1

CP4500 Stereo Bus Compressor / Re: Unable to level match Channel 1

« on: August 01, 2021, 12:12:50 AM »

Ok, I found and solved the issue! After additional testing I noticed that the failure moved from channel 1 to channel 2 and back again. At that point I started thinking there may be an issue with the rack itself. After checking multiple channels I was able to isolate the issue to the cable I was using for the channel 1 input. Swapped out the cable and everything is fine now, across both channels and all slots. 

I am a bit perplexed as how the cable would only cause the drop when the compressor was engaged, but I admit that I am a bit beyond my experience level on the theory side of things. I'd be interested if you have any thoughts on what occurred. 

I am extremely happy with how the build came out and again want to thank you for the support figuring this out! 

2

CP4500 Stereo Bus Compressor / Re: Unable to level match Channel 1

« on: July 31, 2021, 07:20:52 PM »

Apologies, but I may have spoken too soon. Calibration continued without issue until I got to the the balance trim step. When I went to get the channel 1 AC values with 10db of attenuation, I saw that the output level at baseline settings with the compressor engaged was back to the incorrect/low voltage, right around 1.02v. 

I tested on multiple slots, both with and without the extender cable.

Thanks again for your help, it is much appreciated!

3

CP4500 Stereo Bus Compressor / Re: Unable to level match Channel 1

« on: July 31, 2021, 05:01:07 PM »

Thanks JPK! After a reflow of all joints on U7, BR2 and RLY1 I am now able to gain match without issue. 

I really appreciate your help!

4

CP4500 Stereo Bus Compressor / Unable to level match Channel 1

« on: July 29, 2021, 03:57:12 PM »

I am unable to level match using T1 as discussed in step 7 of the set up guide. The max voltage I am able to attain when the compressor is engaged is 1.13V. Channel 2 level matched without issue.

I have confirmed all ICs are in their correct locations. I have also soaked the two main PCBs in an alcohol bath.

I ran through the troubleshooting voltage tests as described in your other post and these are my results (results in red):

Section 1: All up to spec

Section 2:


Section 3:


Section 4:


Section 5:

Section 6:



Section 7: 



I have ordered some additional trim pots in case the issue is localized to the one on T1.

Thanks in advance for any insight you can provide!

Cheers!

(edited post to add step 7 results)

5

CP4500 Stereo Bus Compressor / Clarification on Distortion Trim Setup

« on: July 25, 2021, 04:26:36 PM »

Just looking for clarification re: Step 9 (Distortion setup, Document revision 1.2)

Adjust the trimmer T5 (DIST) for the lowest sound.

I'm understanding this to mean that it should be as low as possible while still being audible. Am I correct?

Thanks in advance for the help! 

Cheers!