Nov Sat 26, 2022 3:00 pm 
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Joined: Jan Sun 31, 2016 8:49 pm
Posts: 70
Location: Hamilton, ON. Canada
From a little more research I've done, it appears it may be an early Soundmaster PA by Hy Bloom in Ottawa Canada. One practice he used was a common Buss bar instead of multiple grounds all over the chassis. Another was those red paint dots indicative of Blooms work. The grill work on the doghouse appears to be the same design as used in his Soundmaster 085 model.

Does anyone have any early information on Soundmaster from Ottawa Canada?


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 Post subject: Re: Who made this amp
PostPosted: Nov Sat 26, 2022 5:22 pm 
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Location: Monteith, Ontario, Canada
https://ottawacitizen.com/news/the-sound-man

http://www.ottawacountrymusichof.org/in ... ybloom.htm

https://www.radiomuseum.org/dsp_herstel ... y_id=18439

https://www.google.com/search?client=fi ... r+%2BBloom


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 Post subject: Re: Who made this amp
PostPosted: Nov Sun 27, 2022 5:55 pm 
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Location: Hamilton, ON. Canada
Here's a picture of a similar amp made by Soundmaster's Ottawa Ont. Canada


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161424908_192654542579587_5271244889226273399_n.jpg [ 318.54 KiB | Viewed 839 times ]
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 Post subject: Re: Who made this amp
PostPosted: Dec Sun 04, 2022 11:41 pm 
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Location: Dayton Ohio 45424
Needs some output iron which may cost you. But the positive is that the output tubes are 807 and you often can get those cheapish. Even compared to the similar 6L6 tubes.

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 Post subject: Re: Who made this amp
PostPosted: Dec Mon 05, 2022 12:46 am 
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Location: Boston, MA
Funny -- that output transformer, small as it is, looks absolutely original. And there is not a lot of room to install anything a whole lot bigger. I'm guessing the amplifier is good for about 20 watts. If you could measure the B+ we could get a better idea of output power.

-David


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 Post subject: Re: Who made this amp
PostPosted: Dec Mon 05, 2022 2:07 am 
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The output looks original to me as well (have more antique amps than radios), looks like someone replaced or resleeved the grid wires since new, but that could be the lighting in photo, too.
Once you replace the caps, that little thing could be the loudest little amp in the world with the affordable 807's powering it!

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 Post subject: Re: Who made this amp
PostPosted: Dec Tue 06, 2022 9:18 pm 
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Joined: Jan Sun 31, 2016 8:49 pm
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Location: Hamilton, ON. Canada
Thanks for the replies on this amp. The original output transformer was a two-bolt design, you're correct, not much real estate in there. I had a Hammond 125D in my junk box which I installed it to get the amp functional. After restoration and running on a Variac at 85% the 807 plates see 325 volts at 45ma., so it's putting out 13 watts. The amp sounds fantastic, with nice clear Bluesy tones.

I have an Electrosonic catalogue from 1954/55, listed in it are possibly what the original transformers were, Hammond 68 or 126. Both listed as Heavy Duty. Here's a picture of the restoration under the hood.


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our Soundmaster amp after restoration.JPG
our Soundmaster amp after restoration.JPG [ 292.82 KiB | Viewed 509 times ]
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 Post subject: Re: Who made this amp
PostPosted: Dec Tue 06, 2022 9:36 pm 
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Joined: Jan Sun 31, 2016 8:49 pm
Posts: 70
Location: Hamilton, ON. Canada
Oh sorry, forgot to mention those grid wires have resistors in them under the hand wired shields. They look original to me, imagine taking the time to hand wire ground shields like that. I liked the technique, so I left them in place. As usual, there were extra electrolytics jumped to earlier leaky electrolytics, often see this in radio restorations as well.

Would have liked to install a Hammond 1750 or 1637 output transformer but there is simply no room for either.

The original two-hole design had a hole spacing of 2 3/8" which seriously limits available replacements. I had to drill another hole to get the 125D to fit, it has a hole spacing of 2 3/4" if memory serves.

John


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 Post subject: Re: Who made this amp
PostPosted: Dec Wed 07, 2022 1:01 am 
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Kind of reminds me of an old Masco P.A. amp.

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