2 AB763 Deluxes Built Into 2 Hammond AO-43 Chassis's = Stereo Guitar Amp

[Toxophilite]

That's curious


How would I recognize negative feedback issues?


I've made amps with negative feedback controls etc so I know what it is and what it does
as well as how they sounds with and without
Is it a phasing issue?


It's certainly easy enough to swap the secondary leads around

[Toxophilite]

Strangely I swapped it around to what it seemed to be in the original format (green to ground(chassis originally) and blk to hot)and it squealed like a banshee
Swapped it back blk -ground, green- hot. Sounds fine


Gave amp number one a good workout tonight for 3 hours at rehearsal
Everything from clean Bossa Nova to very loud distorted rock, Sounds good, Really cuts through through with the big JBL
No magic smoke!
It'll be interesting what it's do through a couple of 10's

[Toxophilite]

Getting along in the build of the 2nd amp
 2 channel deluxe sans reverb and tremelo
This will be the echo and 1/2 dry amp of the stereo pair
Boards stuffed and getting them hooked up, though not yet screwed down


Out of curiousity if I plan to use the 6CM6s (6V6GTs) can I get away with a 25k pot for an adjustable bias control??
I could also get off my lazy @$$ and drive across town and buy one tomorrow..The gas will cost more than the pot!

[sluckey]

can I get away with a 25k pot for an adjustable bias control??

Yes. You may (or may not) need to also replace the 10K resistor with a 22K or 27K.

[Toxophilite]

Thanks!

[Toxophilite]

Well both amps are essentially done
The baffles are ready for grill cloth and I'm currently varnishing the cabinets


While I wait for the cabinets to dry I'm tidying up some loose ends

Amp No 1 has a 6G11 one tube tremelo
It's a cool sounding tremelo
However it doesn't seem to get going until about 4 on the dial
At around 7 it starts to whoop whoop a bit through the speaker

I have -35 bias going to it (that's what the deluxe wants and it gives me the right boas reading at the cathode (25ma)

I am running the B+ to it from point B (the same that feeds the power tubes) and that's sending about 412 vdc to the tremelo tube
with the tremelo off
pin 1 - 200
pin 3 - 2.5
pin 6 - 412
pin 8 - 204

with it on(footswitch) the readings on pin 1 3 and 8 jump around quite a bit

I was wondering what could be causing the tremelo to be a  late in showing up on the depth pot??

[sluckey]

I was wondering what could be causing the tremelo to be a  late in showing up on the depth pot??

Use a linear taper pot like the 6G11-A.

Also, you may need to compromise between an ideal bias point and good tremolo. Adjusting the bias affects the tremolo.

[Toxophilite]

Thanks Steve!


A linear pot, makes sense, maybe I have one kicking around, I'll look


What's a decent range of cathode bias to play with on the 6V6s?
I know 25 is about normal

[Toxophilite]

oh answered my question with some research
At 418 plate voltage about 23.5 puts me in a safe 70% range
(found  a  cool equation  online)

[Toxophilite]

OKay Here's the second amplifier mostly assembled


As it's a re-purposed cab from an early failed build I have to say it's a bit of a homely amplifier.
I might make some new cabs sometime in the future,
I had to modify the existing cabs by making a cutout in the top panel for the controls..Didn't want to feeling for them in the dark at the back. I painted the panel gold,,,now it looks like an Ampex speaker amp unit!!!
There's an identical cab for Amp 1 and the two cabs lock together back to back to make one unit for carrying...mind you it'll be a zillion lbs!
The cabs have about 8 coats on them though I got lazy and the back panels only have 4
There are tube covers for the preamp tubes I just don't have them on in the picture


Still to do:


Handle
flat right angle speaker plug
Attach back panels with screws and cup washers(what'd'ya think , small on top or small on bottom??)
Tilt back arms(gonna make some)
something to cover the staples on the top of the baffle...hahahaha

[eleventeen]

I like the knob assortment. Who needs labels when you can tell them apart by feel? 


Just ribbin' ya, man. Looks good!

[Toxophilite]

Funny Guy!


I'm not too concerned about my knobs. I always know which one is the right one in the dark...
Can you find the right knob in the dark???


Seriously though I have a pile of old and new knobs and I have no problem mixing them up or having my amp look unconventional. THough these cabs look cooler before cutting away the section for controls
I also know what the knobs do.
Thing one has Vol T M B Speed Depth
Thing two has V T M B  V T B


Here's Thing One roughly together and then both
The speakers are kind of something borrowed something blue something old something new
I'm a firm believer in the larger variety of speakers the fuller the sound (I have a bunch of 10" speakers I'm starting with these ones) Also this one has the 2 8 ohm speakers wired in paralell to make 4 ohms . combined with my 4ohm mini leslie in series that makes 8. It sounds really good!
THing One needs more work still


Still to do:


Feet!
Speaker plug flat right angle
back panels attached
Little 1/4 " jack panel for leslie plug etc
Handle
tilt back arms
Maybe faceplate painting though seeing them together makes me want to take the facepaint off of thing 2
Never did like makeup

[rlh5599]

Awesome amps!! 
I just finished an 18 Watt Stout in one of these chassis, and have been mulling over what my next amp will be. 
(I have another AO 43 chassis sitting right here a'waiting). 
I think I want to do a single channel AB763 style, no reverb or trem, just a full tone stack and a master volume.
I have a MOJO 5E3, though, so I may do another EL84 style amp

So cool to reach the end and start figuring out what the next one will be.....

Thanks for posting all your pics and experiences!!

[Toxophilite]

Thanks
It's fun getting to the dress up the amps stage
No doubt more trouble shooting will arise as they get tested in rehearsal and shows




There's probably just enough room on the existing Hammond board to do a single channel deluxe type build
I added some from a defunct hammond to fit in the tremelo on one and the extra channel on the other
You're inspring me to get back to my gulbransen 2 El84 conversion I set aside

[sluckey]

That was a lot of work but those 43s look good sitting next to each other. Well done!   

[Toxophilite]

Thanks a lot!!
Your schematic and mentoring made it possible, that's for sure!



Here's how they go together (though they actually go right together with the edges meeting forming one box I have to clean off the little corner units that fit together, they have a bit of finish on them))


I'm trying to decide upon the best handle solution (they each need one but it would be nice to carry them bot as one)


and a system on the sides that latches them together for carrying and moving
Something string that doesn't rattle


Any ideas?

[Toxophilite]

Sonic Pleasure!
(damned if I couldn't get the &^%*&^ leslie to show it's speaker..must be shy!)

[shooter]

I like the crossbow! what all the stuff in front?


Looks like the winter has been good for ALOT of projects here!

[Toxophilite]

Too bad you can't see the collection of handmade traditional longbows on the wall to the right...or the steam bent recurves on the wall to the left, not to mention all the swords....
Oh yeah and my amps are sounding good too