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Post by vonFrenchie on Dec 7, 2009 15:33:39 GMT -5
So I went on the Morley website and checked out the schematic for their baseline A/B/Y box. www.morleypedals.com/abyes.pdfI drew up this schematic (yeah its messy, I'll have a more clear drawing when I get the chance.  Where it says X Y or Z in a circle, its just an indicator that shows where two spots connect. It got pretty jumbled toward the end so I tried to make it clear. The switch on the far left and the switch on the far right are both stomp switches. The switch in the middle is a small flip switch that bypasses the concentric potentiometer (P1). R1 and L1 and L2 are 3mm white LEDs and L3 and L4 are 5mm violet LEDs. I chose smaller LEDs for the channel indicators so that I can see the mixer LEDs when theyre on. I have two big problems with the circuit I drew, its more of a pet peeve that I want to get fixed. 1: How can I add a 5th LED to indicate that both channel A and channel B are on. 2: How can I set it up so that when the mixer pot is on the channel A and channel B indicators are off. Here is a little chart to describe the LED situation  |
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Post by sumgai on Dec 7, 2009 21:16:34 GMT -5
vF, That's quite the ambitious project there, bunky! I don't suppose you'd be susceptible to learning that Lx is the nomenclature reserved for coils, would you? And that when you call out an LED, you use, what else, LED? Just thougt you'd like to know.  As for your questions: 1: How can I add a 5th LED to indicate that both channel A and channel B are on. Why? Isn't the fact that both LEDs are lit at the same time a good enough indicator? 2: How can I set it up so that when the mixer pot is on the channel A and channel B indicators are off. For this you'll need a third pole on the mini-toggle, IOW a 3P2T unit. (BTW, this could just as easily be another stomp switch, and those are widely (and cheaply) available as 3P2T jobbies - they're commonly used for True-Bypass boxes.) Interrupt the circled Y line with this third pole, and you're all set. Which, if you've been paying attention, will also let you direct the battery voltage to either the pan-pot LEDs, or to the footswitch selected LEDs, but not both at the same time.  For that pan-pot section that controls the LEDs, I believe you're gonna find that 5KΩ may be a bit large (a gap in the center where both LEDs are dark), but that 1KΩ may be too small (both LEDs remain lit, though one is at not-quite-full brightness). You can experiment with a fixed resistor jumpering across the pot, thus reducing the value to somewhere in between those two extremes. Start with a 10KΩ and work downwards from there. One more thing. It's been my experience that when one depends on the jack to act as the power switch, it's probably best to make the I/O jack (from the guitar) the switch. Using only one of the A/B jacks doesn't make much sense, and if you ask someone else to "power down" for you, they'll immediately forget which one is the correct jack - A or B?  Short-circuit that with a terse "unplug me axe, mate", and it's done. ;D BTW, your chart doesn't quite reflect reality. When the mixer is "on", LEDs 3 and 4 are controlled by the pan-pot, so the proper answer should be "depends" or "varies", not "on". HTH sumgai |
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Post by vonFrenchie on Dec 8, 2009 1:41:56 GMT -5
I based my drawing off of Morley's schematic. They use two DPDT stomp switches. The third switch COULD be a stomp switch, but because of me being the idiot I am, I planned on stomping on the fader switch instead of the Y switch or the A/B switch and being thrown off by the lack of change in tone. As for the battery power being connected to the B jack, Morley's fault again. I copied as much as I could vertbatim knowing that I'd go back over it later. This was for drafting purposes only and I had thought about connecting the battery to the I/O jack, but I was too lazy to redraw it. As for the chart, see lazy. It's my vice, specially at 3 in the afternoon on a Monday. For the 5th LED, its just looks. It'll look a lot better and more professional. And no, I didn't know that L was the symbol for coil, thanks for letting me know. I just put down L because L and LED start with the same letter. Lastly, you're saying that if I drop in a 3PDT switch with the Y from the battery at the center and the Y from the switch at one of the ends I can effectively switch between the fader LEDs and the stomp LEDs? If so, I completely overlooked that possibility, gracias senor. Here is the second draft, with gai's additions and edits. All about revision.  Legend R1 390 OHMS ||| R5 10K OHMS ||| LED1 3MM RED R2 390 OHMS ||| R6 10K OHMS ||| LED2 3MM RED R3 UNKNOWN ||| R7 10K OHMS ||| LED3 5MM VIOLET R4 UNKNOWN ||| R8 10K OHMS ||| LED4 5MM VIOLET P1 10K CONCENTRIC POTENTIOMETER S1 STOMP A/B SELECTOR S2 3PDT TOGGLE FADER BYPASS S3 STOMP Y J1 CHANNEL A J2 CHANNEL B J3 INPUT/OUTPUT This set up, in theory, will lower the potentiometer's value to 5K ohms, right between 1k and 10k (kinda, the actual center is 5.5k but who needs proper math). As for the resistors in front of LEDs 3 and 4, I'm not sure if they are necessary and if they are I'm not sure about the values needed. I also just realized that R7 and R8 may not be needed, or they may not be the right resistance. |
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Post by sumgai on Dec 8, 2009 14:16:40 GMT -5
Frenchie, What you've drawn will work, to a degree. I now realize that I overlooked something in your "rough draft", but your newest edition makes it clear - you are feeding the I/O jack to two different outputs simultaneously. No, not the A/B stuff, I mean you're sending that signal to the A/B selector, and also to the pan-pot at all times. By never disabling the input to the pan pot, you are adding load impedance to the input signal all the time, and that's gonna affect your tone, probably in a less-than-desirable way. The solution is the same as with the circled Y line to the LEDs, use a fourth pole (4P2T) to switch the input signal between the two possible output controllers (pan-pot or stompswitch). If you're still married to the idea of a 5th LED, and the first two are off when A+B is selected, then I'll see what I can whip up, but it's probably gonna involve yet another 3 or 4 pole stompswitch. In fact, I know it is. Now that I've dropped that hint, I'll bet you can draw out the circuit just as well as I can. Have at it, good sir! R7 and R8 are probably not needed, but they will change the action of the pot as you rotate the knob (IOW, the taper is modified). If that change in taper action is more to your liking (as you operate the control), then leave them in, they aren't bad or anything. That portion of the pan-pot still needs to be at least 100KΩ in order to maintain good separation between the two outputs. R7 and R8 should probably be no less than 47KΩ each, but I'd probably lean towards 68KΩ each. R6 appears to be placed incorrectly, I'm sure you'll see the problem once you look a bit closer. Other considerations: Part A of the pan-pot must be 100KΩ for good working conditions, but Part B should be no more than 5K or 10KΩ at the very most. Higher values, in spite of any jumpering resistors, will result in very narrow ranges of effect. But finding dual-gang pots of differing values can be a challenge. I think you can get 100K/10KΩ pots OK, but other values, I dunno....  The whole idea has merit, but you may be stymied, at least on the first pass. If so, branch out to the various 'surplus' stores, recycling centers, HAM radio outlets, and such. Antique Radio Supply sometimes has "oddball" stuff like this. HTH sumgai |
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Post by vonFrenchie on Dec 8, 2009 17:39:59 GMT -5
This box is designed for the end of an effects chain. That's where I am going to be using it so a lower value for the potentiometer should be more desirable... right? I could feed the A and B channels right to the toggle switch, from there they could go to the fader or the second and third switches. As for the switching, I could wire up two switches that are exactly the same. Both would be A/B switches. This way if both are set to A then only A is on, both to B then only B is on, and if they are opposite then A and B are on, right? A quick google search sent me to this lovely Canadian website (I guess they aren't all that bad) www.sphere.bc.ca/test/tek-parts/tekpots.htmlRight under "E-Mail Us" in the second section of pots there are two Clarostat potentiometers that are 100k/10k Revision 3  If you can't tell Black is power, red is Channel A, blue is Channel B, orange is output, purple is channel A led power, green is channel B led power The values are the same as before, R7 and R8 are no longer present. The switches have been changed so that both stomp switches are A/B switches and the toggle switch is in front of them to either bypass the stomp switches or the fader. With this revision I am leaning more toward 3 stomp switches instead of 2 and a toggle. It makes more sense that way. Also I have dropped the 5 LED idea. I could easily put an IC in that would control the LEDs, but I'm not that set on the 5th LED. The only major downside I can see is the lack of an "OFF" function but my NS-2 does a great job of silencing hum and keeping feedback away so it isn't entirely needed. Concerns addressed R7 and R8 are removed R6 is drawn better. In the last revision I didn't give myself enough room to put it in so I just kinda threw it in there. True bypass of the fader pot and channel switches P1 is split with two values, I'm not sure which needs to be what value because I didn't have them labeled properly before. Problems remaining Complete circuit true bypass (not needed) LED5 (not needed) P1 values All the R values |
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Post by sumgai on Dec 9, 2009 4:29:45 GMT -5
This box is designed for the end of an effects chain. That's where I am going to be using it so a lower value for the potentiometer should be more desirable... right? The reason for a 100KΩ pot in the audio portion is to isolate the two channels. If you use 10KΩ or some other equally low value, you definitely will have "bleed thru" from one channel to the other, and there'll be no way to eliminate that. This is true no matter which direction you feed the signal through the box. Ahh, the classic xor configuration. A prized darling of the digital world, it's not often found in analog circuitry. I've thought about doing this to my Roland US-20.... Keep us posted on how you feel after using this arrangement for a few weeks, I for one am interested. Thanks. Your schematic: You've got one extra wire in there, between the battery +9v and the right most switch's right-most pole (center). This defeats the reason for the third pole on that Pan-pot/Straight selector switch (formerly a mini-toggle). Other than that, this looks like it'll work as you want it to. The audio goes through the 100KΩ section, as mentioned above about the isolation. The LEDs should be going through the 10KΩ section. True, it's not needed. I now conclude that when you switch out the pan-pot, you remove all possible loading from that pot. Similarly, when you select the pan-pot, you remove any chance of the I/O jack connecting directly to the A or B jacks... hence, no extra loading there either. Well, the jumpering resistors on the pot section for the LEDs are ballpark, but start with 4,700Ω on each side. You might need to go up or down a notch or two to get the desired results. (That would be: 6,800Ω or 8,200Ω and 3,300Ω or 2,200Ω.) After that, I'll let you do the work of figuring out how to determine the resistor value for a LED, given that you know the supply voltage, and that you should know the LED's current draw (it should be on the package, but you might have to review a webpage or two, if it's not). Ohm's Law will give you the needed resistor value. ;D HTH sumgai |
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Post by vonFrenchie on Dec 9, 2009 16:09:07 GMT -5
When I drew it up I checked it over 5 or 6 times. I completely over looked S3's #4 lug being connected to the battery. That would have thrown me for a loop if I had wired it that way.
As for the 100k side, I was reading from the Ernie Ball volume pedals. They use 25k potentiometers in some volume pedals. These pedals are designed to be used after effects or with active guitars. I didn't really think about how having two signals going into it would cause bleeding, just didn't cross my mind. Thanks for the explanation.
I like the idea of two A/B switches. It makes the wiring simple and easy to repair.
So all that is left is finding out R5 and R6 which I'll have to do once I am able to build the unit. I'll put something up, maybe a demo, once its done and a more comprehensive schematic/diagram.
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Short-circuit that with a terse "unplug me axe, mate", and it's done. ;D
The whole idea has merit, but you may be stymied, at least on the first pass. If so, branch out to the various 'surplus' stores, recycling centers, HAM radio outlets, and such. Antique Radio Supply sometimes has "oddball" stuff like this.