Need advice on reverb tank

[arjepsen]

Hey.
I'm in the process of layout'ing and building a aa1164 princeton reverb.
I've built around 10 different amps by now, so I do have a little experience, however, I've never built one with reverb before.
My first question is: Any advice on which reverb tank to use? I'm open to your suggestions here. Personally I don't think I'm too much into too much reverb on the sound, just a little to fill out the empty space between my errornous fiddlings... :-)
(though I also read that substitutin the 12at7 with a 12au7 should help tame the reverb some.)


Another thing I'd like to ask about is the layout of it - anything in particular that tends to give people trouble?
I'd just like to hear about peoples experiences, so that I have a chance to avoid common mistakes and pitfalls.


Regards
Anders

[p2pAmps]

Hey.
I'm in the process of layout'ing and building a aa1164 princeton reverb.
I've built around 10 different amps by now, so I do have a little experience, however, I've never built one with reverb before.
My first question is: Any advice on which reverb tank to use? I'm open to your suggestions here. Personally I don't think I'm too much into too much reverb on the sound, just a little to fill out the empty space between my errornous fiddlings... :-)
(though I also read that substitutin the 12at7 with a 12au7 should help tame the reverb some.)


Another thing I'd like to ask about is the layout of it - anything in particular that tends to give people trouble?
I'd just like to hear about peoples experiences, so that I have a chance to avoid common mistakes and pitfalls.


Regards
Anders

I have build a number of Doug's Princeton Reverbs and used several different tanks.  I have tried Mod, Mojo, and Accutronics.  For me at least, the Accutronics have sounded the best.  http://www.accutronicsreverb.com/

Either Doug's Turret layout or a Fender layout on an eyelet board will do you just fine.  I have been using teflon wire on my PR as it's nice and neat.  On the turrets I drill holes next to the turret that a wire will connect to and run the wire down towards the chassis.  This not only looks neat but it has been nice for noise too.

I have lots of PR build pics around the forum if you need a reference.  Doug's PR in the library is great as well and very nice craftsmanship to boot.

Cheers

[sluckey]

Click on the "Reverb Items" link at the bottom of this page for the correct tank.

[ac427v]

Many like the long delay tanks. I prefer the medium delay tank for a moderate amount of reverb that doesn't get muddy. As always YMMV.
Craig

[Mike_J]

From what I have read it is good to isolate the reverb jacks from the chassis and run a ground wire from the jacks to the negative side of the bypass cap feeding the reverb section. Also best to have the output side of the tank face away from the power transformer.


Thanks
Mike

[HotBluePlates]

... My first question is: Any advice on which reverb tank to use? ...

The stock tank is the 4AB3C1B, 2-spring, long delay tank. As Sluckey said, if you go into the Hoffman catalog, it will tell you this is the standard tank (and lists it as the first option).

Hoffman also has the 9AB3C1B, which is 3-delay lines (Hoffman calls it "3-spring" while Accutronics calls it "6-spring" but it's the same tank). More springs/delay lines equals a more complex-sounding reverb.

However, I greatly prefer the 9AB2C1B to either of these. As with ac427v's preference, this is a medium delay tank with the 6-spring/3-delay line arrangement. Complex sounding, but you don't get drowned in reverb at "2" on the dial.

I've never tried it, but I notice the Reverb pot is a 100kΩ linear. You could try using a 100kΩ audio/log taper if you feel the reverb come on too fast (this is analogous to the "Mix" control on the Fender stand-alone reverb unit). It's also typical to replace the 1MΩ resistor to ground at the 12AT7 grid with a 1MΩ pot to control how hard the tank is driven (this is the "Dwell" pot on the stand-alone Fender reverb unit).

If nothing else, I'd choose to use the different, medium delay, 9AB2C1B tank.

[arjepsen]

Thanks for everyones help so far.
I know there's a perfectly good layout already available, and usually one of the big pointers that are made is: DON'T bozo the layout!
But I can't help it :-) To me - making a new layout is at least half the fun of building an amp.
Here's the layout I'm working on. It's stil very much a work in progress, but it's finished enough for me to ask if anyone sees problems anywhere?

https://www.dropbox.com/s/svs2v6fv0edthjs/Princeton%20layout%20work%20in%20progress.pdf?dl=0


Btw, I should mention that I'm building this in an old used Stage Line GA-1240R solid state amp, which does dictate a bit about the placement of the pots and such.

[Fresh_Start]

I also like the 3-spring medium delay tank. Think I used a Ruby tank. Dwell control too.

Shielding leads going to and from reverb pot may be needed. May not either.


Moving around leads from tank to chassis may help reduce noise so leave some slack.

Stiff corrugated cardboard or 1/4" plywood over open side of tank, taped down. Put tank in bag. I use Velcro ties intended for wire management stapled to cab bottom and wrapped around bag/tank. The idea is to isolate reverb tank from cab at least a little.

Be aware that no two reverb tanks sound exactly the same, at least in my experience.  Don't think there's much QC on keeping springs uniform.  I've bought 5 total and have one dud - it reverbs, just not much.

Chip

[arjepsen]

Yet another question:
I need a transformer for the reverb (125A20B).
Looking over my options at tube-town.net, I can choose between on that costs around 9€, and a hammond (1750A) that costs about twice as much....
How much does the quality of this transformer actually affect the sound?? I believe that a good quality OT is important, but how about the reverb trafo???

[2deaf]

I don't see any reason to spend more on a transformer with a better frequency response when we are only going to cut those frequencies, anyway.

[HotBluePlates]

I don't see any reason to spend more on a transformer with a better frequency response when we are only going to cut those frequencies, anyway.

Agreed.

If you were gonna use the 1750A to build a PRR 1/3w amp (which typically uses a Fender reverb transformer as the OT), then the extra bandwidth might be useful.