quintosardo
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- Joined
- Jun 18, 2009
- Messages
- 22
Yes, my english isn't brilliant 
Sknote PWM - MS4 - Mono/Stereo Compressor DIY Kit
- Thread starter dogma
- Start date
Help Support GroupDIY Audio Forum:
Hi quintosardo,
thanks for the fast reply. Good to see you here.
I don't expect detailed schematics in public. Stuff like 'Active balanced line interfacing by That Corp. "inGenius" circuits' tells me enough.
How is the PWM sidechain signal generated? What chip/configuration? Rough chatty explanation suffices
Assume someone wanted to buy the PCB/kit, what'd they need? Oscilloscope?
Good video on the comp in action on Yutube. I don't speak Italian -- only Spanish, so I understand enough to follow. But that's just me and a few other non-native Italians on the Net
Cheers,
/s
thanks for the fast reply. Good to see you here.
I must have misunderstood that phrase on your website then. So the comp provides easy analogue sidechain interfacing to any external hardware (including software on computers via audiointerface).
I don't expect detailed schematics in public. Stuff like 'Active balanced line interfacing by That Corp. "inGenius" circuits' tells me enough.
How is the PWM sidechain signal generated? What chip/configuration? Rough chatty explanation suffices
Assume someone wanted to buy the PCB/kit, what'd they need? Oscilloscope?
Good video on the comp in action on Yutube. I don't speak Italian -- only Spanish, so I understand enough to follow. But that's just me and a few other non-native Italians on the Net
Cheers,
/s
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
The project started on an italian magazine, that's why the first video is italian, but loading some more videos in english
No secrets of course, trying to describe it here.
Active line interfacing we said. That chips go from bal to unbal loosing 6dB, unbal to bal getting 6 dB back.
No input gain, we choose to use threshold here (as opposite to our Vastaso which uses input gain).
L R get mixed to mono, then through a common sidechain (this comp is always Linked LR, you need two PCBs if you want things like Mid/Side).
Audio is allpassed (to shape time response to freq ranges), then goes through a pair of boost/cut filters (low and high sidechain controls, to shape freq response to freq ranges).
Signal is double wave rectified with timing options (peak/rms, which actually are two different time constants for the rectifier's output).
Then the DC signal goes through a shaping network, which combines some "logifying" passes with some shaping passes. It is done by some diodes and resistors in the right places.
In the meantime, in the middle, you get timing and hard/soft control.
Timing is done by the most classic RC nets, including two double and one triple release constants (by stacking RCs).
Curve smoothing is done by setting the working level of a diode by in and out (to the diode) gain. It is somewhere between "logifying" and "log smoothing" passes, so it is not exactly what you get by, for example, That papers.
This DC signal gets scaled (ratio) and goes into a xx5001 (can't remember now, should be easy) PWM controller, working @500kHz and doing some shaping, too, while PWM range is limited bottom and top, as usual, to avoid 0% and 100% pwm.
Audio stereo signal is filtered, switched, filtered, switched, filtered. First pass because your audio could contain high freqs which could alias to audible range, second and third passes are after a double PWM switching. This is done to reduce the need for PWM range for the same gain reduction. Like using two cascaded VCAs to limit their needed GR range.
Switching is through a quadruple can't-remember-now cmos analog switch. Nothing fancy, after some tests I preferred the non ultra fast ones. You can see its shape @500KHz in the second video. Double pass compensates for its non super fast decay.
Compressed audio gets output gain (here it is gain, not GR compensation) and is mixed to dry for simple and precise parallel compression.
Input to sidechain can be switched from comp input mixed to mono to compressed audio output (feedback mode).
Output gain can be wired in several ways. I prefer two separate gain knobs for L and R but gain and balance is an optional wiring. Pots don't give good stereo alignment, you know.
Ext sidechain input is exactly like L and R ins. It goes to the sidechain starting from the output of LR mix, so it passes through all of the sidechain. So, all controls are active, but the feedback mode which could have different effect because it is fw from ext sidechain input and fb from audio output. Uhm, perhaps it just switches to internal, feedback...
Here you can have fun and extreme control on the sidechain if you start using something else on the aux audio before going to ext sidechain input, because it is an audio input and not some kind of control voltage.
The meter is a double input, 40 steps bar meter.
You can wire DC (for gain reduction), which travels right to left, linear (scale to log is done by graphics, to get a good zooming on low GR), and audio (for level), which goes left to right and is rectified, transcended to log and scaled, slowed down with switchable option. You can set the combinations of readouts through the 3x4 rotary switch (peak, VU, GR). The main choice to get is what to show while in GR mode. I like GR + input level. In the video it is wired for GR+disabled.
What else?
Ah, all filters are Sallen-Key second order lowpass tuned close to 25 kHz
No secrets of course, trying to describe it here.
Active line interfacing we said. That chips go from bal to unbal loosing 6dB, unbal to bal getting 6 dB back.
No input gain, we choose to use threshold here (as opposite to our Vastaso which uses input gain).
L R get mixed to mono, then through a common sidechain (this comp is always Linked LR, you need two PCBs if you want things like Mid/Side).
Audio is allpassed (to shape time response to freq ranges), then goes through a pair of boost/cut filters (low and high sidechain controls, to shape freq response to freq ranges).
Signal is double wave rectified with timing options (peak/rms, which actually are two different time constants for the rectifier's output).
Then the DC signal goes through a shaping network, which combines some "logifying" passes with some shaping passes. It is done by some diodes and resistors in the right places.
In the meantime, in the middle, you get timing and hard/soft control.
Timing is done by the most classic RC nets, including two double and one triple release constants (by stacking RCs).
Curve smoothing is done by setting the working level of a diode by in and out (to the diode) gain. It is somewhere between "logifying" and "log smoothing" passes, so it is not exactly what you get by, for example, That papers.
This DC signal gets scaled (ratio) and goes into a xx5001 (can't remember now, should be easy) PWM controller, working @500kHz and doing some shaping, too, while PWM range is limited bottom and top, as usual, to avoid 0% and 100% pwm.
Audio stereo signal is filtered, switched, filtered, switched, filtered. First pass because your audio could contain high freqs which could alias to audible range, second and third passes are after a double PWM switching. This is done to reduce the need for PWM range for the same gain reduction. Like using two cascaded VCAs to limit their needed GR range.
Switching is through a quadruple can't-remember-now cmos analog switch. Nothing fancy, after some tests I preferred the non ultra fast ones. You can see its shape @500KHz in the second video. Double pass compensates for its non super fast decay.
Compressed audio gets output gain (here it is gain, not GR compensation) and is mixed to dry for simple and precise parallel compression.
Input to sidechain can be switched from comp input mixed to mono to compressed audio output (feedback mode).
Output gain can be wired in several ways. I prefer two separate gain knobs for L and R but gain and balance is an optional wiring. Pots don't give good stereo alignment, you know.
Ext sidechain input is exactly like L and R ins. It goes to the sidechain starting from the output of LR mix, so it passes through all of the sidechain. So, all controls are active, but the feedback mode which could have different effect because it is fw from ext sidechain input and fb from audio output. Uhm, perhaps it just switches to internal, feedback...
Here you can have fun and extreme control on the sidechain if you start using something else on the aux audio before going to ext sidechain input, because it is an audio input and not some kind of control voltage.
The meter is a double input, 40 steps bar meter.
You can wire DC (for gain reduction), which travels right to left, linear (scale to log is done by graphics, to get a good zooming on low GR), and audio (for level), which goes left to right and is rectified, transcended to log and scaled, slowed down with switchable option. You can set the combinations of readouts through the 3x4 rotary switch (peak, VU, GR). The main choice to get is what to show while in GR mode. I like GR + input level. In the video it is wired for GR+disabled.
What else?
Ah, all filters are Sallen-Key second order lowpass tuned close to 25 kHz
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
Here we go with a video we just uploaded.
Improvising compression on stereo buss, describing what I'm trying to achieve and comparing to dry
http://youtu.be/m1BuzT6kA0w
Improvising compression on stereo buss, describing what I'm trying to achieve and comparing to dry
http://youtu.be/m1BuzT6kA0w
shot
Well-known member
Hey Quintosardo! In this demo your compressor sounds really good!! Congrats on the build!
I'll have to finish some projects I've started and I'll seriously think about getting a kit and building one!
I hope you'll think about opening a build thread over here for us non-italian builders. I know it's your decision not to go public with the schematic and it is perfectly fine, but it would be very cool!
Anyway... just wanted to say it sounds fantastic!!
Congrats on the build!I'll have to finish some projects I've started and I'll seriously think about getting a kit and building one!
I hope you'll think about opening a build thread over here for us non-italian builders. I know it's your decision not to go public with the schematic and it is perfectly fine, but it would be very cool!
Anyway... just wanted to say it sounds fantastic!!
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
Nice one! thanks for videos. Why though at 480k only? Glorious 1080 meant I could actually read the faceplate which I cant now. Its super intruiging - whats the single, double, triple switch about? Why does only one bar move on a stereo track?
Keep em coming! Just one more at a reasonable resolution.
Keep em coming! Just one more at a reasonable resolution.
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
It is an extremely hard end of the year here (luckily ) so we have to run extremely fast. A larger video means a lot more time for everything. With these samples I needed to be fast and files to be lightweight. I promise we'll upload better resolution videos. I think today more material less resolution is better
Double/triple is described in my huge post above. Timing is done through RC nets, double and triple are multiple time constants, simply stacked RC networks.
About meters: you can configurate them the way you prefer. Being L/R linked only one GR value makes sense, so you can couple readouts. My favourite one is GR/mixed-in, in the video it is GR/disabled.
) so we have to run extremely fast. A larger video means a lot more time for everything. With these samples I needed to be fast and files to be lightweight. I promise we'll upload better resolution videos. I think today more material less resolution is better Double/triple is described in my huge post above. Timing is done through RC nets, double and triple are multiple time constants, simply stacked RC networks.
About meters: you can configurate them the way you prefer. Being L/R linked only one GR value makes sense, so you can couple readouts. My favourite one is GR/mixed-in, in the video it is GR/disabled.
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
There is a question I get more and more times, so I write the answer here, too
No oscilloscope, no calibration needed for this project. Assembly is extremely simple so everything should just work.
You could send here the main board if you are lost (small and cheap parcel). I'm happy to check it with no cost (still didn't happen).
No oscilloscope, no calibration needed for this project. Assembly is extremely simple so everything should just work.
You could send here the main board if you are lost (small and cheap parcel). I'm happy to check it with no cost (still didn't happen).
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
Hear better by video resolution?
I can send you the wav audio files. I'll put the links here.
I can send you the wav audio files. I'll put the links here.
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
Here we go.
They are uploading, some time is needed.
It is the first song, dry and processed, time aligned files.
http://www.sknote.it/Download/MS4/HW_Video_Loopback1_Dry.wav
http://www.sknote.it/Download/MS4/HW_Video_Loopback1_HW audio.wav
They are uploading, some time is needed.
It is the first song, dry and processed, time aligned files.
http://www.sknote.it/Download/MS4/HW_Video_Loopback1_Dry.wav
http://www.sknote.it/Download/MS4/HW_Video_Loopback1_HW audio.wav
Really hard to tell without a schematic.
In general, I can't understand the idea of making a diy-project without supplying a schematic: Nothing can be learned from this, other than honing your soldering and paint-by-numbers skills. And makes error-fixing or third-party build support unnecessarily complicated.
I have a nagging feeling they try to hype PWM as the new black - which makes me wonder how deep the technological understanding runs...
Jakob E.
In general, I can't understand the idea of making a diy-project without supplying a schematic: Nothing can be learned from this, other than honing your soldering and paint-by-numbers skills. And makes error-fixing or third-party build support unnecessarily complicated.
I have a nagging feeling they try to hype PWM as the new black - which makes me wonder how deep the technological understanding runs...
Jakob E.
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
Hey, I'm here! I wonder how your technological understanding stands
There's nothing "black" in PWM, we define it as an extremely clean gain control, which doesn't correspond exactly to "black".
Try to speak about the topic, not about other people. I could ask how can some things so simple and so cheap be sold so expensive. Something "black" inside?
Stay fair, my friend.
There's nothing "black" in PWM, we define it as an extremely clean gain control, which doesn't correspond exactly to "black".
Try to speak about the topic, not about other people. I could ask how can some things so simple and so cheap be sold so expensive. Something "black" inside?
Stay fair, my friend.
kooma
Well-known member
[rant]
I kind of understand if some one has designed some unique/clever design and doesnt want to share schematics
(in fear of "chinese cloners" etc.)
but on the other hand; since this is DIY-forum, where designs are discussed and explained thru schematics,
it's kind of bummer not to see what going on.
I personally havent buildt anything without schematics.
( for me part of the joy is finding out what does what and why,
I find it so much easier with schematics and in case of something goes wrong
debugging is hell without them)
[/rant]
I kind of understand if some one has designed some unique/clever design and doesnt want to share schematics
(in fear of "chinese cloners" etc.)
but on the other hand; since this is DIY-forum, where designs are discussed and explained thru schematics,
it's kind of bummer not to see what going on.
I personally havent buildt anything without schematics.
( for me part of the joy is finding out what does what and why,
I find it so much easier with schematics and in case of something goes wrong
debugging is hell without them)
[/rant]
quintosardo
Member
- Joined
- Jun 18, 2009
- Messages
- 22
I agree.
I wonder...
...
...
...
... who said there aren't schematics?
I wonder...
...
...
...
... who said there aren't schematics?
I can promise you these guys would do nothing but respect a schem and wouldnt give it to anyone. I like what Ive heard of this comp and think its a good deal for a complete kit.
QUint. Gyraf is responsible for a lot of this sites classic projects (GSSL, G9 and the list goes on). YOu guys should talk. Both brilliant designers. Seriously 2 of the great current designers. Talk fellas!
QUint. Gyraf is responsible for a lot of this sites classic projects (GSSL, G9 and the list goes on). YOu guys should talk. Both brilliant designers. Seriously 2 of the great current designers. Talk fellas!
