The Jazz Guitar Chord Dictionary
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  1. #1

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    Well this kinda got unnoticed on the original thread and I guess it deserves it's own thread.

    An old forum member, quite knowledgeable of electronics, gave me his "instructions" to a an old 80s polytone preamp in a pedal format. Mine is being built by a friend so I can't give feedback on sound but my hopes are high. Mine will be called "Polyclone".

    Hope these files are helpful for others.

    Polyclone.rar - Google Drive

    PS - Sharing was allowed by the mentioned member but please do not use it for commercial purposes.

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    The Jazz Guitar Chord Dictionary
     
  3. #2

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    Many thanks for the great info. Nice pcb.

    I can't see a Mid pot, I'd prefer a Mid pot for more control over the middle freq 400 - 600Hz(ish), like the Mega brute's Baxandall tone stack.

    Polytone in a Pedal-polytone-mega-brute-419715-jpg

  4. #3
    This is based on the old Polys, just bass and treble. My Zoom MS100BT has a parametric eq to cover the mids

    Chris (Franz1997) has some info on how to add a mid pot to the old circuits, he'll chime in for sure.

  5. #4

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    Thanks Jorge, I was just passing...I can't open the files that you posted for some reason.

    I have added a mid control. But be aware that Poly tonestack circuits from different eras have different values; I think the one Guy showed in the other thread was a 90s stack. From memory, this centres the mid frequencies around the 1.2K mark. I find that using appropriately scaled values of around 25n for the mid control caps moves it to a less nasal 400 Hz.

    I prefer the cap values in the 80s era models - maybe your files show that schem. anyway

    It's not hard - but difficult to do without hacking the amp, without a double-gang pot of the correct values.

  6. #5

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    Quote Originally Posted by Franz 1997 View Post
    Thanks Jorge, I was just passing...I can't open the files that you posted for some reason.

    I have added a mid control. But be aware that Poly tonestack circuits from different eras have different values; I think the one Guy showed in the other thread was a 90s stack. From memory, this centres the mid frequencies around the 1.2K mark. I find that using appropriately scaled values of around 25n for the mid control caps moves it to a less nasal 400 Hz.

    I prefer the cap values in the 80s era models - maybe your files show that schem. anyway

    It's not hard - but difficult to do without hacking the amp, without a double-gang pot of the correct values.
    I'll breadboard the circuit and test different caps in the 3 pot Baxandall tone stack and listen.

    Thanks for the info.
    Guy

  7. #6

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    Do you know of any vendor who is willing to fabricate low volume of PCB for consumer?

  8. #7
    A friend of mine gets his from China but no idea which specific site.

  9. #8

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    Quote Originally Posted by r_cc_c View Post
    Do you know of any vendor who is willing to fabricate low volume of PCB for consumer?

    I've not tried them, but:
    https://oshpark.com/

    or ask at

    freestompboxes.org ? Index page
    Last edited by GuyBoden; 06-06-2015 at 11:08 AM. Reason: Too fast typing..

  10. #9

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    Wow - this is all Greek to me but I have wished for something like a portable polytone preamp for years. Is the schematic posted something I could just send to a builder or would they need other info? (Very preferably with a mid knob added like Franz was talking about) All I know is how to solder in pickups and other easy stuff, otherwise I would be all about trying to do this myself.

  11. #10

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    I'm not an expert, but I've built many electronic circuits and I think that you can use this "TONE TWEQ" baxandall type board to build a similar pedal and tweak the tone stack caps/resist to get the sound you prefer. Even change the Dual opamp TL072 to a OPA2134 if you want cleaner HiFi sound.

    Guy
    Last edited by Dirk; 04-21-2020 at 01:24 PM.

  12. #11
    So, it has arrived. First impressions are pretty good and, as my experience has proved, the best impulse response speaker match is an EVM12L in a closed back cab. Will report again and do a few clips soon!

    One first note is, despite being a baxandall eq, it sounds vastly different from other baxandalls (rc booster, rocket eq, shape eq, ampeg amps, even mambo). There's something completely unique about the Polys.

    Also I added a low cut (high pass) filter to the pedal (30hz-300hz), that works passive, this is it works even with the pedal off so I can also use it with my fender pedal. This feature is an excellent one to cut archtop's rumble and should be included in all "jazz amps" (works much better than turning the bass down which brings a lack of depth to the sound and does not kill all the rumble in my experience).
    Last edited by jorgemg1984; 10-16-2015 at 07:08 AM.

  13. #12

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    This has got me thinking, if this is just the Polytone preamp circuit could someone use this and pair it with say the poweramp section of a 5e3 tweed deluxe and make a really awesome little jazz amp that meets the best of both worlds? I know enough about electronics to get me in trouble, but maybe someone here could figure it out.

  14. #13
    It seems perfectly possible... maybe even convert it to tubes?

  15. #14

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    Now we're talking! I love the warmth of tubes but the polytones sound so good.

  16. #15
    I don't have the skills to do it but it seems perfectly doable - a polytone preamp converted to tubes and a 5e3 tube power amp.

    Open back cab with an Altec 417-H?

  17. #16

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    This is doable. I have Polytones from the 70s, 80s, and 90s. I haven't yet dabbled in one with the Sonic circuit. I have or have had, thus, Polytones with the plain Tolex and CTS speakers, the fuzzy cabinets and CTS, the diamond black Tolex with early Eminence speakers, and the blue Tolex with Eminence speakers. The tone stacks evolved from just bass/treble and the brite/normal/dark slide switch, to the bass/mid/treble with slide switch. Some of the early amps also had "room eq" switches that were actually negative feedback loop on/off switches.

    In my estimation, the best sounding Polytones are the ones with the simplest tone stack, i.e., just treble/bass and the slide switch. I would copy this in a pedal that I would make.

    As far as coupling this with an amp/cabinet goes, just about any good amplifier would work. It should not be underestimated, however, how much of the Polytone sound is tied up in really driving an amplifier hard into a low-impedance, heavy-duty speaker in a closed back cabinet. This will sound different than, say, running a Polyclone preamp into a power amp working into a Fender Twin Reverb 15-style open-back cab. That will sound good, but it will be different than a close-back Polytone cabinet with a low-impedance 15" driver.

  18. #17

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    Tube powered Polytone sound gets another vote from here!

    I love my Mini Brute but when I compare it to my Princeton Reverb the "naturalness" and the headroom of the tube amp just makes me breathless and thinking that MB sounds a bit dull. As any SS amp.

    But first I am waiting keenly further reports about the pedal from Jorge!

  19. #18

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    Yeah if the pedal ever becomes available for purchase I'd be all over that.

  20. #19
    If anyone wants this pedal to be built my tech can build one equal to mine.

    miguel.oliveir@gmail.com

    He's based in Portugal but he ships overseas. My pedal has a few custom options (OPA2134, pump charger to 18v, low cut, stereo out) and killer looks but he'll customise to your needs.

    I'll post clips and photos in maybe a week.

  21. #20

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    What is the pump charger to 18v and is the OPA2134 just an IC chip that you prefer?

  22. #21
    The pump charger doubles internal voltage, so you feed 9v and the pedal has 18v internally. Good for headroom.

    The OPA2134 are my absolute favourite op amp for cleans - I modded all my SS amps and eq pedals to have them.

  23. #22

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    Jorge
    the low cut feature will work wonders when the pedal is off for users of the 5e3 Deluxe amp. That circuit has such wide band pass filters that it is flat to ten hz. And, it has no bass roll off control. This will tame the low bass on the Deluxe that can make a muddy tone.

  24. #23
    destinytot Guest
    Fascinating - I'm keen to find out more. The electronics are beyond me, but I do get an amazing tone when I feed a line from an Evans RE200 into a Polytone.

  25. #24
    Quote Originally Posted by Greentone View Post
    Jorge
    the low cut feature will work wonders when the pedal is off for users of the 5e3 Deluxe amp. That circuit has such wide band pass filters that it is flat to ten hz. And, it has no bass roll off control. This will tame the low bass on the Deluxe that can make a muddy tone.
    The low cut has been a life saver. I find that archtops plus humbuckers plus either fender or "jazz amp" tone stacks tends to produce too much low end (I don't have any problem with my flattop or my classical). For years I struggled with that - most of the bass knobs can't even kill all the rumble and even if they do I don't like running bass knobs too low, it makes the highs too shrill (in either fender or "jazz amp" eqs).

    So one day I was in some music producers forum and someone was saying that he always high-passes everything below 150hz in guitar tracks - and after a while I got a Pocket Pod HD from Line6 which had a low cut incorporated and it worked wonderfully. I wish I had found this a long time ago!! My tech build me one I still have and use at a very small board I have in my car for when I use "rental amps" and it has worked great with all amps I tried so far. When I decided on the Polyclone pedal I had to have it incorporated and still passive so it would work with any other preamps I buy. So far it's great with the Polyclone and the Barb EQ and I suspect it will be with other pedals too!

    Funny thing is, it's the cheapest easiest pedal to build (basically the opposite of a guitar tone control).

  26. #25

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    Quote Originally Posted by Greentone View Post
    Jorge
    the low cut feature will work wonders when the pedal is off for users of the 5e3 Deluxe amp. That circuit has such wide band pass filters that it is flat to ten hz. And, it has no bass roll off control. This will tame the low bass on the Deluxe that can make a muddy tone.
    Bruce at Mission Amps has a humbucker mod that allows the use of the normal channel's volume control as a low cut when plugged into the bright channel. It's switched so that you can run the stock circuit or the modded circuit. It's not perfect for this use but works pretty well at taming the boisterous bass of the 5e3 circuit (I run my 5e3 head into a RE 12 so it probably acccentuates the bass even more than an open backed combo cab.). I wonder about pulling the bright cap out of the circuit to result in two normal channels...
    Last edited by Cunamara; 10-17-2015 at 01:07 PM.