Search found 67 matches

by ilya
Sat Sep 09, 2017 11:51 am
Forum: Pro Audio Design
Topic: Log switch using binary coded relays - possible?
Replies: 6
Views: 5126

Re: Log switch using binary coded relays - possible?

I've explored the tapering option and it's not that easy. The problem is: I need the "20" multiplier for the correct taper. When I select the appropriate values for R and R' (2020k and 105k), the minimum resistance (for 16 steps, equally divided for the linear pot) is 58K which is too much. I need a...
by ilya
Fri Sep 08, 2017 6:37 am
Forum: Pro Audio Design
Topic: Log switch using binary coded relays - possible?
Replies: 6
Views: 5126

Re: Log switch using binary coded relays - possible?

This is most helpful! Thanks! Rheostat is what I need. Those taper "bending" resistors are very handy. Will see how it works with linear switching pot.

The attenuator site you mentioned is also a very interesting resource. Unfortunately it doesn't suite my particular need.
by ilya
Fri Sep 08, 2017 2:05 am
Forum: Pro Audio Design
Topic: Log switch using binary coded relays - possible?
Replies: 6
Views: 5126

Log switch using binary coded relays - possible?

I'm trying to replace some obscure pots with switches. However, some switches are so large that I have to reside to relays. My goal is to minimize the relay count. Now, with linear pots it's quite simple to use 4 relays and get 16 even steps feeding binary numbers into relays coils. I can even use a...
by ilya
Fri Sep 08, 2017 1:57 am
Forum: Pro Audio Design
Topic: Comparator oscillation in meter circuit - pollutes audio
Replies: 14
Views: 11372

Re: Comparator oscillation in meter circuit - pollutes audio

Filter inductor? Didn't see that one. Glad you found it! (We hope.) You didn't see it because it's in another part of the circuit, I didn't post a schematic for that. Comparators are physically above the inductors, so the transients were coupling right into inductors. Had to slow chips down with ca...
by ilya
Tue Sep 05, 2017 4:38 am
Forum: Pro Audio Design
Topic: Comparator oscillation in meter circuit - pollutes audio
Replies: 14
Views: 11372

Re: Comparator oscillation in meter circuit - pollutes audio

Had a chance to modify the circuit as was suggested. Unfortunately, it didn't help much. I still get the harmonics from comparator oscillation :(

Edit: FOUND IT! This is the comparator coupling to the nearby filter inductor. Gonna see if some screening helps.
by ilya
Sun Sep 03, 2017 1:52 pm
Forum: Pro Audio Design
Topic: Comparator oscillation in meter circuit - pollutes audio
Replies: 14
Views: 11372

Re: Comparator oscillation in meter circuit - pollutes audio

Ok. I'm going to modify the current splitter and grounding scheme and see if it helps with the issues. Here's the version with all modifications suggested in this thread:
splitter2.jpg
Does this looks correct?
by ilya
Sat Sep 02, 2017 2:10 pm
Forum: Pro Audio Design
Topic: Comparator oscillation in meter circuit - pollutes audio
Replies: 14
Views: 11372

Re: Comparator oscillation in meter circuit - pollutes audio

mediatechnology wrote:
Sat Sep 02, 2017 1:59 pm
I would lower it to 100 nF.
Also bypass the voltage divider node at the non-inverting input.
Be aware of the potential of TL07X latch-up as a follower.
Will do. What would be a better ic for this job? NE553x?
by ilya
Sat Sep 02, 2017 1:12 pm
Forum: Pro Audio Design
Topic: Comparator oscillation in meter circuit - pollutes audio
Replies: 14
Views: 11372

Re: Comparator oscillation in meter circuit - pollutes audio

What JR said. Decouple to "real" ground. Also remove those two 22uF at the output of the TL07X rail splitter. It's not going to like driving 44uF. Add a 47R in series with the rail splitter output and then decouple the rail splitter line with a single C to "real" ground. Something like this? splitt...
by ilya
Fri Sep 01, 2017 3:51 pm
Forum: Pro Audio Design
Topic: Comparator oscillation in meter circuit - pollutes audio
Replies: 14
Views: 11372

Re: Comparator oscillation in meter circuit - pollutes audio

Well, this will actually reduce parts count (2 caps per chip to 1 cap per chip). Will try this when I get back home from tour. Anything else to look at?
by ilya
Fri Sep 01, 2017 3:32 pm
Forum: Pro Audio Design
Topic: Comparator oscillation in meter circuit - pollutes audio
Replies: 14
Views: 11372

Re: Comparator oscillation in meter circuit - pollutes audio

I'm attaching the schematic below. The circuit has negative power supply, so MTR_GND is 0V, _B- is -18V, VIRT_GND is something like -9V The grounding scheme might be the culprit as I'm using a V/2 as a decoupling point and now I don't think it was such a good idea. But if you see anything that may c...