It's ALIVE!

[mlp-mx6]

Well, she's alive! My current ODS-style project is alive. Tweaking yet to do, but all three channels are working. This is in a non-ODS chassis. The front panel runs wide, and nearly every pot has a mini-toggle next to it.

1st tube is a cathode follower. It drives 2 tone stacks - one for a Dumble clean only, the other for an ODS. I took a stab at the switchable HRM on this one too. They feed a built-in Dumbleator, then on to the PI and power section.

Attached is a photo. I still need to replace the twisted tone stack wires with straight, but structurally she's there. Things are tight on the board. I will not use 1/4" spacing for the turrets again, certainly not in the preamp. 3/8 will work better for the next one. (The Dumbleator and PI seemed OK with the 1/4" spacing.)

Just wish I was set up to record a clip...

[Chad]

Looks nice mlp-mx6,Can you post anymore pic's mabey a little closer shot. I see what you mean about the 1/4" spacing on the turrets,little close. still looks good though. Chad

[Bob-I]

If you're not getting any interferance or oscillation I'd leave the tone stack wiring alone. Looks really clean and neat. Excellent build. I love these with 3 channels, tell us more about the design.

[mlp-mx6]

Thanks, guys. I'll attach a pdf of the preamp layout.

The circuit, after the 1st stage, is basically a Hybrid-A schem with some tweaks from Dogears. Last night I changed the 2 snubber caps to 470pF, as it seems a bit bright to me in OD mode. Of course, there are LOTS of tweaks to try in the pursuit of the ultimate OD tone, so I've only just begun.

There are 2 relays - one switches the full ODS section between clean and OD, the other between the output of that relay and the clean-only section.

The switches for the clean-only section include bright, Rock/Jazz, PAB, and a mid-shift. I built each tone stack w/ 2 mid caps, .01 and .047. These go to a SPDT switch to select which mid cap is in effect. The OD-inclusive section has all these switches plus a HRM/no-HRM switch. I'm still getting to know this function.

I do have one deviation from the layout posted - the 22M feedback resistor on CL2 is not connected. Oh, and the "red x's" switchable gain boost is not wired yet. I have to find the best place for another SPDT switch...

The other thing I need to chase down is a bit of power supply ghosting, which is quite frustrating. I have been VERY careful about grounds, especially for the power section.

[Bear]

I'm not sure I'm 100% clear on what the CF after the PI is doing - does anyone want to spell out all the pluses and minuses of this approach? And would this work as well after a concertina PI, and maybe make up for the usual loss of drive from that type?

Bear

[mlp-mx6]

Sorry, I'm not tracking with you here. There is no CF after the PI. The CF is the first stage of the amp, shared between the two channels. It is also a LTP PI, not a concertina. What am I missing?

[Bear]

Sorry, I'm not tracking with you here. There is no CF after the PI. The CF is the first stage of the amp, shared between the two channels. It is also a LTP PI, not a concertina. What am I missing?

You're right. I found the wrong older thread. Someone had done a SSS style setup in more of an ODS build, complete with the CF post PI. Different build. I'm asking in the wrong place. Sorry.

Bear

[mlp-mx6]

No prob. I think you're talking about oldmacman's setup.

[keithrick]

Wow, Looks great. What are you currently set up to switch? Channel and. ?....also did you use the 12v relays and Rat shack transformer from the BOM floating around for your switching?

I am going to wire up my channel and boost switching some time this weekend!

Enjoy the fruits of your labor!