CA VG1 - VCA compressor

[Potato Cakes]

Hello!

I've built mine up to the point where I have mounted transformers and I've come across some issues/discrepancies that might be of note.

First, the 470uF Audio Capacitor listed in the BOM is actually a Low ESR and is fairly tall, but I believe that it will be within the one slot space. The Mouser part number for the audio grade version is 647-UKT1H471MHD (if you want 105C instead of 85C). This probably won't make any audible difference either way, but one should be made aware if they are absolutely wanting a particular capacitor for C61.

Second, the 250k potentiometer on the BOM for the Attack control is physically deeper than the 10k pots. This causes an issue when mounting the boards to the faceplate as it overlaps with IC7, preventing it from being flush.

I also forgot to order the 1M pots and the correct 1uF caps with the 7.5mm lead spacing. I don't have enough of the 5mm ones for all four of the modules, so I might as well order the correct ones with the proper physical dimensions. I was hoping to have these up and running this week. Another box from Mouser just showed up so I guess I'll work on some other projects I have awaiting.

Thanks!

Paul

 

[Potato Cakes]

So close!

 

[Potato Cakes]

Update on the 250k pot. The the product number for the one on the BOM ends in B1, which is the version that includes a switch, which could be fun for a future mod/option, but it still won't fit in it's current placement. The one needed ends in A1 (like the other pots), but that version is non-stocked at Mouser and Digikey. It might be helpful to locate a suitable substitute that is readily available.

Thanks!

Paul

Edit: Arrow.com has them, but you have to sign up for a stupid account, which annoys me as that is guaranteed more unwanted crap in my inbox regardless of not subscribing to their news letters. Sigh...

 

[Potato Cakes]

I received the missing pots today, so I installed them and finished assembling the first one in hopes to calibrate it. I plugged it in and powered it on and in bypass it passed unity gain and top LED was lit. With it switched in it was still at unity but no make up gain control. The Mix control seemed to work as I saw the slight bump in signal that is common with most parallel blending circuits. I looked over the manual and noticed there was a fix for IC12 on V.1 boards, which I have. I installed the jumper and also made a solder bridge for JP2 as I wanted all the LEDs to light and not one at a time and powered it back up. Same thing except the bottom half of the LED array is constantly lit. I've double check solder joints and placement of components with no change. So I assembled another set of built boards and didn't bother installing LEDs. Now with the circuit IN there is no output signal. Assembled a third and same thing. I swapped ribbon cables and checked all the voltages in regards to ICs, DOAs, and relays. The one thing I did notice is that the V- for the 2181 chips is -2.8VDC and I don't know if this is correct. I am also using AD712 for the OPA2604 as the latter are never in stock at Mouser when I need them, and I've used the the AD712 a substitute before with great results.

I have a fourth set of boards built up but I haven't bothered as I'm sure I will get the same results. I feel a but defeated as I haven't had this much failure on a project in a very long time. I'm going to step away for a minute and come back to this later. If there was a schematic to follow along with that would be super helpful. One not working is conceivable but it hard for me to believe I made the same mistake three (possibly four) times when building these units. Are there any other corrections that need to be made for v.1 boards?

Thanks!

Paul

 

[Potato Cakes]

Once again, it is proven that no matter how many times you get a build right, you always have the opportunity to get one wrong...

I had placed 100R for 100k on the remote boards. All is compressing and everything. I do have an issue with the meter, but that again is probably something I did.

Stay tuned...

 

[Potato Cakes]

And finished! Kinda! I just need to find some sweet knobs. There's a fourth one, but I managed to break one of the pushbutton switches and I don't think I have a spare. But everything else calibrated exactly like the manual said except for one module, which I could only go as low as 0.002V for the CV calibration whereas the other two are at 0.000V, which probably just means I get a little overboard during the calibration process. I just wish I hadn't made such carless errors stuffing the boards that would cause me to spend the whole day troubleshooting to find the easiest to see and fix mistakes.

The one thing that is a little odd is the JP2 for the LED mode setting. When it is jumped, all the LED are on then turn off in succession when compression happens, like what you would see when using a noise gate. I was hoping it would be opposite of that like you would normally see for a GR meter, but that's just me being picky.

I haven't had a chance to actually listen to them yet. I'm trying to plow through a bunch of builds this weekend.

Thanks again for this great project! I can't wait to put them to use!

Thanks!

Paul

 

[diystudiotoys]

BLACK FRIDAY SALE!

VG1 kit for 99eu!!!

*The number of kits is limited.

 

[Catrunes]

to thoe who have built this, can you provide me with the standoff lengths needed for the daughter board and main pcb? thank you!

And finished! Kinda! I just need to find some sweet knobs. There's a fourth one, but I managed to break one of the pushbutton switches and I don't think I have a spare. But everything else calibrated exactly like the manual said except for one module, which I could only go as low as 0.002V for the CV calibration whereas the other two are at 0.000V, which probably just means I get a little overboard during the calibration process. I just wish I hadn't made such carless errors stuffing the boards that would cause me to spend the whole day troubleshooting to find the easiest to see and fix mistakes.

The one thing that is a little odd is the JP2 for the LED mode setting. When it is jumped, all the LED are on then turn off in succession when compression happens, like what you would see when using a noise gate. I was hoping it would be opposite of that like you would normally see for a GR meter, but that's just me being picky.

I haven't had a chance to actually listen to them yet. I'm trying to plow through a bunch of builds this weekend.

Thanks again for this great project! I can't wait to put them to use!

Thanks!

Paul

 

[Potato Cakes]

to thoe who have built this, can you provide me with the standoff lengths needed for the daughter board and main pcb? thank you!

Mine are 20mm.

Thanks!

Paul

 

[Potato Cakes]

For the linking, is there any way to utilize Pin 6 (Stereo Link) on the edge connector? This would make things a little easier to install a stereo pair in a rack that has a switch for the Pin 6 link. One could jumper from the link header to the edge connector unless there is something else going on in the link section that we don't know about. I'm just thinking there could be an easier way to go about this because I'm lazy.

Thanks!

Paul

 

[Catrunes]

Anybody able to help out with how to set the grayhills for the ratio switch? Don't know where to put pins and how the shaft should be beforehand.
Thanks
Max

 

[Potato Cakes]

Anybody able to help out with how to set the grayhills for the ratio switch? Don't know where to put pins and how the shaft should be beforehand.
Thanks
Max

12 o'clock and 5 o'clock. Look at the front panel markings as a guide. Double check with switch to make sure you only have 6 total positions. CCW counts as one.

Thanks!

Paul

 

[Catrunes]

12 o'clock and 5 o'clock. Look at the front panel markings as a guide. Double check with switch to make sure you only have 6 total positions. CCW counts as one.



Thanks!

Paul

To clarify, if you're looking at the front of the unit upright as it would be installed, pins at 12 and 5? Thanks paul!
Max

 

[Potato Cakes]

To clarify, if you're looking at the front of the unit upright as it would be installed, pins at 12 and 5? Thanks paul!
Max

The relation is to the switch itself. The relation to the face plate is irrelevant  as you are going to put the knob on however it matches the markings. You can use any build guide that has a Grayhill switch as a guide on pin positions if you are unfamiliar with pin placement on these switches.

Thanks!

Paul

 

[OneRoomStudio]

I got mine built up, but I'm having a strange issue.

When I check for unity gain with the threshold set to +15, ratio at 2:1, and a -22dBFS signal, the output is about 4dB down. The meter confirms this, showing 3-4dB of gain reduction. If I lower the input signal to around -40dBFS, I can get the input and output to match and not show any gain reduction on the meter. It's almost as if the threshold is set far too low (even with the knob at +15). I get the same behavior when the ratio is set to 1.5:1, 2:1, and 4:1, but as soon as I switch to 6:1 or higher, everything seems to behave properly. I'm guessing I have a resistor out of place somewhere around the ratio switch?

 

[Potato Cakes]

If some of the ratios are working correctly then the resistors in that section are the first things I would check.

Thanks!

Paul

 

[OneRoomStudio]

I'm still having problems with mine. I triple-checked all the resistors, and I did find one error, but replacing that resistor hasn't fixed the issue.

When set for unity gain (threshold +15, make up 0, ratio 2:1, etc), I see a 4.5dB drop when the compressor is engaged. This is true for ratios 1.5, 2, and 4. As soon as I switch it to ratios 6-10 though, it's at unity gain. Because of this, I'm unable to fully calibrate the unit. Any ideas anyone?

 

[OneRoomStudio]

SOLVED!

Thanks to @DIYStudioToys! I had the ratio switch stop pins in wrong. For anyone else wondering, one pin goes in at 12:00 (with the top of the switch being up and the PCB being down - NOT with the top of the compressor module being up), and one at 6:00.

 

[Potato Cakes]

SOLVED!

Thanks to @DIYStudioToys! I had the ratio switch stop pins in wrong. For anyone else wondering, one pin goes in at 12:00 (with the top of the switch being up and the PCB being down - NOT with the top of the compressor module being up), and one at 6:00.

I do believe I had mentioned this above. Nonetheless, glad you got it working.

Thanks!

Paul

 

[Flundran]

My ratios is pretty off and the ratio trim doesn't seem to do much.

4:1 is 2,4:1
10:1 is 3,5:1