70's Winson A6 Mystery Amp and Help

[ScoopMyMidsDaddy]

I found this on CL a while back. It was listed as a 70s Winson A6 combo made in the USA.I couldn't find much info on it besides the brand having an amp called A2. I opened it up to replace the filter caps that were shot and took some gutshots. My current issue is the amp sounds really dark and I'm wondering the best method to brighten it up or give it some clarity. Its got an old eminence square back ceramic speaker, which I hooked up to another amp and it wasn't dark sounding. Also any education on the build or similarities to other amps would be greatly appreciated.






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[dmeek]

Can you lift the circuit board and post a photo of the foil side.

[DrGonz78]

I was gonna say it looks very similar to the Marlboro amps from the 70's. Then I see there is actually Marlboro printed on the circuit board. Also, those same amp designs were associated with Hohner solid state amps.

[ScoopMyMidsDaddy]

Can you lift the circuit board and post a photo of the foil side.

Will do on friday morning and follow up. Thanks

I was gonna say it looks very similar to the Marlboro amps from the 70's. Then I see there is actually Marlboro printed on the circuit board. Also, those same amp designs were associated with Hohner solid state amps.

I can't believe I missed that when working on it lol. Looking at some marlboro gutshots and its extremely similar. Can't find a Marlboro with the same control layout but close enough. Guess I'll just start with making a schematic when I get a minute. Doesn't sound too bad, just pretty dark.

[glebert]

I like how generic the chassis is, with holes everywhere, just pick which ones you want to use for a given amp.

[J M Fahey]

Tracks are visible from above that makes tracing easier.

Worst case shine some light under the PCB

Then post it here for comments.

Preamp at least looks very simple, only a couple transistors, and power amp is transformer driven.

There´s even a third tiny transformer, probably for spring reverb tank

Some manufacturers (such as Univox) imported ready built Japanese chassis and mounted them in US made cabinets, with US speakers.

[galaxiex]

Check the input impedance, I'll bet it's on the low side, that can load down the guitar signal and make it dark sounding.

On some of these old SS amps I'll add a input buffer to get the input impedance to ~ 1Meg.

I have a Marlboro amp that has a similar looking circuit board.
Indeed, the whole Marlboro amp looks similar to that one...

[ScoopMyMidsDaddy]

Check the input impedance, I'll bet it's on the low side, that can load down the guitar signal and make it dark sounding.

On some of these old SS amps I'll add a input buffer to get the input impedance to ~ 1Meg.

I have a Marlboro amp that has a similar looking circuit board.
Indeed, the whole Marlboro amp looks similar to that one...

Haven't really messed with boosting input impedance. How would I roughly go about that with a build like this.

another poster pointed out that the my winson's board literally says marlboro on it lol. Somehow I missed it.

[galaxiex]

Haven't really messed with boosting input impedance. How would I roughly go about that with a build like this.

another poster pointed out that the my winson's board literally says marlboro on it lol. Somehow I missed it.

Input buffers are fairly simple.

Here's a page to get you started...

http://www.muzique.com/lab/buffers.htm

I often use the TL071 op-amp buffer, but the other discrete transistor buffers would work as well.
These buffers are intended for 9 volt guitar effect pedals, but work very well on the front end of an amp with higher voltages.
Just have to take power from an appropriate place in the amp and be sure the voltage does not exceed the buffer device rating.

Or.... you can avoid all that and just stick a buffered pedal in front of the amp...