I was looking for schematics and PCB for compressors using THAT chips, the ones I found was based on the THAT4301P. But that chip is not manufactured any more. Is there any new version of this compressor for that the chip and the schematic/PCB is available?

 

https://gb.profusion.uk/media/assets/product/documents/4301-4305_transition-guide.pdf

 

THAT4305, THAT4315, THAT4316, THAT4320.

 

Thanks! Meanwhile I also found some info. The version I need is this, the fully adjustable compressor:
https://thatcorp.com/datashts/dn115.pdf

This schematic is for the THAT4301P, but browsing the database of the company no fully adjustable version for the recent chip versions. Do you know any schematic that shows you how you can build a fully adjustable version on the new chip?

 

Thanks! Meanwhile I also found some info. The version I need is this, the fully adjustable compressor:
https://thatcorp.com/datashts/dn115.pdf

This schematic is for the THAT4301P, but browsing the database of the company no fully adjustable version for the recent chip versions. Do you know any schematic that shows you how you can build a fully adjustable version on the new chip?

YES, there are adjustable compressors in the "audio" segment of the "Schematics for free " website.

 

YES, there are adjustable compressors in the "audio" segment of the "Schematics for free " website.

Indeed, the name of some knobs are not written on it. I found the ones I was missing, but still cannot see which part is the Hard Knee / Soft Knee selector?
https://thatcorp.com/wp-content/upl...or-with-Variable-Attack-and-Release-r0A.1.pdf

 

Rane used to publish schematics on their website; in the past compressors were based on SSM chips, but maybe newer ones use THAT?

 

Have you investigated the Analod Devices audio compressor ICs?? They seemed to offer a good selection 15 years ago, I have not checked more recently.

 

Rane used to publish schematics on their website; in the past compressors were based on SSM chips, but maybe newer ones use THAT?

Rane, they made cool stuff.
https://www.ranecommercial.com/legacy/pi14.html


Most of my current designs have glory parts.

 

This schematic is for the THAT4301P, but browsing the database of the company no fully adjustable version for the recent chip versions.

Use THAT4305 for the design note DN115. Replace the three general purpose op amps inside the 4301 with suitable, external op amps.

Indeed, the name of some knobs are not written on it. I found the ones I was missing, but still cannot see which part is the Hard Knee / Soft Knee selector?
https://thatcorp.com/wp-content/upl...or-with-Variable-Attack-and-Release-r0A.1.pdf

There is no designated hard/soft knee switch.

 

Have you investigated the Analod Devices audio compressor ICs?? They seemed to offer a good selection 15 years ago, I have not checked more recently.

Afaik AD doesn't sell chips (AD, LT, Maxim) to private individuals anymore. Same thing applies to large distributors unless you work for or have a business with a valid VAT number.

 

Use THAT4305 for the design note DN115. Replace the three general purpose op amps inside the 4301 with suitable, external op amps.

Thanks for the advice!

I have just noticed something I did not spot before: in the design 115, it writes that the Attack/Release is added in form of a non-linear circuit. What does it mean in practice? I am constantly having problems with pedals doing intermodulation on the highest notes of the guitar. The Carl Martin Compressor is one of the rare ones not doing it. That uses the THAT4031 chip, and I was told the THAT is a very good distortion and noise free chip. So maybe that is one of the reasons the Carl Martin is free of IMD. But it has no Attack Release knobs. That's why I thought I build the THAT design 115. To have IMD free compressor with Attack Release. But maybe this way that the design 115 has non-linear Attack-Release circuit, I'll fall back to the pit. What do you think will that non-linearity trigger the IMD again on the highest notes?

 

I have just noticed something I did not spot before: in the design 115, it writes that the Attack/Release is added in form of a non-linear circuit. What does it mean in practice?

Are you referring to the "non-linear" filter capacitor for the RMS detector?

The detector usually has only one fixed timing capacitor which means attack and release times are interdependent. Depending on the input signal the non-linear capacitor used in DN115 changes its value on the fly. A low value for fast attack times with large/fast transients and a large value for low ripple on the control voltage line with moderate/slow changes in the input signal.

The biggest source of IMD is the VCA. Either by itself or because of ripple on the control voltage modulating the gain of the VCA. Harmonic distortions are usually also a sign for IMD. The THD of the 4305 is quite good and it's unlikely that it poses a problem. The obsolete 4301 looks better on paper though. A measurement of the VCA at different gain values would show how much IMD is really generated but imo only a live test would tell if the sound is OK or not.
Ripple on the control line of the VCA is dealt with good filtering. At least the manual attack/release part of the circuit should be free of ripple as it compares the old control voltage value with the actual value and either charges or discharges a capacitor.

 

I referred to what the description of the Design 115 mentioned. The notice about the non-linearity is there. But since then the THAT support clarified it and confirmed it won't cause issues in my case.