Wednesday, 14 May 2014

Micro POG Dual Control [modification]

Hahafender on the forum sent some pictures of the guts of his Micro Pog and wondered how This1sMyne and JHS do their dual control mods, hoping to do similar, preferably like This1sMyne with external controls.  We knew from gut shots of the mod that a 4PDT stomp is used, one pole of which is for the LED indication, and so only one pole is used for each pot.

After some probing we knew that lug 1 of all the pots connect to ground and that each control increases its own effect as the pot is rotated clockwise.  The original used 5K linear pots for all the controls, and so if we use 10K for all the pots instead (also replacing the existing pots), keep lug 3 common and just switch the wipers, then we know that the entire value of the pot out of circuit will always be in parallel with the pot in circuit and so we get a predictable affect irrespective of the position of the out of circuit pot.  2 x 10K is the 5K used in the original.  This will alter the taper and so reverse log will be the best choice [see discussion below].

For indication with the 4th pole I've shown a bi-colour LED with a common anode so that you will get a different colour for each "channel" selected.  If you're not bothered about LED indication then of course a 3PDT stomp or switch could be used instead.



44 comments:

  1. This is great idea. Can you do similar schematic to Boss BD2 as I want to have two gain and two level pots and select it with 4pdt footswitch? And what type of pots have to use instead of original schematic? Really thanks

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    1. Yes you could do it with the BD2, just switch both 1 lugs of the dual gain pot and keep the 2 & 3 linked lugs common. For the volume keep lug 3 common, ground both lug 1s and then switch lug 2. Again use the 4th pole of the switch for the LED

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    2. You will of course have to double the pot values again and experiment with the taper to see which works best for you.

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  2. Do I need to to double also gain pots (because they will be not in parallel connction)? I mean that have to double only level pots (these is like pots here in micro pog)

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    1. You need two of every pot you want to duplicate and treat each channel of the gain pot separately:

      Gain 1A 2 & 3 will need linking to Gain 2A 2 & 3
      Gain 1A 1 is switched
      Gain 1B 2 & 3 will need linking to Gain 2B 2 & 3
      Gain 1B 1 is switched

      and the same needs to be done for the other side of the pot. So 2 poles need to be used for the gain pots, 1 pole for the volume.

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    2. But I don´t need to double taper of Gain pots from 250K to 500K because there won´t be any parallel connection between G1 a G2 pots, as it is on Level pots, when pin 1 and 3 of both pots are connected together.

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    3. Look how the Micro Pog pots are wired above. If you want dual controls you need to put the pots in parallel as shown (3 lugs linked, 1 lugs grounded). It's more complicated with the gain control of the BD2 because it has a dual gain pot, but all that means is you do it twice and need to use two poles of the switch.

      The gain pot of the BD2 is 250K dual log because it controls resistance in two separate parts of the circuit. If you want to have two separate gain controls "channels" you'll need 2 x 500K dual pots to do it making the connections noted above.

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    4. Sorry Robo I see what you mean. I actually looked at the BD2 schematic but was still thinking about one of the lugs connecting to ground like the Micro POG. So yes with the BD2 gain pots you could keep it at 250K log and just switch out one side.

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  3. so pad 1 on each pot is empty on the board?

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    1. do we just need the ground to go to any one of the pots then? or all of them?

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    2. Up to you. You can leave them empty or they make convenient ground pads for those ground connections if you prefer to split them a bit instead of having one long daisy chain

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    3. All the pin 1's need grounding, it's up to you how you do that. As long as they're all connected to ground and you don't create a loop then there's no problem if you solder some to different ground pads or daisy chain the lot of them.

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    4. ok sweet. i'll probably daisy chain them. seems cleaner to me.
      one other question though...when buying these pots: http://www.taydaelectronics.com/10k-ohm-logarithmic-taper-potentiometer-round-shaft-pcb-9mm.html

      what is that other lead on the side of the pot? just out of curiosity

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    5. I think they are just clips on the side which can be used to hold them in place, as a sort of strain relief to reduce the tension on the main lugs. That's what I've always thought they were anyway :o)

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    6. oh haha okay cool. alright man. i think i know everything i need to know. gonna order everything, and try it on my POG. not gonna drill anything in the enclosure until it works haha :D but I'm loving how this is gonna come out. gonna leave that 3pdt where it is, put the 4pdt on the bottom right with a red/blue LED to the left of it. im excited

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  4. Is this something that could be done on any overdrive if we wanted two seperate gains, basically creating a two channel pedal? I guess then if you were only adjusting the drive pot you would only need a 3pdt?

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    1. In the case of something like the Timmy, what would you do if the drive clay is 1m, if we need to double the value?

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    2. It depends how the gain control works. With something like the Timmy it is made more complicated by lug 2 connecting to the 3K3 resistor, but it could be changed slightly to move the position of the minimum gain resistor and you could actually switch it with a single pole.

      Again like with the BD2 in my revised note to Robo above (once my brain started working properly today :o), if the gain control in the Timmy is changed to a simple variable resistor by moving the minimum resistor to one side then you wouldn't need to double the pot value.

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  5. very cool! Thanks again
    vince

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  6. You know, ive been doing this trick for years, i first saw the idea in craig anderton's book. But i never changed pot values, it never occurred to me that the 1 & 3 pot lugs were now resistors in parallel! Man, its always the simple things that get by. Now i feel the need the check craigs book to see if he addressed this & i just missed it.

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  7. just got my parts and i've decided to order regular pots instead of the mini. they're just extremely difficult to work with, especially when daisy chaining things

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    1. hopefully it fits... i think it will

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  8. Hey.... so I used those pots as I realized it wouldnt fit with regular ones. I got it to work... except the LED indicator wont light up. dont know why. also... I'm gonna have to order reverse log pots and swap all 6 of them out. with the log pots, the effect doesnt come in until about 3 o clock. real bummer. but at least the effect works. still can't figure out the LED though

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    1. Bummer about the pots, I tried to work it out in my head and was sure it would be log, but must have been having a dense day :o)

      Can't understand the LED not working, it's straightforward and doesn't involve the existing effect circuit at all (other than ground). Are you sure the LED is common anode?

      Anyway I think we can still tag it, I'll add a note about the pots

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    2. Just trying to work out where I balls'd up in my thought process and I'm still struggling. With the original 5K linear pot, at half way rotation the resistance is obviously 2.5K. So I looked at using two 10K pots in parallel, and if we had used linear when the pot in circuit is half way that would give you 3.33K (10K pot in parallel + half of the pot in circuit). So if we wanted it at 2.5K at the centre point of the rotation from fully clockwise, it meant I wanted that resistance to drop sooner which suggested log to me as per this from GEOFEX:

      http://www.geofex.com/article_folders/potsecrets/pottaper.gif

      Where have I got my theory wrong here? :o)

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    3. not sure man... but it's definitely off. I posted a picture of the guts, so maybe you can tell me what's up with the LED. Maybe I got the wrong one... I got this one: http://www.mammothelectronics.com/Kingbright-Waterclear-WP59EBWC-p/1000-102-rdbl.htm

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    4. posted on the forum (requests)

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    5. It doesn't say in the product info whether it is a common anode or common cathode which is ridiculous because you can only guess how to wire it up. Just send them an email and ask them if it's common cathode which I suspect it probably is if it isn't working as per the layout. If it is it's no problem, just swap the 9V and ground connections for the LED, so the CLR connects to ground and lug 11 of the stomp connects to 9V.

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  9. Finally checked up Mr. Anderton's book, seems i missed the boat:) When wired as a variable resistor, all you need to switch is the wiper. When wired as voltage devider he switches out the wiper AND one of the other lugs. Doh. Its in his yellow book pg 111.

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  10. Alright, I finally got around to making this happen. It all works beautifully. I used 16mm 10KC pots. Its true that the sweep of the 3 octaves are not longer as smooth. No real change after about 1 o'clock. But no big deal really.

    As you can see in the pic, I used the old LED space for one of the new pots and just moved the LED to the left of the switch. The "channel" LED is to the right. Lights up green or blue, to match the channels. The selector switch is at the top of the pedal next to the DC input jack.

    I figured I dont really need a 2nd stomp switch as I wont really be switching channels that quickly and that often. Its easy enough to just bend down and flip the switch.

    However what would be cool, would be a momentary stomp switch that would toggle back and forth between the two channels, then you could do some crazy "whammy" type stuff without the gliss, of course. Might end up trying to do that down the line.

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    1. Oops, here is the pic:

      https://lh5.googleusercontent.com/-qqEaFWCH1io/U6BhvweJo2I/AAAAAAAAAts/KIREEQPGO-c/s512/IMG_7883.jpeg

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    2. Nice job, thanks for the pic!

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  11. Has anyone traced the foot-switch wiring for the newer Micro Pog (Rev F PCB)? I would like to do this mod as well as swapping the original foot-switch out for a relay bypass system or something since the original is incredibly loud to me. Tracing it myself has proven more difficult than expected because of the different outputs and the buffered input it uses.

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  12. I am interested in getting this mod. This1sMyne will not answer my emails or facebook posts. Anybody else do this mod?

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    1. I did the mod. Works well. See my comment and photo above.

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  13. Any idea on how I may go about implementing this on my Boss RV-5?

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    1. Well it may be possible but we'd need to see a schematic or pull one apart first to see how the pots are connected to work out how it would need to be implemented. One problem that there is of course is there's just no room for a second set of pots or the extra stomp and so you'd need to create some sort of bastardised Frankenstein's monster with a separate box housing the extras with wires going to the RV5 to make the connections. Personally bearing in mind the pain in the arse and how ugly it would be, I'd probably buy two RV5's.

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  14. Hi, if theres only one footswitch, do you only get either presets ? how do you bypass effect
    ? It would be great to have a list of parts and a detailed instuctions with grafics . I would try it. thanx

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  15. I just did this mod to my Mr. Black Supermoon Chrome, it works like a charm! I'd suggest using stacked concentric pots as they save a lot of room in the enclosure and it cuts down significantly on wiring by just jumping the leads versus wiring them. Thanks a lot!

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  16. So I just did this mod for my friend. His POG had 10k linear as the original. (I guess an older version) After trial and error, 20k linear pots worked PERFECTLY. the taper is exactly the same. so i guess on the 5k version, 10k linear would be the best option.

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    1. Other than opening to find out, how would you know which pog uses 5k and which uses 10k pots as stock? Ive just bought a new POG with the intension of eventually taking on the mod :)

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  17. I know this is a newbie question, but does this build not require a circuit? if so what circuit? does the circuit connect via the three open pins on the 4pdt? Thank you!

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  18. No extra circuit needed, remove stock pots and wire lugs 2,5 and 8 to the existing solder pads on the Pogs board, it says on the diagram which pads to solder too :)

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