Search found 67 matches

by ilya
Mon Sep 03, 2018 5:36 pm
Forum: Pro Audio Design
Topic: Negative impedance converter reactance
Replies: 10
Views: 3272

Re: Negative impedance converter reactance

JR. wrote:
Mon Sep 03, 2018 5:16 pm
So if I google "the bridged-t equalizer" I'll get your schematic?

I'm tapping out now..

JR
Sorry, didn't realize you wanted the schematic. I thought what I posted was sufficient.
I'm talking about this circuit.
by ilya
Mon Sep 03, 2018 2:49 pm
Forum: Pro Audio Design
Topic: Negative impedance converter reactance
Replies: 10
Views: 3272

Re: Negative impedance converter reactance

I'm not ready for production quantities...

This resistor sets the frequency in the bridged-t equalizer.
by ilya
Mon Sep 03, 2018 12:35 pm
Forum: Pro Audio Design
Topic: Negative impedance converter reactance
Replies: 10
Views: 3272

Re: Negative impedance converter reactance

Well, the whole point of this exercise is to get rid of an awkward dual rev log 100k pot and replace it with somewhat more friendly dual 10k linear one.
by ilya
Mon Sep 03, 2018 10:41 am
Forum: Pro Audio Design
Topic: Negative impedance converter reactance
Replies: 10
Views: 3272

Re: Negative impedance converter reactance

NR1 and NR2 nodes are where the circuit from the first post (NIC) connects. There are two identical NICs, one with NR1 terminals, another with NR2 terminals.So they connect in parallel to R33 and R34 and are there to mimick the -11K resistance.
by ilya
Mon Sep 03, 2018 1:55 am
Forum: Pro Audio Design
Topic: Negative impedance converter reactance
Replies: 10
Views: 3272

Re: Negative impedance converter reactance

Sorry, got distracted by kids and forgot to upload the other part. The first snippet goes in parallel with each potentiometer.
by ilya
Sun Sep 02, 2018 4:02 pm
Forum: Pro Audio Design
Topic: Negative impedance converter reactance
Replies: 10
Views: 3272

Negative impedance converter reactance

I'm trying to achieve a specific resistance curve and to do that I need to connect a negative resistor in parallel to the variable resistor in the circuit. I'm testing the standard NIC circuit (see attachement) which works mostly as expected. But at some settings of the variable resistor it looks li...
by ilya
Sun Jun 24, 2018 4:40 pm
Forum: Pro Audio Design
Topic: THAT 202XL recreation
Replies: 26
Views: 14540

Re: THAT 202XL recreation

Hmmmm.... That's interesting. So what are the possible ways of trimming the feedthrough then? Applying step impulses and monitoring the output? EDIT: just saw your last post with the quote from Gary. That's what I heard somewhere as well. So this leaves the first question that I asked: I get the low...
by ilya
Sun Jun 24, 2018 3:41 pm
Forum: Pro Audio Design
Topic: THAT 202XL recreation
Replies: 26
Views: 14540

Re: THAT 202XL recreation

My apologies for not being precise and for possible confusion. Of course there should be an external trim circuit for minimizing THD. As you said, this is often a voltage divider connected between +/- rails and fed into the sym pin of the VCA. I have this arrangement, I just didn't mention this fact...
by ilya
Sun Jun 24, 2018 2:52 pm
Forum: Pro Audio Design
Topic: THAT 202XL recreation
Replies: 26
Views: 14540

Re: THAT 202XL recreation

A quick update. The 2002T curcuit is working fine with diluted tempco as suggested by montemcguir. Thanks for sharing the idea. I'm having a hard time with "VA ADJUST" trimmer though. As is shown on the schematic , the total resistance can be varied between 10k and 60k. As far as I know, this contro...
by ilya
Sat Mar 31, 2018 11:22 am
Forum: Pro Audio Design
Topic: THAT 202XL recreation
Replies: 26
Views: 14540

Re: THAT 202XL recreation

Thanks for your input. It's a pity I haven't seen those platinum tempcos before I put an order with Mouser. What I decided to try was Vishay TFPTL series (https://www.mouser.com/ProductDetail/71-TFPTL10L1000FH5B). They have 4100 ppm +/-400 tempco though, so your SMD platinums look like a more suitab...