Doepfer

Hi Bakis/everyone,
Responses to a couple of posts, and also a correction:

> the A-140's tendency to drift during long sustains). However 
> I can see a possible problem with the A-132/A-140 
> combination: you get max gain from the 132 with a CV input of 
> about 5V, but the 140 sticks out up to about 8V, and the lack 
> of ability to attenuate the CV input on the 132 (which you 
> could do with an A-130) will mean the envelope gets 'clipped' 
> (you could always attenuate with the 138 of course!). (I 

This is incorrect! The 132 is fine with the size of the 140 output - I was confused with the 131 behaviour and the misleading comment in the 132 manual entry, which says that *max* gain comes from an input of approx 5V, in fact it can go higher: at about 5V CV input my module has a gain of about 1.2, and with 10V CV the gain is approx 2.5. Thus with an input signal of +/- 5V, and CV of around 8V, the output is clipped as it is approaching (+/- 10V) the voltage supply rails to the chips. Since the 140 envelope only goes up to about 7.5V, the 132 *is* OK with it, i.e. no clipping. Hence the reason why you wouldn't have noticed it - it is *not* a problem (Adam please note also!) - I do apologise for any confusion I may have caused!

I did some investigation into the clipping at high CV inputs on my 131 (v2) - it is due to a completely different mechanism (the converter to give the exponential response) than that above, and may possibly be circumvented by replacing a single resistor - I'll check it out and report back later.

> what i have found so far:i had some new
> a131(v2.2001).i noticed that if you turn the input
> knob all the way up the output uis much louder than
> the older a131's and it is distorted too...dieter told

My investigation with the 131 above was done with the signal input set to max, and you cannot help but notice on a scope how distorted the output is! I'll try it at some lower settings too now, having read your comments, to see what I can find/hear.

Tim

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> with an input signal of +/- 5V, and CV of around 8V, the output is 
> clipped as it is approaching (+/- 10V) the voltage supply rails to 
> the chips. Since the 140 envelope only goes up to about 7.5V, the 
> 132 *is* OK with it, i.e. no clipping. Hence the reason why you > > 
> wouldn't have noticed it - it is *not* a problem.

This gybes with my experience also. The output of the A132 is *quite* 
hot when used with the A140, but not clipped. The A141 ADSR output 
voltage is much lower than the A140, so it's a good envelope to use 
with the A132 (and a bad envelope to use with the A121 filter, unless 
you, ahem, boost it with the A132).

This takes me back to Florian's earlier discussion about a CV 
amplifier. I was wrong then when I said that the A119 Ext. Input and 
A136 Distortion/Waveshaper are the only A100 modules that work as a 
gain stage. Certainly the A132 does also, and might be the best choice 
for this application.

Joe