1

CP554 Diode bridge compressor / Attack times

« on: May 20, 2024, 03:56:13 PM »

Dear People,

I hope you are doing well.

a few days ago i finished puting a pair of CP554s together.

I enjoyed a lot the process; Thanks JPK for making this possible.

I think both units are doing well and I calibrated as mentioned in the guide.

A little Burn in time I started testing.

I realised that even at 0.5ms Attack my CP554s fail to catch a lot of peaks.

Out of curiosity I did a test.

The test I did is not "super" precise!

I recorded a Sine Wave with 10dB of gain Reduction at different Attack/Release settings and then by reading the waveform i decided where Attack and Release starts and ends.


This is what came out:

Gain Reduction 10 dB/Ratio 3:1

Attack 0.5ms: 10ms - Release 400: 360ms
Attack 1ms: 25ms - Release 400: 300ms
Attack 2ms: 31ms - Release 400: 260ms
Attack 4ms: 97ms - Release 400: 230ms
Attack 8ms: 142ms - Release 400: 300ms
Attack 16ms: 175ms - Release 400: 360ms

Attack 1ms: 15ms - Release 100: 150ms
Attack 1ms: 13ms - Release 400: 270ms
Attack 1ms: 25ms - Release 800: 585ms
Attack 1ms: 22ms - Release 1500: 2200ms
Attack 1ms: 35ms - Release A1: 550ms
Attack 1ms: 10ms - Release A2: 2900ms

The Attack Values I recorded are off by factor of 10-20 compared to the Values on the Faceplate.

This seems to be a lot and maybe I messed something up?

If this behavior is  normal; is there a way to speed up Attack times?


FYI: to spice things up and making the learning part a bit more fun i swaped out some components.

Resistors: Most replaced by Carbon Film Resistors (same Values but twice the wattage 0.5W instead of 0.25W/2W instead of 1W)
EL Caps: Most replaced by specs except for Voltage sometimes (example:1000u-35V replaced by 1000u-50V)
Tantulum: original
Ceramics: original
Film Caps: original
Opamps: Sparkos

Thanks a lot

Stay safe

2

CP554 Diode bridge compressor / Re: CP554 and Matching

« on: January 18, 2024, 09:41:38 PM »

Thanks a lot for the reply.

What about the other diodes?

3

CP554 Diode bridge compressor / CP554 and Matching

« on: January 12, 2024, 09:52:12 PM »

Dear all,

I hope you are doing well.

I found this sentence in an article:


"The diodes also need to be closely matched to maintain low distortion."


I would like to know more... 

Which diodes are they talking about? What about matching 2 Units?

What I found on the subject diode matching doesn't look easy to me. It also looks like quiet a bit of work.

I am myself in the process of assembling a pair of CP554.

With the 2-Bus in mind; Would it be worth to investigate on that subject?

Thanks a lot

Stay safe