D-AOC PCBs - the building and help Thread

[ilfungo]

ciao
is possible to use a

Drip Opto T4B Cell in this project?
how i can connect?
Thanks

 

[bernbrue]

no, I would keep it for a Dual LA2a. Vactrols are recomended for the D-AOC. Moreover they are much cheaper than a Drip T4B.
regards
Bernd

 

[ilfungo]

thanks Bernd!
Can someone explain how to connect the Bypass PCB?
I followed the forum but I am not entirely clear

 

[bernbrue]

http://www.groupdiy.com/index.php?topic=26585.80

look at the bottom of page 5. The 3pin molex are for audio input/output, the 2pin molex is for 5V or whatever your relays need.
regards
Bernd

 

[Silvas]

I posted this on some topic on "Studio A". I think it's worthwile to paste it here.

Anyone else running this baby on unbalanced inputs?

I made the transformerless inputs yesterday. When you connect them, the input trafo secondary is completely bypassed. Wow !

I like this comp so much more now. My slight mismatch between channels, was due to the Edcor inputs. I felt that my DAOC´s threshold was a bit too sensitive, but now, and due to the fact i´m going unbalanced instead 600:10K, i have a more manageable threshold range.

Also, i bypassed the 22u solen fast caps with .1 ERO MKP1840.

I don´t feel the need for the lundahls or whatever nice input trafo right now.

I think i´m leaving my DAOC this way. I´m keeping the edcors for balanced input, but, i think the unbalanced inputs are keepers. My cable runs are usually short.

Should i post this on the main DAOC thread ?

 

[jensenmann]

Hello

I've been enjoying my DAOC for a few months and it is a superb compressor on almost everything i throw on it. I still have a question regarding the stereo link...Is there some way to adjust the stereo match as in the D-LA2A ? I'm using the DAOC all the time in dual mono (on stereo material) without any troubles and the matching and metering is great, but as soon as i link the channels, there's a mismatch of a few dB's (GR tracking remains accurate, tho).

Any ideas of where i can start looking ?

Also, i have a very very small difference between channels (0,6dB) without any compression, and i'm using rotary switches...which will be a good point to fine tweak the gain a bit to compensate ? (just for peace of mind)

I was looking at the schemo, and i was thinking, maybe i can tweak the 470k feedback resistors in the output (or input) stage to fine tune the gain ? or there's a better way? (the 49,9k grid resistors?)

Thanks so much !

I have the same stereotracking problem. I did swap many sidechain tubes, all the resistors in the SC are within 1%, measured levels over there are fine, so it seems that the only remaining source of trouble are the optos. The datasheet states a tolerance of 25%, yuk. Matching these would be pretty expensive and a labour of love. Too bad that I didn´t realize that earlier. Now I have built it as stereocomp but in that way it´s not usable for me. In dual mono everything´s fine, though. Now I have a useless stereolink button on the frontpanel that makes me angry every time I see it. 

 

[Silvas]

Hello

I've been enjoying my DAOC for a few months and it is a superb compressor on almost everything i throw on it. I still have a question regarding the stereo link...Is there some way to adjust the stereo match as in the D-LA2A ? I'm using the DAOC all the time in dual mono (on stereo material) without any troubles and the matching and metering is great, but as soon as i link the channels, there's a mismatch of a few dB's (GR tracking remains accurate, tho).

Any ideas of where i can start looking ?

Also, i have a very very small difference between channels (0,6dB) without any compression, and i'm using rotary switches...which will be a good point to fine tweak the gain a bit to compensate ? (just for peace of mind)

I was looking at the schemo, and i was thinking, maybe i can tweak the 470k feedback resistors in the output (or input) stage to fine tune the gain ? or there's a better way? (the 49,9k grid resistors?)

Thanks so much !

I have the same stereotracking problem. I did swap many sidechain tubes, all the resistors in the SC are within 1%, measured levels over there are fine, so it seems that the only remaining source of trouble are the optos. The datasheet states a tolerance of 25%, yuk. Matching these would be pretty expensive and a labour of love. Too bad that I didn´t realize that earlier. Now I have built it as stereocomp but in that way it´s not usable for me. In dual mono everything´s fine, though. Now I have a useless stereolink button on the frontpanel that makes me angry every time I see it. 

But there must be some way of "stereo adjust" it like an LA2A, right ? not a word on this subject.

I just use it unlinked and tracking is great. I don´t think my optos are the problem.

 

[ilfungo]

I have the same problem ...
the two  channels in stereo mode  behave differently ...
there is a way to calibrate in stereo?

 

[jensenmann]

The only way to stereomatch these thingies is to stereomatch the optos. They have by far the worst tolerance spec of all parts in the sidechain (maybe the toobes, too, but not in my DAOC). I don´t see any other way to accomplish stereotracking. Other ideas?

 

[ilfungo]

how stereomatch the optos?
Thanks...

 

[dingo]

hello there
I'm going to construct my first D-AOC and have some question on input and output transformers,
my plan is to use lundahl5402 for output  have two of them here!!
need to buy input tranny and my choice in lundahl1540
any suggestion on wiring those transformers?
thanks!!
dingo.

 

[Silvas]

Today i've opened my D-AOC looking for some answers.

First, my GR tracking is not as accurate as i thought. VU's are showing quite more of the actual measured GR, but that doesn't bothers me too much. Left is showing more GR than right. I can live with it.

Unlinked, both channels respond exactly the same. Linked, there's a couple dB's GR mismatch. I swapped the sidechain tubes, and found a pair that reduced that mismatch to only 1dB when linked. Unlinked remains perfect regardless of tube changed in the sidechain.

Now, to the questions. Which will be the most adequate way of trimming a bit the meter's sensivity, to make it less sensitive in this particular application ? trimmer in series will be OK ? i played with some resistors in paralell but not much change.

Thanks !

 

 

[Script]

Won't be able to start building the D-AOC before next year. Anyway, just a quick idea:

As the optos seem to have 25% tolerance (örps) and we don't want to buy 10 optos or so to find a close enough match, would putting a multi-turn trim across the opto's resistors (the ones near the input) make sense to match their range?

I posted this on some topic on "Studio A". I think it's worthwile to paste it here.
Anyone else running this baby on unbalanced inputs?

I made the transformerless inputs yesterday. When you connect them, the input trafo secondary is completely bypassed. Wow !

I like this comp so much more now. My slight mismatch between channels, was due to the Edcor inputs.

(abridged)

Sounds good. Does that mean simply bridging the transformers or is there an input buffer involved? If so, what does it look like? Maybe it could even be switchable?

s

 

[j.frad]

Hey guys!
Just looking for approval on one point:
There's no reason it should work inproperly without the meter connected right?
I'm thinking of putting only one meter and a switch between channels, or maybe no meter at all since they track strangely...
Am I thinking correctly?
Thanks

 

[seavote]

the circuit willwork without the meter connected. i havent looked at the schematic in a long time, but check to see if you need to jumper the circuit somewhere.

 

[[silent:arts]]

no meter needed, just leave it out.

 

[Script]

Quoting myself here, good lord

As the optos seem to have 25% tolerance (örps) and we don't want to buy 10 optos or so to find a close enough match, would putting a multi-turn trim across the opto's resistors (the ones near the input) make sense to match their range?

On second thoughts I think that matching optos involves more than total resistance, namely attack and recovery time curves. Maybe it's more of an academic than a real-life problem, but I could easily imagine myself running and comparing test signals for an entire week only to decide in the end that perhaps it's best to feed a dual-channel unit with MS rather than LR signals...

Still, a question to all who built a D-AOC: How many Vactrols did you compare to find a pair that is 'satisfactory'?

 

[Silvas]

Sounds good. Does that mean simply bridging the transformers or is there an input buffer involved? If so, what does it look like? Maybe it could even be switchable?

s

No input buffer. The 1/4 jacks i used for unbal input break the signal from the trafo´s secondary and feed it directly onto the pcb, unbalanced.

 

[Script]

Unbalanced input without buffer directly into PCB. Thank you very much, I will definitely try that too

 

[Soeren_DK]

Increase Cx04 from 100nF to whatever you can maximally fit on the PCB. 220nF was the biggest cap I could insert. I wish there was enough space for 1uF, but real estate was too precious on the PCBs and Volker was too stingy with the real estate. Anyway, the diode within the vactrol is a variable resistor which forms a CR highpass filter with that cap. If you increase the cap, the filter frequency lowers and the compressor becomes more sensitive to lower frequencies. Yes, I know everybody wants a highpass switch for side chains like the GSSL's, but you don't need it here, 100nF is too small for many applications. Even worse: If you push the compressor harder, more current goes though the diodes and the resistance lowers so that less compression happens - quite inept, isn't it?

Don't worry, if you double the vactrols the resistance from two parallel diodes does not become lower, because only one diode conducts at a time, thus the other diode becomes an infinitive resistance for the period of a half signal wave (apart from the leakage current).

1. Does it mean that if I install 2 vactrols more I don't need to increase the Cx04?

2. Do I need to compare vactrols?

3. Can I use the Lundahl LL5402 as output trafo?

Cheers
Søren