THAT4301 compressor

[steves.mastering]

Hi all,

I'm just showing interest in this project.

I'd love to build this with all the bells and whilstles for total flexibility.
- Balanced I/O
- Stepped rotary swtiches
- Hpf on SC
- Attack/Release
- Hard/Soft knee

Got too many projects on the go at the moment, but just wanted to say this looks like an awesome project! Will be keeping my eye on this forum, see how it turns out. The Attack/Release mod boards looks like a great addition.

Happy soldering 

 

[Jitter]

In the That4301 v1.6 of diy-tubes.com. When we use two PCB for build a stereo unit on the slave PCB the caps C7 and C9 are not necesary. But C8 is necesary?
For all caps (C7,C8,C9) is necesary use a jumper in the place of caps.

 

[ungifted]

Hi Jitter,

Please take a look at schematics of stereo version http://diy-tubes.com/image/data/manuals/That4301-v1.6-full.pdf
Note: Master RMS IC (U1P on schema) is determing the "power" of the input signal. It "controls" two channels in stereo mode. Slave RMS detector is not used.
Capacitors at pin 5 are time constants - so we use master RMS IC and use with mater IC capacitors. When you don't use these caps (at slave channel) - simply don't solder them, or find out how to break the circuit when you want two channels to be  switchable: stereo/two mono.

 

[Jitter]

Hi Ungifted.
I have seen the documents for stereo version and have come to the conclusion that all these components should not be placed on the slave PCB for a proper work.

R13
R18
D1
D2
D3
C17
R22
R23
R14
R15
R16
R17
C8
R20
R21
R27
R19
R24
C7
C9
C10
R26
SW1A
SW2A
SW1B
SW2B

It is correct? Or I'm worng?

 

[Jitter]

On Slave U4P, C16 (From 5 pin) is the same that C7 on U1P?

 

[burdoto]

What resistor values has anyone tried for the rotary switches? Threshold, ratio and/or gain?

If the pots are linear, will dividing the full 50k range in 12 steps work?

 

[steves.mastering]

This link may be useful.

http://www.quadesl.com/attenuator.html

 

[Jitter]

What resistor values has anyone tried for the rotary switches? Threshold, ratio and/or gain?

If the pots are linear, will dividing the full 50k range in 12 steps work?

Because you wanna stepped controls?
If you build a stereo version only need 3 pots for control two channels  of compessor.
IMO

 

[Jitter]

About my reply #265... It's correct?

 

[burdoto]

Because you wanna stepped controls?
If you build a stereo version only need 3 pots for control two channels  of compessor.
IMO
[/quote]

I would like to have two separate channels that can be stereo linked. I also like rotary switches. Hopefully rotary switches will allow me to set each channel exactly the same for stereo use. But maybe I will have to use a switch to also link both channels to one set of controls. Or maybe I'll have give up the idea and just build a stereo unit separately or build a gssl for stereo needs.

 

[Script]

Provided your program material is sanely spread across the stereo field, you could build two full mono channels and add a switch to cross-couple CV In at the two VCAs. Then you could use pots (no need for rotary switches unless needed for exact recall) cos minor deviations between left and right (HPF)/THR/RAT/(ATT)/(REL)/GAIN settings will affect both channel VCAs. I know it's a dirty solution, but should work. Actually, it can be quite nifty: If you have heavy bass in only one channel, you could lower settings of that channel to make both amps respond less to it. This solution mangles L and R independently to "sum" them only at the VCA Inputs.

 

[burdoto]

Correct if I'm wrong. I'm reading from the stereo schematic that the cv from the first chip would be sent to both chips in stereo mode. If rotary switches on units were set to the same resistances would the boards behave as if there were only one set of controls?

 

[Jitter]

The best for build a stereo unit will be use a matched components un both boards and use 3 rotary switches (Stepped o no stepped) for pcb master and controlate both units.
But in the schematic of stéreo versión I think that the components don't use in the slave board and not placed will be placed on the slave PCB for a proper work are:

R13
R18
D1
D2
D3
C17
R22
R23
R14
R15
R16
R17
C8
R20
R21
R27
R19
R24
C7
C9
C10
R26
SW1A
SW2A
SW1B
SW2B

 

[burdoto]

On another subject, I'm pretty fresh of the boat on a lot of the basics, so constructing a meter of some sort has required a lot of reading. So I put together the meter circuit described in dn112 and after much confusion, it works. The voltage reference scheme also makes sense to me and i believe i can adjust the resistors to achieve the desired trigger points.

 

[Jitter]

For the future users...
Somebody can explain a minitutorial for build a stereo compressor That4301 with the pcb v1.6 of diy-tubes?
Some instructions and documents are unclear and diffuse.

Thanks.

 

[tata]

my PCB + 4301 just arrived today, built the circuit and im testing it now.
i havent wired the switches yet, but using jumpers to set their position, RMS/Soft knee mode seems to be really nice on a very dynamic vocal. it brings out what i wanted to hear.

but i cant figure out whats wrong with the symmetry -  i hear a slight distortion, and the trimmer doesnt seem to change it.
i use a 50k multiturn trimmer.

any ideas, please?

also.. its not a very quiet circuit, or.. probably i got something wrong? - noise floor is about -77dBFS on my RME FF880 at a setting that i would use in "real world" . (not hum)
i have built a THAT 1206 and a 1646 stage for i/o, if i bypass/remove the 4301 circuit the noise is around -97dBFS.

will do some photos and (waveform) screenshots soon.

thank you

 

[tata]

no switches yet - is this a correct setting of Soft/RMS?

can you spot any obvious errors on this build, please?

 

[plimousse]

Hello,
Please, what is the "extra" PCB  ?
Thanks,

Pascal

 

[tata]

Pascal,

if your question is about the extra panel on my photo : its just a PCB for those 3 pots, with pin contacts to the potmeters and pins for the LEDs under the pots. i had no 16mm B5k pot at hand, but this board has a 5k.

so its just the external Ratio pot.

 

[plimousse]

Hi,

Ok. Thanks.
Cheers,
Pascal