general mcmeat questions

[jmasciswannabe]

If I have a couple of the vactrol 3/2 with three leads can I just cut the middle lead off? The led, I am assuming that is responsive to the envelope as it opens and closes or should it just always be on or off?
Finally, would ussing an rc4559 instead of the lm1528 be all right? They are both dual op amps with the same layout I believe.

Thanks
Ian

[toneman]

Hi J,
don't think the "3lead" vactrols will work.
U need 2 completely independent resistors 4 the filter.
that would B 4 leads on one side.
2leads 4 an internal "dual-LED"  arrangement probably would work,
but this type of filter *needs* 2 completely independent resistors.
i'm not familiar with the vactrol U describe....got a link?
OneMorething...the original uses 3green LEDs.
if U use vactrols, the "visible" LED needs to B the same color(?)
what???
the original uses *all* descrete green LEDs.
i found the visible LED worked fine by itself.
& the (correct)vactrols worked fine by themselves.
But, when i paralleled them as in the schemo, visible didn't come on.
Solution....add a buffer between the currentlimitingR and the LED.
this way the sw arrangement remains the same.
I'm using a 5mm bright blue LED for the visible.
staynonvegan
tone

[jmasciswannabe]

Toneman -

Are you sure about those vactrol 3/2 here is the datasheet:

http://optoelectronics.perkinelmer.com/content/Datasheets/vtl5c3_c4.pdf

I wasn't paying attention when ordering! Damnit! They are expensive little buggers too! I went ahead and constructed the meatnball and I am not getting the envelope sound, but the green light comes on and sound passes through it.

[toneman]

Hey J,
don't know what U R refering 2 when U say 3/2(?)
the VTL5C3 is the one recommended in the McMeat schemo.
that's the one i'm using.
the VTL5C3 ohly has 4 leads: 2 4 the LED; 2 4 the  photoresistor.
if your vactrol has 5 leads...U might have ordered a "dual element".
Means U have 2 photoRs and 1 LED.  PhotoRs are "centertapped".
Isn't there a # on the package.....?
!!! U *can* still use i t !!!   But don't cut off the extra lead right away!!
just use only 2  leads on the resistor side.  Probably the middle & one outside.
Who knows, mayB "paralleling" the photoRs might give U a better response(?)
If u've got envelope-response with the visibleLED, then preamp is working.
**remember what i said previously about the greenLED vs the VTL5C3.**
if U got it wired in parallel with the vactrols,  disconnect one lead of the visibleLED.
see if the filter works then.
staytrolled
tone

[jmasciswannabe]

woops! This one has the 3/2:

http://optoelectronics.perkinelmer.com/content/Datasheets/vtl5c2-2_3-2.pdf

What do ya think? I am using the green led as well.

[toneman]

as B4, your "dualelement" should work.
just use *one* of the 2 photoRs in the package.
so, just use 4 of the 5 leads.....
afn
T