Maestro PS-1A layout...for your pleasure

[peterg]

johnk - great looking pedal all around and inside! Where did you get the LEDs?

[johnk]

johnk - great looking pedal all around and inside! Where did you get the LEDs?

thanks.
those are Fresnel led lenses that I got from Mouser.

[jdub]

Looks killer, man.  Nice work!

[johnk]

Thanks! and thank YOU for posting the pcb.
here's a quick and sloppy sound clip of it:
https://soundcloud.com/johnk_10/ps1-a

[jonnyeye]

johnk, that looks fantastic! Nice to hear a sample with a bass, too - that's what I was thinking of using it on.  Just a quick question - how did you set the trimmers? The sweep on yours sounds different than the clip juansolo posted. (It may just be the difference in FETs...)

[johnk]

I set the trimmer for a symmetrical sweep. the depth was set to be not too deep so that the fast setting still sounded good, and I just set/tuned the jfet bias by ear.

[Hotstuff]

I just finished building this and it sounds fantastic, thanks! The six 2n5485's are still backwards on the layout fyi. I just have one problem:
The phase speed seems to be slower than in samples I've heard. Anyone have tips what could be wrong or how I can increase the over all speed of the oscillator?

Cheers!

[Hotstuff]

Figured it out! Had a 20k instead of 10k connecting the first opamp stage to the second stage in the oscillator. For anyone wishing to tinker with the speeds you can adjust this resistor or change the 0.33uf cap on the first opamp stage.

[grenert]

johnk, you had mentioned adding a JFET buffer on the input.  Did you add this in front of the existing buffer, or replace the existing buffer?  Would you mind sharing the schematic?
Thanks!

[jdub]

Looks like the link to the corrected layout (with proper orientation of the 5485s) for this beastie is no longer working, so here's the working one: http://www.aronnelson.com/gallery/main.php/v/jdub/MaestroPS-1Alayout_zpsaeda6660.png.html?g2_imageViewsIndex=1...and transfer: http://www.aronnelson.com/gallery/main.php/v/jdub/Maestro+PS-1A+transfer.png.html?g2_imageViewsIndex=1.  Wish I could edit the previous posts, but alas...

[grenert]

johnk, you had mentioned adding a JFET buffer on the input.  Did you add this in front of the existing buffer, or replace the existing buffer?  Would you mind sharing the schematic?
Thanks!

Ah, never mind.  I just put a TL072 buffer in front, works great!   

[Davefx]

Did you use just clear LEDS with those lenses?

[kaycee]

Hi folks,
I'm working on one of these. I have a board etched by a friend as per the PCB shown at the top on page one of this thread and referencing the schematic beneath that.

I have it going, but am having trouble understanding the speed switching operations.

I'm seeing each switch as a SPST at the moment, not worring about indicator lights or anything, I just want to understand the basic operation of the speed switching. So, comments say connect the slow and it's 'common' which I am taking as the switch pole so that the slow runs all the time and then arrange a bypass for the circuit in and out. I get that, so if that switch is thrown I should get slow phase? Looking at the schematic, the pole of the slow has a connection to ground? Is that right?

As for the medium and fast phase, once again considering the switch poles as the common, do I need to link the medium and fast switch poles? Looks like it on the schematic...

The other thing I don't get. As you move through the switches from slow to fast, how comes the fastest switch selected overrides the others, particularly if you disengage one of the slower ones? Isn't this putting resistors in parallel, so taking one out should change the overall resistance, no?

As an aside, I'm guessing that the switches could be replaced with a pot, (or a pot added along with a switch for manual or preset speed control), if I understood what's going on here I might be able to hack it in.
Thanks

[tubegeek]

Thanks! and thank YOU for posting the pcb.
here's a quick and sloppy sound clip of it:
https://soundcloud.com/johnk_10/ps1-a

For The Love Of Money!

[chamsdaman]

Trying to replace all resistors on my PS-1A - Does this chart look right?? I quickly went over and matched best I could

[alanp]

Why are you replacing all the resistors?

[orangetones]

Digging this one up.

The layout posted most recently in this thread purports to be the corrected one, however, the 4.7uF cap is still pointed the same way, I believe.  According to the schematic, the positive leg should point towards ground.  It would seem that the other issues were corrected in the most recent image though.

Another question.  The pads seem separated from the traces slightly in some spots (still connected, but there are some gaps.  Why is this?

[iainpunk]

IDK about the rest but those gaps is thermal design. its so you don't have to heat up the surface to much when soldering.

cheers

[orangetones]

The input buffer in the original is not a great design (especially for guitar purposes) - we're talking this part right here:

From the design (DC coupled right to the output!) it's clear that the emitter is supposed to sit at 0V, but that depends on the hfe of the transistor used (the 2N3638A datasheet I found gives a "typical" hfe of 140, which gets to about 100mV off), and likely the reason the bias resistor to V- is given as 470k or 680k is to trim for least error - whatever the error is will appear at the output, potentially messing with whatever comes next in the signal chain and (if true bypassing is being used) causing switching pops. The input impedance is at most 33k, which will load a pickup significantly (loss of both volume and treble).  And there is no RF rejection cap, so radio can get in.

What were the problems with this pedal again? 

The modern fix is to rip out the transistor buffer and replace it with an opamp buffer (Rpop is something 1M and up):

You may get away with leaving the output stock (with the 4.7k output resistor and no cap) with this one - the offset voltage should be small.

Looking at adding a buffer in and taking out the original.  Does this layout make sense?  Also, I am guessing that if using a TL072, I should tie pins 6 and 7 together and tie pin 5 to 0V (ground) on the board?

[orangetones]

Anyone?