[sdiy] EFM LFO5 Sync Help

[houshu at dsp.cl.nec.co.jp]

Hello Romeo,

In Mono/Poly LFO, schmidt trigger is biased, not symmetrical.  I guess
triangle output is always positive, therefore sync transistor can't
turn on without sync pulse.

On the other hand, in your LFO5A, triangle output can be below zero.
The sync transistor can turn on as a reversed transistor, which
results in stop of oscillation.

LFO sync is not so easy.  Reset of integrator and reset of schmidt
trigger are both needed.  Mono/Poly LFO does them in a tricky way.

Hope this helps.

Osamu Hoshuyama

> Date:    06 Apr 2001 22:30:57 JST
> From:    "RFAHL" <8brain at spiritone.com>
> 
> Hello,
> 
> Thanks for the perfoboard recommendations.  Looks like a quick trip to Rat
> Shack is a good place to start.
> 
> I have been working on an LFO that Tom G. of EFM designed.  I've been
> modifying it a bit and need some assistance with that.
> 
> I added a 3pole rotary switch so that I could add a range of caps to extend
> the LFO's range.  This works.
> 
> I tried adding a sync input, like on the Korg MonoPoly LFO:
> 
> http://www.spiritone.com/~8brain/schems/MonoPoly-MG2.gif
> 
> This does not work.  If I connect this to the LFO, it no longer oscillates.
> Inputting anything into the sync input has no effect.  It seems like the two
> LFOs are similar enough that the Korg sync input should work with Tom's LFO.
> 
> I've uploaded Tom's schematic with my mods added to it:
> 
> http://www.spiritone.com/~8brain/schems/lfo5plussync.gif
> 
> If anyone would care to take a look at it and tell me how I might get the
> sync feature to work, I would greatly appreciate it!
> 
> Romeo
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 Osamu HOSHUYAMA                    NEC Corporation  Kawasaki JAPAN
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