Lafa-haha Amp

CabanaBoy

CabanaBoy

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So, I picked up another TLC amp I affectionately call the Lafa-haha Amp. What TLC did it need? Ya - that, oh and that too, and... lol

Sounds great and it's gotz'da'vibes ;)

Lafayette (1).jpg Lafayette (3).jpg Lafayette (4).jpg Lafayette (5).jpg

All the lettering is in tack on the control panel, but I couldn't get a non-glare snap shot of it for noth'n.
 
jtcnj said:
Details?
Circuit, tubes?

Get yer ya ya's out on the lafa hafa!!

View attachment 22923
Click to expand...

It's a little el34 single ended amp. Uses one 12ax7 for pre-amp stages. A second 12ax7 uses one half for tremolo and the other half as the first stage of the reverb circuit. It feeds into the 12au7 side of an ecc832 tube and into the reverb tank via cathode. The 12ax7 half of the ecc832 tube is used to boost the reverb signal back up and and feed/mixed back in to the second half of the 12ax7 preamp. The original output transformer (OT) was attached to the speaker. The speaker was dry rotted and the OT was previously replace with an incorrect OT, so a new OT was installed off to the side of the new 8" WGS speaker. There wasn't enough room on the board for the OT or for the addition of extra reverb circuitry, so I used a second board to build the reverb circuit on. The grill cloth was pretty bad off and by the time I pulled to many staples to count so wasn't the baffle board - so - new baffle board and grill cloth (wife picked out the grill cloth). Changed it over from half-wave to full wave rectification. Decided to change every last cap and resistor, as most had strayed a ways off value. The amp originally used artificial center tap to ground, but I raised it above ground via the el84 pins/traces, which eliminated a little hum. It had the power AC going to the volume control, so I added a new power switch to get rid of a bit of hum being induced due to the AC voltage connected to the volume control. And, a few other things and odds/ends. Ya - it needed TLC to say the least. But, I think it looks and sounds pretty cool and hopefully extended it's life some. I seem to think I have to save old amps or something - lol...

edit:
I would like to add that the little Warehouse WGC G8C 8" speaker is a very nice 8" speaker. Honestly, it doesn't sound or vibe like an 8" speaker when you play it. Very nice 8" speaker for sure...
 
Awesome!
so it did not have reverb and you added the ecc832?
this reverb works without a transformer between the send and the tank?
Does the 12au7 triode provide enough current to drive the tank on its own?
 
jtcnj said:
Awesome!
so it did not have reverb and you added the ecc832?
this reverb works without a transformer between the send and the tank?
Does the 12au7 triode provide enough current to drive the tank on its own?
Click to expand...

It had a reverb circuit originally, but it used a piezo reverb tank and it was dead. I have since found a source for the little piezo bars that 'may' allow me to fix the next dead piezo tank, but for this one I re-vamped the circuit for lack of better words. The one 12ax7 that was original, to which half was used for tremolo and the other half was used to feed the piezo reverb tank, I pretty much as is. But, rather than feeding the piezo tank I feed the 12au7 side of an ecc832 tube ran as a cathode follower. Than, when I came out of the reverb tank I ran into the 12ax7 side of the ecc832 to recoup some signal strength before sending it thru a 470K (maybe 500K) mixing resistor to tie it back into the original signal path. Ya, I know, a lot of headache - but, hey, it's a cool amp and It's Alive, It's Alive... Oh, and it's got reverb from hear on and out to the Outer Limits - lol. Couldn't help myself, had to tie sci-fi in there somehow...
 
Cool amp. I like an R/C coupled reverb. I find that half of a 12AU7 provides enough current to drive the tank, though ones I've done in the past were plate driven into a high input impedance tank. Great job you've done on that. Cheers
 
Thanks, man. Ya, the reverb has more verb than necessary and then some. I couldn't ever see using it past three at the extreme.
 
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