Re: Shure Level Loc Compressor
Posted: 10 Apr 2021, 02:55
I didn't have a big enough piece of veroboard, so I had to hodge-podge two boards together with some DIP strips as braces. Let's hope it's strong enough!
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Shure - Level Loc Compressor
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Re: Shure Level Loc Compressor
Posted: 11 Apr 2021, 03:51
I'm nearly done with my vero build, but I'm noticing that I am getting some volume drop when I touch the switches & the metal shaft of the pot. What could be causing this, a ground problem perhaps? I don't have it hooked up to my 3PDT PCB yet, which has an option for pulldown resistors on the input & output, would that help?
Re: Shure Level Loc Compressor
Posted: 14 Apr 2021, 22:24
Just finished mine up and it's working great! Threw some drums through it and it did its thing, I can see this being very useful.
Cheers for all the hard work and knowledge bow_and_error and Stolen.
Cheers for all the hard work and knowledge bow_and_error and Stolen.
Re: Shure Level Loc Compressor
Posted: 17 Apr 2021, 00:08
That looks great, kizzer! I like the homage to the original switch on the Level-Loc as well.
It seems we both trended towards the "one big ol' knob" look, although yours looks a bit nicer:
Glad to hear it is sounding good on drums. I've been using it at the end of my chain on guitar and it's the most un-subtle, squashed-by-an-elephant compressor I've played. I think it could use an output volume control for pedalboard use, so I may wiggle one in on the top row of the enclosure.
It seems we both trended towards the "one big ol' knob" look, although yours looks a bit nicer:
Glad to hear it is sounding good on drums. I've been using it at the end of my chain on guitar and it's the most un-subtle, squashed-by-an-elephant compressor I've played. I think it could use an output volume control for pedalboard use, so I may wiggle one in on the top row of the enclosure.
Re: Shure Level Loc Compressor
Posted: 17 Apr 2021, 14:02
Looks great mate!
Yeah I could see this needing an output volume in pedalboard use! I may put one in myself in the future.
Might be worth adding a clean blend/mix control as well? Or using it in the loop of a splitter mixer circuit.
Yeah I could see this needing an output volume in pedalboard use! I may put one in myself in the future.
Might be worth adding a clean blend/mix control as well? Or using it in the loop of a splitter mixer circuit.
Re: Shure Level Loc Compressor
Posted: 17 Apr 2021, 17:44
I'm personally not a fan of Mix controls on compressors, but if you want to try it, irfrench's 500-series adaptation has a good solution. I definitely need to try some mono drums through it though, gotta get that Tame Impala sound!
Maybe u/stolen can chime in, but I'm thinking about putting a pot as a voltage divider after C11. I'll probably try a 50k pot, but am a little worried about the output impedance. Does anybody know how to calculate the output impedance of that Q6 gain stage?
Maybe u/stolen can chime in, but I'm thinking about putting a pot as a voltage divider after C11. I'll probably try a 50k pot, but am a little worried about the output impedance. Does anybody know how to calculate the output impedance of that Q6 gain stage?
Re: Shure Level Loc Compressor
Posted: 23 Apr 2021, 04:30
I'm building this over the weekend. My use case will likely be mixing, not guitar (or mic) stuff, so I want to make it as line level-friendly as possible. Given that it's a 9v effect, my plan is just to reamp tracks through it and output to a DI back into the DAW, but I read some stuff earlier in the thread about I/O buffers and was unsure how or if it was reflected in the final layout (i.e. the one in kizzer's build post).
Could anyone who built it comment on I/O levels? Is this layout at some specific impedance (e.g. instrument or line), or is it in some impedance "no man's land"? Any/all help would be much appreciated.
Could anyone who built it comment on I/O levels? Is this layout at some specific impedance (e.g. instrument or line), or is it in some impedance "no man's land"? Any/all help would be much appreciated.
Re: Shure Level Loc Compressor
Posted: 23 Apr 2021, 17:08
This layout has high-impedance opamp buffers at the input & output, so you should be OK. The Level-Loc is pretty sensitive to the input signal level, so you may want to play with the value of the two PAD switch resistors (R44 & R45). I actually socketed mine so I could change the values for line-level signals, but found that 100R & 20R worked fine.
Because the output impedance is so low (probably under 1kohm), you may not need to use a DI to bring it back into your DAW. The input impedance (aka Load Impedance) of a line-level input on your interface is ~10k or higher. The output impedance (aka Source Impedance) of the pedal is less than 1kohm. You usually want the Load Impedance to be 10x that of the Source Impedance, which works out in this case.
Interestingly enough, I built mine WITHOUT the output buffer, and ran into some high frequency loss when I plugged it into my mixer's Send/Return - likely as the result of the higher impedance output on Q6 (maybe ~10kohms?). I'll have to try it with the buffer & see if that fixes it.
Because the output impedance is so low (probably under 1kohm), you may not need to use a DI to bring it back into your DAW. The input impedance (aka Load Impedance) of a line-level input on your interface is ~10k or higher. The output impedance (aka Source Impedance) of the pedal is less than 1kohm. You usually want the Load Impedance to be 10x that of the Source Impedance, which works out in this case.
Interestingly enough, I built mine WITHOUT the output buffer, and ran into some high frequency loss when I plugged it into my mixer's Send/Return - likely as the result of the higher impedance output on Q6 (maybe ~10kohms?). I'll have to try it with the buffer & see if that fixes it.
Re: Shure Level Loc Compressor
Posted: 29 Jun 2021, 00:17
Hi guys, I've continued to play around with the Level-Loc and wanted something that looked a bit nicer (and with a smaller board footprint). I love the metallic badges from classic Fender Rhodes piano and Tweed amps, so to give it an era-appropriate look, I decided to try making a PCB faceplate. I haven't seen these used too much for effects, but I saw quite a few Eurorack modules that use them to replace expensive etched aluminum or UV printed faceplates.
I used the Inkscape extension SVG2SHENZHEN to format and export a file for Kicad and generated Gerbers there.
This was my first completely DIY PCB, but JLC PCB was easy to use and pretty cheap. Unfortunately, I chose the cheapest shipping option & the PCBs took ages to ship, but I just finished assembling the first one. It sounds awesome! There is sooooo much compression on tap, and I think I dialed the controls in to just the right range.
If you want to hear it, I uploaded some audio demos of drums run through what I’ve named the ‘Level Lacquer'. I've cycled through different Threshold and Release settings so you can hear the difference.
In my tests, the input and output circuitry helps it play nice with guitar, bass or line level signals. And the input pad switch can drop hot signals into a range the FET can play with. The Attack (fixed) and Release settings are incredibly fast, and sometimes signals with a lot of low-end will overwhelm the compressor, but switching to a longer release will clean it right up. The highest Threshold setting (+++) will crush your signal like a lead elephant, which can totally change the feeling of drums.
Overall I’m super happy with how this turned out. My one gripe is that the faceplates tend to pick up fingerprints, and I’d like to protect them and level off the surface finish. Any suggestions on a durable clear finish that would work on metal and soldermask?
I used the Inkscape extension SVG2SHENZHEN to format and export a file for Kicad and generated Gerbers there.
This was my first completely DIY PCB, but JLC PCB was easy to use and pretty cheap. Unfortunately, I chose the cheapest shipping option & the PCBs took ages to ship, but I just finished assembling the first one. It sounds awesome! There is sooooo much compression on tap, and I think I dialed the controls in to just the right range.
If you want to hear it, I uploaded some audio demos of drums run through what I’ve named the ‘Level Lacquer'. I've cycled through different Threshold and Release settings so you can hear the difference.
In my tests, the input and output circuitry helps it play nice with guitar, bass or line level signals. And the input pad switch can drop hot signals into a range the FET can play with. The Attack (fixed) and Release settings are incredibly fast, and sometimes signals with a lot of low-end will overwhelm the compressor, but switching to a longer release will clean it right up. The highest Threshold setting (+++) will crush your signal like a lead elephant, which can totally change the feeling of drums.
Overall I’m super happy with how this turned out. My one gripe is that the faceplates tend to pick up fingerprints, and I’d like to protect them and level off the surface finish. Any suggestions on a durable clear finish that would work on metal and soldermask?
Re: Shure Level Loc Compressor
Posted: 11 Sep 2021, 14:38
Nice work!
It looks and sounds fantastic.
It looks and sounds fantastic.
Re: Shure Level Loc Compressor
Posted: 25 Sep 2021, 21:59
I finally worked up a schematic from changes I made after playing with the original PCB. The biggest changes I made were the addition of an Output Volume control before the output buffer, and a modified Pad switch circuit for lower noise & to suit a better range of inputs. In addition, I added a hefty power filtering mod from the Drewtronics Sherlock as this circuit is quite prone to noisy power supplies & interference. There are also some small changes including the addition of input & output pulldown resistors + a few values changes.
I am still having some intermittent trouble with distortion, which seems to be fixed by power cycling. Any ideas?
I am still having some intermittent trouble with distortion, which seems to be fixed by power cycling. Any ideas?
Re: Shure Level Loc Compressor
Posted: 26 Sep 2021, 20:18
Are your polarized caps oriented the correct direction?
R25 is 22k on the schematic. If you are indeed using 22k (instead of 2.2k), that may raise the voltage at C9 to be more positive on the negative side.
It may be worth checking all the polarized capacitors to make sure they are oriented the correct way. I can't think of any other reason "power cycling" would cure a distortion issue.
This is a cool project. I plan to mess with it. Thanks for the hard work!
R25 is 22k on the schematic. If you are indeed using 22k (instead of 2.2k), that may raise the voltage at C9 to be more positive on the negative side.
It may be worth checking all the polarized capacitors to make sure they are oriented the correct way. I can't think of any other reason "power cycling" would cure a distortion issue.
This is a cool project. I plan to mess with it. Thanks for the hard work!
Re: Shure Level Loc Compressor
Posted: 27 Sep 2021, 16:49
Thanks bmxguitarsbmx! I'll have to double check the cap polarities as I remember having to fix one during assembly and not being 100% sure on it.
I think you're right on R25. If I remember my simulations, the voltage across C9 was low, but possibly a different sign on the build vs. LTSpice.
I think you're right on R25. If I remember my simulations, the voltage across C9 was low, but possibly a different sign on the build vs. LTSpice.
Re: Shure Level Loc Compressor
Posted: 27 Sep 2021, 17:50
This is just AWESOME!! Oh, man.... is there any possibility to share that beautiful PCB?bow_and_error wrote: ↑29 Jun 2021, 00:17 Hi guys, I've continued to play around with the Level-Loc and wanted something that looked a bit nicer (and with a smaller board footprint). I love the metallic badges from classic Fender Rhodes piano and Tweed amps, so to give it an era-appropriate look, I decided to try making a PCB faceplate. I haven't seen these used too much for effects, but I saw quite a few Eurorack modules that use them to replace expensive etched aluminum or UV printed faceplates.
I used the Inkscape extension SVG2SHENZHEN to format and export a file for Kicad and generated Gerbers there.
This was my first completely DIY PCB, but JLC PCB was easy to use and pretty cheap. Unfortunately, I chose the cheapest shipping option & the PCBs took ages to ship, but I just finished assembling the first one. It sounds awesome! There is sooooo much compression on tap, and I think I dialed the controls in to just the right range.
If you want to hear it, I uploaded some audio demos of drums run through what I’ve named the ‘Level Lacquer'. I've cycled through different Threshold and Release settings so you can hear the difference.
In my tests, the input and output circuitry helps it play nice with guitar, bass or line level signals. And the input pad switch can drop hot signals into a range the FET can play with. The Attack (fixed) and Release settings are incredibly fast, and sometimes signals with a lot of low-end will overwhelm the compressor, but switching to a longer release will clean it right up. The highest Threshold setting (+++) will crush your signal like a lead elephant, which can totally change the feeling of drums.
Overall I’m super happy with how this turned out. My one gripe is that the faceplates tend to pick up fingerprints, and I’d like to protect them and level off the surface finish. Any suggestions on a durable clear finish that would work on metal and soldermask?
Re: Shure Level Loc Compressor
Posted: 27 Sep 2021, 20:39
I may in the future, but I don't have it a build doc or anything, so it would be kinda hard to follow without a bunch of work on my side. I've built a few for friends, so once these run out maybe I'll make an updated PCB + docs!
Re: Shure Level Loc Compressor
Posted: 02 Oct 2021, 15:46
The envelope generator reminds me a bit of the Ross Compressor one so it makes me think, is there a way to add attack and release controls for this?
Re: Shure Level Loc Compressor
Posted: 02 Oct 2021, 18:05
The sidechain shares a lot of similarities with other compressors like the Ross, as it's a simple full-wave rectifier. Q7 acts as a phase splitte, with the fully rectified control signal tapped from the Q8/9 collectors.
The currently Release control is a switch that increases the Release time by adding either C27 or C28 in parallel with C14. You could try a low resistance potentiometer to blend between different caps, but I've found the 3 Release settings to be enough variability.
A defining characteristic of a FET compressor is it's ridiculously fast Attack time, which is ~500uS. You could try increasing it, but the circuit likely won't support the kind of Attack times you'd get from an opto or OTA compressor. If I remember correctly from playing around in LTSpice, changing the Q8 & 9 emitter resistors (R33/34) did have some effect on the Attack time, and R31/32 may do the same.
The currently Release control is a switch that increases the Release time by adding either C27 or C28 in parallel with C14. You could try a low resistance potentiometer to blend between different caps, but I've found the 3 Release settings to be enough variability.
A defining characteristic of a FET compressor is it's ridiculously fast Attack time, which is ~500uS. You could try increasing it, but the circuit likely won't support the kind of Attack times you'd get from an opto or OTA compressor. If I remember correctly from playing around in LTSpice, changing the Q8 & 9 emitter resistors (R33/34) did have some effect on the Attack time, and R31/32 may do the same.
Re: Shure Level Loc Compressor
Posted: 02 Oct 2021, 18:13
You are correct on the release control capacitor switch and thank you for confirming my suspicions regarding the envelope generator bit, the idea was not to make the attack faster, but slowerbow_and_error wrote: ↑02 Oct 2021, 18:05 The sidechain shares a lot of similarities with other compressors like the Ross, as it's a simple full-wave rectifier. Q7 acts as a phase splitte, with the fully rectified control signal tapped from the Q8/9 collectors.
The currently Release control is a switch that increases the Release time by adding either C27 or C28 in parallel with C14. You could try a low resistance potentiometer to blend between different caps, but I've found the 3 Release settings to be enough variability.
A defining characteristic of a FET compressor is it's ridiculously fast Attack time, which is ~500uS. You could try increasing it, but the circuit likely won't support the kind of Attack times you'd get from an opto or OTA compressor. If I remember correctly from playing around in LTSpice, changing the Q8 & 9 emitter resistors (R33/34) did have some effect on the Attack time, and R31/32 may do the same.
Re: Shure - Level Loc Compressor
Posted: 27 Oct 2021, 04:47
Hi, Looks like you just used the Auxout of the circuit. Did you tried using de regular out ? (The E point in the original schematic)
Re: Shure - Level Loc Compressor
Posted: 27 Oct 2021, 04:54
r10 value shound't be 4.7k instead of 47k according to the original schematic?