PLAN B analog blog

There's a lot of words on this problem on this and other lists.

It's ain't the M15's fault, partially an attribute of the
Frequenstiener's open loop transistor-based final amplifier stage and
largely due to the fact that Doepfer, Analogue Solutions and Analogue
Systems daisychain the ground connections on their busboards.  Big no no.

In fact you'd be able to hear LFOs out of the Frequen. if there was
one if those powered in the same rack.  It could be Doepfer's, A.
Sys's, A. Sol's or mine. Put a Harvestman microp based module in the
same rack and your filter frequency will wiggle as if slightly
controlled by a squarewave LFO.  Sounds like I'm bagging these guys,
I'm not - they're my friends.  I'm making a comment about the
potential risks of daisychaining ground connections - those part of
the power distribution system AND those used on the circuits
themselves, in audio applications.   You'll find on most Plan B
modules the grounds go on their own trace directly to the power
connector.  These are the types of safeguards you must put in play to
keep things a quiet as possible.  BUt this type of safegaurd goes out
the window on a power buss that ties it's grounds n a row instead of
individual feeds directly back to the PSU return.

One thing you can do to kill the potential from the M15 contributing to this keeping the square wave pot adjusted to the far left far right when it's not being used, thus holding the square in it's DC range and not generating a signal.  

While we're at it, an even more interesting attribute of the Steiner circuit is if metal can 2N2222 transistors were used, putting your finger on one or more of them while the unit is under power,  depending on your location you'll receive AM and Ham radio transmissions through the speakers.  Your location does not govern if it happens or not, your location onlydetermines how busy the airwaves are, increasing the likelihood there's a station at the filter's frequency band.  basically there's an antenna in play.  I've pulled this anomaly from Cynthia, Ken Stone's and Elby's Stiener filters - it's not them, it's the circuit.

But in particular I need to stress this isn't Mike's issue.  I was there when he put this together, I got the Synthasystem schematic from Nyle for him. Mike did an excellent job of reconstructing the original design and I commend him for that.  Not Mike's fault, it's the circuit but as a filter it sounds marvelous, so (in a nice way), deal with it!  

Also remember that the original Steiner system was line level.  Euro
is four times hotter. With that, the potentisal of this occurring is four times as great.  Such is the way things are in the 21th century when people are pulling circuits from the old days and integrating them into environments they weren't intended to be exposed to.  Know though that I'm as guilty as the rest of them with the M13.

To chill this down a bit, try increasing the 10mf electrolytic caps
which filter the power inputs of the Frequenstiener.  Then increase
any bypass caps used in the circuit.  I'd be careful though - a cap is
littered with caps, some as bypass, and some part of the filtering
circuit.  Basically the .01's should be increased to .1 but do a
listen test after each to make sre the particular cap isn't part of
the filter structure. Sorry, I can't publish the Stiener circuit, this
comes form a request of Nyle's.  The Synthacon schematic is all over
the place, this one is very similar but has more diodes in the ladder.
 Yu know what 90% of white noise circuits are based on?  Diodes or
transistors configured as diodes...it's a tough thing keeping them
hushed form picking up any sort of noise floatng around the power buss.  

Also try putting the filter in a rack without any alternating current
sources or modules whih have microps, especially Harvestman.  This
improves things a lot. As a last resort, consider the purchase of the
Plan B cases when they are released Q1 2009. All of our ground
terminations, from every terminal on the busboard lead directly to the
ground source on the PSU - no daisychaining!

- P






--- In PLAN_B_analog_blog@yahoogroups.com, "theglyph2000"
<theglyph.aaron@...> wrote:
>
> My model 15 can be heard through my FrequenSteiner through the power
> rails.  Not a big deal but just curious.
> 
> The 15 and the AFG are working f@#$ing great for me!  Peter and Mike
> are doing it right!!!
> 
> Cheers,
> theglyph
>