Champ reverb schematic

[xtian]

Re: reverb, I think these questions are best answered AFTER you build the amp and have a chance to evaluate the stock circuit, which is lovely, in my opinion. You're talking about "tweaking" the amp after it's built and running, which is something everyone should do. You build, play, listen, tweak. Listen, tweak, repeat.

[Firestorm]

What I do in my single-ended amps to reduce ripple (hum) instead of CLC is CRC, in my case, 50uF - 100 ohm - 50uF. The capacitance values aren't critical (50uF x 2 cans are plentiful, but you could use 40s or even 32s - also plentiful). This reduces hum dramatically, takes less space and money than a choke, and is easy to tweak for voltage. Build the amp, see what the B+ is with a 100R, then calculate the resistance you need to achieve the desired B+. In Class A, the current at full signal is only a tiny bit higher than at idle, so there's no sag or compression to deal with. Caveat: the resistor has to handle the amp's full current, so needs the appropriate power rating.

As to reverb, I love 12AU7 drivers in blackface circuits, but you can tame 12AT7s. Replace the 1M with a 1M pot for a true dwell control. Also compare the BF Princeton Reverb circuit with the BF Deluxe Reverb. The 470K off the reverb pot is paralleled by a 220k in the DR. This cuts the reverb by about two thirds, but also cuts the dry signal by about the same amount because the 3M3/470K voltage divider has become a 3M3/150K divider. You can change the dry/wet balance by fiddling with the 3M3. A 2M2 here will boost the dry signal by about 40%. This is still only about half what you had with only the 3M3/470K divider, so you could add add a bypass cap to the final preamp stage to compensate.

The possibilities for tweaking are endless.

[jjman]

The Tweed switch will cause a loud "POP" unless the volume is down at that moment. A solution is to place a large value resistor across the 2 switch contacts. I forget what I use in my Vibro Champ's tweed switch mod. I suggest 1 or 2 meg. Much quieter pop that way and no noticeable reduction in the tweed boost thing.

[andyfromdenver]

glad you like/d my thread op.
The 400 ohm resistor is to drop B+.

The original goal/ challenge is to retrofit this in an actual Fender Champ.
hence losing the tube rectifier to help accomodate two additional twin triodes.

with a change to solid state rectification, your resultant DC voltage will be higher, hence sentence 2.

I hadn't revisited that thread as some members of tdpri annoyed me and i left for here and some guys here annoy me so i am not going to post often.

anyhoo, if I didn't update my scheme on tdpri and i didn't look at yours, if you are chosing (or interested parties) SS rectification, I recommend a 100mfd pwr smoothing cap (1st one). This will get your sweet little cadillac champ up to studio scrutiny. plus redo the top piece of tolex in a cool color

p.s. leaving the cathode bypass cap off the make up gain stage was a personal preference, sounded better in use.

happy soldering.
Andy
[color=darkred][/color]

[andyfromdenver]

also, since it's my work you are going from.
I don't like your tone cut option. do what i did and put two values of resistor off the bass pot on a pull switch.
a mid cut and mid boost. it's better imo.
and just live with a little pop, it's not like you are gonna be running over and doing it during recording pr something. it'll either be engaged pr not.

[Firestorm]

I hadn't revisited that thread as some members of tdpri annoyed me and i left for here and some guys here annoy me so i am not going to post often.

Our loss, probably.

[MickeyP73]

@JJman, good catch. @andyfromdenver: I am honored by you checking in! Sorry to hear you got annoyed, I really liked your thread and appreciate your efforts. It was the best/clearest info on the internet I could find on adding reverb to a Champ.

Thanks for the insight on the 400 Ohm resistor and cathode bypass cap, that certainly helps. Still learning here, and as I really have no technical background to speak of, all info helps.
I am building the circuit in a 5E3 chassis, so plenty of room, and I am going with a 5Y3. So I might need to play around to get B+ in the right area.

Well I just got the parts in, which I really needed to plan my layout as I had no idea what size everything was.

[andyfromdenver]

[quote="Firestorm"][quote="andyfromdenver"]I hadn't revisited that thread as some members of tdpri annoyed me and i left for here and some guys here annoy me so i am not going to post often.[/quote]
Our loss, probably.[/quote]

my loss. I like to share stuff, but I'm sensitive etc.

[andyfromdenver]

[quote="MickeyP73"]@JJman, good catch. @andyfromdenver: I am honored by you checking in! Sorry to hear you got annoyed, I really liked your thread and appreciate your efforts. It was the best/clearest info on the internet I could find on adding reverb to a Champ.

Thanks for the insight on the 400 Ohm resistor and cathode bypass cap, that certainly helps. Still learning here, and as I really have no technical background to speak of, all info helps.
I am building the circuit in a 5E3 chassis, so plenty of room, and I am going with a 5Y3. So I might need to play around to get B+ in the right area.

Well I just got the parts in, which I really needed to plan my layout as I had no idea what size everything was.[/quote]

I think the tube rectifier w/ 40mfd will be sufficiently quiet.
and to elaborate and opine, I think what makes this amp cool is having the clean blackface w/ verb sound in a low pwr format (so neg fdbk and mid scoop'd).
I imagine if you want the tweed tone, a 5f1 would be a quick and fun build and you can have two amps on an aby!

if you can find a spdt (i used a dpdt and just doubled up) pull switch on the bass pot, you can make one value ~7-10k and the other 20k, then your bass pot will be a pull boost.
you can also use a spst pull pot, and a two 20k resistors, but then the pull will be mid cut which might seem coutnerintuitive to a user.

also, if you are scratch building and have room, I always like a hi-lo input, you mak want to run kybrds thru there.

and best wishes with your build!