500 series Level-Loc project

[Eliani]

Hey Guys,

great to see you guys are still interested in this project, I know that's why I picked it up. I am not really finished with this project because I would like to re-introduce a transformer-based I/O and I'm not really liking the not-so-true bypass, the layout has changed a bit already so I guess you guys would like to go with Rev002?

So while I finish this project how about we make a list.

- SKJGProject: 2
- electrisizer: 2
- Winetree: 4
- mishagolin: 2 (maybe)
- manulaudic: 1
- Gianni: 2
- Madreza: 4
- SubhumanRecords: 2

Total: 19

for those who might be interested, I'm actually selling 3 of the finished Rev001's on the black market: https://groupdiy.com/index.php?topic=73844.0

 

[madreza]

Hi
interested in 4

 

[Winetree]

No hurry here. Make it great.

 

[Eliani]

Hi
interested in 4

added to the list

 

[SubhumanRecords]

I’m in for 2 boards.

 

[Eliani]

I’m in for 2 boards.

Noted

 

[Eliani]

Hey guys,

just a quick follow up...
I'm trying to gain some real estate for the true bypass waiting to be put on the board so when there's no power to the unit, or the 500-rack for that matter then all audio will pass the unit..

 

[Eliani]

still not finished with this project, but I've found it hard to find time to do so. I do have 10 of the first revision PCB's available...
so I'm thinking €25 each plus shipping...

 

[grid_stopper]

decided to build myself a pair of these, but i dont have a 500 rack, so i slightly altered the etch file, knocked together a PSU, and called it a day. still a few bugs to chase out, but im extremely pleased so far.

EDIT: wow those are jumbo let me resize lol

 

[manulaudic]

still not finished with this project, but I've found it hard to find time to do so. I do have 10 of the first revision PCB's available...
so I'm thinking €25 each plus shipping...

I'm interested for 2 ! would you have front panels as well? Anyone?

 

[Miami Nice Studios]

i would be interested in 1 pcb + front panel as well.

 

[Jeremy.Starseed]

In my very limited spare time I finally managed to finish these yesterday.
Nice and easy build. Big thanks to Ian and Marek. Would also like to thank "Indecline" for the Mouser cart
I based my own cart from.

They sound cool when you don't hit them too hard. I find them rather noisy though. I ended up not using
my sleds that I bought, maybe I should to screen them more. Also touching the controls makes a little buzz.
It doesn't ruin the performance, but do anyone have a tip to make them less sensitive and less noisy?

Best regards
//Magnus

Hi. Would you care to pass on this Mouser cart, or point me to it?

Would be most appreciated

 

[irfrench]

Oh man, its been a long time since I visited here!

Those boards looks great - thank you for keeping it alive and moving it on!


Ian

 

[Aleguitarpro]

I bought PCB+panel from Eliani and finished.

Testing it I have 2 doubts that I'd like to check to people who completed it, too.

Is normal having a lot of hiss/noise with mix control at 100%?
I measured about -65dBu of noise with mix at 100% and input gain at "on".
Changes a little putting input gain at max.
I used ina134/drv134. Transistors listed on BOM.
Everything works as it should but there's this hiss/noise above 10khz.

Another thing I noticed is that is difficult to make an A/B before and after this processor because level is always lower compared to dry signal (is possible to compensate this with mix knob adding more dry signal to compressed) but I'm wondering if there's something strange in my build or this project works in this way.
When I put in bypass sounds always louder until I reach 9 o'clock on mix control (but at this point I'm listening the same uncompressed signal passing through the processor).
It's usable in tracking in my opinion but it's difficult to integrate in mixing due to this hiss and this discrepancy in levels.
I only have to know if this is normal or not.

Thanks for reading

 

[Aleguitarpro]

Ok, I did my homework.
As noise didn't change moving input control I started checking signal in various points.
I found that everything works as it should before ub-ret point (all discrete part works).
In schematic r43 is indicated as a double value (10k or 3k3).
Noise increase a lot because ic3d boost 12dB with 3k3 indicated in BOM letting this noise very high in my build.
Reading this thread 3k3 was used to compensate signal loss of compression to let blend part works better but as I already wrote with mix at 100% I still have a signal loss.
I know that Shure original circuit isn't on clean side but I'm wondering if it's possible to reduce this hiss/noise (is like a 12dB boosted 1176 at max output).

 

[Eliani]

I bought PCB+panel from Eliani and finished.

Testing it I have 2 doubts that I'd like to check to people who completed it, too.

Is normal having a lot of hiss/noise with mix control at 100%?
I measured about -65dBu of noise with mix at 100% and input gain at "on".
Changes a little putting input gain at max.
I used ina134/drv134. Transistors listed on BOM.
Everything works as it should but there's this hiss/noise above 10khz.

Another thing I noticed is that is difficult to make an A/B before and after this processor because level is always lower compared to dry signal (is possible to compensate this with mix knob adding more dry signal to compressed) but I'm wondering if there's something strange in my build or this project works in this way.
When I put in bypass sounds always louder until I reach 9 o'clock on mix control (but at this point I'm listening the same uncompressed signal passing through the processor).
It's usable in tracking in my opinion but it's difficult to integrate in mixing due to this hiss and this discrepancy in levels.
I only have to know if this is normal or not.

Thanks for reading

Sorry about answering this late.... but in your picture you did not jumper UB_OUT to UB_OUT2 (maybe you did on the bottom?
As I wrote answering your email, I did not experience this hiss. But I did use all PCB soldered switches, make sure they are just connected as if they were on top of the PCB. There are no wires that should cross.

level loc workings:
The "Level-Loc" Audio Level Controller is basically a
low-noise preamplifier with unity gain from the microphone
level input to the microphone level output or
60 dB of voltage gain from the high-impedance microphone
level input to the auxiliary level output. The
input and microphone level output contain matching
transformers so either high- or low-impedance operation
may be selected. In addition, a high-impedance
auxiliary output is provided capable of driving any
high-impedance amplifier, mixer or tape recorder input
requiring 1 volt or less. This preamplifier has the additional
capability of reducing its gain as the input
signal increases, thereby holding the output signal
constant. After a predetermined input level threshold
is reached the output level is "locked", that is, it
remains constant even if the input signal increases
by as much as 100 times (40 dB). This reduction in
gain, which results in a constant output level, is
obtained without introducing significant distortion or
transients into the program material. The DISTANCE
SELECTOR switch determines the input level at which
gain reduction (Level-Loc action) begins."

if the problem persists, you could take the blend/mix function out of the circuit completely by jumping UB_IN to UB_SND and UB_RET to UB_OUT, thus going back to the original circuit... this will detach the input PAD, mix potentiometer and the bypass circuit, but it might tell you where to look next...

 

[Aleguitarpro]

Thanks for answering.
I tried to remove blend/mix circuit and I tested only this part of the circuit.
Blend/mix circuit add part of this noise because it boost wet signal in order to "make up" level and blend it to dry signal.
However, noisier part is original part of circuit and I'm only asking if it's so high noise in general in other builds.
I changed and tested everything and nothing changed or improved exchanging parts (in general, capacitors and transistors/fet).
I'm attaching a short audio of my unit. I'm changing Threshold during file because is the only parameter that affect the noise.

Please can someone who build this unit confirm if it's normal or not?

This is my settings:

MIX 100%wet
PAD doesn't affect noise
INPUT doesn't affect noise
I'm changing only threshold during file

Thanks

 

[Eliani]

Ale,

I've asked a budy of mine to listen for this noise in his pair of level locks I built for him. because he wanted them to operate them atmic-level.
But the cuircuit, including the pads, was adapted to be used at line-level. so maximum level input will bring you less moise I presume.

 

[Bobby Baird]

I finished mine they are a bit noisy. I get 60hz hum when I touch the switches. Evident on spectral graph.

 

[Aleguitarpro]

I had this noise when I had module outside lunchbox. Inside lunchbox not.
You can solve when you are testing them connecting with an alligator clip cable your audio gnd and a toggle or panel or pot body.
Have you measured total noise ? It's similar to mine?
I posted an audio file with total noise. Please can you listen it and compare to your build? I changed and tested all part of the circuit in order to understand if it depend on the project or in any part I used in mine...