trinityamps.com

I picked up one of these the other day. Never heard of the company before, but the amp is from the mid-60s and appears to be a possible copy of a Vox Pacemaker, with a single tone control. It uses a 6CA4 rectifier tube, a pair of EL84 output tubes and a pair of 12AX7s. It has tremolo and it looks like it uses a phase shift oscillator to modulate the power tube bias. Sounds cool and has a pretty warm tone. I like it!

So, the question is, has anyone here ever even heard of this amp? And even more doubtful, has anyone ever seen a schematic for it?! There is one glued to the bottom of the enclosure, but it has suffered water damage and it has become largely illegible...

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PJM

http://www.diyguitarist.com

For anyone interested, here is what the amp looked like when I got it: http://www.diyguitarist.com/GuitarAmps/MarkX.htm

And here is what it looks like now:
http://www.diyguitarist.com/GuitarAmps/MarkX-Mod.htm

I think I am going to attempt drawing up a schematic for it. It won't be easy as the wiring is kind of a rat's nest...

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PJM

http://www.diyguitarist.com

OK, here's a schematic I have drawn up using the schematic attached to the amp as a guide - which was a PITB. I still have to fill in a few missing values, but I will verify those in the next few days. Let me know if you see anything that looks funny!

http://www.diyguitarist.com/PDF_Files/MarkX-Schem.pdf

Very simple little circuit. Sometimes the simple ones sound the best! It's not quite an exact copy of a Vox Pacemaker, but it's very similar.

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PJM

http://www.diyguitarist.com

Nice job on the refurb Paul and that's a nice little schematic there. I'm curious how the trem sounds? Can you compare it to anything you ever heard before? This might make a nice little practice amp for an aspiring young player.

I hadn't heard of this mfg. until you brought it up here.

Very interesting. Very simple! Nice!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks coco. The tremolo sounds kind of what I hear on some Bill Frissel recordings. It's nice sounding to my ears. It will throb with the intensity control at max with no input. I suppose that's normal for a bias type tremolo?

On the schematic, trash the one linked above! I pulled the chassis out last night and verified everything. The schematic on the amp didn't even match what I found in the chassis in a lot of areas! Here's the new schematic: http://www.diyguitarist.com/PDF_Files/MarkXSchemR1.pdf

I think this could make a nice practice amp/recording amp. I am going to take it to church next week and see if it will hang tough or not. I think it would be loud enough to use there, since it's miked and all, it's basically a stage monitor for me. If my 5 watt Octal Fatness can do it, I'm sure this little 10 watter can.

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PJM

http://www.diyguitarist.com

Just for fun, I did a chassis layout that follows how the amp is wired. I kind of like the way it's laid out, it seems pretty practical. It can be seen here: http://www.diyguitarist.com/PDF_Files/MarkXChassis.pdf

Just FYI.

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PJM

http://www.diyguitarist.com