What makes a 500 series lunchbox have uneven stereo channels with stereo units?

[canidoit]

I was having trouble with my SB4001 stereo unit thinking it had issues, but I have now discovered it is the lunchbox I am using.

The levels would be about 6db difference between left and right channels on the SB4001 compressor.
- If I don't use it for a few weeks and turn it on, the levels would be fine, but then after 5-10 minutes the levels would start to become faulty again.
- The level issue would only occur when the compressor IN is engaged, in bypass it does not occur.

I moved the SB4001 to another lunchbox, and the problem does not exist.

What usually causes this? It is weird because it only occurs when compressor in is engaged. I can have the threshold high so that it does not compress, but it still has the issue.

I am thinking, maybe when the compressor is engaged, the SB4001 draws more power and one of the slots of the chassis has power issues causing the SB4001 to sound lower on the left channel? Is this a possible cause?

Anyone have any idea what could be causing this?

Thank you.

 

[TwentyTrees]

6dB would be the difference between a balanced and unbalanced connection - if there was an issue with one output XLR on your lunchbox (eg marginal solder joint that fails when the lunchbox warms up, or the connector needs cleaning) then you might see something like that. How do other modules behave in the slot that had an issue? Is your cabling (and any patchbay) all OK?

 

[canidoit]

6dB would be the difference between a balanced and unbalanced connection - if there was an issue with one output XLR on your lunchbox (eg marginal solder joint that fails when the lunchbox warms up, or the connector needs cleaning) then you might see something like that. How do other modules behave in the slot that had an issue? Is your cabling (and any patchbay) all OK?

Hi TwentyTrees,

It is not the patchbay, because I have repatched on other patchpoints and also direct cabling and the-same issue occurs.

I didn't notice it with other modules on the same slots because they were single pre-amps, so I would just adjust the gain accordingly. It is the fact that it only occurs when I put the SB4001 compressor engaged in which I find strange. If I have not used the lunchbox for a few weeks, then it works normal for a few minutes then the issue occurs, but again when the compressor is engaged.

It is my only stereo compressor unit that takes up the two slots.

Does the SB4001 change the current draw on each slot once the compressor is engaged in? It uses two 500 series pin backplanes at the rear, so the Left and Right must be independent in someway? I am assuming, once the compressor engages in, the current draw is boosted, and then some of the lunchbox slots cannot handle it, maybe because it is faulty? This inability for the lunchbox to feed the SB4001 the appropriate current is leading to a lower level on one side? Is this feasible, or will the SB4001 just stop working and not actually lower the level on the weaker slot?