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Vintage threads from the first ten years
Dunlop Uni-Vibe mods
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 5/27/1999 10:38 AM |
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Dave |
Dunlop Uni-Vibe mods Howdy, I just got the Dunlop Uni-vibe schemo in the mail the other day and now I can see why it sounds so bad compared to the original. First off, theres an op-amp preamp. The phase stages are exactly the same. Next is the out put mixer. Its WAY different. It uses two opamps and two FETs to do the switching between chorus and vibrato. I then runs through a two stage op-amp booster/buffer type thing. The LFO is pretty much the same except they use a dual opto-isolator w/ a driver for the speed control. The lamp driver is way different too. Uses one op-amp and an MPS-A18. The un-effected signal seems to run through whole set of op-amps too. All the switching seems to be the Ibanez/Boss type stuff w/ a relay. By looking at this, it could be easily converted to original specs. First, Dump the preamp and output stages for the original ones. Next, Remove all switching in favor of DPDT The schemo says the lamp driver is on a seperate board. If so, you could make another board w/ the original driver section. With this done, I would think that it would be pretty close to the original and it should also free up lOT of room on the inside. Ok, RG, heres where you come in.... Dave |
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| 5/27/1999 1:43 PM |
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R.G. |
... umm... it might be as simple to just replace the mess. I like using the dual opto for a speed control, I've tried that and it works well. I've never looked inside a reissue Univibe, for obvious reasons. My latest incarnation of the Neo-Vibe has the board down to 3.25" by 1.9", and it adds to the original circuit core a high impedance JFET input buffer to prevent signal loading, stereo outs in "chorus" and "vibrato" modes, a tremolo setting like the 'vibe precursor RT-18, and the dual LDR speed control. By selectively not putting parts in, it can be made as a verbatim copy of the original, as well. It's not a beginner's board. I was trying for the smallest I could make it, and I let my usual conservative layout ground rules get tighter. I used 0.015" traces on 0.05" centers, 0.062" pads, and stood the resistors on end to conserve space. I also moved the rectifiers off-board, reasoning that you could power it from a DC-output wall wart. I don't think it's practical to make this by toner transfer, as it's tight enough that I had to make two runs at it to get a good one, but it is easily within the standard ground rules for commmercial boards. I still haven't decided whether to release it or not. |
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| 5/28/1999 1:45 AM |
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| hys chip |
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