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SSL SiX Channel Compressor Distortion
Old 8th November 2019
  #1
Gear Head
 
Its Mork's Avatar
 

SSL SiX Channel Compressor Distortion

Since I discovered its existence the SiX is the heart of my little setup and I just love it! But as already mentioned in the ultimate plugin analysis thread I stumbled upon some unusual distortion when I engage the channel compressor. I passed simple sine waves at different frequencies through the line input, the result can be seen in the screenshots attached. When I disengage the channel compressor the distortion disappears almost completely. I also tried the GBus comp for reference - no unusual amount of distortion. I also measured my KT 76, even patched into the channel insert - no unusual amount of distortion.

Since 50Hz appears in the bottom part of the distortion, which is our AC frequency here in Germany, it seems to be somehow ground related. But why does it only show up when I engage the channel compression? I know there is auto gain compensation going on, but even with the compression knob completely counter clockwise there is a tremendous amount of distortion (see screenshots).

Please tell me I am an uneducated hobby noob and I am doing something wrong, because that is what I am hoping for.

Edit: I forgot to mention that it’s the same with channel both channels.
Attached Thumbnails
SSL SiX Channel Compressor Distortion-ssl_six_nocomp.jpg   SSL SiX Channel Compressor Distortion-ssl_six_channelcomp.jpg   SSL SiX Channel Compressor Distortion-ssl_six_channelcomp_100hz.jpg   SSL SiX Channel Compressor Distortion-ssl_six_gbuscomp_100hz.jpg   SSL SiX Channel Compressor Distortion-ssl_six_nocomp_777hz.jpg  

SSL SiX Channel Compressor Distortion-ssl_six_chcompccw_777hz.jpg   SSL SiX Channel Compressor Distortion-ssl_six_chcompcw_777hz.jpg  

Last edited by Its Mork; 8th November 2019 at 09:35 PM.. Reason: See edit
Old 8th November 2019
  #2
I do see what you are trying to say, but i have one question. Do you hear it?
Old 8th November 2019
  #3
Gear Head
 
Its Mork's Avatar
 

Hehe, I know what you are getting at and believe me, I used to be the analyzer guy, reading about standards and majoring the minors. Sure you should do your homework but it’s like in this thread I mentioned: It shows that basically all top plugins introduce non harmonic distortion and are therefore „unusable“ - the same plugins that you can hear in probably most of your and my favorite mixes...
To finally answer your question: Maybe. There is always a level bump when the circuit is engaged so it’s hard to compare. Plus I usually used it after the KT76 which already introduced distortion. It‘s at least not a bad as it looks, although the compressor is already known to „fart“ with bass heavy content. This may have something to do with this, maybe not. Now I will first have to „unhear“ it.

Let me add that I just want to know what’s going on. I’m fine with „Yup, that’s what it‘s like“ as much as with „You‘re an idiot and hooked it up all wrong“ or „Please send in your unit“.
Old 8th November 2019
  #4
Quote:
Plus I usually used it after the KT76 which already introduced distortion
If its audible and interfering with your sound, i would take this out, since you have proven that its making the distortion in the signal chain
Old 8th November 2019
  #5
Gear Head
 
Its Mork's Avatar
 

Sorry, do you mean the 76kt? It’s an 1176 clone which is supposed to distort. It’s not in the chain I measured, of course. I measured DAW out —> Input channel —> Main out —> DAW in.
Old 8th November 2019
  #6
Quote:
Sorry, do you mean the 76kt?
I quoted you.
Quote:
usually used it after the KT76 which already introduced distortion. It‘s at least not a bad as it looks, although the compressor is already known to „fart“ with bass heavy content. This may have something to do with this,
You said you use 76kt in your chain
Old 9th November 2019
  #7
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Its Mork's Avatar
 

That was meant to explain why I am not quite sure that I‘ve heard the SiX compressor distort (while mixing), because I usually put an already distorted signal signal through it, like a vocal. That makes it more difficult to spot the added distortion. The measurements were taken without any added sources of distortion of course. Sorry, I should have been more clear about that
Old 11th November 2019
  #8
Here for the gear
 

Yes, I can confirm that the SSL SiX channel compressor distorts on bass-heavy signals. It's not even subtle.

I was hoping that I would be able to track bass guitar using the SiX SA channel, with the comp smoothing out the performance. Unfortunately, the results are unusable.

The sound is as if the attack and release are set in such a manner that it is repeatedly opening and closing down based upon the input waveform.

The comp sounds fine on vocals. Sucks on bass guitar. I'm new to the unit, so have not really tried pushing it with any other sources.
Old 11th November 2019
  #9
Gear Nut
 
Bollinja's Avatar
 

Quote:
Originally Posted by jbreher View Post
The comp sounds fine on vocals. Sucks on bass guitar.
Someone mentioned something similar on another forum.
Old 11th November 2019
  #10
Gear Head
 

How is the buss comp on the bass frequencies?
Old 11th November 2019
  #11
Gear Head
 

Here is the forum, or a forum that mentions this.

https://www.soundonsound.com/forum/v...65524&start=60


It seems that the channel comps are for vocals etc and not designed for bass.
It is not a design fault but has fixed parameters-only the threshold is adjustable.
Old 12th November 2019
  #12
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Quote:
Originally Posted by BEEHIVE View Post
Here is the forum, or a forum that mentions this.

https://www.soundonsound.com/forum/v...65524&start=60


It seems that the channel comps are for vocals etc and not designed for bass.
It is not a design fault but has fixed parameters-only the threshold is adjustable.
But I still think it is an engineering fault. I am a bassplayer and I have owned and tried a lot of different compressors and limiters, among them many cheap ones and some not at all designed for bass. None of them showed this kind of behaviour. The channel comp of the Six - otherwise a great great piece of gear - goes into a kind of self-resonance (but not the moog or 303 kind of self resonance) as soon as it is confronted with ordinary bass frequencies. For example: a simple Fender Precision plugged in.

What I don't like about it at all: this can totally ruin otherwise brilliant recording takes.
It's not that it sounds not good with bass. I could live with that. It's that self-resonating rattling distortion.

A decent piece of audio-gear like a mixer should handle signals from 20 to 20.000 hz without creating such mess. The SiX is ten times the money of mixers with channel compressors that don't ruin the entire audio-chain when confronted with bass material.
I can live with it and don't use the channel-compressor for bass. But for the reputation of a company like SSL this is embarassing. Did they never try it with ordinary audio material fed to the channels before selling it???

https://www.dropbox.com/s/d59jl8ufg8...0comp.mov?dl=0
Old 12th November 2019
  #13
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Its Mork's Avatar
 

Quote:
Originally Posted by BEEHIVE View Post
How is the buss comp on the bass frequencies?
I didn’t do a separate 100 Hz measurement for the buss comp, because it is nothing like the channel comp and handles bass heavy material very well. By now I used it enough (far more than the channel comps) to confirm that it absolutely rocks!
I would add a screenshot unfortunately I am on the road at the moment. If I don‘t forget I will add it when I am back home and have the time to do so.
Old 12th November 2019
  #14
Gear Head
 

Quote:
Originally Posted by DirkP View Post
But I still think it is an engineering fault. I am a bassplayer and I have owned and tried a lot of different compressors and limiters, among them many cheap ones and some not at all designed for bass. None of them showed this kind of behaviour. The channel comp of the Six - otherwise a great great piece of gear - goes into a kind of self-resonance (but not the moog or 303 kind of self resonance) as soon as it is confronted with ordinary bass frequencies. For example: a simple Fender Precision plugged in.

What I don't like about it at all: this can totally ruin otherwise brilliant recording takes.
It's not that it sounds not good with bass. I could live with that. It's that self-resonating rattling distortion.

A decent piece of audio-gear like a mixer should handle signals from 20 to 20.000 hz without creating such mess. The SiX is ten times the money of mixers with channel compressors that don't ruin the entire audio-chain when confronted with bass material.
I can live with it and don't use the channel-compressor for bass. But for the reputation of a company like SSL this is embarassing. Did they never try it with ordinary audio material fed to the channels before selling it???

https://www.dropbox.com/s/d59jl8ufg8...0comp.mov?dl=0



Agree.

A compressor is for audio signals generally i would have thought , whatever the range of frequency. Seems odd that it should differentiate which signals it would work with and not others have to say. Also odd that users have had to find this out for themselves OR is it a feature that is described in the manual- that the channel comps only work with such and such audio signals?
Old 12th November 2019
  #15
Gear Head
 

'I didn’t do a separate 100 Hz measurement for the buss comp, because it is nothing like the channel comp and handles bass heavy material very well. By now I used it enough (far more than the channel comps) to confirm that it absolutely rocks!'

Thats great.
Old 12th November 2019
  #16
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DirkP's Avatar
Quote:
Originally Posted by BEEHIVE View Post
'I didn’t do a separate 100 Hz measurement for the buss comp, because it is nothing like the channel comp and handles bass heavy material very well. By now I used it enough (far more than the channel comps) to confirm that it absolutely rocks!'

Thats great.
afaik the buss compressor has a high pass filter and simply ignores bass. makes not much sense to use it for bass or just as an effect that leaves the low frequencies untouched. for a bus comp this makes sense to prevent the bass from ruling the entire compression, for bass compression not so much.
Old 12th November 2019
  #17
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Its Mork's Avatar
 

The buss comp has a high pass at 50Hz in the sidechain, the compression is wideband. You could absolutely use it on bass guitar, never tried it though. I guess it could be cool if you’re going for a punchy sound. Now I HAVE to try it
Old 13th November 2019
  #18
Gear Head
 

Wonder if SSL will adjust the channel comp to be able to work with all signals?
Old 13th November 2019
  #19
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Its Mork's Avatar
 

I got an answer from SSL. Part of the distortion is normal part of it is not. It would be great if someone else could measure the channel comp to have a comparison.
Old 13th November 2019
  #20
Gear Head
 

Quote:
Originally Posted by Its Mork View Post
I got an answer from SSL. Part of the distortion is normal part of it is not. It would be great if someone else could measure the channel comp to have a comparison.

Oh? Wonder what that means?


Going to get one anyway. Initally it put me off, not sure why.
Old 13th November 2019
  #21
Gear Maniac
 

Quote:
Originally Posted by Its Mork View Post
I got an answer from SSL. Part of the distortion is normal part of it is not. It would be great if someone else could measure the channel comp to have a comparison.
So are they offering to replace / service yours? If the distortion is "not normal" then I imagine they're saying yours is faulty, no?
Old 13th November 2019
  #22
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Yes they do. But I would prefer to see some comparisons before going through the hassle of swapping it out.
Old 14th November 2019
  #23
Lives for gear
 
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Quote:
Originally Posted by Its Mork View Post
Yes they do. But I would prefer to see some comparisons before going through the hassle of swapping it out.
Did you listen to the example I've sent?
Old 14th November 2019
  #24
Gear Head
 
Its Mork's Avatar
 

Yes I did, but unfortunately this is „normal“. I also noticed this with subby Bassdrums and I really hope they fix the compressor design. Swapping out the desk will not make any difference in this regard which is why I am interested in measurements by someone else, to see if the amount of distortion is the same especially in the midrange.
Old 20th November 2019
  #25
Here for the gear
 

Use the HPF and G BUS comp when tracking.

Add in some extra eq / doubling further down the chain.

You want your bass to pop on laptop speakers just as much as a sub.
Old 3 weeks ago
  #26
Gear Head
 
Its Mork's Avatar
 

To finally sum this up:

SSL sent me a new PSU. The distortion decreased and some of the low end peaks are gone completely.
They said the old PSU „measured like a faulty PSU“ whereas the new one measured as expected. However, both PSUs met the specs. This is as specific as they would get. I asked them for measurements of their golden unit, but they don‘t give measurements out to the public.
I want to give a shoutout to SSLs support team! They have been very helpful and never tried to just get rid of me.

Now the juicy part, does it sound different? YES! The whole desk sounds different. To me the old PSU feels more forward and the new one more smooth. I joked around that I now have an E and a G PSU

I recorded a quick Reason drum loop „through“ both PSUs and will add the files when I get back home next weekend. I will also add the final measurements.

Cheers

PS: I still would be greatful if someone could measure his/her channel comp. Just put a 400 Hz sine through the channel comp and measure the return of the desk with something like SPAN.

Last edited by Its Mork; 3 weeks ago at 12:48 PM.. Reason: See PS
Old 3 weeks ago
  #27
Gear Addict
 

Great original post. Based on some reading, it looks you had an unlucky combination of a bad power supply and an input source unfavorable to the fixed-control channel compressors.

I see the mixdown eq/comps on the SiX as kind of a lottery. If they hit well on the sound sources, then you won the lottery. Otherwise, do the signal processing with an outboard piece or in software. You still get analog summing, 100mm faders, SSL sound, monitoring with dim/mute, etc. And you might get an added bonus that the eq/comps give your mixdown some extra punch somewhere.
Old 2 weeks ago
  #28
Gear Head
 
Its Mork's Avatar
 

Here are the sound files and final meaurements, as promised. PSU1 is the old "broken" one, PSU 2 the new one.
"Clean" means no comp or eq, "Comp" is obviously with the channel comp engages. I didn't touch any faders or knobs (except for the comp button), just unplugged one PSU and connected the other one.

Still looking for someone to add his/her own measurement.
Attached Thumbnails
SSL SiX Channel Compressor Distortion-psu1_400hz_comp.jpg   SSL SiX Channel Compressor Distortion-psu1_allfadersdown.jpg   SSL SiX Channel Compressor Distortion-psu1_deviceoff.jpg   SSL SiX Channel Compressor Distortion-psu2_400hz_comp.jpg   SSL SiX Channel Compressor Distortion-psu2_allfadersdown.jpg  

SSL SiX Channel Compressor Distortion-psu2_deviceoff.jpg  
Attached Files

Drums-PSU1-clean.wav (1.01 MB, 287 views)

Drums-PSU1-Comp.wav (1.01 MB, 293 views)

Drums-PSU2-clean.wav (1.01 MB, 291 views)

Drums-PSU2-Comp.wav (1.01 MB, 286 views)

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