Wet/dry Parallel Processor

Where we discuss new analog design ideas for Pro Audio and modern spins on vintage ones.
User avatar
terkio
Posts: 299
Joined: Thu Feb 07, 2019 4:17 am
Contact:

Re: Wet/dry circuit

Post by terkio »

I overlooked the non linear conditioning asked on Ec s.
In my quick and dirty wave handing solution I was aware of some conditioning but thought it was going to be linear, easily implemented with op amps.
I need a close look at the actual gain(Ec) transfer function to fully work out the panning using two VCAs for each channel. Too bad this asks for some exponential or log function.
On the dark side this could be implemented with MDAC s, but this needs microcontroller clock and programming.
User avatar
mediatechnology
Posts: 5119
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Wet/dry circuit

Post by mediatechnology »

I think the cleanest solution is a 4 gang pot for someone not wanting to use a stepped switch.
A 2 gang pot could also be used for an "Add" mode but not "Mix."
I'm going to try and get a quote today from State Electronics.

Using VCAs, the cleanest solution looks to be using a second VCA in the feedback path of the control op amp to log Ec and linearize the overall response.
218X VCAs are so hard to get right now that the thought of 6 per board is a little overwhelming.

The diode breakpoint solution is do-able but the temperature drift bothers me.
As a practical matter -50 to -60 dB VCA cutoff is sufficient but the level of expectation I and perhaps others would have is that "Off" is really "Off."
Douglas Self created the word "Offness" and the term applies here.

Using a Log amp for linearization might allow better VCA offness.
I wonder how much gain drift would be tolerable at 0 dB or at 50/50% Mix though.
User avatar
mediatechnology
Posts: 5119
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Wet/dry circuit

Post by mediatechnology »

Let's see how much this 4 section 10K linear "ModPot" is going to cost:

It looks like potentiometers.com stock 10K in linear, log and rev-log tapers in just about every series both plastic and cermet.

Image
User avatar
mediatechnology
Posts: 5119
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Wet/dry circuit

Post by mediatechnology »

I just got a quote back from State Electronics.

The original series-70 (Allen-Bradley) ModPot is now EOL.
State suggested the S159 ModPot2 series which looks to be the original Clarostat design used by SSL, MCI et al.

There is a $50 US setup charge plus $70.95 for the pot; total is $120.95 US.

Image

This makes more sense to me than 6 VCAs and 3 or 4 dual op amps.
User avatar
mediatechnology
Posts: 5119
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Wet/dry circuit

Post by mediatechnology »

I just bought 2 4-section pots.

Time to draw a schematic.
Fragletrollet
Posts: 12
Joined: Sat Oct 31, 2020 9:55 am

Re: Wet/dry circuit

Post by Fragletrollet »

Glad to see there's progress! Looking forward to have a look at the schematics when they are ready.
flyboy71
Posts: 61
Joined: Thu Nov 21, 2019 7:56 am

Re: Wet/dry circuit

Post by flyboy71 »

I'm coming in on the tail end of this but I'm harkening back to my compressor project where I took the ADC input of my PIC chip and used a lookup table to generate a log function for the PWM. This would get complicated though unless you added a DAC to the PIC plus programming it. I know I've used this approach on other projects to linearize or non-linearize a voltage. Just an idea and may not be practical on this especially now since PICs are harder to get.
My project and tutorial site: https://ornerscorner.neocities.org/

"Things are more like they are now then they ever were before" - Dwight
User avatar
mediatechnology
Posts: 5119
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Wet/dry circuit

Post by mediatechnology »

Thanks for stopping by.
I thought of using something like that too.
Many MEs wouldn't even want a VCA in the transfer path or any kind of non-mechanical control.
It's why I still use relays for basic switching which are also getting hard to get due to delivery times.

If I did use VCAs (instead of PWM) it would be tempting to use a PIC to linearize the control voltage.
User avatar
mediatechnology
Posts: 5119
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Mix/Add Parallel Processor Schematic

Post by mediatechnology »

Mix/Add Parallel Processor Schematic

Image
KA Electronics/Rockmore Labs Mix/Add Parallel Processor Schematic

Large Format: https://ka-electronics.com/images/png/P ... ssor_3.png

I'll post a circuit description shortly.
User avatar
mediatechnology
Posts: 5119
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Wet/dry Parallel Processor

Post by mediatechnology »

State Electronics processed my order promptly and I now have two 10K Lin X4 multi-section pots to experiment with.

UPS delivered these around 9 PM on a Saturday night...

Image
10K X4 Linear Pot For A Mix/Add Parallel Processor.

State Electronics assigns a part number for this assembly that anyone can use to order.

The part number is: L50261

These are conductive plastic and very smooth.

I need to wire a shielded pigtail for it and begin some experiments.
Post Reply