Sonny Jr 2

Technical assistance and general discussion on harp amps

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Sonny Jr 2

Postby SuperBee » Sat Sep 09, 2017 1:22 pm

I just landed an SJ2. This is an unusual amp, and I haven't mapped it yet, but it has 2 parallel power amps, each driving 3 8" speakers.
Each power section is running a pair of 6L6 tubes. Claimed wattage is 25w per OT
Can remove tubes from one section and plug all speakers into one OT. I'm yet to try it.
Preamp shipped with 12AT7' and 12au7 PI. Preamp is wired parallel but this is where I've stopped looking so I'm unclear exactly what happens after that.
I believe it will be loud enough, sounds loud at close quarters but maybe won't project like a 410. Can run 2 extension cabs, perhaps this was designed to overcome the limitations of the 8" if needed. I dunno how many were made, mine is number 80. I'd like to see a schematic to save me peering inside with a lamp and magnifying glass, but expect may be no published picture
SuperBee
 
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Re: Sonny Jr 2

Postby T-Bone Bruce » Sat Sep 09, 2017 5:35 pm

Hi Dave, Congratulations on getting the SJ2.
Preamp is a bridged 12A*7, with a big plate resistor (220K) running to volume and tone controls-the SJ1 only has a single treble cut, but yours should have a TMB tonestack... Phase inverter is a paraphase with a shared cathode resistor IIRC. Check out Jim Rossen's "Janamp" layout- it's based on the SJ1, so I would suspect something similar?
https://sites.google.com/site/jimdramps ... amps-files.
What on earth was I thinking when I played THAT?
T-Bone Bruce
 
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