looking to build an AA764 Vibro Champ for my nephew

[stingray_65]

I'm poking around the schematics, trying to find something new for me that might match up to a mess of parts I been collecting.

I found an old 5F2A build I was experemnting with and have robbed most everything but the iron. The PT if I remember right was out of an old SE HiFi and gives out 300-0-300 and a big 6V winding maybe 4 amps, The OT is a Mag Comp SE 6V6.

So I find this Vibro Champ,, never heard of one let alone heard one played.

It looks cool the way the tremolo wiggles the 2nd gain stage.

how does that sound??

I think I have plenty of current to push another tube, Extra gain stage maybe??

Just thinkg out loud and looking for some direction.

I want to finish it for Christmas and give it to my nephew with his new guitar.

Ray

[sluckey]

I believe TubeGeek built one a few years back. He may have some sound clips on his website. Maybe he'll ring in. This was blackface era, kinda AB763 front end into a SE output with trem thrown in. I've been tempted several times to build one. Go for it!  

http://www.glacieramps.com/Glacier_Amplification/Mooseolo.html

[stingray_65]

I'm pretty sure this is the one to build, Doug's not going to make any money off this build, I rounded up about 95% of the parts out of my bins.

Speaker choices I have laying around:

'58 Jensen P12P, small tear in the surround can be patched with tissue paper and glue.
12" Celestion Super 65.
10" Weber ceramic sig 10

Except for chrome corner protectors I think I have enough 13 ply Baltic Birch for a small combo cab about 16 x 18 x 9, tolex,  grill cloth, feet and handle. I think I'll do the "stealth" tilt back back on this one too.

I'll have to buy a baffle board, 3/8"? or 1/2"?
3/8" should be plenty at about 5 watts right?

I also have half dozen or so Stainless steel bins that would make a nice chassis.

LOL like I said, kinda thinking out loud and bouncing Ideas around.

OH, the guitar is sort of Tele-ish, 2 single coils,Gibson scale length. should actually be a bit warm sounding, not as bright as a Tele.

Ray

[HotBluePlates]

So I find this Vibro Champ,, never heard of one let alone heard one played.

It looks cool the way the tremolo wiggles the 2nd gain stage.

how does that sound??

I think I have plenty of current to push another tube, Extra gain stage maybe??

Have you noticed how all blackface Fender amps have the same basic sonic character, with maybe just a little difference depending on output power and speakers? In other words, they all have a "family-resemblance" right?

The VibroChamp is no exception. I've owned a number of them over the years. It's a low-watt version of the blackface sound (thanks to the blackface preamp topology). If you like trem, and don't need loud, you'll love the VibroChamp.

The amp will distort, but at much higher volume-knob settings than a tweed Champ (but same volume level, because the output stage is basically the same). That's because there's more loss in the typical blackface tone stack.

So do you want the authentic blackface sound, or a gain machine? If gain machine, you can use the trem parts as an extra gain stage, just add a master volume before the 6V6. I like the amp stock myself.

[jjasilli]

I like mine hotrodded, with tremolo.

[Fresh_Start]

How about stock with an available boost?  You could easily replace the buffer triode in the tremolo circuit with a MOSFET, then take the "extra" tube triode and put it in parallel with the first gain stage.  Switchable cathode network for the parallel stage and presto - boost switch.  You also could play with lower gain 12A_7 variants for the input tube.

Sorry I don't have time to flesh this idea out more right now.

Cheers,

Chip

[stingray_65]

Chip!

I was thinking along those same lines today,

What I think I decided, because the PT has plenty current on tap, I'd just add another 9 pin socket and a double row of maybe 6 or 8 turrets and plan on later mods.

With any luck I'll have him another week next summer and that could be a fun project.

I'm wondering, If I add a FX loop like Tubenit puts in all his amps, could I jumper from the send of this amp into the return of his dad's TOS I built him last Christmas?

What about the other way round? have a small SE TOS?

I keep thinking I should Tweed this amp, but the nephew is a Jazz affectionado and I think the cleans and high headroom of a BF might be a better fit for him.

OH! I measured the PT today. 245-0-245... and no 5V tap so a full wave pair of diodes should put me about  345VDC right? Maybe a little less under load?

this too low? or am I worrying about nuthin?

Ray