Seeking layout thoughts on a CONN chassis

[eleventeen]

I have this CONN organ chassis which looks very promising in terms of an amp-build. Yet, on closer examination, it's kind of problematical and I thought I'd submit this to the forum for ideas.

This originally used 2 x 6L6's and so I am perfectly confident that the iron will be fine for my imagined end-result, which is more or less an AB763 Deluxe Reverb w 2x 6V6. I may lash up the two channels in a switchable fashion, but for now let's figure the same tube complement (and quantity) as an AB763 DR.

So...it's got this really nice long chassis which would obviously handle a turret board just dandy. One of the long sides of the chassis has no holes in it, so there's at least a good stab at having enough room for the req'd knobs.

And yet...note the positioning of the power transformer. Kind of in the middle of things instead of at the end of the chassis. Position of the 6L6 sockets is fine, but...they kind of crowd out the real estate for a 9-pin tubes. The variable cap disappears. I suspect I'll have to fabricate a metal plate to allow moving the power trans all the way to one end; cover the old hole, provide for a new one. I'm willing to strip this down to pretty much bare chassis; heck, once you start it's not that big of a deal.

Who's got the genius idea they can offer?

[tubenit]

I like innovative ideas. I like using stuff like Bogen amps to build something new & have done so successfully.

Having said that, I personally would not attempt a AB763 in that chassis.  With 3 gain stages and reverb, I think you have a strong chance of having serious oscillation problems.

Patching up holes to move a PT & OT that need to sit thru a chassis, is gonna be about as much work as just buying a blank chassis and punching it out. And if that is a steel chassis, it's gonna be alot of work making new placements.

I hope Sluckey weighs in on this one.  I think his opinion would be an accurate realistic one.

Just my two cents.  With respect, Tubenit

[eleventeen]

Thanks, man! Even advice like "don't do it!" is welcome. Maybe I'll downsize to a single channel AB763...that'd be a lot less ambitious, real estate wise. I suspect I could line up 3x 12a_7 along the short side. Trouble is, that OT is still right in the smelly middlle of everything....and looks to definitely be in the way of all the knobs, as well. Frankly, the "new chassis" idea is one I hadn't considered, and I could easily see putting darn close to $125 or so worth of metal hacking labor and busted blades into this beast. Keep 'em coming!

[DummyLoad]

6l6g stout... 2 x 12ax7, 2 x 6l6g,  1 x 5u4g - simple ckt, plenty of clean and/or dirty, great tone with minimal controls and near mirror to the existing tube compliment less the regulator...

--ISO

[sluckey]

Having said that, I personally would not attempt a AB763 in that chassis.

Neither would I.

That laydown style OT is gonna be a challenge even for a single channel AB763 if you use a turret board. It's might be easier to go true point to point. If I just had to use that chassis, I'd cut the top off, leaving a 3/8" lip around the perimeter. Then I'd cut a single plate to cover the entire top, screwing it to the 3/8" lip. Then you can be more creative with your layout.

Here's a recent build from 18watt.com that faced some similar challenges. The project started as a Hammond AO-35 conversion, but had so many layout issues that the guy finally ripped the guts and stuffed it into a new blank chassis. Might give you some ideas how to adapt your chassis though.

[dynaman1]

Thanks, man! Even advice like "don't do it!" is welcome. Maybe I'll downsize to a single channel AB763...that'd be a lot less ambitious, real estate wise. I suspect I could line up 3x 12a_7 along the short side. Trouble is, that OT is still right in the smelly middlle of everything....and looks to definitely be in the way of all the knobs, as well. Frankly, the "new chassis" idea is one I hadn't considered, and I could easily see putting darn close to $125 or so worth of metal hacking labor and busted blades into this beast. Keep 'em coming!

Yeah, I've done the "top plate" thing a zillion times. Don't know the dims of your chassis, but I did just that with a schem provided by Sluckey a while back. "Normal" channel of a SR and fit it into a used chassis that measured 17" X 7". I wound up removing most of the metal and simply fitted a new plate to the top. Your chassis does look cramped.

[eleventeen]

Yup. I've pondered the "top plate" route at modest length. It has some things going for it, and if you just get the machete out from the beginning it isn't as bad as it seems at first glance. If I could re-arrange everything on there exactly as I'd want, I could actually dupe the layout of a Deluxe pretty closely. And then nothing would be in anything's way.

Anyone ever try a Mojo chassis? Seem fairly decent, though I'm not that happy with the metal junctions on the back, least as far as I can see. $135 including nice front & back (Vibroverb) faceplate is decent.

I used to have a '63 brown Vibroverb. I sold it to Austin Pittman.

[PRR]

> advice like "don't do it!" is welcome.

Don't do it.

That is a power amp chassis. It takes 1V in. There's no fancy controls. The driver is simple and small.

You want to come up from 0.02V and do some fancy diddle. You can't set that much gain in the small space available next to 6L6 plate leads. You can't fit the fancy stuff for tone etc. Rip-and-slide is fairly silly when properly laid-out guitar amp chassis are fairly available.

Build a fancy-dance preamp in another chassis, run audio to this chassis for final boost. Use the stupid 0A3 hole to feed 350V and 6V (AND GROUND!) to your preamp.

[tubenit]

Doug doesn't carry blank amp chassis. But if you get on ebay and type in chassis amp, you can find blank chassis for $25. It would be cramped but since you could control the layout ......... you might be able to move the PT, OT and sockets etc......... to a new chassis and make it work?

http://cgi.ebay.com/TUBE-AMP-CHASSIS-ANGLED-FRONT-4-X-14-5-X-2-5-/220676267319?pt=LH_DefaultDomain_2&hash=item3361549d37

With respect, Tubenit

[eleventeen]

That's a reasonable option...that particular chassis is by my reckoning about Champ size, but they appear to have others. Well priced, too. I also like the thick aluminum.

I'm also looking at Mojo products, which appear to be steel and "back bent" like Fender chassis.

Meanwhile, it appears your typical (genuine) Twin Reverb chassis sans tubes and in general "as is" goes for around $350-$375, delivered, on fleabay. That's more amplifier than I want....but I couldn't source the parts for that for less than $400. Maybe I should buy one of those and resell the blank chassis.