Pro Audio Design Forum

I am a little busy to dig into this too deeply right now. I am unclear whether you are talking about the group delay of a servo per se, or a 3 pole Bessel filter. Once again, good practice in my judgement is to place the servo poles way down in frequency, then use a high quality film cap to generate...

The concept of a servo is to use an opamp so you can get away from large caps, or are your 1UF caps film? If they are they will probably be physically large.

What kind of reaction time does a DC servo need?


JR

The 5V supply is probably not noise free, so perhaps a small cap across the 12k feedback resistor, and/or a cap to ground from the middle of r3. Especially useful if we experiment with back off c8 to see if noise cancellation there is useful. The 5V supply will probably have HF noise so cap probably...

Indeed lets see some smoking guns. The best cap is no cap, after that give me a good film cap maybe with a good opamp wrapped around it. IIRC I was arguing that the performance of the servo amp can matter. I know some folks who use lots of servos with no problems, I haven't used one since my last ph...

Hi all, may I throw in an aspect which seems to go by unnoticed in all the posts posted ahead? Fact: An audio circuit with a DC-servo to squeeze out that DC offset is, by all means, a HPF. true fact dat... It is the matter of group delay distortion. I have been dealing a lot with this subject, as s...

Let me see if I've got this right: It seems that the scale of the VCA is determined by the maximum DAC output (4.1v) times the buffer's Rfb (1K in my case) divided by the total series resistance of the CV path (aprox 10K2 in my case) which lands around 400mV for each CV port - roughly half of the s...

The issue with the -12v supply is not just slow start, but if you want to manage that way it must fall before the +5v on turn off also. If you're going to invest any effort into this approach a simple tracking supply can probably be made from one opamp... but this may not be necessary if we lighten ...

Please provide a schematic of exactly what is connected to the DAC outputs now. It is also possible the DAC was partially damaged before and failed later,, If the DAC is only connected to the top of C8 through a few K resistor and still failed I am surprised. If the filter cap is in middle of around...

You should be able to find design equations for MFB in filter design texts, If you can't I can dig out mine from old Burr Brown Operational Amplifiers book. Typically the input R and output R back to that input node are the same value for unity gain inverting response below tuning. The Cs are genera...

Yes simple inverter NG=2, simple follower NG=1. I killed a bunch of brain cells thinking about this last year or the year before and I did not come up with a simple, cost effective solution. The VCA wants to see both a very low impedance at the Ec ports and very low noise. Using a resistor pad to fe...