Search found 69 matches

by terkio
Fri Mar 29, 2019 10:38 am
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 5786

Re: Op amp matching

Thanks for these reviews on ADA4522-2 and OPA2189 for dual DC servo uses. Giving more than datasheets. Good to know about beats from asynchronous clocks, an effect one can hardly guess beforehand. BTW: Which dual servo do you use ? A differentiel Deboo integrator ( that has one cap ) or a more usual...
by terkio
Thu Mar 28, 2019 7:01 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 40
Views: 35028

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Thanks for your answers.
I forgot I do have a microchip PIC developement kit :D Unused for so many years..... :lol:
It might very well support what I need for audio projets.
by terkio
Thu Mar 28, 2019 1:42 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 40
Views: 35028

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

@JR. Wonderful, I am glad to see a DSP with a DAC built in, a perfect solution for this and many more.

EDIT: I spotted dsPIC33F 4 bucks !
Can you recommend a kit with a DSP and DAC, I could play with, plug and play ?
by terkio
Thu Mar 28, 2019 1:13 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 40
Views: 35028

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

This thread revived an old time where I struggled with LF oscillators for measuring distortion with the double T bridged filter. The best I achieved was nothing to praise, distortion measurements capable of 0.1 %, that was good enough for me. I remember the struggle to achieve an amplitude stable an...
by terkio
Wed Mar 27, 2019 8:48 am
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 5786

Re: Op amp matching

I just discovered the LMP2021. It has very low offset and it is pretty quiet. http://www.ti.com/lit/ds/symlink/lmp2021.pdf Fantastic Vos. Trouble is, for me, I need +15V -15V op amps. I just couldn't get the choppers quiet in my circuit, though they are also working for me. How bad is it ? How to c...
by terkio
Wed Mar 27, 2019 7:51 am
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 5786

Re: Op amp matching

What can be expected with offset compensation with a trimmer ? For instance considering OPA2277: Vos 20µV typ, 65µV max Vos drift 0.15µV / °C Can I expect with proper trimming a final Vos based on drift only. Considering à 10°C to 60°C temperature span, if trimmed at 35°C, this would give about 4µV ...
by terkio
Wed Mar 27, 2019 3:12 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173537

Re: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851

To minimize loop area this is an interesting way, however there are other objectives. Some components better be on the same side of the PCB for better thermal matching. It is likely there is less temperature gradient for components close on the same side rather than closer but on opposite side. Prac...
by terkio
Mon Mar 25, 2019 10:33 am
Forum: The Peabody Lounge
Topic: Amazon-Free: A Two Year Anniversary
Replies: 26
Views: 2390

Re: Amazon-Free: A Two Year Anniversary

opportunity pricing around the internets... This drives me mad. They heavily do it on air flight prices. Years ago I was used to book from an internet travel agency, until I noticed that if I was not bying right away, prices were jacked up, the next times looking for the same flights. Now, I forgot...
by terkio
Thu Mar 21, 2019 3:13 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 483
Views: 173537

Re: Bias Current "Assistance"

Change from previous schematic: Added R32 and R33. +15 mV is developed across R33 to satisfy an estimate of the common mode bias current of Q1 and Q2. What good is removal of common mode biais current of Q1 and Q2 ? This + 15 mV lifts the inputs close to ground, removing DC at the source input, is ...
by terkio
Mon Mar 18, 2019 11:43 pm
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 5786

Re: Op amp matching

In my quest for low Input Voltage Offset, a key point for an integrator circuit, I lost hope in matching op amps. What is better than OPA2277 ? Are they better ones, at low input voltage offset ? Is chopper op amps the way to go, in audio applications ? EDIT chopper op amps like: Zero-drift amplifie...