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MB-6582 What about dpdt switch instead of double ganged pot for SID feedback???


lief138
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I got lots of switches and not a single daul ganged pots. I figure it would be the same as if I switch the jumpers of from on to off. I like the full feedback on sound.

Do other people tend to tweak those knobs regularly?

Does anyone have a compelling reason why one might not want to do this?

Also what about some rotary switches in there? I have some of those that would fit also. I figure it would be kind like a pot if I used different resistors?

Im just looking for some feedback from the cool kids.... ok I guess the un-cool kids could pipe up also **

Lief

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If you're happy with the two options (on/off) method, then the dpdt switch should be do-able.

You are also right that a multi-postion switch with different resistors is more or less equivalent to a pot.

You could perhaps experiment with, say, a toggle switch and a momentary switch, wired in 3-way configuration:

2-way-switch-wiring-diagram.jpg

(please ignore the use of words like "mains", "live" etc...)

If you had one toggle and one pushbutton momentary, then the toggle is used to set the pushbutton as either "momentary on", or "momentary off", ie two modes for feedback: "button=feedback on", and "button=feedback off". This would allow for a little bit of tweaking, or at least rapid changes...

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You use pots to control how much feedback to use. When you enable Ext In (i.e. filtering the external input, and thus filtering the output fed back into the input), and of course band pass, you can get a resonance boost or a full blown self-oscillating squeal. You could in theory choose the right amount of feedback using a pair of trimmer pots and just an external switch to turn on/off feedback.

If finding these pots is proving difficult for a lot of people, I can find a good bulk source somewhere and buy a bunch...

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My problem is Im pissed off at this point as I just ordered the pots from mouser along with a couple other things I needed for another project and when I got done spending $2.5 each (when Im used to paying $.5 each) get them home and realize I made the mistake I was warned about and got the big ones. They dont come close to fitting. Now with nothing else immediately needed I dont want to spend the extra 7 dollars for shipping as I hate the idea of 4 pots costing me $30+.

My new question is why cant you just use a normal pot and solder two wires (1 from both SID) to each lug?

If this wont work I a dug up some 3 position dpdt switches (on-off-on) I was planning on having up be all on, down go through 250K resistor and center obviously off.

Perhaps Ill do this until I come across the right sized pots.

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For what it's worth I bit the bullet and bought these from Hong Kong Superseller:

http://cgi.ebay.com/6-Dual-500K-Blend-Balance-Pickups-Pots-Potentiometer-DP_W0QQitemZ290268557894QQcmdZViewItem?hash=item290268557894&_trksid=p3286.c0.m14&_trkparms=72%3A570%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318

They fit perfect, and I have two left for the 2x 6581 box I plan to build.

For knobs I just manhandled some knobs meant for a D-shaft (in other words, I just forced 'em on).

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My new question is why cant you just use a normal pot and solder two wires (1 from both SID) to each lug?

That would be bad. You would be joining audio outputs together, which is bad. Audio outputs go up and down in voltage, and if one was higher than the other, current would flow from the higher one into the lower one. The point of the dual gang is to keep them separate and maintain the stereo signals, not mix them to mono.

Since you have some dual gang pots already (just too big), wire up one anyway and have a play with it. Then you'll realise that "all on" is mostly useless, and that there'll be a nice sweet spot on the pot that gives a nice resonance boost at res=230 and self-osc. squeal at 255. Keep in mind that it's not just one resistor value - the pot is being used as a voltage divider, so that you get between 0% and 100% of SID output fed back into input... that's why the pot "ends" are connected to SID output and ground, so the "wiper" can be anything between (0%=ground, 100%=SID output). If you continue on the switch idea, then you can use any trimmer pot inside the case (wired the same way as the dual gang feedback pots, i.e. voltage dividing!) and a DPDT switch on the SID input that can switch between the pot wipers and ground.

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For what it's worth I bit the bullet and bought these from Hong Kong Superseller:

http://cgi.ebay.com/6-Dual-500K-Blend-Balance-Pickups-Pots-Potentiometer-DP_W0QQitemZ290268557894QQcmdZViewItem?hash=item290268557894&_trksid=p3286.c0.m14&_trkparms=72%3A570%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318

They fit perfect, and I have two left for the 2x 6581 box I plan to build.

For knobs I just manhandled some knobs meant for a D-shaft (in other words, I just forced 'em on).

100 of these can be had from HKSS for $138.  Maybe somebody should do a bulk order.

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Well I would go in on the group buy. At next month I would organize it if people are interested.

Umm the stay puft hasn't shown up yet so Ill definitely not cross the streams...

I can see full on might not be appropriate at all times.. its hard though because it goes against my personal philosophy

"why kill when you can overkill?"

or

"why eat a hamburger when you can eat the hell out of a hamburger?"

or the recently dropped

"why show up late for work when you can never show up at all?"

OK well lets see what we can do about those pots?

Thanks for all the info people

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I haven't been messing with the feedback thing for a while now, but the "pre-tuned sweet spot switchable" idea might work nicely. I actually thought of doing it while experimenting with the feedback - I always ended up adjusting the pot to about 100 kOhm (using an 8580).

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