THAT4301 compressor

[mus1k_freak]

almost ordered a pair of these last night, can anyone comment on how they sound/work? would be fun to stick in a 500 module

 

[mus1k_freak]

is there a mouser cart for this by chance? im feeling to lazy to type all those parts in to order 

3nity
That guy is me. Please let me know how it goes. Thank you!

Tekay
Yes LM393 is not dual opamp, but I've seen both versions (THAT DN with LM393, and redrawn design with TL072).

I'll try to find some time to return to process...

 

[ungifted]

Still no lucky with attack/release mod. It's not stable. I'll try to make new design if i find more time...
But i've got updated docs for the basic pcb (interconnections added).

 

[hazel]

Still no lucky with attack/release mod. It's not stable. I'll try to make new design if i find more time...
But i've got updated docs for the basic pcb (interconnections added).

Thanks for your time and effort

Your AD797 mic preamps work like a charm, by now i'm designing front panel, gain switch and a couple of bells and whistles

 

[shot]

Still no lucky with attack/release mod. It's not stable. I'll try to make new design if i find more time...

I've built attack/release mod using the pico schematic. That's the one without 2sk170, using three 3904 and 3906's and I've used one TL074. It worked without problems. I can post my pcb layout but it's not that clever and neat as your board layouts. It's for self etching so it has a lot of bridging wires on the bottom. Ugly but it works.

 

[hazel]

Still no lucky with attack/release mod. It's not stable. I'll try to make new design if i find more time...

I've built attack/release mod using the pico schematic. That's the one without 2sk170, using three 3904 and 3906's and I've used one TL074. It worked without problems. I can post my pcb layout but it's not that clever and neat as your board layouts. It's for self etching so it has a lot of bridging wires on the bottom. Ugly but it works.

That would be great!

I'm just prototyping a Stereo 4301P and manual control option is what i was looking for

 

[shot]

This is Ungifted's thread and his build. Since he already started working on AR board, I believe it would be unfair if I post my layout without his consent. And also, it is built using Pico's schematic as a reference so it's not ok to post it's schematic here. You know that Pico stuff is forbidden... 

 

[emrr]

I wouldn't obsess over the attack/release circuit.  It hardly gets used, out of the list of possible timing circuits.  Not that it's bad, it's just not the best thing these units do. 

 

[Script]

I wouldn't obsess over the attack/release circuit.

I agree. In combination with "Auto Att/Rel" it's somewhat adaptive but really kind of subtle.
RMS compression and soft knee is where the THAT design note circuit should excel.

 

[hazel]

can anyone comment on how they sound/work? would be fun to stick in a 500 module

I'm not experienced with diy-tubes compressor but i got two 4301P DEMO BOARDS from THAT and have to say they're just transparent!

I still don't installed gain reduction meter but listening to loop-back recording through audio interface i confess i have to squash audio to start listening artifacts. The overall result is smooth almost "invisible" compression.

This is Ungifted's thread and his build. Since he already started working on AR board, I believe it would be unfair if I post my layout without his consent. And also, it is built using Pico's schematic as a reference so it's not ok to post it's schematic here. You know that Pico stuff is forbidden... 

I was thinking the same after posting for both topics:
- this is Ungifted thread and product
- Pico is commercial now so no partial or full schematic can be posted

 

[L´Andratté]

I still don't installed gain reduction meter but listening to loop-back recording through audio interface i confess i have to squash audio to start listening artifacts. The overall result is smooth almost "invisible" compression.

Yes, first time on breadboard, I though, hell, this thing isn´t working , until I turned compression up just a little more and realized I had about infinite compression ratio  ;D

But that´s exactly what I want a vca compressor to sound like, especially as stereo compressor... All in all 4301 is a total winner, very pleasant sound. Softknee+RMS=vanilla

Hey ungifted, what about an peak detector with a/r and routing THAT into the rms input? Maybe switchable?
Or parallel and then mix with rms output? You can tell I´m a feature creep victim...
But I still think that superimposing a/r on the rms OUTPUT might only degrade what  is  already highly usable (and by definition not rms anymore).

Another thought I need to try is a pot for panning the cv (buffered of course) between +cvin and -cvin for expander/compressor action (only on my mind for now!) I also find a peak limiter at the output useful.
Sorry for stream of thoughts, this is probably not wanted for the original design, but I´m curious what people would think about these ideas...

Fwiw, here´s another link to a design that goes slightly beyond the data sheets:
http://users.telenet.be/Rogy/IEMFinalizer/Multiband%20comp/Comp%20w%20dual%20detect%20&%20crest.pdf
This designer mixes the ´usual´ sc with a second crest factor thingie, that I don´t get. Also notice the stereo sources mixing before the rms detector input (no true power summing a lá appnote).

Anyway, have a good time all!

 

[iprovlek]

Yes this 4301 VCA compressor from Diytubes are amazing, but it is very important to assemble GR meter!

I dont like to dont know how much gain reduction is!!!

Without it, its like blind riding...

Maybe I wrong  but this is just my opinion...

 

[dogma]

Hey guys I've been following this for a while. Excellent work! As you guys know this circuit very well by now - I once had one had one of the last pico pcbs before Roger went commercial. I never got to build it but always for some reason have been intruged by it. I can't afford Rogers anymore so I'm wondering how close this is - I know the pico was very close to the app notes

 

[emrr]

If you never heard a Pico does it matter?  Many things using the 4301 are going to be close to the app notes, there's a whole list of similar 4301 compressors on the market. 

There's always this at $100:

http://www.thatcorp.com/datashts/THAT_4301-Demo_Datasheet.pdf

 

[hazel]

If you never heard a Pico does it matter?  Many things using the 4301 are going to be close to the app notes, there's a whole list of similar 4301 compressors on the market.

+1

I've never listened a Pico but i can only say good things about 4301 app note compressor, and i just plug it, i still have lot of work to do: stereo link, Peak/RMS, Hard/soft, GR meter...i think i'll pass on A/R manual mode but i'll add an INPUT GAIN pot to vary compressor behaviour, it's well known that 4301 goes faster as you hit it harder at input

 

[L´Andratté]

(...), it's well known that 4301 goes faster as you hit it harder at input

Yes, but not well known by me, thanks for the hint.
Could that be boiled down to lowering the ´reference´ resistor at the rms detector input, if I wanted to let the audio gain unchanged?

 

[emrr]

it's well known that 4301 goes faster as you hit it harder at input

Never heard it, and strongly doubt it.  Not a thing I have heard in years of use, not a thing I see in the circuit.  Maybe if you overload it so it's clipping transients?  It does have a window for best operation between -30 and +20 dBr with detector law beginning to change outside of those ranges, and detector output vs. frequency is rolled off in the treble increasingly below -10dBr.

 

[JohnRoberts]

it's well known that 4301 goes faster as you hit it harder at input

Never heard it, and strongly doubt it.  Not a thing I have heard in years of use, not a thing I see in the circuit.  Maybe if you overload it so it's clipping transients?  It does have a window for best operation between -30 and +20 dBr with detector law beginning to change outside of those ranges, and detector output vs. frequency is rolled off in the treble increasingly below -10dBr.

The nature of THAT corp's log convertor with the smoothing cap applied directly across the logging semiconductor junction means that the time constant RC will be affected by the effective R not a fixed real R. At higher current the effective or equivalent R of the semiconductor junction is lower impedance (faster) than for small signals and low current (slower).

Of course it's a little more complex than that.. but there is some there there.

JR
 

 

[emrr]

OK, but the response charts I referred to (page 5) suggest 'slower' is below -10dBr, a level at which virtually no one operates with this part. 

http://www.thatcorp.com/datashts/THAT_4301_Datasheet.pdf

The log-domain filter cutoff frequency is usually placed well below the frequency range of interest. For an audio-band detector, a typical value would be 5 Hz, or a 32 ms time constant (τ). The filter’s time constant is determined by an external capacitor attached to the CT pin, and an internal current source (ICT) connected to CT. The current source is programmed via the IT pin: current in IT is mirrored to ICT with a gain of approximately 1.1. The resulting time constant τ is approximately equal to 0.026 CT/IT.

CT/IT in the example circuit is 10mfd/2Mr, so I don't see level affecting time constant in any appreciable manner within expected operating levels.  Slower is going to be slower than 'already slow', and faster can't be significantly faster than 'already slow'.  I still vote 'clipping'. 

I may be wrong, YMMV. 

If you run it in peak mode, you stand more of a chance of seeing a difference, but I still wouldn't expect anything significant. 

 

[hazel]

Maybe this is a noob question but i was trying to add DN115 attack and release and found LM393 can be feed with single / dual supply but..where do i connect -V??

LM393 datasheet says:

PIN 1 output 1
PIN 2 IN 1 -
PIN 3 IN 1 +
PIN 4 GND
PIN 5 IN 2 +
PIN 6 IN 2 -
PIN 7 output 2
PIN 8 Vcc

according to THAT DN115, do i connect +15V to pin 8 and -15V to pin 4?? it's supposed to be GND, isn't it?