Seventh Circle Audio

The instructions say "Add the ceramic capacitors C1, C2, C3, C9, C11, C16, C18, C20, C24, C26, C30, C33, and C36." There is no mention of C21, C27, C47, or C48, although they those four are shown in the illustration. I'm assuming they need to be installed, but I wanted to make sure there wasn't a revision to the instructions that doesn't require them or something like that.

...and is it just me, or are the jumpers for J1 and J2 -really- loose?

Trust the schematic more than the instructions.

The jumpers should fit snugly on the headers. If they don't, figure out why not.

Shazbot...I soldered the short sides facing up. Is it OK to jumper from the rear?

It's OK, as long as there's room back there (no interference with an adjacent board), but I'd fix it.

OK, I flipped them around. Note to self - long sides go up!

when looking at the board with the XLR connectors to the right, how are the U1 and U3 pins oriented? Is it -

1 5
2 6
3 7
4 8

or

1 2
3 4
5 6
7 8

or

1 8
2 7
3 6
4 5

If it's the third orientation, I'm getting -14.60 at U1 pin 4 and 12.87 at U1 pin 8. U3 gets -14.60 and 12.91.

Your question is an excellent one, and one to which I don't have a definitive answer. If it's not the third option, then my C84s are screwed up big time. I don't think they are, but I actually haven't mounted them in the chassis yet. If it is the third option, then my channels measured 14 and -14 like they were supposed to. I think it's the third option.

ErikB \$m[1]:OK, I flipped them around. Note to self - long sides go up!

I did the exact same thing.

The 'third option' is correct. The best way to verify this is to do a search for OPA2604, and look at the data sheet. This is a good way to get the facts for any electronic device. They all have a 'data sheet' which describes the electrical and physical characteristics of a part.

Plus, this is the standard way that DIP (dual inline package) IC's are numbered.

Good point, Digikey has manufacturer's data sheets for just about everything they carry. Just based on the numbers I felt that the third orientation was correct.

Are the numbers I got within an acceptable range to move on?

Are the voltages acceptable? I need to move on with the second C84...

They're close enough that I'd move on to the next step, which is adjusting R68 and R72 for +18 and -18.

tele_player \$m[1]:This is a good way to get the facts for any electronic device.

Though, if this information were included in the assembly instructions, it would really help.