Doepfer

normally, the noise output of A118 should be +/- 3 volts Peak to peak.


 
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________________________________

 From: "pmclean_80207@yahoo.com" <pmclean_80207@yahoo.com>
To: Doepfer_a100@yahoogroups.com 
Sent: Tuesday, September 17, 2013 5:06 AM
Subject: [Doepfer_a100] Really low A-118 (noise) signal level.
 


  
The signal-level of my A-118 is really low.  About -1V -> +1V (in contrast to the A-110s which have -5V -> +5V).  I don't think this has always been the case.

There is no trim-pot for output signal level (or anything) on the A-118PCB.  Is there a resistor that can be changed out to increase the output?

Thanks,
Paul McLean
Denver/San Jose, USA

> The signal-level of my A-118 is really low.  About -1V -> +1V (in
> contrast to the A-110s which have -5V -> +5V).  I don't think
> this has always been the case.
>
>
> There is no trim-pot for output signal level (or anything) on the
> A-118PCB.  Is there a resistor that can be changed out to
> increase the output?
>
>
> Thanks,
> Paul McLean
> Denver/San Jose, USA

Since end of 2011 the A-118 is equipped with a trimming potentiometer (P5)
to compensate the level tolerances of the noise transistor. Until then the
noise transistors were selected to obtain at least 5Vpp level. If the level
is only 2Vpp probably the transistor may have changed it's noise behaviour
over the time (and your message implies that the module had earlier a higher
level). I see two solutions: increase the amplification of the internal
amplifier by decreasing the value of R3 or replace the noise transistor Q1.
Contact me directly for the position of R3 (hardware@doepfer.de). There are
four different pcb versions of the A-118 with different positions of R3.

Best wishes
Dieter Doepfer