DEMO 401k Compressor (Keeley 4 Knob Compressor)

[MichaelW]

Build Rating

5.00 star(s)

Of course since @Robert released another compressor, I had to build it hahaha.

This is the older version of the Keeley 4 knob. I did some comparisons to my retail Keeley current version and I actually like the old one a lot better.

The 401k has a clipping control for input trim instead of the fixed toggle on the current version.

It's also MUCH quieter. This has got to be the quietest OTA compressor I've built yet. It's knocked the Squishy (Boss CS-2) off my board for now.

As usual it's really hard to "demo" a compressor. Also with my limited fingers, it's just a lot of strumming. I hope it comes across.

This is a HIGHLY RECOMMENDED build.

 

[DailyDovetails]

I have a Wampler Ego that I have been wanting to replace with a DIY. This seems like it could be a good replacement. I will add this to my list.

 

[MichaelW]

I have a Wampler Ego that I have been wanting to replace with a DIY. This seems like it could be a good replacement. I will add this to my list.

I've had the Ego, great compressor but this is a LOT quieter and more transparent. I'm really impressed,

 

[MichaelW]

Also with the Clip control on a pot it's much more versatile for using with other instruments. Like Keys or bass.
The current Keeley has 2 fixed trim settings for "single coil" and "hum bucker". I've always found that to the somewhat limiting.

BUT having said that, the Keeley was my favorite compressor until I got into DIY.

 

[Robert]

I wonder if the AS3080 is responsible for the lower noise floor?

This is the first circuit where I've used one of those.

 

[MichaelW]

I wonder if the AS3080 is responsible for the lower noise floor?

This is the first circuit where I've used one of those.

I used a CA3080E.

 

[MichaelW]

Hmmm I wonder what's in the retail Keeley? I should take a peek.

 

[Robert]

I want to say it uses one half of an LM13700.

I traced one of those a while back but can't remember what was in it.

 

[MichaelW]

Yup it’s a LM13700.

 

[MichaelW]

I’m gonna chalk it up to the SUPERIOR LAYOUT of a certain reverse engineer

 

[jessenator]

Wonderful!

 

[almondcity]

Where'd you locate the chip for this?

 

[MichaelW]

Where'd you locate the chip for this?

CA3080AE - Transconductance Opamp

Top Quality Parts for Guitar Effects Pedals and DIY Music Devices. Knobs, Pots, Switches, Kits, LEDs, Enclosures, Jacks, Wire, Resistors, Capacitors, Semiconductors

stompboxparts.com

 

[Robert]

Ahh nice, I didn't realize StompBoxParts had them!

This is the one I used, but it's out of stock:

Cabintech Global LLC

Specialty analog and digital audio semiconductors, synthesizer, and guitar effects modules from Coolaudio, Xvive, Alfa Rpar, and others

cabintechglobal.com

 

[music6000]

Ahh nice, I didn't realize StompBoxParts had them!

This is the one I used, but it's out of stock:

Cabintech Global LLC

Specialty analog and digital audio semiconductors, synthesizer, and guitar effects modules from Coolaudio, Xvive, Alfa Rpar, and others

cabintechglobal.com

Does the CA3080E have the linear diodes or is pin 1 floating?
Technically they are half a LM13700

 

[juice886]

Michael, how does it compare to Engineer's Thumb in terms of transparency and changing an original tone? as I like the Thumb the best as a natural sounding one though didn't try Keeley.

 

[MichaelW]

It's much quieter than the ET. But the ET being a VCA based compressor is inherently noisier but has more compression.

 

[MattG]

How about compared to the General Tso?

 

[MichaelW]

How about compared to the General Tso?

Well it's pretty different from the Tso. It's an OTA compressor vs an Optical.
The Tso is pretty special but it's also a lot more subtle than the 401k, which is based on the DynaComp/Ross.

Having said that, this is the quietest OTA compressor I've built (or bought). It's amazingly quiet.
Definitely more squish on tap than the Tso.
But it doesn't have that extra little sumpin sumpin that the Tso has.