adding a tube driven reverb to a champ clone

[Mandopicker]

Thanks for the kind words, but I didn't draw up a schematic. Sorry. I did draw up a layout, though.

Given the complications of finding the correct reverb tank, transformer, etc. for a one tube reverb, I thought it would just be a lot easier to use fairly easy to find parts. Adding two tubes seemed to me, to be as easy as adding one, if you have the space. Once I determined that I had the room...I just took a good hard look at a Princeton Reverb and a SF Champ and blended the two. (With a few more of my own personal touches of course.)

My friend requested twin reverb sized reverb, so using the standard Fender design made sense. Ultimately, my final design worked very well the first time through, so I knew I was on to something. Just a bit of value tweaking to get the circuit under control and it all turned out great.

Features:
DC filaments seemed like a cool thing to try for this design. I had done it a number of times in other projects with great success and never once a failure. (Believe it or not, the parts for DC filaments are real easy to get and cheap at Radio Shack.

My friend also wanted all the bells and whistles, while also making the amp bullet proof...and so it is.

As for the resitors... I have made several fantastic amps with a variety of types because I am not much into the voodoo of resiter types. That said, my friend who commisioned the amp, requested CC's. Ultimately, I think it was a good choice for this amp.

The use of sheilded cable...placement was specifically chosen for those areas that would be prone to oscilations...after all I did add two tubes which bumped up the gain of the entire circuit. Used in the right places...it is the correct thing to do.

All said and done, this amp is unbeleivablly quiet and free from any strange noises and now I want one.

Tomorrow I'll upoad shots of the cabinet to you can all see it complete.

Thanks for being interested and good lckg to wagdog with his project.

[wagdog]

A drawing of the layout would be helpful - just of the reverb circuit would be great if you don't want to send the whole thing. No worries if you can't, but I wouldn't mind seeing it.

[wagdog]

Yeah, good point.

I'm going to pick up parts next week, so I'm looking forward to getting this going.

[Mandopicker]

As promised, here are photos of the cabinet of the Super Champ Reverb...front and back (w/o back panels.) (Modified SF Champ)

Note the really cool 10" JBL speaker and the short reverb tank.

[imaradiostar]

That's a really nice build! I miss having a vibro-champ. That amp seems like a way better option.

I still think the OP's idea could be implemented more simply with his original plan- a compactron. A pair of 12ax7 triodes or even a single 12ax7 section will drive a tank well enough to make plenty of reverb. A single section could recover. It might be worth breadboarding a few ideas before you commit to it. I would say the Fender design with the 3M3 resistor is overkill in a champ and robs some of the simplicity that makes these little amps fun to play. I also dislike the shelving effect of the capacitor in the 3M3 circuit- it's fine on clean sounds but for me, destroys distorted tone with excessive treble.

Personally I'm working on a blackface based amp with Merlin's SRPP verb driver and an LND150 for recovery, right into the phase inverter. It should make for an interesting experiment. The thing I've learned with this design (relative to the Fender design) is that the higher impedances are helpful to getting a balance between the wet and dry sounds. A 1 meg reverb pot allows for more control than a 100k verb pot and the LND150 is happy driving the parallel combination of a 1M pot, a 220k to 470k blend resistor from V1B, and the roughly 2 meg input impedance of the phase inverter. It would not work as well driving a 100k pot directly.

jamie

[jimboyogi]

I've got 2 suggestions.

1. Use a 12DW7. I've done some trials with this as a 1 tube reverb and it works well imo. I use the 12AU7 side to drive a cap coupled high input impedance tank (Type F - 1.5K input impedance), using a version of the drive circuit from Merlin's website. Take the input signal for this 12AU7 via a 500pF cap from the plate of V1a. If you don't want to include a dwell pot (I have, but I don't think that it's really necessary) you will have to play around with some sort of attenuation of the input signal to avoid overdriving the 12AU7 grid too much. Maybe attenuate by around half, using a voltage divider.

Use the 12AX7 side of the 12DW7 for the recovery. I am inputting this into the "other" side of a LTPI, but obviously you can't do this in your Champ! So the best option is probably the one outlined previously, using the reverb pot as one half of a resistive mixer at the grid of V1b. If you are losing too much gain at this point due to the mixer, then you could lower the amount of NFB to compensate a bit?

2.Use a compactron as you were initially thinking. Use a 12AU7ish triode to cap couple drive the high input impedance tank as for suggestion 1. Then use a high Mu triode for recovery. Then use the remaining triode as a cathode follower, and inject it's output into the cathode of V1b. Crazy talk?