Vibrochamp

[firemedic]

Hey all, I'm almost done with a AA764 Vibrochamp build, from the ashes of my 5879SE that fried. Due to limited knob space I'm replacing the FMV T/B stack with a simple 5F2 one-knob deal, preceded by a .02 or .03 coupling cap. Other than that & a choke, I don't plan on any earth shattering changes. Surely this has been done before, any thoughts, questions, comments or suggestions are always welcome.

[HotBluePlates]

What kind of speaker are you using?

The original seemed to roll off some bass response (though you could get plenty of bass). As a result, those who have used a full-range speaker have sometimes run into hum issues, due to the SE design. The solution was to add a stage of filtering ahead of the plate node of the power supply.

[jjasilli]

Other than that. . .  I don't plan on any earth shattering changes. In the guitar amp world the change from E or F tonestacks to FMV is THE earth shattering change!!!

[firemedic]

I'm using the one-knob stack, not FMV which is stock AA764. Should give me more overall gain I imagine. As I get better at my playing I'm really appreciating the Tweed tone.

@HBP: The speaker is a Chinese 8" that came stock with the Kustom Contender I butchered to make the amp. It sounds fine with enough bass for me.
I'll see if using a choke will control the hum. My 5879 SE was pretty quiet w/ less capacitance than the V/C on the main cap. If needed I can add the extra filter later.
 I just wanted to use what I had laying around to rebuild my little practice amp, all I needed to buy was a new PT. 

[jjasilli]

OK. [Note that the Big Muff tonestack is a one knob equivalent to FMV.]

[firemedic]

The build is complete. And pretty quiet. Chokes and shielded wire are good things.

Full volume at @6, then all breakup. Like I like it. The tremolo works nicely, and as we all know, tremolo is the only effect you really need.

The 1M tone pot may be too much, if anything. I see the princeton uses a 250k pot there, I may try that or a 500k. But all the tone settings are usable.

I also have a 47pF bright cap across the volume terminals & may remove that. It's a little too bright.

Other than that, I have a real nice little practice amp that sounds good & didn't cost too much (extra).

[HotBluePlates]

I also have a 47pF bright cap across the volume terminals & may remove that. It's a little too bright.

Yeah, most single-knob tone plans can balance bright better than a simple treble bypass cap.

Congrats to a good build!

[firemedic]

Settled on a 500k tone pot & scrapped the bright cap. Nice sounding little amp. With the intensity turned up over halfway, somehow the treble becomes attenuated a little & it's got a FZ 200 motels kind of tone, very nice.

[HotBluePlates]

I've probably owned 4-5 VibroChamps over the years, and I kinda wish I'd kept at least one...