Tube Amps / Music Electronics
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|5/18/1998 9:27 AM|
I have a question regarding the Uni-Vibe.
Is it possible to use the
phototransistor optoisolators found
in the Mouser catolog???
If so, how would I modify the circuit
to use them?? If they cant be used,
where can I find a CLM6000 or suitable
OK, another question. I'm interested
in building a flanger and dont know
which one to build. The only schematics
I can find are the MXR and EH one's.
Which of the two sounds the Best??
Also, is there a PCB layout available
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|5/18/1998 9:42 AM|
I went through this a bit when I did the first vibe pcb layout.
(a) No. Phototransistor optoisolators will not work. It requires a variable resistance, not a variable current like you get with phototransistors.
(b) You probably can't, not within the limits of what would make it still recognizable a univibe clone. It would take a massive effort to change the circuit to use them.
(c) You can probably use the H11F1/2/3 series LED/photofet optos, or the CLM6000, or the VTL54C3 or the Silonex NSL32 LED/LDR modules, and in fact my first layout was for these modules. The CLM has been reissued as the CLM600, but I don't know a commercial source for the DIY'er yet. The VTL and NSL parts are available from a few suppliers, Newark in the case of the VTL.
However, the sonic results of these LED/LDR modules was judged disappointing by a number of people after listening tests, not the same as the original incandescent bulb/LDR. You may or may not like what you get. I still have that layout somewhere if you'd like to buy a toner sheet for it.
Why not just use the indancescent lamp and four discrete LDR's like the original 'vibe and like the clones on my web page? [I know, I know - you want to run it on a 9V battery and the bulb eats too much power. Can't help there. Been there. Done that.]
(d) No opinion about the sonic differences of MXR and EH
(e)Not that I know of. I think I've done most of the PCB's available for DIY'ers on the net, and the others that I know of are not for these two. Stellan's web site is a possible exception, haven't checked it for that recently. You might check it.
|5/18/1998 1:50 PM|
(c) You can probably use the H11F1/2/3
series LED/photofet optos, or the CLM6000,
or the VTL54C3 or the Silonex NSL32
My initial experience with the H11F1/2/3 chips is that the rise/fall times are much too fast to make them a suitable replacement for the CLM6000, although they might work in a circuit that has attack/delay capablities engineered into it.
Many circuits depend on the slow rise/fall of the CLM opto for control of the attack/delay parameters and become too 'impulsive' when the FET opto is used.
The VTL and Silonex modules should work well. Seems like I was looking at the VTL5C2 as a replacement though (if my failing memory is correct).
FWIW, Jack Orman
|5/18/1998 4:00 PM|
>>My initial experience with the H11F1/2/3 chips is that the rise/fall times are much too fast to make them a suitable replacement for the CLM6000, although they might work in a circuit that has attack/delay capablities engineered into it. <<
They are indeed too fast for general purpose replacement, you have to limit the rate of change on the LED current - which the 'vibe circuit does inherently, so they have a reasonable chance of working, at least enough to consider. Of greater concern is the limitation they might have on signal level handling. They're probably OK in the 'vibe at only 3-4x guitar levels, but it needs tested in each application.
>>Many circuits depend on the slow rise/fall of the CLM opto for control of the attack / delay parameters and become too 'impulsive' when the FET opto is used. <<
True. You always need to know your application; we always used to get a good time out of the freshly minted new designers that would simply assume a new part from a data sheet was a drop in to ANY application. We'd let them get a ways down the road and them make them show it to the boss. Good times for all.
>>The VTL and Silonex modules should work well. Seems like I was looking at the VTL5C2 as a replacement though (if my failing memory is correct).<<
They have been reported to work well in isolated instances as a CLM6000. There is probably not a general purpose replacement (except maybe the CLM600).
However, in the univibe circuit, all of these are cautionary. The result will phase, all right, but it won't have the same feel of the phase movement as the bulb/lamp. I suspect that you could curve-shape the LFO drive waveform to get a match (and further that that is what Mayer is doing in his extremely expensive clone) but the simple path of current-mode LFO as in the basic 'vibe gives more linear-response LED's and odd swing.
|5/18/1998 11:54 AM|
this my take on this, most flangers can be purchased for as much as it would cost to make one but if you want a univibe ya gotta
fork out about $750 to 800 I have r.g. keens board and I must say its a work of art.
still gathering parts for it. so I dont know how it will sound, plus he has a bunch of mod's on his site, this seems to me to be the best place to start...now if we could just get R.G. to do a toner sheet on his ultra-vibe
with input buffers, stereo output mixer, and feedback control, chip
|5/19/1998 3:14 PM|
|Mark Hammer||Re: Flanger choice|
A quick inspection reveals that the MXR Flanger lacks any sort of noise reduction other than low-pass filtering.
I had one of these "classics", and was only too happy to sell it some 15 years ago. I found the clock noise extremely objectionable, although I lacked a schematic at the time, and probably could have done something to tame the noise if I had had a schematic. IMHO, this was not one of MXR's finer efforts.
I used to own a PAiA Phlanger, and it was actually a pretty nice unit. Very flexible, with possibilities for voltage control. POLYPHONY had some mods for it to tame the noise a bit, and improve frequency response.
I have schematics for 4 different flangers from Craig Anderton: the pedal flanger (coupla chips, SAD1024, no noise reduction), the DEVICE Flanger (SAD1024, NE570 companding, voltage control), the PAiA Hyperflange+Chorus (SAD1024, companding, every bell and whistle you can imagine, including LFO waveshape and voltage control), the Chorus (Justin Philpott has it at his site, I think; SAD4096, companding, voltage control).
Although PAiA (www.paia.com) does not carry either the Phlanger or Hyperflange as kits anymore (scarcity of the much-needed SAD1024, and in the case of the HYperflange CEM3340), they might have a board lying around to sell you.
If you intend to use the flanger with single coil pickups, then preserving as much high end as possible is desirable. This means that you want to use companding for eliminating clock noise, since the low-pass filtering needed in the absence of companding would just gut anything about 6khz or higher.
Of the various Electric Mistress schematics which might be available, go for the one with companding.
If you want KILLER flanging, try and dig up an MN3011 delay line chip, and some info on these things. They were the heart of the A/DA STD-1 (ah, simpler times, when STD could mean Stereo Tapped Delay, rather than what we use it to mean nowadays). The MN3011 is a conventional BBD chip but has 6 delay "taps" at non-harmonically related intervals. This means that you can create astonishing stereo flanging by taking two different delay taps off the chip, which was what A/DA did.
If I'm not mistaken, the MN3011 was really designed to be an ersatz solid-state reverb chip (you know, multiple unrelated repeats). A/DA were probably the only folks to do anything remotely credible with it. I suspect it died a hideous death when digital algorithms and cheap memory made digital reverb easy/cheap to design/construct; the market for uber-flangers is probably a...um...niche market, somewhat unsuited to the costs of producing a chip like the MN3011.
|5/20/1998 8:02 PM|
As I recall DOD made a chorus unit with the mn3011 chip. It also had companding. It was very quiet but the chorus effect was kind of weak compared to some of the other units I've heard.
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