Thursday, 14 January 2016

Prescription Electronics Experience

Here is the well known Prescription Electronics Experience, a Foxx Tone Machine with extra switchable Swell effect.






Octave & Swell Switches Diagram:

26 comments:

  1. Thank you Alex . I cant wait to make this one been looking to buy one for a while they are impossible to find. What happened to Prescription electronics? Every single pedal they made was fantastic. The univibe they did was just killer as well.

    ReplyDelete
  2. This comment has been removed by the author.

    ReplyDelete
  3. I have one of the early, swirl paint versions and it is fantastic. An amazing pedal. Of course, we all know the Foxx Tone Machine is a great fuzz, but the additions of the octave footswitch and swell really make it special. I was going to make one of my own until the swirly one came my way at a great price. Thanks for posting the vero though. I will save it and maybe make one of my own in the future.

    ReplyDelete
  4. This comment has been removed by the author.

    ReplyDelete
  5. I have the board made the pots connected and the box ready. I am a little confused on the switching. For the FUZZ/ ON switch what do I use for lug 5 or the out? Do I use the out from the swell switch? Ill mess with it tonight just trying to figure this out before I start soldering .Anyway you could do a diagram of the wiring since this is pretty in depth? Thanks again Alex you the man I am so happy to see new layouts every few days. I cant wait to verify this one.

    27 January 2016 at 19:35

    ReplyDelete
    Replies
    1. I've double checked the notes and they are correct.
      The Swell switch only works with the Oct on.
      You can use 3PDTs if you want LEDs
      I've added a diagram to make it simpler.

      Delete
  6. This comment has been removed by the author.

    ReplyDelete
  7. thanks Alex. lug 5 from the octave switch will. go to lug 4 of the fuzz/on off correct?

    ReplyDelete
  8. God! I've just understood your question! I must be getting old.
    You wire the Bypass switch normally.
    The circuit Output is the "OUT" from the Oct Sw (pin 5)

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
  9. well i finished the first of three last night. I get good fuzz and good octave the switches all work the volume fuzz and sustain pots work great but when i kick on the swell it just gets quieter. the swell pot controls the volume and i get about a 50 percent volume loss but its not swelling. I triple checked cuts, placement, wiring ,and for bridge solders. I will finish another one this weekend and see if i made a mistake somewhere.I am probably off on something and hopefully one of these other 2 boards i did will work when wired up. Thanks Alex ill keep you posted

    ReplyDelete
  10. hello shouldnt the 680R be a 680K ? i am wondering could this be the issue for my no swell and volume drop ? I Will check this out

    ReplyDelete
    Replies
    1. Also what is the difference between the .022 and the .220 . What is it going to change sound wise?

      Delete
  11. Ok well I got it working. Please fix the layout and change the 680r to a 680K. It a real quirky circuit.I am not happy with it yet. The swell is very quirky but the originals are as well. I found some PE experience instructions online. You need to keep the swell barely cracked and all the other pots at 9-11 oclock . I highly reccommend using the lower gain 2n3904 (250-300 hfe)transistors.This is a noisy circuit. I used 2n5088 and man its too mean mine were in the 580-600 hfe way to hot. I am also going to try and use some 1n4001 diodes to open it up a little it I think the low forward voltage on the 1n34a may cut or compress to much and make the swell not as good. The real experience pedals use the 1n4001 diodes the foxx tone machine uses the 1n34a. I will let you know if this change has an effect on the swell circuit.I still have some tweaking to do and will report back.
    Still wondering about the 78k resistor neither layout or schematic shows one I cant tell if it should be a 68K or 100k . Ill work on this as well. It has great octave going on. I have made the tychobrahe and the PE COB this is very prominent as far as the octave goes.the Fuzz is really good as well. Not better or worse than the others but its own thing. All are very good at what they do just a matter of taste.Verified

    ReplyDelete
  12. Updated.
    The 78K resistor is here:
    http://www.freestompboxes.org/download/file.php?id=9103&mode=view

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
    2. Thank you very much Alex. I appreciate all your doing for the site I think every one does. I tried to use the link but it doesnt work . You need to mark it Verified thanks again

      Delete
    3. Thanks, mate!
      Have you copied and pasted the link?

      Delete
    4. http://tagboardeffects.blogspot.com/p/forum.html

      please look at this one. these are very noisy and i am wondering why. I was looking at this version and couldnt figure out why your layout was different. if you look at the actual pcb layout there isnt a 78k i believe its a 68k i will see if this changes anything much. thanks Alex

      Delete
    5. Oh ya i figured out the link I was logged into freestompbox but on my work computer they have blockers so we cant do what i was trying to doo ha ha.

      Delete
  13. Ok well I got it working. Please fix the layout and change the 680r to a 680K. It a real quirky circuit.I am not happy with it yet. The swell is very quirky but the originals are as well. I found some PE experience instructions online. You need to keep the swell barely cracked and all the other pots at 9-11 oclock . I highly reccommend using the lower gain 2n3904 (250-300 hfe)transistors.This is a noisy circuit. I used 2n5088 and man its too mean mine were in the 580-600 hfe way to hot. I am also going to try and use some 1n4001 diodes to open it up a little it I think the low forward voltage on the 1n34a may cut or compress to much and make the swell not as good. The real experience pedals use the 1n4001 diodes the foxx tone machine uses the 1n34a. I will let you know if this change has an effect on the swell circuit.I still have some tweaking to do and will report back.
    Still wondering about the 78k resistor neither layout or schematic shows one I cant tell if it should be a 68K or 100k . Ill work on this as well. It has great octave going on. I have made the tychobrahe and the PE COB this is very prominent as far as the octave goes.the Fuzz is really good as well. Not better or worse than the others but its own thing. All are very good at what they do just a matter of taste.Verified

    ReplyDelete
  14. i have it up and running . I am getting a lot of noise like groundhum on all three that i made. i assummed it was because they were un boxed but after boxing i had little difference.I wonder if I should use some shielded cable on the inputs and outputs. any ides how to get this hum down. its got an amazing octave and the fuzz is killer. the swell isnt as good as i had hoped but from the actual prescription electronics instruction sheet that these came with im probably in the ball park.

    ReplyDelete
  15. I've built it before (with an older, crappy layout that included the 78K resistor) and I had no problems, apart from the Swell pot being practically pointless.
    No hum.
    Does it do it with the Swell off?
    Have you checked your power supply?

    ReplyDelete
  16. Mark???ok solved the hum issues but swell is weak . I used shielded cable between the three switches. it made a major difference . I didn't shield all of it just the inputs from jack to switch and then to board then i shielded the wires from the oct sw out to the main on off button . I was going to do more but stopped to check it and it was much better . I really like this one. The swell is almost worthless did you ever get the swell to do much? You have to set all the knobs at 930-10 oclock that seemed to help but its not as swelly as the real one from the demos i have heard . Maybe IVIark could weigh in. Any ideas Mark?

    ReplyDelete
    Replies
    1. Have you tried any other transistors for Q5 and Q6? The BC546 could have been anything from 100 to 800 hfe and if the swell circuit is very gain dependent then that would make all the difference.

      Delete
    2. My Swell was working well with a dark tone, otherwise it was pretty useless.

      Delete