Q & D compressor SSM2166 chip

[Stephen]

Bought the chip form Small bear and perf out one of these... It is the best sounding conpressor I have done.

For the money this chip is worth the investment...I know a lot of you have probably built this but I thought it would be another CHUM compressor..years ago so never tried!!!

This has a gate and a limiter according to the scheme... I changed the orientation of the gain pot and the comp ratio pot as CW I thought would mean clockwise or ground side of pot ..

For the money you cant beat the sound you get...It is easy to wiring, it perfing it!!!   TRY one I have two of these chips and will surely do another for kicks.....

Wonder why they stop making this chip

[markm]

Congrats!
Ya know, I like this comp alot too myself but, I find the volume it produces to be an issue for me.
With the gain turned completely OFF it is a unity.....anything more and it really boosts the amp.
Do you have this issue with yours?

[Stephen]

YEAH I have a lot of gain but it seems as if you can dial in almost anything!!!!

I dont think you would want another gain pedal, such as  a booster or distortion ...as this is enough gain and comp and gate and limiter...

Not a Keeley or Ross comp ,but a very cool pedal indeed......

I think this would be really nice in front of a little dirty amp..havent tried yet as is is not in a box but I used headphones with a little dirty  channel and it is like a distortion or a BOOSTER TOO really...

How do you use yours?

[markm]

Right now I don't use it because of the over abundance of gain it has is really a problem for me.
I was thinking about putting a resistor on the output of it to bring the gain issue under control allowing more control over the volume of it.
However, in doing this it probably kill whatever high end it has!
The reason this circuit has so much gain is that it operates at line-level so the signal is quite hot.

[Johan]

Congrats!
Ya know, I like this comp alot too myself but, I find the volume it produces to be an issue for me.
With the gain turned completely OFF it is a unity.....anything more and it really boosts the amp.
Do you have this issue with yours?

why dont you just set a fixed gain with resistors and add a volumepot at the output then?...

johan

[markm]

That's a good thought.....
I'll have to take a look at it and see if this is possible to do on my board.

[Stephen]

This thing sounds Okay....Would you put a fet buffer in the front?? Mark Hammer mentioned it!!!

[markm]

This thing sounds Okay....Would you put a fet buffer in the front?? Mark Hammer mentioned it!!!

He had mentioned that in one of the various threads on this comp.
I suppose it would be a good idea since the impedance on this unit is quite low.
When I have time I'm going to explore the possibilities of taming some of the gain this baby has.
It's just a bit much for me from a comp ya know?
I mean......I have plenty of boosters to choose from I don't need a boost with a compressor!

[lovekraft0]

Wonder why they stop making this chip 

The chip is still available, RoHS-compliant too, it's just not available in a DIP package. You can still get all you want in a 14-pin SOIC.

http://www.analog.com/en/prod/0,,765_1075_SSM2166,00.html

[majormono]

I built a 2166 comp using my own layout (not dissimilar to the QnD) and had the same volume problem, which could be partly solved by setting the input buffer to 0dB (10k -> wirebridge) - but it's still way too much. Another thing is the way the chip is purpose-designed for speech systems as an AGC (keeping the volume even) and has no "standard" controls, I especially miss a proper Threshold while the "ratio" is rather useless and the downward expander doesn't work either for me (shutting the whole thing off or on).
Shunting the output with a pot or R also gives on-or-off somewhere below 1k (keep in mind the output impedance is 75R!).
While nice sounding and with no audible distortion (well expect from the high output overdriving my amps input) I find no use for this thing in this way.
There might be an error in my schematic (always my first thoought ;-), but I found none and tried changeing the suspect components with no avail.
A buffer at the input is really useful when using it first in chain, I put a simple offboard FET buffer in front.

I wonder where my error is, since people seem to get it working properly... sometimes DIY gets frustrating (but that's part of the fun).

[Stephen]

WHO diy would use surface mount???
Thats a good thread to start....
The chip has its limits but it does a real good job for me!!!

[markm]

For the most part, this is a superb sounding compressor.
It can give the real Squish with out the drop-out that you get from others. It seems to compress all frequencies equally and seems to let the true tone of the guitar shine through.
It's just too dang LOUD! 
I think there are a few here who use SMD technology.....I'm not one of 'em though!

[majormono]

What's wrong with SMD?
I simply enlarged the DIP footprint to SMD pads and soldered the chip in belly up - works perfect while a little cumbersome ;-).
This way I can use DIP or SMD interchangeably (and since I got the SMD  through the sample program for free...).

[theman]

Bought the chip form Small bear and perf out one of these... It is the best sounding conpressor I have done.

For the money this chip is worth the investment...I know a lot of you have probably built this but I thought it would be another CHUM compressor..years ago so never tried!!!

This has a gate and a limiter according to the scheme... I changed the orientation of the gain pot and the comp ratio pot as CW I thought would mean clockwise or ground side of pot ..

For the money you cant beat the sound you get...It is easy to wiring, it perfing it!!!   TRY one I have two of these chips and will surely do another for kicks.....

Wonder why they stop making this chip

Did you use the Orman schematic to choose the pot values? For example, I noticed that in the Q&D schematic, the comp ratio pot is a 25K linear pot. Setting this at max (25K) yields a compression ratio somewhere between 2:1 and 3:1, according to the AD datasheet. However, if you want 15:1 compression, you have to go up to 400K.  Maybe a 500K audio pot would allow you to go up to the max compression. Any thoughts?

[markm]

I noticed that in the Q&D schematic, the comp ratio pot is a 25K linear pot. Setting this at max (25K) yields a compression ratio somewhere between 2:1 and 3:1, according to the AD datasheet. However, if you want 15:1 compression, you have to go up to 400K.  Maybe a 500K audio pot would allow you to go up to the max compression. Any thoughts?

Interesting thought.
Perhaps even a 100K or 250K would make a difference in the compression.
For that matter, a larger value on the gain may bring that more under control as well.
I'll have to give that a try.

[Stephen]

I dont think you need anymore compression.. You cant really turn it all the way up but it will sustain for a long long time half throttle....I think it would be overkill..I dont know I like the way it is, I reversed the wiring seems that the clockwise turn would work better for more compression... I was wondering about a fet buffer in front though..May do that!!

[markm]

 


Anyway.....

What's wrong with SMD?
I simply enlarged the DIP footprint to SMD pads and soldered the chip in belly up - works perfect while a little cumbersome ;-).
This way I can use DIP or SMD interchangeably (and since I got the SMD  through the sample program for free...).

There's nothing wrong with SMD and as a matter of fact, your method for using SMD is good for future reference when they discontinue more DIP through hole stuff!

[theman]

I dont think you need anymore compression.. You cant really turn it all the way up but it will sustain for a long long time half throttle....I think it would be overkill..I dont know I like the way it is, I reversed the wiring seems that the clockwise turn would work better for more compression... I was wondering about a fet buffer in front though..May do that!!

Just curious about doing more compression since a lot of people in the studio apply ratios higher than 3:1 -- even for some guitar parts. It would be nice to be able to do this, or even use it as a device for other instruments.

Regarding the FET buffer. The SSM2166 doesn't have a high input impedance, but it may not matter depending on the source. I would typically use it after devices that are low impedance, so it won't make too much of a difference. For a guitar pickup, where the impedance may be higher, it could make a difference, but let's assume the loading won't affect the tone of the guitar -- only the amplitude. This is where the gain knob might come in handy, to boost the signal up. 10-20 dB of available gain seems to be more than enough. Now if the loading does affect the guitar tone, esp on higher gain higher impedance pickups, then the buffer could be warranted. Though people who use such high-gain pickups (and high impedance) have such high gain distortion anyways, any tone loss is indistinguishable!   

[Stephen]

You might have a point about higher compression ratios..

This thing is a whizzzzz to do and sounds good...Really does the noise and the compression good.....Although it is not a smart gate or something and it does have some background noise ..floor noise??  The compression is excellent!!! Whoolup of gain........

Info is appreciated about the buffer it just takes up room!!

[majormono]

Just to throw in 2 more cents regarding ratio....
Since the only way for me too keep volume somehow even I have to use full limiting (what usually means ratio 8:1 but it's not referenced IIRC) what renders the ratio control useless. So for me this is a loud limiter ;-).
I wish there would be some refernce how the compression threshold is set, as this is normally the most important control and I really miss it here.
Does anyone have the downward expander working (as I said it's more a non-triggered on-off switch for me)?

Hm, I've used many compressors and I'm used to the SSL mixcomp and 1176 most but this thing reacts so completely different and is hard to control... even my 3080 comp is nicer (except the distortion issue), but that's just me - so congratulations to anyone who gets good use of it!

Just for reference if anyone cares, here's my schem http://www.grol.de/DIY/2166_SCH.jpg and layout http://www.grol.de/DIY/2166_PCB.gif (o.k., it was a build for fun anyways).