D-AOC PCBs - the building and help Thread

thanks for the reply:
"what's your (loaded) regulator output voltage?"

165V (see the diagram in previous post)

"the neon bulb doesn't need to light (and won't with only 51V)"
the neon lights with 51Vs . left does not?

"not compressing: you need a really hot signal at the input in "stock" mode."
I'm using the full wave Kubi mod. i should have mentioned this. the over all gain of the unit does seem low. i cant really judge as im putting it through an unfamiliar amp at work. i am using a dynamic mic to test with but input is full up and theshold knob ,compression, is full up .

"do you have an oscilloscope?
put the probe at the right pin from the stereo link connector.
can you see a signal there?"

i have no oscilliscope. i do have access to one however and i knew there would come a time  to learn how to use one.(i learn more with every project, more on this project and the tube mic i had to troubleshoot than the projects that worked on first try). i did check the stereo link for continuity and all was fine. i'll get that oscilliscope. familiarize myself with it and perform the test you suggested. thanks for the ideas.
                              chris v

Hi Chris,

looking at the measuring  I doubt a dynamic Mic will have enough output to make it compress, even with the Kubi Advanced mods.

one other thing to check:
remeasure the voltages of the good channel with the tubes of the other channel removed.
any changes?

Chris, my version has several of the Kubi mods ( cap changes etc ) and a 1:5 Lundahl input transformer.
Even so, with a quite meaty DI'd bass on input I have to have the compression control at 2 o'clock to
get any compression !
From a dynamic mic ( this isn't mic-pre type gain at the front ) you will have nothing going on, just not
enough level going in to compress.
It's expecting balanced line level input to do it's thing.
Best of luck with the voltage problems, you will find the reason for that - what are your voltages after the
regulators looking like ?

MM.

the link to "the kubi advanced version" on the first page doesn't work. Can't find it. Would be nice to see what the mod does.

ChrioN said:

the link to "the kubi advanced version" on the first page doesn't work. Can't find it. Would be nice to see what the mod does.

Click to expand...

Perhaps there is a reason for Kubi's version details being deleted, I would suggest sending him a PM ( Darius )
and ask if you can get the details for this mod.

MM.

ChrioN, I've got it in a Word format!
pm me your email, I will send it to you.

cheers.
Jr.

It's still on his website....

http://audio.kubarth.com/daoc/

dagoose said:

Not sure if it may have come up before but i wanted to let you all know.

Last night one of my channels let me down, no sound coming through.
troubleshooting a stereounit is quite simple and so i soon found out that i had a dead R105 (R205) 47k resistor.
When i looked at the schematic i found out (already measured that) that is quite an important resistor for the high voltage of the tubes and i thought it was a bit strange to see it's just a 1/4 watt resistor.
Could it be that it burned down because of the high voltage/power it's handling? Didn't really check if it runs hot though, it's back in the rack again.  ;D
I didn"t have any 47k's at hand so i paralled 2x 100k to get 50k which did the job (did this on both channels) and with that i also doubled the wattage of the resistors.
So.. are 1/4 watt's ok here or should it indeed be bit higher?

Click to expand...

strange, because i had the same fault on one of my channel
few weeks ago, one channel had a fault, no sound coming thru.
i thought that a tube brokes, and i bought some new.
yesterday i opened the DAOC to repair that channel.
after swapping some tubes, that one channel still have that fault.
next step was tracing the signal from the input to the output.
the first tube stage gives no output.
diagnose: no B+ supply on the ECC81 tube (V101A) caused by a broken 47k resistor (R105)
you can't see visually damages on the resistor, but after measuring the resistor is definitly broken.
i measured on the other (working) channel the voltage drop in the 47k resistor (R205) and i measure 108V
that gives a power rating of 108*108/47k = 0,248W.
i think a 0.5W (or parallel, serial two right resistors) gives a better lifetime
because i had my DAOC almost one year in use and nothing happened.

in this way i can mod a little bit. i will replace my current 1:1 input transformers to 600:10k.
and one channel with kubis mods (increasing some cap values) to can make a listening comparison.

I may have a problem with my D-AOC's input.
I used Lundahl LL 3815's wired as 1 : 5 and when sending a balanced input from my DAW
this seems to "bottom out" quite easily IE: There's bottom end "thumps" and distortion, unless
input gain is reduced by about 6 to 8 dB.
It's working fine otherwise but makes switching between D-AOC / Pico / GSSL for mastering comparisons a
little fiddly.
Should I replace with something that's perhaps a 1 : 2 stepup ?? .... or just leave the input gain down on
the D-AOC  ( worried about noise s/n ratio etc )

Ta,

Marty.

can't find a datasheet for the LL3815 

mhm, the input control is after the transformer.
same symptoms with no compression (threshold all down)?

[silent:arts] said:

can't find a datasheet for the LL3815 

mhm, the input control is after the transformer.
same symptoms with no compression (threshold all down)?

Click to expand...

It's all fine if I reduce the DAW output but the other units seem to accept this level with no problems.
It's the same with no compression, just seems like an input gain issue.
I will look at my gain structure a bit more, here's the LL3815 details that I have :

• 
LL3815 is a small mu metal core microphone / line input transformer, turns ratio 1+1 : 5
•
• Usage, 1 : 5
•
• In+ pin 1 + pin 4
• In- pin 2 + pin 3
•
• out+ pin 8
• out- pin 6
• Shields pin 5
•
• no pin at 7

[silent:arts] said:

It's all fine if I reduce the DAW output but the other units seem to accept this level with no problems.
It's the same with no compression, just seems like an input gain issue.

Click to expand...

oh, I might have misunderstood reducing the "input gain"
you don't mean the D-AOC input control?
you mean lowering the output of your DAW?

this makes more sense.

MartyMart said:

LL3815 is a small mu metal core microphone / line input transformer, turns ratio 1+1 : 5

Click to expand...

does not sound like this transformer can handle too much input level.
+4 and more dBu at 1:5 is a hard job for a "small" transformer, especially if build for low microphone levels.

Marty, you could try rewiring it to 2:5, or just put a PAD in front.

Hi Volker, thanks for the "tips" - I'm actually hitting it quite hard from my system, so in
a mix situation with some "headroom" at the DAW end I think it will be OK.
I was checking with a "maximized" stereo mix and it was quite "FULL ON"  !!!

If I get more issues down the line, I can simply swop the transformers for something a
bit more "beefy" as I have a set of Edcors for this and some bigger 1 : 2 Lundahls too.

Sounds wonderful with tracks through it and not even compressing !! ... hmm ..... Valves

MM.

hello after making some progress with my project i hoping some one more knowledgable may help diagnose my builds problem. right channel works fine. the left channel seems to do everything it should except compress. had the same input going into the left channel that allowed the right channel to compress so it shouldnt be an issue of input level. i've checked r111 and r127 by removing one leg from the board.changed the neon bulb to a 1n5371. the main symptom that presents itself and is probably a good clue to finding the error in my build is that the voltage on the zener diode side of r127(where i should be getting 62V according to the posted voltage values) is variable when i adjust the trimmer RV104. my next attempt is to replace the trimmer. but i've already lost two pads on the pcb while doing some of kubis mods and repairing the PSU etc so if any one has an idea based on the symptoms please let me know. the readings are the same with the meter attached to the board or not. stereo link attached to the board or not and with the stereo link switched on or off. tubes in or out.  thanks for any ideas
chris v

Hi Chris,

the voltages around the neon / zener doesn't affect compression, this is only the metering circuit. I doubt replacing the RV104 will change anything - the variable voltage there is fine, it is to null the meter.

if it passes audio fine, and does anything expect compression there are only two possibilities:
- a faulty vactrol
- an error in the sidechain amp
compare the signal from both channels (referenced to GND / PL102 Pin1) with the same input signal at PL102 Pin2 (stereo link)
Threshold pot (RV102) comes in mind too.

thanks for the "heads up" (us slang only?) u
after some more thought i did relize the trimmer was probablynot the problem,but did n't know where else to start looking.

"the variable voltage there is fine"

i thought it was significant because the right channel (the working channel) does not show this behavior.
i believe i checked out rv102 but i've done so much poking around with my DMM i'm not sure. i'll start there to make sure.

compare the signal from both channels (referenced to GND / PL102 Pin1) with the same input signal at PL102 Pin2 (stereo link)
i dont follow what your telling me. pl102 is stereolink connector yes?
compare dc Voltage readings?  ac readings with an audio signal present? wave form with a oscilliscope, as discribed above?
also pin 1 of stereolink is not connected to ground on my build. since it is not used i thought it would make no difference. your just using it for reference to ground in this instance yeah?
sorry im so "thick" (more slang)

no englsich us slang from me, I have never been there. might be just my crapy english and adapting questions language to answers  ;D ;D ;D

let us concentrate to the sidechain amp:
the PL102 is the stereo link connector, yes.
but it contains the signal going to the vactrol.
this signal is neither rectified nor DC, it is an AC audio signal. never tried it, but should be easily heard with a headphone / little speaker. threshold closed there should be nothing, threshold up there should be most.
if both channels are the same there, it is - to 99% - a faulty vactrol.

the ground reference at the stereo link is only to easily use shielded cables for the stereo link wiring, but it comes in handy for measuring.

"heads up"(a warning)
you misunderstood . i was just wondering if this phrase in native to US only or if it is used in other English speaking countries.
its good to narrow down the possible causes of the problem to a small area. i'll be using this unit soon!!

armed with my high tech audio tracer (a 1/4" plug attached to 2 alligator clips plugged into a bass amp) i discovered the audio signal was making its way to the stereo link.great! 99% chance its the vactrol ! ordered my new vactrol and installed. ... ouch still not compressing.  but since you(silent arts) pointed out that i should be looking at the sidechain for problems, i took out a copy of the schematic and highlighted all the components in that part of the circuit. befor long i discovered a bad (non) connection between  pin 2 of the the threshold molex connector and the PCB trace. both channels are now working correctly and are quiet. just have to hook up the meter lampps and calibrate the meters. thanks for the PCB and all your help. cant wait to run the compressor thru its paces!!!

good news  8) 8) 8)
enjoy your D-AOC  ;D