Studio PA (tube version)?

[AdmiralB]

I just picked up a Studio PA from a pawn shop on eBay.  I've never seen one before, nor any reference to one.

Schematically it appears to be a 60W version of the tube Coliseum PA.  Lots of interesting things in this one, though.  I'm having a hard time dating it, and there is no date in the chassis.  The chassis number is 00820.  It's got 'DMH' red-pencilled inside but nothing else.  

The tube chart indicates KT88s, it has the late-'60s grillcloth, and numbered knobs as opposed to a numbered faceplate.  The choke is Sunn-branded and the transformers are Schumachers - the OT is stamped with the 6-OT designation and is date-coded mid-'68.  The PT doesn't have a Sunn part number, it is stamped 28-2360 and is date-coded mid-'69.

Internally, the filter caps are dated early '67 except for the 20uF on the mic input 12AX7s, which is from late '66.  Also there is a 16uf/350V cap in parallel with the 20uF/250V that is dated 3/70.

The pots all date spring of '66 except for the volume, which is early '67.

The only thing that doesn't look 'right' is the extra filter cap.  The amp is covered with dust, so if it was fiddled with, it was a LONG time ago.

It's got the proper ss plug-in rectifier module for ~'70s Sunns.

Anybody familiar with these?  It has all the appearances of being assembled from a mishmash of leftover stuff circa early '70.

[Isaac]

I have one, complete with the speaker cabinets. Beyond that, I can't say I'm particularly familiar with it. Still has the original tubes in it, too.

[AdmiralB]

Well, I cleaned it up and the chassis does have the remnant of a date on it - can't make it all out but it is 2/?/67, which would suggest that both transformers have been replaced, likely when it was rather young.  They are the proper parts at least.

I took out the extra filter cap and cleaned the pots.  One of the 12AX7s was bad, had AC leakage from the heaters.  I'll put a grounded mains cord on it, but otherwise it runs great.

I'll likely sell it, since I have a couple 200S heads and this one doesn't really sound any different (I thought that it might have more gain, with the extra preamp stage).

[elektrohasch]

I have one too, I guess mine is about '68 and it distorts pretty nicely with guitar because of the different impedance of the microphone inputs I guess. Basicly it's the same as the Coliseum PA, though my Coliseum sounds better. It is said to be the Leslie West amp and also offers the typical Mountain cruch. I use mine in combination with a Soldano SL 60, each with 2 Fender GE 412s and depending on the venue size I take the Studio or the Coliseum - as the Studio definitely only delivers 60 Watts and is not loud enough on some occasions...