Champ Reverb Build

[pompeiisneaks]

well now that I notice that, there's a reason most put the anode of the power tube before the CLC and other CRC filters. It doesn't need super clean power. So honestly you could shift all the nodes left and accomplish what I'm mentioning.

Sadly the more devices you put on a single node, the more the noise that node will have due to the current demands. also the power supply filter capacitors provide some per stage decoupling as well, this would help keep the first input stage more 'separated' from the reverb and PI. So it's somewhat of a one two punch.

You can try it as is, but if you sense the amp being noisy, it could be due to not enough decoupling and filtering in that first input stage.

As for operating points, those are a bit easier to tweak with dropping resistors in the CRC chain, and you can adjust as you develop the amp, and see how it operates.

~Phil

[JGK]

Hi all I tried 2 different types of Master Volumes on mine and was never really satisfied with either replaces the 220K resistor with on and did the Train wreak type 4. Both were pretty ratty sounding and I had some problems parasitic feedback with both. If you going to use a 6l6 or EL34 it moves the Champ a bit above and late night bedroom amp. I looked and doing a double pole switch to allow for a 6v6 change but I really like the el34.

[telentubes]

Nice looking build. I still really like mine, which is quiet at idle and has lovely tone. I got it back a week ago as it had been out on loan, with another Champ (no reverb), to a friend who was running them in stereo. Mine is bare bones compared to yours. I am interested in how you like the choke. I have the parts for a couple more, and wanted to try a choke in one of them. I like the 12" speaker more than the 10", although there is a Cannabis Rex 10" on order that we will check out. I'll keep you posted on that.

[bryankloos]

Thank you.

I still need to polish up the schematic, and run some simulations to get ball park values for the PS filtering Rs and TC. Once I decide on my operating points, I should be able to nail something down in PSUD2.

I"m openly soliciting feedback on the circuit. Some questions I'm curious about:

1. How does the blending of wet/dry look. I"m guessing I'll have plenty of wet to mix in, but don't want my pots to only be useful in the 0-3 range.
2. Negative feed back R valuse? Pot or switch?
3. I was thinking about switchable SS vs Tube rectification. Pros/Cons?

Any other issues that I may have screwed up?

Thanks!

BK

[bryankloos]

Hey Guys,

I need some help/blessing with the PS R values.

What do you think?

Thanks!

Bryan

[JGK]

Moving on with mine

Did a bit of tweaking changed the cathode resistor to 360 Ohm and added a 5.6k grid stopper. 380 on the Plate with 22 volts or so across the cathode and according to the bias calculator its running about 92% Reduced the reverb mixer to 2.2 Meg. There still is allot of reverb you can do Dick Dale with this it gets a little ratty when maxed. EL34 makes it loud not really a bed room amp although with the extra Filter cap and the choke it runs impressively quiet even with single coils plugged in. Did a 250K mid/raw pot ups the grind a bit as you max it, not as raw as just grounding out the tone stack though. Been playing around with pre amp tubes and fine tuning things a bit. One thing about Champ type amps I think you can really hear the difference in both Pre amp and power tubes.

Running a JJ el34 and a solid state rectifier I think JJs sound a bit harsh going to swap it out for a Tunsol when they come in. Love the Celestion 10" Gold absolutely a killer speaker. Vol to about 4 with the treble up and reverb sounds pretty Fendery. Turn the reverb down and push the volume up its gets pretty Brit sounding. It is a loud amp I could probably do small bar gigs if I keep my drummer in check. Takes pedals really well too.

Got the cab just about done tore a hole in the top with the router I was putting a vent in plugged it with a piece of pine and will drive on from there. Waiting on aqua tolex to finish it.

Overall I'm very happy with the amp will see how it progresses. Thanks for all the info on this site Makes for great projects.

[bryankloos]

JGK

Can you tell me what your PS looks like, and what voltages you are seeing?

Im trying to figure out L and Rs for my clcrcrc filter.

No hum is the goal for me on a 10”.

All help is appreciated.

[JGK]

Hi using a Allen TP20 looking at about 400 volts coming into the amp filter caps are 22Uf,40Uf,22Uf,22Uf. There is a 4H 50Ma Choke between the 1st 2 filter caps and I ran my OT from the 2nd filter cap about 380 volts with 22 volts across the cathode. The dropping resistors I used were 2 1Ks. Reverb power comes off the 3rd filter cap at around 367 volts and the main 12Ax7 is running around 240 volts. you can use a 10K dropper in the last position and it will give you about 220 volts on the 12AX7 I feel a bit more voltage give you a bit more clean headroom. I think the extra Filter cap and the choke really help with the noise, my amp is extremely quiet. Hope that helps JGK

[bryankloos]

Thanks JGK

Are you feeding both V2 and V3 from the 3rd filter and just the input from the 4th?
What are you feeding the grids of the el34?

[JGK]

Here's a Picture hope you can make it out. The grid stopper resistors are the usual Marshall configuration and you may be able to get by without. I changed the last dropping resistor to 1K to get a bit more voltage on V1,V2 and V3 V1 and V3 are between 230 and 240 depending on the tube while V2 is around 365 because its coming off the Reverb Transformer and the Triods are connected. You might be able to get by without the grid stopper resistors. And you could run the OP from the 1st Filter Cap. I know that right now this Amp is loud and very quiet running in this configuration.

[bryankloos]

Thanks again JGK.

I'm updating the design to include 4 nodes of the PS (A-D).
Is this complete overkill, and if not, are there any downsides to the design?

I'm looking to kill any SE hum associated with AC ripple on the PS, hence the CLC before the first node.

Thoughts?

Bryan

[Colossal]

Thanks again JGK.

I'm updating the design to include 4 nodes of the PS (A-D).
Is this complete overkill, and if not, are there any downsides to the design?

I'm looking to kill any SE hum associated with AC ripple on the PS, hence the CLC before the first node.

Thoughts?

Bryan

Looks good. That CLC filter will pay dividends. I would get rid of the standby switch, or if you have to have it, bypass the switch with 100-220k so the caps can slow charge as the rectifier heats up. I would also select a robust output transformer, something with a decent amount of steel, unless you are going for "vintage".

[bryankloos]

Super. Thanks for the positive feedback.

For Iron, I'm using Allen's TO11S which I expect should do the job well. 4000 primary into 4 or 8 ohms switchable.

I'm also going to run a SS/VR rectification switch to play with diodes vs tube rectifier. I'll work up the appropriate dropping R to give me the same voltages between SS/VR. I'll work that into the schematic in the next couple days.

Assuming nothing looks too out of whack, I will start work on the layout next.

I'm hoping to get faceplate and backplate samples made up soon by precision design...

Things are coming together.

[JGK]

Looks good

Should be very quiet. I went with 4 and mine runs very quiet.

JK

[bryankloos]

Hi All,

I'm working up my layout, and I was hoping someone could put eyes on my coupling between V3 and V4.
I have a 220K off the plate of V3 feeding the coupling cap, then through a 2.2K grid stop into V4.

Does this look right to you all?

Thanks,

Bryan