D-AOC PCBs - the building and help Thread

[alexc]

A few months now of usage and my respect for this unit has grown alot.

The combination of atom smashing gain reduction levels as well as amazing transparency has made it my new favourite for guitars.

Acoustic and bass.

One place where it really stands out is for the Rick 12 string semi - a beautiful instrument but a complete d*ck to play and record. I love it and hate it. Simultaneously.

Physically it's difficult to play and even harder to tune. I just did some maintenance on it and redid the bridge and intonation and all that.

Electrically it's all over the place, dynamics wise. Booming bottom end hard to control pickups as well as delicate but easily shrill top end. A horrible combination, really.

Well the d-aoc really tames the sound beautifully. 12db+ of GR and still all the highs are there and the mandolin-like harmonics all all coming thru - without the brutish thump in the bottom end. I can actually dial in a great tone without everything all bashing into itself.

Really gets me a lot closer to Mr McGuin.

D-AOC - my new goto compressor for all manner of guitars!

 

[imo]

I have a question regarding the groundplane.
I moved the lm350, but in doing so borked the pcb, so had to do a bit of dremeling to break the groundplane. With the DC heaters, do i have the H+ voltage going to pins 4-5 on each tube, and 9 as the ground reference? It seems to be that way, but i couldn't tell from the schematic or layout and wanted to be sure.
BTW, definitely mount this off board if you haven't. Mine had almost melted through the board when i checked.
Thanks
Ian

 

[imo]

got it. 9v is the ground ref.

 

[imo]

So wanted to say, i had to do some work on the AOC. I had a few resistors(mainly the 22k's) that were getting off colored from heat. Those 1/2w are barely enough in some places. Also, as i said before, the underside of the board was getting pretty toasted. It was a task getting the big heatsink off the board, thus extensive dremel use, but i got it mounted to the case-much better. I also took the meter lights off of the heater voltage(don't know why i wired it like that in the first place) and instead did a string of LED's for meter illumination.
Anyhow, since i had to take it apart, i decided to do some of the "Kubi" mods. I switched C2 and C5, and put a 2.5u cap in C4! I placed it where i can change it if it is too much. I've gotta say though, it sounds amazing! I am using Lundahl 1521s on the input and the Edcor on the output. The Lundahls don't have the step up but i didn't feel like buying any more transformers for the time being.
Right now i have super bright led AP(anti-parallel), red led AP, 10k, 100k, and super bright Parallel. I am thinking of simplifying the switch.
Also have tried to match the tubes, which are no more that 1-2 volts at any point.
I am going to run some AC tests in the next couple of days.
Also thinking about putting switches instead of the pots.
I want to echo Alex and say that it kills on things like 12 strings, drums buss, etc. It has a nice way of catching transients that is very "opto" but obviously much faster than an LA2A
Ian

 

[Scrappersa]

So wanted to say, i had to do some work on the AOC. I had a few resistors(mainly the 22k's) that were getting off colored from heat. Those 1/2w are barely enough in some places. Also, as i said before, the underside of the board was getting pretty toasted. It was a task getting the big heatsink off the board, thus extensive dremel use, but i got it mounted to the case-much better. I also took the meter lights off of the heater voltage(don't know why i wired it like that in the first place) and instead did a string of LED's for meter illumination.
Anyhow, since i had to take it apart, i decided to do some of the "Kubi" mods. I switched C2 and C5, and put a 2.5u cap in C4! I placed it where i can change it if it is too much. I've gotta say though, it sounds amazing! I am using Lundahl 1521s on the input and the Edcor on the output. The Lundahls don't have the step up but i didn't feel like buying any more transformers for the time being.
Right now i have super bright led AP(anti-parallel), red led AP, 10k, 100k, and super bright Parallel. I am thinking of simplifying the switch.
Also have tried to match the tubes, which are no more that 1-2 volts at any point.
I am going to run some AC tests in the next couple of days.
Also thinking about putting switches instead of the pots.
I want to echo Alex and say that it kills on things like 12 strings, drums buss, etc. It has a nice way of catching transients that is very "opto" but obviously much faster than an LA2A
Ian

I did those same Kubi mods. I think the reason I wasn't completely thrilled with mine was because of the second vactoral. I took it out and put in a slope switch with blue led, red led, reversed blue led, and a couple of resistors (can't remember which ones off the top of my head), and I love it so so much more. I think the second vactoral was just a bit too much. I love having the option of the slope, and I love when I turn it all the way, it really saturates. I think it would sound even better without the edcors though. How do you like the Lundahls on the inputs? I always figured I would change the output transformer, but I'm wondering what would have a more pronounced effect on the sound.

 

[Holger]

... and at D-AOC number 5 you get a free D-AOC shirt ;D ;D ;D

Volker, be prepared. I've recently finished #4: 4 RU, 350 mm deep, my first one with two meters. Size does matter...
Noise @-88 dBu (at uni gain settings) S/N 92/94 dBu, depending on your reference level, measured with my Neutrik Minilyzer.
Excellent frequency response. Kubi mods, Carnhill 9600:600 transformers. Stereo link works very well. My first build with operating hours counter.

Nice combo:

 

[pH]

Holy crap Holger! When are you gonna open your faceplate store?!?
Beautiful.

 

[imo]

I never went with the second vactrol. I like the different characteristics of the LED's, reverse LEDS, and resistors. Not sure what the unit sounds like with any other input trannies as i've had the Lundahls the whole time. The cap switch(ala Kubi) was the biggest shift for me.
I remember reading that the OT in this design wasn't a big change to the sound due to design, though i can't add to that.
I'm still slightly out of balance with the threshold levels when not engaged in stereo link. The right side seems more sensitive. DC levels are pretty similar, and so far AC levels as well. I think i may have mismatches on the switches with the paralleled LED's

 

[rob_gould]

... and at D-AOC number 5 you get a free D-AOC shirt ;D ;D ;D

Volker, be prepared. I've recently finished #4: 4 RU, 350 mm deep, my first one with two meters. Size does matter...
Noise @-88 dBu (at uni gain settings) S/N 92/94 dBu, depending on your reference level, measured with my Neutrik Minilyzer.
Excellent frequency response. Kubi mods, Carnhill 9600:600 transformers. Stereo link works very well. My first build with operating hours counter.

Nice combo:

Oh my oh my!  Holger, that is a fine piece of work!

 

[[silent:arts]]

Since Holger can't reach number 5 without PCBs I ordered some more today  8)

 

[alexc]

Holger - awesome!!

That's some very, very impressive build and layouts.

I used mine on the piano for a few weeks - I very much like the passive/aggressive nature of opto comp in general for instruments.
But it is mainly for guitars, especially bass.

I have it connected last in a relay bypassable chain of transformer DI and  api-312 style pre -> PeterC api style EQs -> DoaC.
Has a lot there for sure. It remains probably my most used path in my 'studio' room.

I replaced it with a discrete traffo opto, a 'What Comp' 1RU build  I did.

Sure enough, it sounded really very good and has transformed the outputs of my old K2000.
It's outputs are a little weak and unbalanced. The WHat Comp just instantly gave it it's youth back.
That's not moving out of there in a hurry. The Rhodes samples just incredible.
All the hifreq stuff amongst the dirty rhodes audible the first time in years.

Its really good. I may well see if I can add a Blend control to the DOAC.

I just want to have a tool completed that can do transfer functions automatically.
Those  different sidechain options are pretty profound in their effects. Be nice to see them graphically  e

 

[trancedental]

Well I finally got a front panel made so many thanks for the help from a local forum member so I'm finishing off my build, the longest ever I reckon :-\

Done a quick test by using a tone generator & sound is getting through fine & the compressor works, I knew the voltages were OK from when I powered it up before & it didn't blow up 2  years back!!! 

I'm just wondering if the Edcor i/o  transformer pins (marked 2 or 6 C.T.) need to be grounded to chassis on the side that goes to & from the board, like the 3 pin connections  on the sides going to & from the XLR connections are?

Once I finish I'll post some pictures for your amusement!!! 

 

[braeden]

Holger those units are absolutely incredible.
I hope you don't mind me stealing some of your great front panel ideas

Braeden

 

[trancedental]

My DAOC is up & running but I don't like the Edcors, I've got WSM 600/10K on the imputs & these sound fine without connecting up output transformers but then connecting the WSM 10K/600 on outputs makes this compressor sound tinny like everything below 1K has gone missing 

There's a pair of Carnhill  line outs 9600K / 600 just arrived in the post  ;D I'll try them when I get back home tonight!!!!!

Just wondering how to connect these up, I assume I bridge some pins together 2-4 & 6-7 like on the EZ1290 builds but do I still need the 1K5 resistor & .01uf cap across the ouput leads?  http://s3.amazonaws.com/EZ1290/assembly3.pdf

 

[alexc]

Something is definitely wrong with the hookup if Edcor 10K:600 on outputs is missing below 1K.

That's just not .. natural.

I would check that again - these units don't use the CT connections on the Edcors so just leave them unconnected.

The Edcor 10K:600 I initially tried in the DOAC worked fine - full frequency response and all that.

I replaced it with a Carnhill 9600:600 because I prefer it. I think the sound is 'smoother' and less 'grainy' at the top end.
Have done this a number of times and am happy.

Perhaps you might think about subbing the inputs away from Edcor to something else. I never much cared for the XSM in the input position for various reasons, not least because unshielded. I used Jensens in 1:4 and would say that ratio is the minimum imho.

Cheers

 

[trancedental]

Thanks AlexC

I've taken the XSM's away from my inputs now as well, as using them the sound was still not as full sounding as running unbalanced,  compared with the original sound.  The CT connections didn't make any difference.

Now the DAOC sounds really good & even when compression is turned off the sounds of the valves really enhance the material being played.

I've got some old Brimar 6060 "Yellow T" military ECC81's on the input & Mullard ECC82's on the output valves, sidechain's  are just some cheap chinese ECC82's but they're not part of the signal chain I'm assuming, just like a vibrato tube on a guitar amp! Maybe I'm wrong ?

The Carnhill's line outs have just gone in & all my sound has come back and more  ;D Running a quick stem mix off the desk from a TSR8, sounds great & even better with compression, heavy compression & the sound is still there, big, detailed & with the beefiest low mids, you all know what I mean!! I left the cap & resistor across the XLR pins out, I would guess they were for oscillation prevention? Don't hear any of that problem at all.

I'm not sure about putting input transformers in here now, might be too much thickness & warmth for using on a mix with the valves adding to the sound?

Don't know why the Edcors sound like tin cans, LOL!! inputs & outputs were the same. they seem to test OK so I haven't got a clue what the problem is?

Just got to tidy it all up but here's a photo!

 

[nashkato]

has anybody tried the Lundahl LL5402 on output ?
should be possible with prim in series and output parallel ?

 

[braeden]

Could anyone recommend a set of transformers (input & output)? I was going to go with Jensen but after sending them an email a week ago I still haven't received a reply ???

If I was to go with Carnhill or Sowter which transformers are suitable? At the moment I have VTB9046 as the input transformer and VTB9122 for the output, is this correct and how is the VTB9046 mounted?

Any help is appreciated,
Thanks!

 

[braeden]

I decided on Sowter 1290 for the Output TX and Sowter 8540 for the Input TX.

I'm going to mount them to the rear panel. The 1290 has a threaded grommet with flying leads and the 8540 will plug into an 8-pin octal socket on the rear.

This is my first time building a D-AOC. I've decided on a 4U enclosure from Modushop with 89.9mm diameter vintage style Simpson VU meters.

Jan (mistadchan) is selling a whole lot of great kit and I managed to obtain a Blue D-AOC board from him.
I discovered soon enough that there are H/W bypass boards available, he sent these to me at no extra cost so big thumbs up to him there.

I'll be using JJ matched & balanced tubes (I thought I'd pay a little bit extra, although it probably won't make much audible difference).

Mundorf Supreme capacitors in the circuit with the standard Solen Fast DC blocking capacitors you see on most D-AOC.

Let's hope it all goes according to plan!
I may start a build thread... :

Braeden

 

[dagoose]

just out of curiosity.
When you switch on the D-AOC the meters go to 0 right away, but after a few seconds the meters drop a few DB and then go back to 0 again.
What is causing that? is it a cap charging?