Search found 101 matches

by terkio
Wed Apr 17, 2019 1:20 pm
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 10054

Re: Op amp matching

I am not familiar about the effect of noise on an integrator. May be naive, I see integration, filtering out noise. I see the noise at the input averaged, buried in the integrating capacitor. 1/f noise looks scary because going to infinity for f going to 0 while gain of an integrator goes to infinit...
by terkio
Wed Apr 17, 2019 2:57 am
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 10054

Re: Op amp matching

About low Vos balanced integrators I am afraid we are stuck with OPA2277 or go the route of choppers with adaptation board. I do not see how to use two OP07 with two trimmers. I see no way to trim correctly those two that will interact. OTOH. One trimmer for the two op-amp makes the adjustment possi...
by terkio
Sat Apr 13, 2019 5:11 am
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 10054

Re: Op amp matching

From the data sheet, one can expect 5µV Vos with trimming using OP07E.
It comes in two flavors OP07E ( better ) and OP07C.
There is another flavor OP07D ( not so good, lower cost ).
by terkio
Wed Apr 10, 2019 11:46 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 492
Views: 193273

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

LM4562/LME49720 and now-discontinued LME49860. I am shocked to see Texas Instrument continue publishing datasheets for these op-amps tooting low noise: 2.7 nV / rt Hz. And they continue to sell an op-amp they have discontinued without any warning like "not for new design". Clearly, they clear their...
by terkio
Tue Apr 09, 2019 4:19 am
Forum: Test, Measurement and Repair
Topic: entropy continued?
Replies: 34
Views: 6714

Re: entropy continued?

Bad contacts before, good after contact cleaning spray. So, there was some contact contamination: Corrosion, oily film, some residu left from manufacturing, storing, handling. Who knows wether the culprit is the socket or the IC. Well, you are stuck with those, all you can do is to keep the stabilan...
by terkio
Mon Apr 08, 2019 11:06 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 492
Views: 193273

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

LM4562, LME49720, LME49860 the same chip. Better than NE5532, pin compatible.
2.7 nV/rt Hz THD 0.00003% 55 Mhz 140dB capable to drive 600 ohm ( Iout +/- 26mA ).
Please, double check.
by terkio
Sat Apr 06, 2019 7:54 pm
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 10054

Re: Op amp matching

With 10µV accuracy at the integrator input, I get 10mV spikes when switching gain 1000 to/from 500. That is with no input signal. The spike is a steep front followed by a RC like decay. I do not switch at signal zero crossing. With signal, the spike is blended with the signal. I have simulated this ...
by terkio
Sat Apr 06, 2019 3:00 pm
Forum: The Peabody Lounge
Topic: karma
Replies: 8
Views: 1440

Re: karma

At my place, they quickly bill on estimated readings, with a chunky over estimation. Once I had the meter kid coming while I was deep at digging and moving stones and soil. Because of my back, hurting at that time, I asked him kindly to lift the quite heavy concrete cover for me. He "smartly" lifted...
by terkio
Sat Apr 06, 2019 8:40 am
Forum: Pro Audio Design
Topic: Preventing mic preamplifier HF oscillation
Replies: 7
Views: 2275

Re: Preventing mic preamplifier HF oscillation

The schematic in the original post shows two 100µF on +12V -12V at the op-amp :shock: You do need two 100nF as close as possible to the op-amp pins. These are a must. Add those, keep the 100µF, for general decoupling. I always put 100nF Multy Layer Ceramic caps at each and every IC supply pins. Rece...