CA VG1 - VCA compressor

[OneRoomStudio]

I'm building up another one now, but it looks like the BOM and the build manual are no longer on dropbox. Did anyone save copies that they could share? Thanks!

 

[Upacesky]

I might. I'll have a look tonight

 

[Potato Cakes]

Here you go.

 

[OneRoomStudio]

I got the second one built up and working, but I can't manage to trim the ratio into spec. In 2:1, with the ratio trim pot maxed out and the threshold set to compress 2dB with -18dBfs input (-20dBfs output) I'm still seeing around -11 dBfs output when I feed it -8dBfs (I should be seeing -15dBfs). Same with 10:1 ratio - with the threshold set to compress 2dB with an input of -18dBfs (output of -20dBfs), I'm seeing around -15dBfs when I feed it -8dBfs (I should be seeing -19dBfs).

I double checked all the components and don't see any mistakes. I can only think of two possibilities:
1) the ratio trim pot, which only measures at around 415 ohms instead of 500 is too far out of spec and I need at least 500ohms.
2) the THAT 2181B's I bought aren't working as well as the ones I bought for the first one, years ago. Part of me is wondering if they're fake. I got them from Mouser, but the markings on them doesn't look like the ones I bought before, and look a bit smudged.

Anyone else have any ideas? Thanks!

 

[Potato Cakes]

Unless you have other 2181s to test your bad component hypothesis, I would say that you still do indeed have a bad/missed solder joint or a misplaced component. In one very rare instance I had a bad transformer that was new. Other times I have had bad components is when I got some fakes or when I have reused it too many times causing a failure, which is also a fairly rare occurrence. Troubleshooting the most frustrating part of the process.

Thanks!

Paul