Search found 66 matches

by terkio
Fri May 03, 2019 5:24 am
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 2187

Re: Op amp matching

At the Integrator ( dual, non inverting ) with OPA2277 I have 30K 10µF for the time constant I need. From the data sheet OPA2277 Vos max is 50µV, Ios and Ibias max is 3nA I am not sure I understand correctly these figures, a bit confusing in the data sheet. With these figures: 3nA x 15K gives a 45µV...
by terkio
Thu May 02, 2019 4:08 am
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 2187

Re: Op amp matching

I realize Ios and Ibias can be as important as Vos about the quality of an integrator. The capacitor isolation resistance IR must be hight, easy with film caps, but that is not enough, the capacitor should not leak via the op-amp input pin. The OPA 2277 has a 3nA Ios and Ibias. About this specific p...
by terkio
Tue Apr 30, 2019 12:21 pm
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 441
Views: 155687

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

My tester for EMI, hum, thermal drift is a hair drier. A cheap tool that does it all. An anecdote about thermal stability: A design of mine about a test equipement to test TV reference monitors. When they put my proto, in thermal testing to check the compliance with requirements about stability of l...
by terkio
Sat Apr 27, 2019 8:06 am
Forum: Pro Audio Design
Topic: A Low Noise Balanced Input Moving Coil Preamp Using the ZTX851
Replies: 441
Views: 155687

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

First off, thanks to show all this nice work.
I do want to get some mu-metal....and I'll try lining the metal Hammond box with it.
I am very interested about this.
by terkio
Wed Apr 17, 2019 1:59 pm
Forum: Build
Topic: Simple pcb design program
Replies: 28
Views: 34327

Re: Simple pcb design program

I see these software are mostly locked to: Output = Ordering PCBs to a specific manufacturer. PCB express has a netlist file, how could it not have it, however I found no way to import or export to LTspice for instance. Gerber files, same thing. Is there a true free software, open to alternate softw...
by terkio
Wed Apr 17, 2019 1:20 pm
Forum: Pro Audio Design
Topic: Op amp matching
Replies: 44
Views: 2187

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: 2187

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: 2187

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: 441
Views: 155687

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: 2280

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...