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ID this early power amp

gadget73 said:
looks like plated solid copper boards. Maybe 2 sided copper at that. Depends how its done, but usually the large surface is grounded so it provides shielding.
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Tin plated double sided copper boards? what is the purpose of the Tin plating?

I will get an underside photo of one, but at the moment I am just enjoying listening to it too much to open it up again..

I think I am going to go back to the guy I got it off and see if I can trace anymore information...I wish I could get two more of these
 
RuffzGuts said:
What makes you say Dr. Marshall Leach?

Regarding these circuit boards? has anyone ever seen anything like this in any other application?
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The finish and layout remind me of the original Low TIM amp that Marshall Leach publish in Audio magazine in about 1977-78 or so. I purchased a set of them and the companion preamp but never finished the project. All had ground planes like you see in the picture.

You'll find a lot about him and his students from Georgia Tech over the years with Google searches.

Cheers,

David
 
Well it gets better, I dropped into see the guy today who has been clearing out the house as its sold, and he had found some more pieces of the puzzle that he was happy to give to me.

I couldn't get much more information on the origins, apart from the original owner was a friend of his fathers and possibly an engineer for telecom ...or Telstra

So what I picked up was the matching pre amp and impedance matching module for the turntable...

When I plugged this pre amp in...I tell ya, this set up smokes anything I have...and I haven't even plugged my good speakers in yet!......

check this stuff out. pics
 
pre amp

Marked Precision fidelity, but I don't think its related...
 

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more pre amp

Again the work of an artist
 

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TT impedance module

again very nice....might add I found a very nice cartridge thrown in a bucket carelessly with some random electrical junk that was included in sale....I wont say what it is right now as I am in talks with the guy about buying the TT...fingers crossed....
 

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gadget73 said:
keeps the copper from oxidizing. Same purpose as varnishing the board, but you don't have to scrape it off to solder things to it.
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I figured as much, but I thought there may be a little more too it, in regards as to where you would find this kind of application
 
I find it interesting, I just don't have much of use to add. Its nicely made stuff, but that much is obvious. I've never seen an MC matchbox like that, though admittedly I have almost no MC experience. Does the preamp have moving coil level inputs as well then ? That was fairly uncommon back then.


the Precision Fidelity name brings things up, but it seems that the company that existed in the 70s and early 80s made tube kit. Wonder if maybe someone didn't just invent the name and stick a label on .
 
No, there is only one phono input option on the pre amp...But I am guessing that is what this is...?
 

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Power supplies

Here are the power supplies for the pre amp (Right) and impendence module (Left)

As you can see Telecom transformers have been used here...At this stage, looks to me that the guy that built this set up was an Electronics Engineer for Telecom, He had access to all the equipment and components.

And was very good at what he done.
 

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The battery powered thing is an amplifier of some sort. Maybe a split rail supply too, depending how those batteries are wired. Fair guess that it may be the step-up amp for an MC cartridge to boost it to levels that an MM stage can work with.


Nice Classic. Looks exactly like mine.
 
Perhaps this was a project for his engineering students. :scratch2:

http://users.ece.gatech.edu/mleach/lowtim/

http://users.ece.gatech.edu/mleach/lowtim/bckgrnd.html


Student projects.

robinson2.jpg


im344291d2.jpg
 
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I am still puzzled by the all metal circuit board. Is each of the components mounted through a rubber grommet? What do those boards look like from underneath? :scratch2:
 
Boards are grounded, appear to be etched not drilled where components enter...Iam not sure what they are coated in...here's the best pick I can get of underside of main amp board with out cutting wires...
 

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I guess I had kind of hoped some of the so called big gun electronics guru's round here would have made comment on the components and circuits used..
 
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