1

CP4500 Stereo Bus Compressor / Re: Comp not engaging when ‘in’

« on: August 17, 2023, 03:24:27 PM »

No it acts as if it were bypassed. 

Though I did have it briefly engage when turning the gain pot. But only for a second. Behaviour I haven’t been able to repeat 

2

CP4500 Stereo Bus Compressor / Comp not engaging when ‘in’

« on: August 08, 2023, 12:20:25 AM »

Hi!

My compressor after working fine for a year + started behaving strangely. 

Now when the compressor is ‘in’ it passes signal and meters fine but the comp seems bypassed. 

When I first noticed this it was intermittent and I had some strange behaviour with the gain pot. But now it just seems dead.

The unit looks like it’s working and I hear the click when I hit the in button. But signal remains unaffected.

You actually helped set this unit up and did a basic repair when I first built it as I had the meter spade connectors attached the wrong way.

Thanks in advice for your help!

3

CP4500 Stereo Bus Compressor / Re: Comp not passing audio

« on: September 16, 2021, 05:03:20 AM »

Is it still there if you remove only U6? YES - The whole left side was very noisy in general. But the crackling/popping remained
Is it still there if you remove only U2 to U5? Seems to clear it up (so no noise). Though when I first patched in like this I initially heard it, then it disappeared and remained stable. On a second attempt at a later time at this after running all other suggested tests it was clear (no noise)
Is it still there if you remove only U1? Yes possibly reduced its regularity/volume though
Is it still there if the Mix pot is on 0%?
Does it changes character when you change the threshold and/or makeup?


With all ic's inserted the the tests suggested in the last two points seemed to make no difference. The noise is fluctuating in volume and quite intermittent/irregular but as far as I could tell the crackle/pop was unchanged by turning any of the pots 

When I tested again at a later time with all ics inserted after running all of the above, it did seem to have dropped in regularity and volume a little with further testing. But I assume this Is possibly down the the inconsistent nature of the issue. Which seems to really fluctuate a lot. 

As an aside, I could be wrong but the issue of the relays/switch not behaving did seem related. I.e. if I hit the in switch to bypass the comp when the thing was really crackling and popping away, it seemed quite likely the switch would not disengage properly. Whereas when I hit the switch when it was quiet it seemed to work okay most of the time.

Thanks very much for all your help!

Rohan

4

CP4500 Stereo Bus Compressor / Re: Comp not passing audio

« on: September 14, 2021, 08:48:54 AM »

I’ve ordered a few replacement parts to re wire the vu meter (header and spade terminals etc) as I reckon wiring there may be a little sketchy. So I’ll see if that makes any difference when it arrives. (Any tips for pulling off the large spade terminal connectors off the back of the vu?)

Regarding the switch it looks totally free and fine to me. 

I’m also getting a bit of high frequency crackling at very low level when the compressor is engaged. I didn’t notice it at all as it’s so low, but once I put a mastering limiter after it it brought it right up. It’s mainly on the left but in both channels. Only loud enough to just hear when the unit is idle. It’s also intermittent.

Any thoughts?

5

CP4500 Stereo Bus Compressor / Re: Comp not passing audio

« on: September 10, 2021, 05:41:40 AM »

Thanks for your quick response! Turned out it was operator error in testing and I had my tone turned down

Seems to pretty much all be working. Sounds great!

The only small issue I'm having is the in/out switch very occasionally cuts one side (varying sides) when hitting 'out'. And the meter light sometimes turns right off when hitting 'out'. Sometimes it stays on. I've looked at all the solder joints on the switch and they look good.

Any thoughts of where else to look?

I'm a little hesitant to go digging too far as in operation it actually works fine. The meter light is always on when the comp is engaged and the switch issue is just a matter of depressing it again to resolve. Could a slightly faulty switch be causing both issues??

Thanks heaps! Love it!

6

CP4500 Stereo Bus Compressor / Comp not passing audio

« on: September 08, 2021, 07:49:44 AM »

Hi there,


I've just gotten up to the testing of channel 1 phase and have hit a big hurdle.

The voltages when testing power voltages seem ever so slightly of +16.3 and -16.3 approx on the V+ and V- pins. Other than that the readings were as expected.

the next step, running 1k sine wave into the comp i don't seem to be passing any audio at all.

I checked the pinned post above n case your CP4500 doesn't work as expected and the only abnormality I could find in the voltage testing was that testing between OV and pin 12 gave me a reading of .0012 as oppsed to .0000. It did behave as expected when turning the pot to +20 however.

Thanks in advance for your help!

Rohan