Pro Audio Design Forum

Tried several things and cap on the output worked the best. No traces of high frequency garbage that was otherwise getting inside the circuit (even with the cap on the input). Thanks gents! I'll insert the 1K protecting resistor at the input as well.

Series Rin will be too noisy. I estimated a suitable R as 500K, which gave me a -97dBv Johnson noise. Cap on the output worked though. Where is it better to connect it? Before R56 or after? I'm getting different values of the cap depending on its position (roughly 100 times difference in capacitance).

I'm building a simple FET DI input and it has too wide bandwidth as it is. What is the best way to incorporate an LPF in this design? I've tried different things, but the most obvious is a cap across the resistor as shown (470p gives a good cut-off frequency). Are there any drawbacks to this method?...

JR. wrote: ↑Fri Nov 24, 2017 11:53 am enjoy the math (I don't) http://www.thatcorp.com/datashts/dn128.pdf

JR

Ugh..... Seen than. This stuff is far above my math grade unfortunately((((

I don't think that's correct. If you look at the 2181 datasheet page 2 table 3 it shows a +0.33% gain control tempco. You still need -0.33% to correct it. Also see equation 1 on page 5 of the 2181 datasheet for the delta-T term in the denominator: http://www.thatcorp.com/datashts/THAT_2181-Series_D...

Sent a letter to THAT and it turned out I don't need tempcos for 2181 any more because it's already there on the chip. Now, if I understand correctly, I just remove the tempco (R8 in the 202XT circuit). Do I still need the R7 (6R8)? Can't figure what its function is. Everything else seems to be pret...

I hate always being the wet blanket but WHY??????? (maybe I don't hate it, or I would stop doing it). I actually have a patent for a VCA (US04818951 roberts 1989), and stopped using my own after we (Peavey) could buy better ones from dbx.... The last generation IC VCA from THAT corp is superior to ...

I'm thinking of building an equivalent ov 202XL VCA for my compressor. I've studied the documents here: http://www.proaudiodesignforum.com/forum/php/viewtopic.php?f=6&t=34 While circuits look simple enough, there're a couple of things I'd like to clarify. All circuits use 3300ppm tempco resistor...

I'm playing with a simple DI circuit in the simulator and here's a very strange thing that's happening. I'm following the output of the DI with a basic non-inverting op-amp block. When I use JFET op-amps, everything is fine. But when I put BJT op-amp, the input and output pins show a huge DC offset....

This is an EQ project, so replacing a pot with a rotary switch is a very useful option. Especially if this pot is a dual rev log beast. My concern is tracking between the decks (which in rev log may be horrible). Slugging is an option, but it will require a higher resistance value pot, in my case ar...