Some ideas for the P90

[Ben Lyman]

Ok, thanks Mark, I was afraid you might say that   
You know me, simpler is betterer... less knobs equals more music.
I think i will leave out the vibrato switch and stick with my magnavibe for that job.

As for the increased gain at the input, I am very happy with my decision on that for the vibe because as JCM had it, there was a very slight drop below unity when the effect was engaged. I think when stomping on a pedal it's better to have the volume come up a tiny bit if you can't have it stay equal, but not down.

Thanks for clearing that up, I can actually understand what you are saying and I guess the MXR phaser can have a 10k on that input but maybe a vibe needs a little extra

[Ben Lyman]

This has a 2M R25 and 3M R5 (my schematic)
pretty good sweep control. Could probably even replace the pot with a 3-way toggle.

Bias is still just a trimmer, i'm not sure when i last adjusted it so it may not even be in the optimal position right now.

Some failed experiments with mix pot:
B25K pot, U1 out to U2 out and wiper on output cap
B10K pot with 10K on one side to U1 out
B10K pot with 10K on other side to U2 out
B10K with 5K1 on both sides

gonna stick with the Magnavibe for all vibrato tasks, though if trying to sell pedals it would be a good gimmick for the customer who wants more options.

[duck_arse]

on the topic of output mixers and stereo outs, I've hacked this outta wot kipper had, with that switch.



I dunno if it is right, or will go, but there it is. the second version might be more interesting than the first. assume all resistors are 33k, as per kippers, but as I've said before, I'm not good with gain around opamp mixers.

[Ben Lyman]

on the topic of output mixers and stereo outs, I've hacked this outta wot kipper had, with that switch.

Very cool Duck, thanks! I can't wait to try this out and see what I get. In the meantime, I've put together my layout for the next mono vibe.
It's pretty close to my last layout except the bias trimmer and now with "Hammer Sweep" 

[Mark Hammer]

It's pretty close to my last layout except the bias trimmer and now with "Hammer Sweep" 

It isn't "Hammer Sweep".  I was just recommending something the Commander Keen drew up 15 years ago on the GEOFEX site.

[Kipper4]

For this demo
Bias is a set 50k trimmer
R5=1M2
Hammer Sweep mod (so called for reference to this thread, Thanks to Commander Keen too.)
R25= 1M5 + series B1M i prefered the 1M+1M pot though
R29=12k
C12=4u7 I'm gonna change this back to 10uf
R9=12k

[Fender3D]

on the topic of output mixers and stereo outs, I've hacked this outta wot kipper had, with that switch.



I dunno if it is right, or will go, but there it is. the second version might be more interesting than the first. assume all resistors are 33k, as per kippers, but as I've said before, I'm not good with gain around opamp mixers.

I can confirm the upper schematic as working, Duck.
I'm using it in my stereo pedals...
R1 may be tossed...

[Kipper4]

Please Ben what dimensions are you using for the DIYLC resistors?

[Ben Lyman]

It's pretty close to my last layout except the bias trimmer and now with "Hammer Sweep" 

It isn't "Hammer Sweep".  I was just recommending something the Commander Keen drew up 15 years ago on the GEOFEX site.

OK, sorry Mark. I was actually just going to call it "Depth" because I think the average guitar player can better understand terms like that.
Hmm.. but maybe I'll call it the "Commander Keen Control" 

Fender3D, thanks for confirming, I will try the upper one and see how I like it.

Please Ben what dimensions are you using for the DIYLC resistors?

0.2 inch x0.125 inch. I squeeze the legs gently with needle nose pliers to make them fit the "3-hole" spaces but sometimes I span "4-hole" lengths.
I don't know if it's bad practice but I've been doing it for a few months now with no ill side effects yet. 1n914 diodes can be squeezed into a "2-hole" space

[Kipper4]

Thank you man.
I dont think i'll squeeze the legs.
When I use them in 2 or 3 holes i tend to put them upright in a hair grip kinda thing.

[duck_arse]

thanks, fender. I'd be interested to know what comes out of the second circuit, if anything.

sounds good, kipper.

[Kipper4]

Thanks mate

[Mark Hammer]

This is what happens when you do it wrong.

[Fender3D]

^^
I thought it was an emitter follower...

[Ben Lyman]

Dang! I didn't know Commander Keen was already a real thing 
I guess I will just call it the "Captain's Knob" 

[Mark Hammer]

RG and I have known each other since this was a popular sidescroller game (actually before.  I think CK came out in '93 or 94).  I use the title "Commander Keen" tongue in cheek because, as a very authoritative source, he IS a commander, even if still a kid at heart. 

[PRR]

> I think CK came out in '93 or 94

'90-'91 in the US; but perhaps banned in Canada and Texas for some years.

[Mark Hammer]

Actually, now that you mention it, my older son was playing it in early 1991...in Canada.

Banned in Texas?  Nah.  Id software was based in Dallas (actually Garland, I think).

[Ben Lyman]

After all that, I decided to just put a simple "S" and "W" above the knobs... and then forgot to do it 
Oh well, at least it still sounds good 

[Ben Lyman]

Well, I'm back on the P90 again, I searched for threads about matching the JFETs but I turned up some discussions that I'd rather not be the one to revive 
Note that this old thread has gone from P90 to P45 into a "V45" and now I'm talking about the P90 again. So much useful info here that I'm glad I had another look at it.
I'm making a much simpler version of my previous P90 with all the knobs, this one is more traditional with just one speed control and a switch to break open the dry path for vibrato.
I've figured out what changes I want to make to the rate control and the (preset) depth, thanks to Mark Hammer's posts in this thread.

Now, as to matching the FETs... I must've been very lucky to get such a thick sound out of my first one with the FETs that I threw in it.
This one, not so great at first. I had a look at the GEOFEX FET Matching link but when I got home I tried something else:
I put in one 2N5457 and turned the trimmer until it was swooshing.
Took it out and put in another (without touching the trimmer) and another... and another... and so on...
Then, bingo, I found another FET that starting swooshing with the trimmer in the same spot as the first one.
Lot of work I guess to find two that matched? DO they match?
Does that make sense, anyone else do this?

I set those two aside and continued until I found another, then finally a fourth.
Put all four in and blammo, a real P90 sound issued forth from my breadboard!