Infinite Melody CGS32

[prgdeltablues]

I'm working out how I want to implement the Infinite Melody module: thinking of including an internal fast clock and white noise source (with their outputs available on the front panel), all six MBx through pots for the mixer, but with a fixed value feedback resistor rather than a master gain. Same for the three fixed outs, fed by the resistor ladders.

I was wondering, if I am going for fixed (unity) gain rather than a variable gain, on the three outputs, whether I could replace the inverting summer - inverter two opamp output with a single non-inverting summer - or rather just a voltage follower, since it looks to me as if the R/2R resistor ladder simply presents a single voltage to the input of the opamp, there isn't actually any summing involved. but maybe I've not understood that right.

I assume for best accuracy, the 100k and 200k resistors in the ladder should be matched to 0.1%?

Peter

[andrewF]

i haven't tried it but in theory it will work. Remove the 100k resistor that connects the resistor ladder to pin 2 of the op amp. Connect your voltage follower to the resistor ladder where the 100k used to go. I prefer to have it the way Ken designed, so there is the option to adjust the gain and can obtain an inverted output.

Its good to have 1% resistors, or just go thru a batch with a multimeter and choose all the ones the same value. This will ensure the steps will all be the same size and changes will be proportionally correct.