D-AOC PCBs - the building and help Thread

[Hobbyist]

@Script Many thanks for sharing the magic. Lots of inspiration for my second unit.

the image below is how I made mine some years ago. 1 slope switchable with 5 default settings ( I ) and 5 settings ( II ) with a 5 pin socket to test out with less pain. Everything installed on a board with lots of molex stuff.

I've tested my unit to mid/side passively with LL1540 because i was too curious, and it works great to my surprise, thinking to make it switchable with tons of relays but i'm afraid the PSU can't handle it. i'm using this mostly hybrid in the digital domain and it sounds so good to compare with digital emulators.

I was lucky enough to work years with my unit on a daily base without safety resistors . Thank you for the input everyone !

Long live this unit and community.

 

[boji]

But mind you the schematics, circuit idea and basic mode of operation is patent-pending, I claim.

I'd layout some best combos over a 10 pos switch, and call it "Threshknee" or "Kneshhold"

 

[Script]

I'd layout some best combos over a 10 pos switch

Absolutely. I wanted a pot, but the pot can be replaced by fixed resistor values. Also I wanted the three LEDs on the faceplate, so my rotary works by bridging/shorting out components, rather than switching them into circuit. (Default setting is two LEDs in circuit.)

 

[Script]

Also, I tube-rolled the unit -- to little avail cos of NFB, as I mentioned before. Finally settled for 5965 in place of 12AT7, as mentioned by Analag somewhere back in 2008, which sounds a tad more interesting to me.

 

[fragletrollet]

Good to know. I've got a set of 5965's to try with my unit, that is currently residing in my girlfriends closet awaiting a front panel for final assembly.

 

[analag]

My baby has grown up. Nice.

 

[living sounds]

A vactrol died in one channel of my D-AOC fit with two vactrols per channewl, so I modified it back to using a single vactrol per channel, since the original ones are now unobtanium. Now the threshold is way too high to get compression action even at the lowest threshold pot setting.

@ Script: I'm afraid I don't grok your hand-drawn schematic. The curve plots you posted look flatter than the ones from the original posting by silent arts. Is there more going on than a LED added to the sidechain part of the vactrol in antiparallel? Is there maybe one simple mod to make the slopes almost like the original, but with the threshold reaching lower? I've read through the thread and couldn't find anything conclusive. I'm not looking for a complex network of possible combinations and extra front panel real estate here. What should be modified in the original schematic to more or less simply lower the threshold overall?

Thanks!

 

[Script]

What is the limiting ratio with two Vactrols? I wouldn't know cos I never tried it. Would like to know too.
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The THR sits at -22dB in my plots cos I used input TX with ratio of 1:2. Should I need lower THR, I simply send hotter signal into the unit. But could also use 1:4 input TX (additional benefit of better signal to noise).

In my unit, with all the added circuitry and at 'normal' input level, the max limiting action ranges from about 5:1 to 11:1, I think.
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With just one vactrol, the threshold is very high, yielding little to no limiting (see 'No Mod' in the original slope mod chart). Could drive input higher with 1:4 TX. Or use the slope mod chart and add the component that 'sounds' best to you.

The steepest (=most limiting) I see is LED red in parallel. LED blue anti-parallel is less steep but has lower THR, while resistor 1K is steeper but has a softer knee (which was important to me).

I ended up using LED orange in anti-parallel as basic mod/substitute cos I didn't have a third and fourth Vactrol. Does it behave the same as two Vactrols? I don't know. And in my case it's actually thru series of 1K minimum into LED orange.

Next step for me was to use 1K minimum in series with LED red in anti-parallel -- if I grok my schematics correctly . Easy to tell if LED is really in anti-parallel cos it starts to light up.
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To my ears, this unit does not serve for heavy limiting cos of the fixed attack (described by someone above as getting 'clicky' under heavy limiting). I use it for rather mild condensing. And with the added circuitry I can intuitively set the balance between the range of condensation and sharp transient attacks slipping thru (at least that's what I think I hear ).

 

[living sounds]

Thank you, I'll experiment some more.

 

[Script]

Please report back

And would you have time to plot your channel with the two working Vactrols? For you to compare when adding stuff to your non-working channel, but also I'm just curious...

...as I still have an empty slot on my rotary, but never sat down to roll by myself, compare and match more 'optos'..

 

[KrIVIUM2323]

A vactrol died in one channel of my D-AOC fit with two vactrols per channewl, so I modified it back to using a single vactrol per channel, since the original ones are now unobtanium.

Nope chinese clones are availlable as Xvive Vtl5c4/2.
I initially was skeptical about the product but got some (other ref vtl5c9) and they are not worst than original vactrols i compared them too, so i'm pretty sure it will be true for the 5c4/2 too. And afaik they are ROHS compliant ( which surprise me but if it's true then it's for the better).
You can order them there if in EU: https://www.banzaimusic.com/xvive-vtl5c4-2.html

 

[Gold]

I ended up using two vactrols for the detect circuit but only use one vactrol for the limiting action. That way the side chain is full wave rectified but the compression is smoother with only one vactrol. I always felt like two vactrols, even if they were matched closely, were fighting against each other.