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Wednesday, 23 May 2018

ProCo Solo

From the source:

The SOLO is the newest member of the Pro Co family of stomp boxes. Although it is housed in the same indestructible and road worthy steel enclosure that has come to be a trademark of Pro Co stomp boxes, the SOLO marks a departure from the RAT series of pedals in more ways than just the new cosmetics. With its enormous range of tones, 3 way selectable “hot, melt, & burn” modes, and highly interactive “scoop” and “tone” controls, the SOLO just might be the most versatile pedal in your arsenal.  

Don’t let the name fool you, the 100% analog SOLO is no one trick pony. It is equally at ease in both lead and rhythm capacities, and with a wide variety of amplifiers and guitars. Capable of going from vibey, chewy, warm low gain tones, to deliciously mean and crushing high gain tones, the Solo still remains remarkably true to the sound that matters most: The sound of you and your guitar. And speaking of staying true to the sound of your guitar, true-bypass switching ensures that when the pedal is off, there is no coloration of your sound.  

 Even in its highest gain settings, the SOLO remains extremely tube-like, articulate and touch sensitive. Complex chords ring out with clarity, leads sustain with ease. Roll back your volume knob and it cleans up, just like a good tube amp would.  The solo uses three pairs of carefully matched (or should we say, carefully mismatched) clipping diodes to produce asymmetrical clipping. The three pairs are accessible via the “hot, melt, burn” slider switch. This has the effect of making the SOLO clip very much like a tube amp going into natural power tube distortion.





You'll notice there's plenty of room to add 3 more clipping options if you want to use a 6 position rotary switch.
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35 comments:

  1. skajaquada23 May 2018 at 02:27

    Bit nitpicky, but why not put Volume 1 on the opposite end of the ground wire? That way vol 1 and vol 3 are on the same side...

    Also, you have Scoop 1&2 wired in, but at the bottom says Scoop 1 to Tone 3. Is that a mistake?

    Sorry!

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    Replies
    1. Zach23 May 2018 at 02:35

      i have a thing about the number of wires on each side of the board, and typically i don't like one side to have more than the other if i can help it. the bottom was a type-o and has been fixed.

      Delete
    2. skajaquada23 May 2018 at 02:37

      Understandable. Personally, I like all wires to a pot to be on the same side if possible. I like avoiding wires that have to cross the board. Personal preference, I guess. Like I said, it was nitpicky :)

      Now it says scoop 2 to tone 3... Is that right? Scoop 3 left open?

      Delete
    3. Zach23 May 2018 at 19:54

      shit, hit the wrong key again. finally fixed it. it should be scoop 3 to tone 1.

      Delete
  2. Anonymous23 May 2018 at 07:39

    Thank you so much for doing the layout guys!

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  3. IvIark23 May 2018 at 08:09

    Nice job mate, how does it differ from the Rat other than the diode options?

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    1. Anonymous23 May 2018 at 08:46


      scoop pot, pin6 1k and those 100k’s by the input of the circuit differ as well. I’m sure there’s a few other small changes but that’s all I can think off from looking at the layout*

      Delete
    2. Zach23 May 2018 at 09:00

      It doesn’t seem all that different then a standard rat. The major difference is the scoop pot, which I think shifts the frequencies affected by the tone pot, and has 3 different clipping options. From what I was reading about it’s supposed to be higher gain, more compressed, and some have said it’s much more versatile then the original rat.

      Delete
    3. GGBB30 June 2018 at 16:57

      Great layout BTW! The only differences are the switchable clipping and the tone section. The old tone pot, resistor and cap are replaced by a big-muff-pi style tone control with scoop pot. Gain is the same as is everything else. I love the RAT - it is my go-to distortion pedal - but in all honesty I really don't like the SOLO at all (I have a factory unit). The tone and scoop allow you to dial in a huge range of sounds, so it is more versatile than a stock RAT in that respect, but overall it doesn't quite have the same edge no matter how you set it up.

      Delete
  4. Anonymous23 May 2018 at 08:45

    This comment has been removed by the author.

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  5. Moda24 May 2018 at 11:41

    Im assuming an op07 chip can be used as substitute for the 308?

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    Replies
    1. Elijah-Baley27 May 2018 at 09:30

      The op07 is the IC that the Rats have today. So I think it's okay.

      Delete
  6. DIYdude1331 May 2018 at 15:09

    Is it possible to add the scoop pot on a normal rat layout?

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  7. Elijah-Baley31 May 2018 at 21:35

    I think it's not so easy, but maybe not impossible.
    The thing is that the Solo haven't the classic Rat filter pot, but a classic tone control with that scoop pot to adjust the amount of the mid. I tried to edit the layout on my computer, but then I let it go because it was a bit tricky.
    Maybe I'll try again, but try by yourself, too.

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  8. oshun23 June 2018 at 23:34

    do somebody know cmat mods ratified scheme? https://youtu.be/pAevu-yKjWI

    ReplyDelete
  9. Unknown14 July 2018 at 10:04

    Sorry for the stupyd question but im new on this.. where the output comes from vero?

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    1. Zach14 July 2018 at 11:41

      Hey man. The output comes off out 2 if the volume pot. All off board wiring that’s not coming directly off the vero is always in the notes at the below the layout.

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  10. MAO8 August 2018 at 04:14

    Sounds nice.

    The Tone and Scoop controls add a huge range of tones.

    Made diode changes per schematic found on FSB (Solo with Recovery Stage).

    D1,D3,D4 = 1n4148
    D2,D6 = BAT46
    D5,D7 = Red LED

    The combos with the LEDs sound nice and crunchy, the other is a bit grittier/fuzzier.

    Thanks Zack!

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  11. MAO12 August 2018 at 19:30

    Sorry, I used my own layout. But it started out as the posted layout so it's probably fine.

    ReplyDelete
  12. Detrital Fragments8 October 2018 at 00:17

    I'm not getting a lot of gain out of this pedal. I'm using a Motorola LM308HZ and I used a 2N5457 instead if a 2N5458. The distortion pot measures 96k ohm. Any suggestions on what I should check, or some better alternatives for Q1?

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    1. MAO8 October 2018 at 02:52

      I too had used a 2n5457 until the 5458 arrived, and there was plenty of gain. It's being used as an output buffer, no additional gain, so any just about any jfet should be fine.

      Is the 5457 known to be good/legit?

      With power removed,double check the resistor value tied to pin 3, should be 1k.

      Also, if you used a socket for the LM308, remove the LM308 and check resistance across socket pins 2 and 6. With the distortion control maxed, you should read the 96k across those pins.

      If those check out, then the issue may be in the diode section.

      I ditched the shottky's I had originally used, and went with just LEDs and 1N4148s for a bit more output volume.

      You can disconnect the SWA connection to temporarily remove the clipping diodes all together. If your pedal comes alive, then something is up in the diode section.

      Do you have an audio probe?

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    2. Detrital Fragments8 October 2018 at 07:46

      I haven't tested the 5457 but I think got it from smallbear.
      I get a good output level so it should be OK.
      I'll replace it if I cant find any other faults.

      Resistor tied to pin 3 is 1k.

      I did socket the LM308, resistance between pin 2 - 6 is 96k.

      I used LED's and 1N4148's too. I haven't disconnected SWA yet, but the LED's light up when I play and I have the same issue regardless of switch position.

      The rest of the values check out OK.

      For now I've changed the distortion pot to a B250k and that should get me by to try it out at rehearsal tonight.

      I'll take a deeper look on the scope at work tomorrow and post how I go.

      Thanks for the help MAO

      Cheers,
      Brendan

      Delete
  13. Detrital Fragments11 October 2018 at 01:15

    No luck yet finding the fault on my board. I've given up on the Solo and started building a 1986 Rat instead.

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  14. Antti24 October 2018 at 21:14

    1P3T Rotary switch seems to be pretty hard to find. Do you think ON-ON-ON flick switch or slide switch could work as an alternative, or are there some better options?

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    Replies
    1. Zach25 October 2018 at 04:45

      You need to use a rotary switch because you’re selecting between 3 completely different options. With a toggle or slider you will have a mix of the two end settings with that if the middle. You can use any rotary switch, just only use 1 pole.

      Delete
    2. MAO25 October 2018 at 05:21

      Hey Zach,

      You can also wire a DPDT on/on/on as a SP3T. I've done this many times.

      Referring to the layout connections:

      Assuming lugs 1&2 and 5&6 are shorted in the center position of the DPDT on/on/on, you wire together lugs 1&5, lug 2 goes to the SWA connection, Lug 4 goes to SW3, Lug 3 goes to SW1, and lug 6 goes to SW2

      No overlap, all three switch settings are independent.

      Switch Down - Lug 2 is connected to lug 1 which is already hard wired to lug 5 which is now also connected to lug 4. Which means lug 2 is now connected to lug 4 which means SWA (lug 2) is connected to SW3 (lug 4). This will select just the 2 silicon diodes and have the lowest output level.

      Switch Middle - Lug 2 is connected to lug 1 which is already hardwired to lug 5 which is now connected to lug 6. So lug 2 is connected to lug 6 which means SWA (lug 2) is connected to SW2 (lug 6). This selects just the LED pair and should have a louder output than the diode pair.

      Switch Up - Lug 2 is connected to lug 3 and lug 5 is connected to lug 6 (and also lug 1) This means SWA (lug 2) is connected to SW1 (lug 3). This selects just the asymmetrical LEDs which may have a slightly louder output. Note: SW2 (lug 6) is connected to lug 5 which is connected to lug 1 which is connected to nothing.

      Try it, you'll like it :0)

      NOTE: If the middle position of your DPDT on/on/on has lugs 2&3 shorted and lugs 4&5 shorted then you hardwire lugs 2 to 4 and connect the common (SWA) to lug 5. Then reverse the other connections too. 4 would now be 1, 3 would be 6 and vice versa. (I've had on/on/on switches both ways, you need to check which style you have)

      Delete
    3. MAO25 October 2018 at 06:13

      Here's a diagram of the switch wiring

      http://guitar-fx-layouts.42897.x6.nabble.com/Using-a-DPDT-on-on-on-as-a-SP3T-tp44424.html

      Delete
    4. Antti25 October 2018 at 20:43

      Big thanks! I thought that on-on-on could work.
      Cheers!

      Delete
  15. Andrew Wasson5 November 2018 at 06:43

    Hey, I’m looking to bang one of these together in the next couple of days. I don’t think I have any LM308’s kicking around. If I sub in another OpAmp, do I need to pull the compensation cap from pins 1 - 8? It’s the 30pf on the top left side of the board. Also, any recommendations for a different OpAmp? CA3130, 5534, TL061, 071, 081, etc....

    Thanks,
    Andrew.

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    Replies
    1. MAO5 November 2018 at 07:15

      If you have to purchase an IC, I'd go with a OP07 - And I could not hear a difference with or without the 30pf, but you might want to socket that cap if testing other ICs.






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    2. Andrew Wasson5 November 2018 at 14:54

      Thanks MAO. Good idea. I will socket the cap just in case. Thanks for the OPAmp recommendation.

      Delete
  16. Tassieviking28 February 2020 at 10:38

    Is that a 1uF capacitor on pin 3 on the IC to earth ? I think it should be a 1nF capacitor.

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    Replies
    1. Percy Hornickel19 July 2020 at 02:40

      Yes I think you are right, the original schematic shows a 1nF cap.

      Delete
    2. Brett_Oz9 June 2021 at 07:32

      i built a dual op amp Rat last year (switchable from LM308 to CA3130) - the CA3130 is absolutely killer in this circuit :). My notes from chip swapping:
      TL071
      • obvious difference to stock chip. Retains a lot more high-end and has a metallic pick attack. Thinner, probably more aggressive tone. I like it as a point of contrast.
      LM741
      • Quite similar to LM308 and makes an excellent Rat. Retains a little more high-end - possibly a little more focused/less woolly than the LM308 at identical settings. I really like it.
      CA3130
      • Wow! Needs at least a 330 pf compensation cap to tame the high end. But when you get there, it’s great. More aggressive, modern and gainy than the LM308, with an oscillation whistle at about 2pm on the distortion pot on one pickup (middle position ok). The additional gain is especially noticeable when you wind the guitar volume back a little- it certainly cleans up slower than the stock chip. A great option if something a little wilder is required. Personally, I think it’s my favourite.
      NE5534
      • less drive and thickness but more clarity/crispness than LM308. Retains an aggressive pick attack with more high-end and would certainly cut through a mix. Perhaps veering more towards overdrive. Probably the least rattiest but a nice contrast with the stock chip.
      LM301
      • very close to the 308, but with a little more clarity on the unwound strings and certainly less wooliness at high distortion settings. I like this and it would make an excellent rat

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