Help identifying / any ideas for this amp?

sthslvrcnfsn · Post by **sthslvrcnfsn** » Wed Apr 25, 2007 4:16 am

I found about 6 of these at a surplus store in a rackmount chassis for $10. They are Honeywell "Direct Playback Amplifiers". They have edge connectors on the back that plug into the chassis, which still has all the signal and power supply wiring intact! I think maybe these are line amps or preamps for a tape machine's playback curcuit. Or maybe they were for some more specific tape-based installation. Maybe something non-audio...

Any ideas about what these were originally for? If anybody has any bright ideas about using these in my "studio", please let me know!

The tubes coming out of the top are as follows: 12AU7, 12AX7, and 7025. I think the two large objects coming out of the top closest to the face of the unit are capacitors. They are labeled "C-115" and "C-116". You can barely see the edge-connector on the left of the side-shot photo. I'm not sure what the knob on the very bottom is for.

Thanks
-jim!

emrr · Post by **emrr** » Wed Apr 25, 2007 7:48 am

A.E.C. (Atomic Energy Commission) and Sandia is government stuff, and those tape speeds suggest data recorder and/or seismic measurement equipment for atom bomb testing. Seismic gear tends to favor sub-audio and low frequency audio range at the expense of high freq. But no telling. I see no transformers, so they are probably Hi-Z in and out.

AstroDan · Post by **AstroDan** » Wed Apr 25, 2007 8:46 am

emrr wrote:A.E.C. (Atomic Energy Commission) and Sandia is government stuff, and those tape speeds suggest data recorder and/or seismic measurement equipment for atom bomb testing. But no telling.

If that is the case, then you would take the Blue Ribbon in every 'Best Pawn Shop Find' thread known to man.

I bet Tom Dowd would have known all about these, if he were still with us...

RefD · Post by **RefD** » Wed Apr 25, 2007 8:54 am

"As used to record the final airburst test over White Sands!"

dsw · Post by **dsw** » Wed Apr 25, 2007 10:23 am

and 60 ips? Wheeee!!

??????? · Post by **???????** » Wed Apr 25, 2007 11:20 am

I bet the old stock 12AX7s and 12AU7s in them are worth what you paid.

trask · Post by **trask** » Wed Apr 25, 2007 1:45 pm

damn! anyone know what those little stoplight looking bastards are in there? Are they some weird resistor or something? Everything else is familiar, but I've never seen those... Anyway, they look cool, and therefore, I want them.

emrr · Post by **emrr** » Wed Apr 25, 2007 2:24 pm

trask wrote:damn! anyone know what those little stoplight looking bastards are in there?

capacitors; those are very common.

trask · Post by **trask** » Wed Apr 25, 2007 2:38 pm

emrr wrote:
trask wrote:damn! anyone know what those little stoplight looking bastards are in there?
capacitors; those are very common.

Nice. I've got this odd thing of really wanting to use certain caps/resistors that I find visually appealing, regardless of their actual characteristics.. I've got some caps laying around waiting for the proper project just for that reason.

I think I have a problem...

sthslvrcnfsn · Post by **sthslvrcnfsn** » Wed Apr 25, 2007 4:06 pm

The reason I was thinking that these could possibly be audio-related is because of the popular tape speed settings on the front. Correct me if I'm wrong, but 1 7/8 ips is the speed that regular tape cassettes run at. And then there is 7 1/2 ips, which I think is common for consumer-grade reel-to-reel machines. And of course 15 and 30 ips from professional tape machines.

But then again, there haven't been a whole lot of manufacturers of tape machines, so maybe a company that made audio recording tape machine was contracted to make machines for seismic use. They probably would've used the same motors and other similar parts in order to save money. That would explain away my "common tape speed" theory.

Well, I'll try to get these things powered up. I'll try poking around on those edge connectors with a multimeter, too.

emrr · Post by **emrr** » Wed Apr 25, 2007 4:14 pm

There are tons of companies who made data recording devices, none of whom would be common knowledge in audio realms. Honeywell is/was a very large instrumentation company. I bet I could come up with a list of more than 30 tape machine manufacturers in short order.

Not commonly known is that there was a company making 2" 24 track data recording heads in the early 1950's; I have the announcement in an old tech magazine. Audio is ALWAYS the poor third world behind-the-times bastard step-child.

Mane1234 · Post by **Mane1234** » Wed Apr 25, 2007 6:46 pm

That rocks...What a great piece for a studio even if you never use it....

sthslvrcnfsn · Post by **sthslvrcnfsn** » Thu Apr 26, 2007 2:29 am

Doug-

Since you seem to know a lot about stuff like this piece, can you hazard a guess as to whether or not it'll have any audio applications? As you'll see in the following pictures, there are simple inputs and outputs for each channel located on the back of the chassis. That will save me the trouble of having to identify every contact on the edge connector at least.

Even if these guys don't work, at least they'll look cool once I get them cleaned up and racked! If you are looking at the pictures and wondering, yes, I found them that dirty. They were in a surplus store/warehouse, buried underneath boxes of resistors, 1994 Halloween party favors, and a case of unused, empty and blank cassette tape boxes. It was just that kind of place where a treasure might be waiting if you spent the time digging.

-jim!

emrr · Post by **emrr** » Thu Apr 26, 2007 8:45 am

That's a pretty mild case of dirt for old gear.

Right off the bat, we have BNC connectors for everything, which suggests unbalanced in and out, high frequency use, and high impedance use. Key word here is SUGGESTS. Could be totally wrong, except for the unbal part. And the Hi-Z input part. The output could be a cathode follower lower-Z. Or not. Equalized for playback purposes; that's what the speed switching would do.

You might be able to bypass all the EQ and use them as DI's. Or mic preamps with adddition of input transformers. Again, key word is MIGHT. MIGHT be a s#$%load of work beyond reason. Dependent on gain, EQ, and impedances. And noise level; probably being data recorder preamps could mean that audio noise is not judged significant to the task at hand, and they may not be quiet.

Of course you have to find that one extra unit, or build a perfect clone to fill it out.

You might want to get a geiger counter and check for slightly higher levels of radiation too.

AstroDan · Post by **AstroDan** » Thu Apr 26, 2007 11:32 am

So...what kind of tubes are in there?

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Help identifying / any ideas for this amp?

Help identifying / any ideas for this amp?

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