Author Topic: High pass filter in deprofundis delay  (Read 265 times)

jamierichards1234

High pass filter in deprofundis delay
« on: March 07, 2019, 03:41:14 AM »
Hi,

I've built a deprofundis delay and I'm very happy with it, but I get a bit of low level low frequency motorboating noise. I guess my PT2399 is a bit dodgy as I've read that this is often the case. I was thinking if I could add a high pass filter to just the wet signal (at maybe 100hz) this would be a good improvement. The only problem is I don't know how to do this..

I've gone some reading about simple R-C high pass filters, but I'm not sure where in the circuit to add it. Also I've found a 'calculator' that will tell me how to get the cutoff frequency, but obviously different numbers will get to the same result - How do I know if I should use 15k/100n, or 150k/10n etc?

If anyone can help I'd be very grateful!

Cheers,

Jamie




antonis

Re: High pass filter in deprofundis delay
« Reply #1 on: March 07, 2019, 07:47:04 AM »
Place a 1n5 cap on Input (just before R1) to take advandage of already existing 1M pull-down resistor.. :icon_wink:
(and not modify anything inside circuit..)

About RC values selection: Usually, bigger caps need more board space (and more money..) where resistors of any value (with the same wattage) need the same space (and money..)
Restriction factor of max resistor values should related with "secondary" issues, like noise..
Can't follow your signature changes, Stephen..!!
but I like what follows:
"put the coffee down, Antonis, and nobody will get hurt."
"Arggg, Jim ...."

jamierichards1234

Re: High pass filter in deprofundis delay
« Reply #2 on: March 08, 2019, 06:39:04 AM »
Ok thanks that all makes sense.

I'd quite like to try and add a high pass filter to just the wet signal though as I would like to experiment with the cutoff frequency a bit without messing up my dry signal. Any clues of where I could add it in the circuit to achieve this?

Thanks

ElectricDruid

Re: High pass filter in deprofundis delay
« Reply #3 on: March 08, 2019, 07:44:06 AM »
You could reduce C6/1u. It's feeding the wet signal to the output mixer. Since the input resistor is 22K to a virtual ground node, that's the R part of your RC highpass. Adjust the 1u cap to taste to get the cutoff where you want it.

HTH,
Tom

jamierichards1234

Re: High pass filter in deprofundis delay
« Reply #4 on: March 08, 2019, 08:17:46 AM »
Excellent, I'll give that a try.

Thanks!  :D