Engineer's Thumb Redux vC.4 vero

[befey]

After playing around with this some more, I've noticed the following:

The Gate works great.

The high pitched whine gets much louder when the Ratio knob is turned clockwise. This also makes everything louder, so that makes some sense. I still don't have this in a box, so the whine may go away. I haven't ruled out shielding the input wire, or using the specified ceramic filtering caps as possible solutions.

I'm not noticing a ton of compression happening. The ratio knob does have an effect on the overall volume. Counterclockwise, quieter (more compression?) Clockwise, louder (less compression?). There's plenty of range on the volume pot to make up the loss of volume. Looking at the schematic, I guess the RATIO is actually more of a MIX?

But as I said, any actual compression and in fact the effect of the threshold, attack and release knobs seems fairly subtle. With the exception of the extreme settings on the range knob.

The LED I have to indicate "GAIN REDUCTION" as per the schematic lights up when the gate is switched on, and goes dim as I strum according to where I have the gate pots set.

If the gate is switched off, the LED is off and doesn't seem to react to strumming. Changing the various compression settings doesn't effect the LED.

[befey]

Playing around some more, I think I've got a better grasp on the controls.

I'm going to replace the caps with ceramic and see if that helps the noise. I've also noticed it goes away slightly when I hold my hand near it. So probably putting it in an enclosure will help too.

I still wonder why the gain reduction LED only works when the gate is on? Is that the correct function? It didn't seem so from the schematic.

Also, when I have the ratio pot all the way clockwise (no compressed signal mixed in?) the output gets quite distorted. That seems strange to me. It should just be a buffered version of the input signal right?

[befey]

Ok, so I replaced all the 10u caps with ceramic ones. That has helped the high pitched whine, but not eliminated it completely.

I also realized I had the "Gate Enable" switch wired incorrectly on my layout. I reversed the leads for that switch. Once that was corrected, the gate and compression work the way I would expect. With the leads the wrong way around, the switch acted as a Gate and Compression enable. Oops.

The RATIO knob still seems to act more like make-up gain than what I would think of as compression ratio or mix.

[rankot]

If you are using 7660, it has two versions - one works at 10kHz and that's probably the whine you hear. Try with LT1054.

[befey]

I used 7660SCPAZ, which does indeed say Switching Frequency:    10 kHz according to Mouser.

[rankot]

That's it.

[befey]

So the LT1054IP I'm seeing has a switching frequency of 25kHz. I guess that would still whine, just higher than audible.

What about TC7660HCPA with switching frequency 120kHz? Then maybe it wouldn't bother passing dogs.

[befey]

Looking at the data sheet for the TC7660HCPA, it looks like it should work. It says you can use 1u caps instead of the 10u.

But it also says that it approaches 100% efficiency if large caps are used. That means leaving the 10u caps I have would actually increase efficiency vs swapping them for the 1u?

[rankot]

So the LT1054IP I'm seeing has a switching frequency of 25kHz. I guess that would still whine, just higher than audible.

What about TC7660HCPA with switching frequency 120kHz? Then maybe it wouldn't bother passing dogs.

LT1054 can work at 50kHz, just add a 10p capacitor. See data sheet.

TC7660HCPA will do the job, if you can get it.

[befey]

Yeah, they're only $1 on mouser vs. 3 and change  for the 1054. Also since I have this vero already built, adding a 10p to the layout is a little more tricky.

[bluebunny]

I used 7660SCPAZ, which does indeed say Switching Frequency:    10 kHz according to Mouser.

This is the correct part.  Any variant with "S" is OK.  But you have to short pins 1 and 8 to get the higher frequency (inaudible) clock.

[befey]

Aha! Checking the data sheet more carefully. I see what you mean. So it looks like I can just run a jumper between pin 1 and 8 and the whine should go away.

[befey]

I added the jumper and this thing works perfectly. No noise, compression seems like what I would expect. I'll follow this up in a little bit with the final layout I used.

[befey]

Ok, I'm calling this one verified.

https://drive.google.com/file/d/1sC7b4FeeRdvqw_m8mgmC96KhnVr5BcW-/view?usp=sharing DIYLC File

[befey]

Here's the jack I wound up using for the switched sidechain input :

https://www.amplifiedparts.com/products/14-jack-stereo-pc-mount-fender-amps-88-99

[KoenT]

I'm unfamilliar with a sidechain input. What is it for?

[bluebunny]

It's for controlling the compression from something other than the input signal.

[TryToImagineThis]

This design looks amazing! Would you be wiling to upload the source Altium files to your google drive, jonny.reckless?

[jonny.reckless]

This design looks amazing! Would you be wiling to upload the source Altium files to your google drive, jonny.reckless?

The PCB Gerbers and NC drill files are on the drive: https://drive.google.com/drive/folders/1uDm68DC3-kBmsD8tjBbgSBP8TAeJKR3r?usp=sharing
Do you specifically want thee schdoc and pcbdoc files from Altium?

[TryToImagineThis]

This design looks amazing! Would you be wiling to upload the source Altium files to your google drive, jonny.reckless?

The PCB Gerbers and NC drill files are on the drive: https://drive.google.com/drive/folders/1uDm68DC3-kBmsD8tjBbgSBP8TAeJKR3r?usp=sharing
Do you specifically want thee schdoc and pcbdoc files from Altium?

Yes, those four Altium files would be perfect!