xefe
Active member
- Joined
- Apr 15, 2009
- Messages
- 43
Hi.
I recently bought a used Motu 24i/o and after some test to make sure the unit was in perfect condiction i opened it up to see what's happening.
I must say i was impressed with some building details such as separate tranformers for analog and digital circuitry - both linear psu's-, all schotky diodes with huge capacitances in smoothing and a low dropout burr brown regulator for the digital circuit.
Now the strange stuff. The psu for the analogue circuit is not regulated, just the schotkys and 9400uf of capacitance for each rail (-10v and +10v) ???;
Also the unit doesn't have any input or output coupling capacitors... Dc coupled? those NJM2115's and JRC4580'sdon't look like precision opamps to me... ADC/DAC chip have built in hi pass filter, so no DC on the ADC/DAC.
1 - Should i work a way fit some 7806's on the positive and negative rails?
2 - Leave as it is, makes no difference?
Already swapped two NJM2115 for LME49720 on one channel. Not yet tested the sound but the modded channel gave slightly better results in Rightmark Audio Analyzer.
Any opinions are welcome.
thanks!
I recently bought a used Motu 24i/o and after some test to make sure the unit was in perfect condiction i opened it up to see what's happening.
I must say i was impressed with some building details such as separate tranformers for analog and digital circuitry - both linear psu's-, all schotky diodes with huge capacitances in smoothing and a low dropout burr brown regulator for the digital circuit.
Now the strange stuff. The psu for the analogue circuit is not regulated, just the schotkys and 9400uf of capacitance for each rail (-10v and +10v) ???;
Also the unit doesn't have any input or output coupling capacitors... Dc coupled? those NJM2115's and JRC4580'sdon't look like precision opamps to me... ADC/DAC chip have built in hi pass filter, so no DC on the ADC/DAC.
1 - Should i work a way fit some 7806's on the positive and negative rails?
2 - Leave as it is, makes no difference?
Already swapped two NJM2115 for LME49720 on one channel. Not yet tested the sound but the modded channel gave slightly better results in Rightmark Audio Analyzer.
Any opinions are welcome.
thanks!