Gates SA-70 restore and rack

Here's a process log.  Restored and racked these for a client (had lassoharp help with some of the restoration work), he had the amp modules and sent them to me.  He wanted all the modern conveniences, along with padding for line use as well, so the input pad is -20/30/40.  The interstage gain control was on the module originally, and was not meant to be used other than as a pre-set trim, I've brought it out to the front panel after checking that response was not affected.  I found a real Gates logo for the front panel.  PSU's are all DC and off-the-shelf.  Linear B+ and filament, switching 48V.  Case is Bud, with optional internal chassis panel for PSU isolation.  I've passed it off to another studio for performance evaluation, now that I've finished my own eval, and they love it so far. 

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That's a box of happiness.  Great work!

very nice!
These are the UTC version if I remember your previous post correctly. Any idea what quad shielded means, and how many dB of shielding?
And how equivalent are these to the LS series?
I assume there is no crosstalk between adjacent channels?
Again, inspiring work.

No crosstalk.  Noise better by at least 10 dB than Gates specified.  According to Gates paper, the input is LS-10X equivalent.  They measure like a preamp built with LS iron.  Quad shielding means there are four individual interleaved shield cases, which Kenyon appears to have initially patented.  Four gives 90dB external hum rejection. 

Output equivalent is a ls-50?
The ls-10 and ls-50 have -74 dB hum rejection from their 1955 catalog, while the ls-10x is -90 db, so that lines up.

The output in this case is rated for 20mA, unless it's a typo of 2.0mA. LS-50 would work here.

emrr said:

The output in this case is rated for 20mA, unless it's a typo of 2.0mA. LS-50 would work here.

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I'd vote typo. (based on given specs)

Engineering meets art right here.

What a top-flight rebirthing for some very nice vintage pieces.

They never had it so good 

Perfect for the 4th of july! 

Very nice! thanks for sharing!

Couple q's:  Are the pads just U pads up-front? Are you just swapping the shunt R?

Umm, I'm eventually going to be racking a few RCA's   and wondered about the PSU.. I'm sure you've used all kinds of PSUs in the past..  Have you noticed an improvement between simpler non-regulated DC PSUs and these uber-PSU's?  I like the little 48V-er, I was going to use some sort of multiplier off the heater PS, but this will be easier.

Oh yeah, what did you use for the labels?

pad: build out on the series resistors

PSU's can sound different.  Or the same.  No easy answer.  For client work these have commercial application safety ratings, and are also the cheapest path when you factor labor cost.  I've never had one go bad so far.  They are adjustable for voltage.

Laminated sticker paper with clear coat over them. 

Oh, that's a beaut, Doug!!

Wow .........Astounding Beautiful Work Doug ....!

emrr said:

pad: build out on the series resistors

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sorry I had a short-circuit in my brain...

thanks again for posting!

emrr said:

pad: build out on the series resistors

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Nice build, thanks for posting. Can't see it, are those blue toggles Miyama? I just build almost the same thing, although 1ch and my psu. Beside -20 and -40dB U pad it also has -30dB position which needed to be O pad, otherwise it had too high impedance for a mic. Did you do the same or used U pad?

It's all U, I envision -30 used for line sources, but fine with mics too. The AP tells me input Z is over 20K for 0, -30, -40, and around 18K with -20.  You can't completely trust the AP with inductive loads, but it gives a relative idea.  Switches are Mountain. 

Outstanding work as usual Doug!
Could you share which PSU units you used? I'm about to do a rack-up similar to this (a pair of RCA BA-21a and pair of GE BA-1-F in a shared chassis) so power requirements look about the same. I only hope my end result is as nice as this...

Thanks,
Paul

International Power for B+ and fil, Mean Well for phantom.

Beautifully done.

Thanks everyone.

It's back from the other studio, they didn't want to return it.  Off to the client this week. 

Great, clean and nice work!