D-AOC PCBs - the building and help Thread
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bernbrue
Well-known member
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
regards
Bernd
bernbrue
Well-known member
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
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
Well-known member
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?
Anyone else running this baby on unbalanced inputs?
jensenmann
Well-known member
Silvas said:
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
Well-known member
jensenmann said:Silvas said:
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.
jensenmann
Well-known member
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?
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.
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
Well-known member
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 !
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 !
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?
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
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?
(abridged)Silvas said:
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
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
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
Well-known member
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.
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[silent:arts]
Well-known member
no meter needed, just leave it out.
Quoting myself here, good lord
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'?
Script said:
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
Well-known member
Script said:
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.
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
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
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