Building Sluckeys AC15 with reverb

[jim]

Check out this layout before I work the chassis.  11 x !7--a bit wider but shorter than the usual space.   I really want reverb in this amp but it looks crowded.  I have tucked the board as close to the pots as I could. Some notes: I am using a 300 V power transformer but am  knocking down output with a 39 V zener on the center tap.  I am not sure where to insert the reverb circuit before the PI and the best way to source the voltage.  I am a hobbyist/player and we do Beatles--so I need some way to make this work. I can build it up with terminal strips.  One tube reverb sounds like cymbal sizzle to me and I prefer Fender style.  Thanks, Jim

[sluckey]

That's gonna be a big challenge just to put the AC15 in that 17" chassis, not to mention reverb! If I want reverb on my AC15 I'll plug in my revibe. Very few Beatle songs use reverb.

[jim]

I think I'll just let it go--the amp itself is complex enough all by itself.   I can use a pedal ..... Thanks for being the voice of reason,    Jim

[tubenit]

You could simply install a passive effects loop between the volume and the phase invertor to place a reverb pedal.  I use a Digitech RV-7 and I'm pretty happy with it.

With respect, Tubenit

[davidwpack]

I built this and actually prefer it over a real Reverb tank. https://www.modkitsdiy.com/pedal/verb-deluxe

[SILVERGUN]

On a tight build I was able to squeeze most of the circuit into the back corner, as pictured.
The only things that aren't there are the plate and cathode resistors/caps. I added them to the board.
I was was ok with having the reverb controls on the back panel.
I am a bit of an experimental builder.

So, just in case you wanted to see what that looks like.
The heavy black lines you see are wire ties that I should have picked out before I took the pics.

EDIT: I remembered that this was a Dumble reverb circuit which was very similar to the Fender circuit.
With the standard Fender-verb you would not need the biggest orange cap you see there. That is a NFB touch that Dumble used that would not be present on the Fender-verb.

[jim]

The back corner Dumble reverb is intriguing but risky for me --a rule follower.. I do like the idea of a passive effects loop.  My Boss reverb pedal sounds much better in an effects loop then on the front end. I am a set and forget reverb guy.   It perhaps has enough gain so that a send buffer may not be necessary and the absence of a tone stack may make it better still.  Is the implementation info in the library?  Jim

[tubenit]

Regarding the passive FX loop ………               You have the EF86 channel and the Vibrato channel each going into "it's side" of the phase invertor.  You would need to have two sets of passive effects loops to accommodate the FX one each channel  which might not be a bad idea.  Do something like a delay pedal on the EF86 side and a reverb on the vibrato side? 

OR ……………    You run both channels into one side of the phase invertor and use 220k "mixing resistors" to keep the channels from interacting.  I think this would work fine?  I think the only change in how the amp sounded might be a very very slight lessening of high frequencies?  My best guess is that even A/B-ing the amp in a blind test that you would NOT be able to tell any difference in tone?  Many Fender amps use 220k mixing resistors in a similar manner.

Having said that,  Sluckey is waaayyyy more knowledgeable then I am on amps and electronics.  He is familiar with the amp and has built it.  I haven't built one.  I would suggest you ask his thoughts on this approach and follow Steve's suggestion and preference and not mine IF they are different. 

I strongly prefer any of the reverb and/or delay pedals I've tried to be in a FX loop (passive or active) instead of on the front end of the amp. That's just my personal preference and not necessarily "better".

With respect, Tubenit

[jim]

I'll build it first as per Steve's layout and get it working.  Then we experiment further....many thanks!  Jim

[sluckey]

I think it's a good idea to get the basics working before modifying. That does not mean you shouldn't plan ahead for the addition of an fx loop. Leave some space on the rear panel in a noise free area just in case.

A passive loop is very easy to cobble together for testing without ever drilling any holes. Also, mixing the two channels together as tubenit suggests is easy and also reversible.