Champ type practice amp with reverb and tremelo?

[Toxophilite]

Is there a schematic around for a Champ type practice amp but with reverb and tremelo?


I have a chassis to build into, it was running all minature 7 pin tubes. 6X4 6AQ5 and 3 6av6s. I can put in a 12 pin sockets if necessary. Probably stick with the 6aq5 as it seems similar to the 6V6 at lower voltages and it's what the power transformer was chosen for.


I'm looking for low volume clean sounds, similar to fender 60s 70s amps. Something loud enough to practice with a standup bass and snare acoustically. Not looking for a distortion machine but a bit could be handy for recording.


probably switch to solid state rectification


I'm also curious about 6aq5s in pushpull but that might overcomplicate the build


Here's the original schematic. I wasn't too keen on how it sounded, however the chassis and PT are useful. the original OT was TINY!
The tremelo sounded good but had no intensity control.
I don't need full on fender reverb, even a simpler less deep reverb would be cool.

[st]

An amp with both trem and reverb, let alone push-pull power stage, will tax the power transformer too much. P-p would also require (well, usually) a different output transformer and yet another preamp stage (for phase inversion). Also, it would then be a Princeton, no longer a champ-like amp.

For any champ-type build, keep in mind that the 6aq5, which in most aspects is equivalent to a 6v6, can handle less plate voltage.

Have you considered modifying the existing amp tot produce a more likeable tone? Keep the trem and forget about reverb (get pedal instead?). After all, it's already a champ-like amp...

[shooter]

Gibson GA-15RVT

[Toxophilite]

I'd like to keep it sub 10 watts. I have a princeton/deluxe type amp that's probably 16-18 watts and 28lbs or so that I've been using (which I never get past 2 maybe). As I carry a space echo, a large archtop, and a small box of cables and tiny pedal board. I'm aiming for something smaller, lighter and lower powered. 10" speaker, maybe under 20lbs sub 10 watts. Doesn't have top have verb but it would be nice., THe chassis I have is kind of small too. I will get a picture up of it.

[Joel in Texas]

Toxophilite, you might want to edit your initial post, where you said "3 6v6s" when I believe you meant to say "3 6AV6s".  Anyone who opens up your attached schematic will understand this was a minor error or typo on your part, but leaving it as-is might cause confusion or distraction for those who want to help you with your project.

[shooter]

I'd like to keep it sub 10 watts

the version rvt I looked at wasn't bias wabble trem so put whatever PA floats your boat, PRR's 1/3W 12AU7A comes to mind

[Toxophilite]

Fixed the typo, thanks.You're thinking using the front end of the Gibsons GA-15RVT ?
 I will have another look
If I used the existing PA it would be nice to be able to use a better EQ, probably needs another gainstage. Maybe replace 2 of the 6av6s with 12ax7 to provide more options

[Toxophilite]

Looking at the GA-1RVT, some interesting ideas. It would need another gainstage for an EQ probably

[shooter]

EQ
that's what guitar knobs n pedals are for 

[vampwizzard]

vibrochamp territory? It would do everything but the verb but you may be able to find whatever swart or gries did on that platform to get it there.

Milkman half pint would be the other example of that.. but im pretty sure he uses solid state tremolo in which case you could make a vibrochamp

Heres someone who added verb: https://sites.google.com/site/ntasher/vibro-champ-reverb

[MFowler]

Or Uncle Doug's Tremo-Verb amp.


See his youtube video and download final version info.


File to large for me to upload.


Mark

[tubenit]

Proven design shared by forum member Physconoodler some years ago in Canada.  He is an accomplished amp builder and amp innovator/designer.  There have been several Champ style amps done by forum members over the years with reverb on board.

Look at his schematic and compare with a Vibro-Champ which also has tremolo. 

I do NOT see any reason why you can't have a Champ style amp with reverb and tremolo.  Having said that,  I am not a big fan of single ended amps because of the floor noise compared to push/pull amps.   I'd rather have a push/pull amp that is 7-9 watts using 6K6 or 6BM8 tubes if needed a low watt practice amp.

With respect, Tubenit

[shooter]

the floor noise compared to push/pull

Ya that can be an issue, I've worked around by using REALLY stiff PS, FWB, ~ 100uf at PA tap n 47uF each downstream tap.  I shoot for <2vac on the PA tap

[Scsoul]

   Check out the Epiphone galaxie 33rvt it use 6aq5 and 6eu7 pre amp tubes.

[tubenit]

I think you should build whatever you want and I am NOT pushing anyone to build one of these ideas. These are draft ideas that I think anyone of these would make a wonderful small low wattage practice amp with reverb and tremolo.  CHECK for ERRORS!

7-9 watts and with push/pull some hum cancelling you may not get with single ended amp.

There are 3 tone stack topologies:

Marshallish
Dumblish style with mid-boost and PAB (preamp boost)
Fenderish AB763 and Princeton Reverb style

I love the sound of 6BM8 tubes!  They've become one of my favorites along side 6V6 & 6L6/5881.  I think they have a great bass response to them for a small tube.  Plus they come with both a triode/pentode in each tube.

So these 3 ideas would involve a 225-0-225 PT, three 12A_7 tubes for preamp and reverb and vibrato, and two 6BM8 tubes.

These SCH editable schematics to match these are here:  http://el34world.com/Forum/index.php?topic=25046.new#new

IF anyone sees a problem with the tremolo approaches, please respond on this thread with a correction and hopefully corrected schematic. 

With respect, Tubenit

[Toxophilite]

Hmm, Cool!
I only have the one 6BM8 tube. I have a couple ECL86 though.

[2deaf]

In keeping with the Champ theme, here is my entry.

[st]

No doubt all are good suggestions. But again, if the plan is still to keep the original PT, it will not or just barely supply the filament current needed for some of the designs posted here, even if you throw in the 6v rectifier heater supply.

[sluckey]

Have you ever considered building a Revibe unit?

[DummyLoad]

In keeping with the Champ theme, here is my entry.

i'd add pi filter network for the entire amp. i HATE buzz.


--pete

[2deaf]

i'd add pi filter network for the entire amp. i HATE buzz.

Something like this?

[kagliostro]

Current availability problems can be solved using a mosfet reverb circuit, on the forum there are more than one example
 
Franco

[DummyLoad]

i'd add pi filter network for the entire amp. i HATE buzz.

Something like this?

yup a bit stiffer though - 47/50uF for each C.


--pete

[kagliostro]

I've find an example of Solid State Reverb circuit



Full Mikede Project here
http://www.mediafire.com/file/aflnirflqgrftm6/mikede30.pdf

Franco