mystery concert head

[tedw]

I've come across a Sunn head I can't find any info on - it just says Concert on the front and has 3 inputs each with hi and lo jacks, an expression jack, reverb with level and tone knobs. On the back are 2 speaker jacks (200W) and a 7 pin footswitch plug and preamp in and out. 7 transistors on a full length external heat sink. Inspection sticker inside says 4/13/77. Black tolex. Anyone else have one and know more about it? Thanks.

[JoeArthur]

I believe there was a Keyboard version of the Concert. The expression jack makes me think this might be one. 

How about some pics?

I'd like to see the 7 transistor cases on the heat sink as my latest schematic from 1976 still shows only 5 (4 outputs plus the driver). With two extra outputs these could survive 2 ohm operation much better than the usual 4.

[fatlizzard]

I have a concert keyboard that I used for parts for my concert bass and slave,
It does sound like one but it should say Concert Keyboard on the front!!!
(Post some photos)

[tedw]

"Mystery" solved. The word Keyboard was covered with black tape. It actually only has 5 transistors in back. So this is a Concert Keyboard.  Still don't see much info about it anywhere.  The 7 pin jack in back looks to be Reverb related, the Expression jack not sure about.  Looking for a circuit breaker for it now, no luck at Mouser (amp works fine when it is bypassed).  Anyone use these for guitar? Thanks for the replies.

[rick.heil]

Being meant for keyboards I would hazard the guess that it's going to be pretty clean, almost more like a PA head... just a thought.  Not sure what kind of tone you're going for.