Fender 6G15 REverb Unit - Reverb Tank questions

[corliss1]

Hey everyone,

I'm doing a 6G15 build from scratch, trying to stay true to original as possible. I'm using all original parts values and Mercury Transformers.

What reverb tank should I use in this build? Is there a current production Accutronics that would work well for this? Are they of the same quality/tone as the originals? Should I head to the bay to look for used Hammond or Gibbs?

[Bruce / Mission Amps]

In my honest opinion, Accutronics builds VERY very mediocre tanks these days, the Beltons aren't any better either... none sound as good as the old ones.
However, since there is a reissue one out, what's wrong with using that one? With some audio tweaking you can get them to sound better.
I'd try the ones that is the standard replacement one for Fender with a 12AT7 driver tube and 8 ohm out.

The new MOD tanks from AES seem to be decent and the brag about being 1960's tone:
http://www.tubesandmore.com/cemirror...OD-4AB3C1B.GIF

[corliss1]

Thanks for your quick reply, Bruce.

Is it safe to assume that I can use any tank that's either 4AB or 9AB equivalent? I've built a 5F1 and 5E3, but never worked with reverb before, so I thought this would be something a bit different to change it up. If you have any other reverb thoughts I should know/watch out for/be warned about those are certainly appreciated too.

[Bruce / Mission Amps]

The actual reverb circuit is one of the stupidest simple circuits out there.... getting it to mix into a pre-existing preamp section is a little tricky so watch what the other amps with reverb are doing to mix the wet and dry signals.
Hum and noise pickup is a bit of a problem when home-brewing and takes some good-decent building and layout technique, so pay attention to what Fender and others have done already.

[jmaf]

My 2 cents: A few quick tips I've learned when I "made up" my own reverb circuits.

1) Drive the tank hard but use a lower gain return. This will help you with the inevitable single coil hum and buzz from the tank. Better than driving the tank weakly and using higher gain return.

2) Tank input ground must be isolated from return or you'll have a head on meeting with the ground loop monster.

3) Like Bruce said, the mix is a bit tricky, for several reasons(loops/oscillation/etc). One amp I made wouldn't have reverb on volume 10, because of the way I mixed it the dry signal would swamp the reverb.

Hope this helps.

PS. One trick I've never used is to drive the reverb from the speaker output with some resistance added, would love to hear opinions on that.

[tubeswell]

On what Bruce said about the gain structure, the dry/bypass circuit (CF stage) in the stock 6G15 is designed to run straight off a guitar pickup signal. The recovery stage on the wet channel is only a single stage and therefore it only has enough gain to 'match' a guitar-level dry signal. But if you put even one additional stage in front of a 6G15, you immediately increase the strength of the dry signal going through the bypass stage, so that it overpowers the wet signal, even with the mix control maxed out to 'wet'. I'm embarrassed to admit I found this out by painstaking trial and error (and now you can use my stupidity to your advantage).

[corliss1]

Thanks so much! I've heard some good things about the Mod tanks as well. For $18 or $20 you can't really go wrong.

I've been a long-time lurker on this forum - although my join date was Dec '07 this was my first. I was really excited that I got a reply from Bruce and Tubeswell! Thanks for the great advice!

If I run into any issues with the build I'll be sure to post again. Also, living 3 blocks from Enzo's shop doesn't hurt either!