Any thoughts on this little guy?

[glebert]

Had this amp head thrown in with a bunch of other gear I was buying. I probably wouldn't have even bothered powering it on but my kid took a shine to it and also I wanted to teach him how to power up stuff on a variac and LBL, test for DC on the output, etc. It turned out to have a bad bridge rectifier. The amp itself is kind of odd, it looks like it has an interstage transformer before the driver transistors, I think. IIRC Sunn did this on SS amps too. The transformers look to be dated 1969. I think the little side circuit board is the tremolo. Doesn't seem very loud, even for a low power amp.

Can't tell if this control plate actually goes with this amp or not, the cutout for it looks like a beaver on ritalin made it, not to mention the exposed metal edge seeming a little odd. No brand, model, or function markings whatsoever.

For some reason that gold patterned control plate makes me think Gretsch, not that I think that is what it is.

[loudthud]

How many wires does the transformer have ?

[J M Fahey]

Probably very similar to this old Kay 708
"2W" ... on a good day.

[nosaj]

Did ampeg ever make something like that?

nosaj

[glebert]

How many wires does the transformer have ?

Six, two each of blue, red, and brown

"2W" ... on a good day.

That is about what it sounds like, but it seems like it could do considerably more. I didn't say it, and you can't see it well in the pic, but the output devices are TO-3, mounted underneath the board and stuff soldered to the pins and mounting screws on the top side. Single voltage rail of +26V, output is capacitor coupled similar to the Kay diagram above.

edit: looking at the Kay parts list it has fairly stout output transistors, so maybe that isn't the best indicator. I would think you could get 10W or so, but I guess it is also all about how much gain there is in the preamp. The output of this is totally clean, no distortion. I haven't hit it with pedals yet

[J M Fahey]

Ok, then drive it to just clipping into a load and measure.

[Nashvon]

My father played with such a thing for a long time to fix it, as I remember he was missing a few wires, they were burned out. And the problem was that no wires fit in place of the old ones, honestly, it took him half a year to get it to work at least somehow. Good luck with that friend!

[glebert]

My father played with such a thing for a long time to fix it, as I remember he was missing a few wires, they were burned out. And the problem was that no wires fit in place of the old ones, honestly, it took him half a year to get it to work at least somehow. Good luck with that friend!

Well, I have it working about as well as I could expect, just by putting in a new bridge rectifier. Sounds really great being driven with a vintage Ross distortion pedal. I have been using it with a pretty inefficient 8 ohm cabinet, something else would probably be much louder.

It looks like the gold on the control panel is may be a decal applied by a previous owner. Part of me wants to take the decal off to see if there is a brand on the panel, but since my son loves it as it is and has named it the "Funky Disco Amp" I plan on leaving it as is, at least for now.

[glebert]

Thread revival for this funky amp. Took off the gold sparkle adhesive stuff off the front and it turned out to be a...Rosac Nu Amp VI? LIke this one but the adhesive pulled almost all of the blue paint off the front, I have not had it apart again to compare the schematic to the Kay that Juan provided above, anyone seen a specific schematic for it? I can't find much info at all on the Nu Amp (don't even get me started on the VI part, since there is no evidence of I through V).



I am totally loving the sound that I get from this with reverb and dirt pedals, don't really know what it is, maybe the compression?

I used it in the intro to this terrible Youtube video. https://youtu.be/7U2KdwA6JzI

[The Dude]

Cool! That sounds amazingly like John Deacon's Deacy amp- used by Brian May on some of the early Queen stuff. Just curious, are the transistors germanium?

[glebert]

Just curious, are the transistors germanium?

No idea! At this point I like the sound so much I'm treating it like Schroedinger's amp and worry if I open it up I will somehow lose the magic.

The distortion in the audio clip is all from dirt boxes (Boss Super Overdrive -> Maxon ROD 880 Real Overdrive), it is pretty much a clean amp so not like a Nu Fuzz. The tremolo is a totally separate board, and I think they did a tremolo pedal and wonder if that circuit board is just a pedal brought into the box.

edit: maybe they didn't do a tremolo pedal...

[g1]

Cool! That sounds amazingly like John Deacon's Deacy amp- used by Brian May on some of the early Queen stuff. Just curious, are the transistors germanium?

Interesting article about the Deacy here: https://hackaday.com/2017/05/08/a-qu...the-deacy-amp/
I have a feeling our nosaj is the jason that Mitch mentioned in the comments section.

[tedmich]

Here is some info about the company Rosac that was out of Bakersfield CA until it closed in 1978.
https://www.effectsdatabase.com/model/rosac#
They made several amps including the Bassmaster, Leadmaster and several versions of the Malibu. They came out of the ashes of Mosrite, and not a single schematic exists for any of these that I can find, although their pedals are a different story!