Help with rullywow Plexicruise

[Cortexturizer]

Well...once in a while a project comes and you just can't make it out what's wrong. This simple pedal means such a project for me. Has been on the test bench for weeks and still can't figure out what went south. I attached a couple of pictures for you guys, it is still in testing mode so wires are ugly and all that.

The problem with the build is that it has less gain than it should, it has about as gain as I've seen on demos of this pedal when they dial the gain knob to about 30%. I used j201, I get perfect voltages on them, dial em perfectly. I measured every resistor in there, it all checks out beautifully. Electros positioned properly, no wrong values to the other caps either. Just have absolutely no idea what to do next. The gain potentiometer checks out too.

Any ideas would be great.

[rumbletone]

Which demos are you comparing it to?

That's tough to troubleshoot (compared to no signal at all or something). Have you tried swapping in different J201s?

[Cortexturizer]

Actually, I think I have solved it...it was the gain potentiometer after all...why is it that it's only after one seeks for help that usually that same person resolves the issue the same day he asked for help hahaha!

Still, I don't think this has the gain that I need. Maybe a 1M pot will help? Sounds pretty good but I'd like just a tad more. Maybe I'm imagining and in reality, on rehearsal, it will be enough into a tube amp.

[rumbletone]

The PlexiDrive is not very gainy. I think of it like a JTM45 - great for mid gain rock rhythm tones - but hit it with an OD for anything more than that. Wampler's new deluxe version has a TS-style built right into it.

[Cortexturizer]

I'll definitely get a sound clip going later in the evening, I still think it should have more gain than this. I would love you guys to prove me wrong.

[Cortexturizer]

Ok, here's a link, this is with maximum gain

https://drive.google.com/file/d/0B--6F_4JB7SYaEJuRFRkcEZhemc/view?usp=sharing

how is it in comparison with yours? These pickups are not weak, those are alnico 5 wide range humbuckers. I have an SG and it sounds pretty much the same with the G.

[rumbletone]

hmm . . . it's in the ballpark, but does seems a bit less gain then I get from my PlexiCruise or from another version that I've built (the VIPfx). I just plugged in my tele with single coils, and cranked the gain on 10, and it seemed to have a bit more gain than in your clip (though that's with 11's and picking hard, through CH1 of an HC30 running quite clean). On my LP with burstbuckers it would have even more gain.

So, while I might otherwise suggest it's just variances in the setup (pups, playing style, etc. . . ) and component tolerances, it may be that your build should have a bit more gain. Perhaps some others will listen to the clip and chime in.

As for how to further troubleshoot, I don't know - especially if you've already checked the biasing on the J201s - but perhaps one of the J201s is misbehaving? If you have them socketed, I recommend trying some different J201s to see if it makes a difference.

[drolo]

I had the same feeling with a "perspex drive" I had bought already assembled from tremster.
The circuit was working fine, I just wished it had a bit more beef.

I think it's very sensible to the input level fed into it. Maybe the demos are made with guitars with stronger pickups.

What I did in the end was strapping a 1uF cap across the source resistor of the first Jfet. With that in place I could still dial back to light overdrive but also crank it considerably more.

[Cortexturizer]

Thank you for your opinions on this guys. I should have mentioned that this was without the bass switch engaged, with it engaged it does bark a little bit more.

I will definitely try your idea drolo asap. Although the whole point of me building this was to benefit from it's clean-up possibilities...

Will report once I've tried it out some more. I originally tried it with 2n5485 (or 2n5485) and I actually think it had more gain that way. Will revert to those for a short try-out as well.

[Cortexturizer]

Ok, so, I increased the source resistors on Q2 and Q3 to 2K and that improved the situation a lot. At least now I can play some Jeff Beck without too much struggle. (distortion-wise of course, nobody plays like Jeff Beck...)

The 1M pot for gain didn't do much so I stayed with 500K.

But the increase of resistance on the source definitely improved the situation and allowed for the same cleanup possibilities.

Also, I like mine set up like this on those drain pins:

Q1 - 5V
Q2 - 3.8V
Q3 - 5V

This just sounded best to me. I don't like it when it's surgically precise in gain saturation like the sound you get with 4.5, 4.5, 4.5, or 5, 5, 5.

This is my experience with this pedal.

All in all, I think for a bedroom player, it definitely asks for more gain and oomph, but I figure on stage levels, with any tube amp at all, this thing probably sings just right.