THAT4301 compressor

[Diydiy]

R23 has nothing to do with Ratio; it justs shifts the threshold control.
Without R27, 2:1 should be with the ratio pot half-way, and 4:1 at 3/4 rotation. With R27, the taper is modified so they come closer to CCW.

Yes, thank you. R27 is there and and 4:1 should be somewhere around 50% pot setting.  Let's see how the device will work with vocals (hobby). Professionals may need totally different equipment

 

[abbey road d enfer]

Professionals may need totally different equipment

Not necessarily. The basic 4301 compressor is quite a competent piece of gear.

 

[Diydiy]

Not necessarily. The basic 4301 compressor is quite a competent piece of gear.

Thank you confirming my faith This has been a nice project, although a bit "jumpy"; I mean that some component values have changed. I just checked my comp against the latest 1.7 schematic, and replaced one resistor. No audible changes though. Commercial solutions of 4301 may use transformers, I don't know where. Input? Output? 

I built my gr-meter  following this schematic and using 1dB/led configuration.

http://www.ka-electronics.com/picocomp/PCB-Kits/Documents/GR_Meter_10/GR_Meter_10.htm

 

[abbey road d enfer]

Commercial solutions of 4301 may use transformers, I don't know where.

I doubt it. I would rather think they use the 1206/1646 combo of bal/debal chips. Mainly for cost and bulk reasons, but also in continuity with the low THD design.

 

[iprovlek]

I just wanna inform you guys that this new 1.7 ver. THAT 4301 compressor works and works great!!!

There were lots of errors from first versions but this work now without problem!!!

I finished it today after buying it after summer but Im happy now.....

And thanks a lot to Diy-tubes!!!

Cheers

 

[steves.mastering]

Just got my version 1.7 PCB’s, thank you, delivery was so fast.

Looking forward to getting started on this

 

[Rocinante]

I have seen pico comps use Edcor and Cinemag transformer in all sorts of configurations. 
So I am building  a stereo that4301 using the 1.7v of Ungifted's boards, and plan on doing DOA in to either that1646 or transformer out.
I would appreciate a little clarity though: has anyone made a stereo version using 2252s as per THAT design note 116? If I  understand correctly; in a stereo version I would tie both boards to single gain pots for threshold, ratio, and gain?  So not to dual gang pots? because the 2252 is doing the summing?
And finally has anyone figure a clever way to make it switchable from dual mono to stereo?  Which controls do you use?  In Ungifted's 1.7 build manual there is a master and slave THAT4301.

 

[Rocinante]

Umm any chance anyone could answer my questions?

 

[abbey road d enfer]

I have seen pico comps use Edcor and Cinemag transformer in all sorts of configurations. 
So I am building  a stereo that4301 using the 1.7v of Ungifted's boards, and plan on doing DOA in to either that1646 or transformer out.
I would appreciate a little clarity though: has anyone made a stereo version using 2252s as per THAT design note 116? If I  understand correctly; in a stereo version I would tie both boards to single gain pots for threshold, ratio, and gain?  So not to dual gang pots? because the 2252 is doing the summing?

Because dual pots have less than perfect tracking, so threshold, gain or ratio may be off by 3-4dB.

And finally has anyone figure a clever way to make it switchable from dual mono to stereo? 

You'll have to figure this out; you need to switch the wipers of the gain, ratio and threshold pots and connect the Ct pin of the rms detectors together.

 

[Rocinante]

Thanks Abbey. I got both up and running as dual mono using JLM Dingos. They work good.  Gonna have to thinkh on the stereo bit. *edited.

 

[Rocinante]

So one could use a rotary switch with resistors to set the ratio... Probably a better idea than about 50% turn is 4:1.  I have some spare grayhill 10 position rotaries that I could tie some 5k resistors to since it calls for linear pots. Am I wasting my time?

 

[abbey road d enfer]

So one could use a rotary switch with resistors to set the ratio... Probably a better idea than about 50% turn is 4:1.  I have some spare grayhill 10 position rotaries that I could tie some 5k resistors to since it calls for linear pots. Am I wasting my time?

If you go this way, you'll have to do it for the three controls; it would make no sense if not... Anyway, for proper stereo operation you would need to connect the Ct pins of the rms detectors and disconnect one of the timing caps.

 

[Rocinante]

If you go this way, you'll have to do it for the three controls; it would make no sense if not... Anyway, for proper stereo operation you would need to connect the Ct pins of the rms detectors and disconnect one of the timing caps.

Agreed. Still ruminating on how to go from dual mono to stereo. I'm sure it will take a multi gang switch and a lot of wiring. Or I just leave it dual mono or just make it stereo.  Thanks again.

 

[abbey road d enfer]

Agreed. Still ruminating on how to go from dual mono to stereo. I'm sure it will take a multi gang switch and a lot of wiring. Or I just leave it dual mono or just make it stereo.  Thanks again.

I think you need a 4PDT switch

 

[Ricardus]

Someone just told me about this project and I'm interested in building some of these. I've read the whole thread and it doesn't look like the balanced in/out board and the attack/release board haven't been developed yet?

 

[steves.mastering]

Someone just told me about this project and I'm interested in building some of these. I've read the whole thread and it doesn't look like the balanced in/out board and the attack/release board haven't been developed yet?

I’m with you Ricardus, looking forward to see if there’s any movement on the Attack/Release boards.
Think I saw that someone had made their own PCBs and done the AR mod. Would love to hear if it worked out?

 

[steves.mastering]

I see the THAT4301 chip itself has been discontinued
I hear some people have had success obtaining them from
https://m.aliexpress.com/item/10050...gqbiggcavawj17d2d451fdf1896b2d8312be52&gclid=
I’ve just ordered myself some. Will let you know when they arrive if they’re legit

 

[abbey road d enfer]

I see the THAT4301 chip itself has been discontinued

Indeed. It's been replaced with the 4305 (available only in SMD -SO16 is manageable, though) and it does not include the 3 opamps, which actually makes for an easier PCB layout.
I use the 4305 for replacing the defunct 2252, via a small adapter board.

 

[L´Andratté]

(...)and it does not include the 3 opamps, which actually makes for an easier PCB layout.(...)

+1!

 

[FIX]

One comment about stereo linking. I found that hard linking collapses the image quite a bit, and when I designed the 2500, I put in the variable link control, and it usually sits about 50%. If you link an old 1176 or 525, they link at 50% which allows both sides to be attached but 50% of the CV from the left hits the right. So if a mix has a strong element in one side, it doesn't suck the other side down. A 3 way switch would work, L=hard link, center off, R=50%...