Seventh Circle Audio

Hi Tim,

I have a revision 3.3 board that I am only just now building. I found a post that said to change the URL to R33 to get the right assembly instructions - but they are still not right. The board doesn't match those instructions, and I also tried version 3.4, 3.5 (didn't work), and v 3.6 - but none matched.

Do you have in your archives the correct assembly for this version of the board? I'm close to finishing it and I want to make sure I have the right voltages, setup for the trimmers, etc. Just looking at the schematics doesn't help me; I'm not that advanced. But I'm very meticulous.

Thanks, the build has been very smooth so far even with the wrong instructions.

Mike

Hi Tim et al,

Just wanted to say I was able to complete the build, and successfully calibrate the J99!

I have yet to pass audio with it (will this weekend), but I wanted to thank-you Tim for your kick-a$$ project that was fun and I can tell super high quality!

You were right about my concerns about v3.3 vs 3.6 documentation; I just used the 3.3 docs until they differed from my board, did a little R&D to compare part numbers in the BOM's old vs. new, and it was cake!

Thanks again. I'll post back my impressions on the unit soon.

Mike

I just finished a build (using the pdf instructions from the website) and found these to be the errors in the instructions:


On p10, the power connector is incorrectly identified as J7, when it is J8 on the board and parts list.

On p11, the gain trim control is incorrectly identified as R17, when it is R24 on the board and parts list.

On p15, orienting the IC required some guesswork, since it was unclear what "according to the silkscreen meant--in other cases (like in the C84) the ICs actually had indentations on one side that matched the indentation on the silkscreen. The only thing I could go off of was the lettering. I orientated the IC according to the lettering, like the lettering of the other ICs. And the lettering on the IC is very faint, especially in the picture.

Likewise, on p17, checking the pins on U3 requires some guesswork, since the pins are not numbered like in U1/U2. It works assuming that the pin numbering works the same way as U1/U2 (starting with 1 on the bottom left and going counterclockwise.) An enlarged picture of the IC on the board with the pins numbered would help both these issues with U3.

On p18, instruction 45 has a few typos. It says: "Turn off the power and remove the op-amp from U1/U8. Install the second op-amp at U2/U9. Don’t use the same op-amp you just used at U2/U9..." Clearly, that last "U2/U9" should be "U1/U8" since that is where we used the other op-amp.

Then it continues, "Connect the DMM between U2, pin 4 and U2, pin 6." Assuming that these directions are parallel to the first set, this second measurement should be at U1, not U2--measuring the voltage at the pins of the op-amp that is NOT installed.