500 series Level-Loc project

[Bobby Baird]

@Bobby Baird wow, thank you for all that info! Very helpful indeed!

Okay, so to sum up, it would look like this, right?

Bypass - DPDT on-none-on
Threshold - DPDT on-off-on
Release - SPDT on-off-on
Pad - SPDT on-off-on

YES

IC1 - THAT1246

Yes

C17-C20 - 0.1uF electrolytic caps

Yes

Out of curiosity, you show a picture above that appears to show several ceramic caps connected between Input and Chassis ground. Would you mind elaborating on what that is? Is that also to do with the 1246, or unrelated?

From THAT 1240 series datasheet

To reduce risk of damage from ESD, and to
prevent RF from reaching the devices, THAT recommends
the circuit of Figure 4. C3 through C5 should
be located close to the point where the input signal
comes into the chassis, preferably directly on the
connector. The unusual circuit design is intended to
minimize the unbalancing impact of differences in
the values of C4 and C5 by forcing the capacitance
from each input to chassis ground to depend primarily
on the value of C3. The circuit shown is approximately
ten times less sensitive to mismatches
between C4 and C5 than the more conventional
approach, in which the junction of C4 and C5 is
grounded directly.

 

[JMan]

Very cool! I had seen that on the datasheet but had been totally obtuse as to its application. Presumably you feel that this is worth doing in this circuit, since you in fact did it, and so I think I will too. Do I understand correctly that this modification is independent of the rest of the components on the board? (i.e. it doesn't require changes elsewhere)

 

[JMan]

Hey @Bobby Baird , first of all, thanks for your help so far on this! I've taken your suggestions, and I'm nearly done with the build, although I had to reorder some switches because the SPDTs that I got ended up being momentary in one position (info which was so deeply buried in one of those million-mile-long cover-all-variants data sheets that I totally missed it).

Anyway, I was thinking of using your .fpd for the front panel. However, I noticed that the indications on the panel are a bit different from the .dxf provided by @Eliani (specifically the release and threshold controls, which on Eliani's are pretty much linear from left to right), and I'm wondering if this represented further modifications that you made to the connections. The pad values are different as well -- wondering if this is to do with the 1246 vs 1250?

 

[Bobby Baird]

Hey @Bobby Baird , first of all, thanks for your help so far on this! I've taken your suggestions, and I'm nearly done with the build, although I had to reorder some switches because the SPDTs that I got ended up being momentary in one position (info which was so deeply buried in one of those million-mile-long cover-all-variants data sheets that I totally missed it).

Anyway, I was thinking of using your .fpd for the front panel. However, I noticed that the indications on the panel are a bit different from the .dxf provided by @Eliani (specifically the release and threshold controls, which on Eliani's are pretty much linear from left to right), and I'm wondering if this represented further modifications that you made to the connections. The pad values are different as well -- wondering if this is to do with the 1246 vs 1250?

Yeah his panel design to my knowledge was incorrect in the layout. Threshold controls by switch position can easily be determined by voltage divider. More resistance to ground more signal. Switch center I found to be normal. Throw to the left was more or crunch, throw to the right was most or crush.
Just use your continuity meter to trace the circuit voltage divider to the switch pad. This will tell you the relationship to the switch. Same with the release. Bigger cap longer release. The values are in parallel with the center posistion 1uF cap c14 so they add up. 1uF fast 2uF medium 5.7uF slow. So, if 1uF is the center of the switch there is no way Eliani's panel layout is correct. Pad, I determind by just pasing a sine wave through at unity center switch position is your default, so why even give it a reference? I saw a -20db drop on my cubase meter when switched to the left and -10 to the right. Just get yours built up and confirm for yourself. Fill free to use the panel or change anything. Eliani's panel mounting holes to secure the panel to the rack were not even centered correctly. I fixed that in my fpd file.

 

[Bobby Baird]

Correct me if I'm wrong.

 

[Bobby Baird]

Only mods I made were the 1246 input for unity in bypass .1uf op-amp power bypass caps, and the card edge connector RF filter.

 

[JMan]

Correct me if I'm wrong.

Edit: I only saw your last two posts at first. Just read the one before, and am up to speed! Thank you!

 

[JMan]

Finally got a panel made (many thanks to Frank for his great work) and racked this up. Still needs permanent knobs, but it’s otherwise finished and working as expected!

The discussion above is correct, this front panel layout more accurately reflects what the switches do.

This is quite the dirty compressor, as advertised! So far I’ve run a kick and a snare through it and gotten some really cool sounds, and the mix knob is quite useful. Just for fun I sent some mono program material through it, which is like, not a good choice, but I got a chuckle out of it nevertheless. A very fun and funky bit of kit for the arsenal!

 

[MonoCutter]

Looks really good!

My low budget panels from tube-town arrived this week and i'm also undecided for the knobs.

 

[JMan]

I kind of like those knobs you’ve got on there, and I love the Lego man!

 

[Forcemusicgroup]

Where can I get one of these

 

[Forcemusicgroup]

Bump

 

[MonoCutter]

https://groupdiy.com/threads/level-lock-500-series.73844/
Hi, you can ask Eliani if he still has a few pcbs.

 

[manulaudic]

So I've built it as well, following all the mods here and the ceramic cap filter on input with 1246 but I am getting really high pitch noise...
Here is a small clip where first is the unit with no audio and mix 100% wet then I turn the knob to 0%, noise goes away and drum loop sounds good (you can hear low noise but that's because I didn't have the unit attached to chassis" then I drive the Wet knob back to 100% and it's crushing like hell (love it) but the noise is really loud...

If anyone can help me I'd greatly appreciate it !

Manu

 

[Bobby Baird]

Without the unit in a chassis testing on bench it will make a lot of noise. Especially when you touch the bare metal. The boards implementation of ground plane and supply trace layout is a contributor most likely. Although with a device of this nature any noise is going to be amplified by the limiter. These units are just noisy that's part of its character. Try it in chassis with some knobs to isolate touch.

 

[manulaudic]

thanks but it was in the chassis, the hub as i mentioned was just because i didnt have the screws in there but when i screwed it in place the hum Ground disappeared. Though the hiss noise is there constant when the mix is anything but 0%...

It's a little unusable like this, i don't know how you guys use it if it picks up so much high Frequency noise. Anytbing else i could try?

 

[JMan]

This unit is inherently noisy. It’s not a utility comp, for sure, it’s for when you want something grungy and bad-in-a-good-way. I remember trying the Soundtoys Devil Loc plugin for the first time and being shocked at how low fidelity it was, to the point that I initially thought it was “unusable,” as you said. These days I look at this thing (the plugin and now the hardware) as an effect more than a true dynamics tool. There may be ways to reduce the noise floor, but honestly I think that effort would be better spent on building another compressor that is already designed to achieve what you’re after.

 

[manulaudic]

I hear you guys, and I've used the real level loc as well as the soundtoys but they do not have that loud noise. It's not just hiss... It's clearly a pitch noise if you have had a chance to listen to the file I attached.

Noise floor on this would not be a problem, I use guitar pedals in mix all the time and they sound this way too but now I am hearing more of a power supply noise or something.

But I guess everyone is having that same noise ?

 

[MonoCutter]

Hi,
i build two, but only tried out one yet. It's also noisy, but without the tonal component that i heard in your soundfile. Mine has no mods.

 

[Bobby Baird]

You could try the sherlock filter mod I posted on post #204. See if that works. I haven't tried it yet.