Ampeg Bassamp 820/830 schematic?

[glebert]

Because I love buying old junk I acquired a 1956 (?) Ampeg 830 Bassamp project. Example and basic info here (http://www.ggjaguar.com/830f.htm)

Mine isn't marked as an 830, but is single preamp and 30 watt. According to this flyer an 820 should be the same except less power. Mine has also been rehoused into a head-ish form in what looks like an old fruit crate.

I have a schematic for a later 835 but don't know how much stuff changed. The flyer makes it sound like these were built onsy-twosy, I don't know if models tended to stray from the schematics even within a certain model.

[J M Fahey]

Beautiful.

[glebert]

I was wrong, it is an 835, the schematic I have seems to match up perfectly. I was thrown by the seller saying it was '56, which was before the 835, but obviously some of the parts may be older. There are some tremolo 835s as well so that adds much confusion when trying to figure out the model number.

[glebert]

Beautiful.

Mine not so much

[Steve L]

My experience with older Ampeg amps from that era is that they mixed and matched a lot of preamps, power amps, speakers and cabinets into several different models.

Here are a few pictures of what was called a D-50 (if I recall right). It has the 833 preamp, here labeled "Duette", and a 35W power amp that I could never find a schematic for and I have almost all of them.
I say 35W because that is what it measured. They may have tried to sell it as 50W.

It was an interesting power amp circuit in that it had two output transformers.
One was used in the normal manner and the other looked it was wired as a means of negative feedback.
Someone had tried to fix the amp, but did not succeed. It worked somewhat, but had a 60-cycle hum that would not go away. I bought it from them.

Because of the lack of a schematic and the possibility of it being mis-wired at some point, I ended up completely changing the power amp circuit to a 1961 B-15N circuit, using the same power supply and one output transformer.
That worked perfectly. A friend has the amp now. The tremolo is the best I have ever heard. Nothing comes close.

I hope yours turns out well.

Steve

[J M Fahey]

Post some schematic, at least from a close version.

[glebert]

Post some schematic, at least from a close version.

So far this one seems to match well with mine.

835 Bassamp.pdf

[glebert]

I did find a reddit entry (https://www.reddit.com/r/ToobAmps/co...oration_album/) of someone working on an 820-ish amp and he said the power amp was like the 835 but the preamp was more like this one.

bassamp625preampschem.pdf