Doepfer

According to the response I got from Dieter, the A150 User's Manual 
has been UPDATED to describe the -8V - +8V restriction. I guess if a 
product doesn't meet it's prospectus, update the prospectus ;)

Also, the FAQ on the Doepfer home page now describes this problem, and 
suggests either using attenuator patch cords with a resistor in the 
plug, or a user-applied modification to the A150 which would make it 
operate over the 0-16V range instead of -8V - +8V. This would make the 
A150 unusable for AC - audio or LFO signals.

I'm wondering if it's possible to mod only half of the dual switch.

Joe

--- In Doepfer_a100@y..., "stinchcombe_t" <tstinchcombe@q...> wrote:
> [Apologies if this appears twice - seem to be having 'finger 
trouble'
> with Yahoo.]
> 
> Hi Joe,
> 	I looked back over my old notes on this one: I still don't 
fully
> understand it, but can offer the following. When you get the bleed
> through, do you leave the other input unconnected? If so, try
> grounding it, as this seems to improve matters considerably (I've 
been
> partially inserting an unconnected patch cord to short the input to
> ground - not the most reliable of connections - but connecting a CV
> input set to 0V should do it too. Make sure you get your in's and
> out's round the right way - shorting the gate or trigger signals to
> ground through the switch would probably not be very nice!). You may
> still get some bleed through, but from my experiments it is
> considerably less, i.e. instead of the full signal, its down around
> 100mV or so. Also swapping inputs (I/O1 <-> I/O2) makes a difference
> too - its worse one way than the other. The problem is exceeding the
> +/-8V limit specified in the manual: despite some diodes apparently 
to
> protect the chip, some excess voltage does get applied to it, and so
> it's normal operating range is exceeded, and it thus stops working
> properly. The 'DID NOT' signals you listed will almost certainly be
> within +/-5V (I don't have a 155 or 191 so can't actually check 
these
> two, the rest certainly are); of the 'DID's the 160 and 190 signals
> are 0 - 12V, and I also strongly suspect the others are too (again I
> don't have these). If anyone else has knowledge of/can point me to a
> suitable reference for why the FET circuitry in the 4053 chip 
behaves
> in this manner, I'd love to know it!
> 
> Tim
> 
> [The views expressed above are entirely those of the writer and do 
not
> represent the views, policy or understanding of any other person or
> official body.]
> 
> 
> --- In Doepfer_a100@y..., "buechlerjoe" <buechlerjoe@t...> wrote:
> > I decided to try a number of signals patched to my A150's I/O2 
> > (Normally Open) jack. I wanted to see which ones would trigger an 
ADSR 
> > envelope by bleeding through the O/I jack, even though nothing was 
> > patched to the A150's CV jack to close the switch.
> > 
> > Signals that DID NOT bleed through were:
> > 
> > A145 LFO Pulse
> > A147 LFO Pulse
> > A155 Trigger
> > A156 Trigger
> > A190 Clock
> > A191 LFO Pulse
> > 
> > Signals that DID bleed through were:
> > 
> > A155 Gate
> > A160 Clock Divider
> > A162 Trigger Delay
> > A165 Trigger Modifier
> > A190 Gate
> > 
> > What's even more worrysome is that I'm fairly sure that I've 
> > successfully switched an A190 Gate signal with the A150 in the 
past, 
> > so now I'm concerned that the A150 is actually deteriorating in 
this 
> > regard. I wish I could be more certain about this.
> > 
> > There was an earlier response from Dieter on this issue, in which 
he 
> > ascribed the problem to user abuse of the A150. I'm certain that 
he 
> > misunderstood the symptoms, though, because he was talking about 
> > signals patched to the CV input, rather than the switch inputs. In 
any 
> > case, in was in the middle of preparations for the Frankfurt show 
and 
> > he probably didn't give the issue a lot of attention.
> > 
> > I've sent a copy of this post directly to Doepfer by email.
> > 
> > Joe