THAT4301 compressor

[ForthMonkey]

Try this:

http://www.thatcorp.com/datashts/dn132.pdf

Thanks!

I want to build like like DBX 160 and made something like this...

Correct?

 

[hazel]

I want to build like like DBX 160 and made something like this...

Correct?

I think it's ok, it'd be a nice add, switching between GR meter or just Above/Below indicator...just to use my ears more than my eyes

 

[hazel]

I'm about to finish my Stereo 4301 build but i'm having some problems on stereo linking...

By now i've just:
- disconnect pin 4 on slave channel
- cross connect pin 5 on both THAT 4301
- cross connect EC- or EC+ on both  THAT4301 (it depends on which pin you use, diy-tubes PCB uses pin 15 and THAT DEMO BOARD and DATASHEET uses pin 16)

But it doesn't work...i don't know if i have to disconnect more parts of the circuit...i'm a little bit lost by now, here's a pic of schematic.

I assume only a set of pots controlling both channels for stereo operation

 

[ungifted]

hazel

Did you check stereo version of the schema in this thread?
http://groupdiy.com/index.php?topic=52021.msg671219#msg671219
It's on the second page of the project docs
http://diy-tubes.com/image/data/manuals/that4301-pcb-v1.5-1.1.pdf
Sorry for obvious advice...

Thank you for supporting the project!

 

[hazel]

Did you check stereo version of the schema in this thread?
http://groupdiy.com/index.php?topic=52021.msg671219#msg671219
It's on the second page of the project docs
http://diy-tubes.com/image/data/manuals/that4301-pcb-v1.5-1.1.pdf

Thanks for your answer ungifted...i've studied schematic on your page and THAT desing note but i'm not able to find what's wrong. It's driving me nuts!

I assume i must leave pin 4 disconnected and also the rest of the circuit behind (Threshold, Ratio and Gain circuits).

Does it make a difference using pin 15 or 16 for control voltage?

 

[ungifted]

Does it make a difference using pin 15 or 16 for control voltage?

It depend on how we used OA2 - invert/non-invert.
PS: BTW it seems that's why I wasn't lucky with AR mod. ))

 

[hazel]

It depend on how we used OA2 - invert/non-invert.
PS: BTW it seems that's why I wasn't lucky with AR mod. ))

Haha LOL i see...you use pin 15 and THAT corp uses pin 16 for control voltage. I finally found my mistake, worked on protoboard but when soldering i have some strange issues. It's a question of time to get this stereo compressor working with all bells and whistles.

So what Attack/Release circuit are you using? the one in THAT design note or the one using TL072? does it work ok?

Question to everybody building this compressor: how about Hard/soft knee switch? did you added? does it make an audible difference?

 

[ungifted]

hazel
Please don't miss new schema version (1.5.2). Check values of R15 (30k), R16 (30k), R20 (25k), R19 (removed). This should align gain for OA1 and OA2.
Optional R27 and R19** for ratio pot skew (4:1 at the center) need to be tested.
I've tried TL072, DN115 and pico AR mods. No time for tests now. Hope someone will find some time...

 

[hazel]

hazel
Please don't miss new schema version (1.5.2). Check values of R15 (30k), R16 (30k), R20 (25k), R19 (removed). This should align gain for OA1 and OA2.
Optional R27 and R19** for ratio pot skew (4:1 at the center) need to be tested.
I've tried TL072, DN115 and pico AR mods. No time for tests now. Hope someone will find some time...

Thanks for your effort ungifted, i'll take a look as soon as possible. AR controls are not a must for me.

You can find pics of my building in my Instagram profile, link below

 

[L´Andratté]

Hi hazel!
From That! design notes I figure the stereo version would use just one sidechain path, with both channels joining
their respective rms detectors on pin 5, but only one rms detector having pin 4 conncted to the side chain.
The output of the latter than feeds both vcas.
Hope I´m not stating the obvious, have you done that and it didn´t work?

 

[hazel]

Hi hazel!
From That! design notes I figure the stereo version would use just one sidechain path, with both channels joining
their respective rms detectors on pin 5, but only one rms detector having pin 4 conncted to the side chain.
The output of the latter than feeds both vcas.
Hope I´m not stating the obvious, have you done that and it didn´t work?

Hi L'Andratté

i messed wiring but now works as stereo compressor and works great. My last add-on will be Hard/soft knee switch then i'll assemble blocks (I/O, filter sidechain, PEAK/RMS/AUTO, etc)

One last question:

I know filter sidechain have to be placed before sidechain detection so...it's before pin 1??

 

[L´Andratté]

Yes, because it is the right point before pin 1, after that it´s dc... E.g. you could simply make c6 switchable for 1st order HP.
I will build a stereo version too soon (well, let´s see) but it´s all soft knee for me, a matter of taste and appliance I guess.

 

[hazel]

Yes, because it is the right point before pin 1, after that it´s dc... E.g. you could simply make c6 switchable for 1st order HP.

Thanks for your answer L'Andratté, i was almost sure of that.

it´s all soft knee for me, a matter of taste and appliance I guess.

I prefer soft knee in all cases even for parallel compression so i must decide if make KNEE switchable or leave it fixed Soft

 

[hazel]

So here i am again finishing my stereo 4301 but i'm finding some issues working on hard/soft knee:

first pic comes from THAT 4301 DEMO BOARD i'm currently using, i zoomed hard knee section...

 

[hazel]

and here it is the same section from THAT design note 115 (full adjustable compressor) and diy-tubes project...

on previous post you can see D2 is in different position than this pic or maybe i'm missing something 'cause is driving me nuts...

It's just as easy as connecting R14 (30k) into cathode or anode of 1N4148 to make it hard/soft??

 

[L´Andratté]

You mean D5 (not D2) certainly, both circuits are the same functionally, D5 is included or excluded from the feedback loop of U2D by SW2A. In the latter case the diode drop of D5 isn´t compensated, so an offset is added by D1/SW2B.
Really that easy ;D

 

[hazel]

You mean D5 (not D2) certainly, both circuits are the same functionally, D5 is included or excluded from the feedback loop of U2D by SW2A. In the latter case the diode drop of D5 isn´t compensated, so an offset is added by D1/SW2B.
Really that easy ;D

I mean D2 on the first pic and D5 on the second one, sorry for the misunderstood...

So connecting R14 to anode then 1N4148 is included in the feedback loop and hard knee is on

Then connecting R14 to cathode 1N4148 is excluded of feedback loop...i was doing right!

I tried it and then threshold and ratio acts totally different from hard knee setting, on soft knee mode i set threshold to minimum and ratio to max and i barely get 4 to 6dB of gain reduction...but what a soft and gentle compression!!!!

Is this an expected behaviour?

 

[L´Andratté]

No, softknee makes only a gentle *transition* from no compression to heavy compression (still high ratio is possible).
Did you include the offset from D1, if not it would raise threshold one diode drop...

 

[hazel]

No, softknee makes only a gentle *transition* from no compression to heavy compression (still high ratio is possible).
Did you include the offset from D1, if not it would raise threshold one diode drop...

This is what made me think i'm doing something wrong, i use Soft Knee on compressors and i love te way it smooths audio...

Take a look at pic, D1 is still in the feedback loop.

Red arrow shows how i wired it up for soft knee

I have recorded some tracks with Hard and this-kind-of Soft knee and have to say i love it although i'm not 100% sure the circuit is ok

 

[L´Andratté]

I think it´s a misunderstanding. I´m talking about the other drawings D1 sorry : that is connected to the 2nd switch pole of the knee switch...the rest looks fine to me.