D-AOC PCBs - the building and help Thread

[jensenmann]

Hello!

Musikding in Germany does not sell the toroidal power transformer anymore. I've tried to find an european alternative, without luck. Any suggestions?

I have all my custom trannies done from this company: http://www.mueller-rondo.com/
I can highly recommend them. No freakbusiness but german precision engineering!

 

[Miska]

Banzai carries some of these, and is in Germany too

Which transformer do you mean? I checked through Banzais trannies twice and couldn't find anything even close to the specs for D-AOC.

 

[petermontg]

Hello!

Musikding in Germany does not sell the toroidal power transformer anymore. I've tried to find an european alternative, without luck. Any suggestions?

I have all my custom trannies done from this company: http://www.mueller-rondo.com/
I can highly recommend them. No freakbusiness but german precision engineering!

Did it set you back much?

 

[jensenmann]

no, 50VA trannies are app 40€ + shipping

 

[MicDaddy]

For those who will build (have built) D-AOC sans transformers:

On the input, is a cap necessary to prevent possible unwanted DC bias problems at the grid?  If so 1uF puts the pole at ~10Hz if I use 15k as R.  Is there some other input relationship math needed here?

How about for the output, I haven't tried any math to figure the OP impedance but assuming it's 10k, will it be unhappy driving anything less if I take output straight off the 10uF cap?  How about some buffer with op-amps, anyone tried this? 

 

[Silvas]

Hello,

I've just replaced the edcors on my DAOC : LL1540 (from Sahib) on the inputs and XS1100 (directly from Edcor) on the outputs.  They sound fantastic. Great combo and far superior to the original edcors.  No need for zobels, etc....I ran my DAOC transformerless input for years but the specified edcor outputs still ringed a bit on their high frequency limit.

I also replaced all audio tubes with 6N1P. After playing with many of them, i've found a combo of 6N1P which gave me around 0.1% THD at +20dBu with no compression. I guess because of better match between triodes ?

The sidechain tubes were left as-is (12au7).

I measured individual vactrol GR amount on circuit. Three of them are almost the same, one of them off by almost a dB. I guess i'm getting a couple more vactrols to get a more accurate match.  I tried to compensate using series resistors on the led side of the vactrol but it seems to affect the lowpass corner frequency formed by C104 and the LED, so compression accuracy was screwed a bit on bass-heavy material.

I replaced r126 (33k and "TBD" on LA2A schemo) with 50K trimpot on board to adjust needle precision so i can get accurate readings on both channels at up to 5-6dB GR. I also moved zero adjust trimmers to front.

Now, i wonder if the HT PSU can be further cleaned.  I usually get a significant ripple reduction on the TL783 by bypassing the adjust pin to ground with a 22u/450v cap, but i didn't tested this yet on this particular PSU.

Hope this help. I've always loved this compressor.

 

[druu]

Is there a source for matched vactrols? I've also found the 500r trimmer on the vactrol leg isn't super accurate.

 

[Potato Cakes]

Hello everybody!

So I'm slowly gathering parts to build one of these later in the year. In the meantime, I have been working on a front panel since I haven't been able to find anyone who has case readily available for this. I decided to share it with everyone in the event there were others who are going to build a D-AOC but weren't sure how to get a front panel made. PM me and I'll send you the files as I can't attach them here. Everyone is free to use it and make changes to suit your needs.

Here are links to the products that I am using for the cut outs:

Power switch:

http://www.digikey.com/product-search/en?KeyWords=R1966ABLKBLKEFBLU-ND&WT.z_header=search_go

Note: This is a 125V switch. I have not found this same switch in 250V

Meters:

http://www.hairballaudio.com/shop/product_info.php?cPath=39&products_id=59

Push button switch:

http://www.don-audio.com/Classic-British-Console-Pushbutton-Switch-Illuminated-Yellow

They also have it in blue:

http://www.don-audio.com/Classic-British-Console-Pushbutton-Switch-Illuminated-blue

The option for the different slopes to be selectable is included to make it as complete as possible. I'm going to use a 12 position switch for the slope (stop pin at 6) and 24 position for everything else (stop pin at 21). Right now I'm looking at doing Elma's for the 24 position and Grayhill for the 12, but that may change. The drill hole sizes for the switches will have to be adjusted for different manufacturers.

I've attached a PDF of the panel as a preview of the layout. I hope this will be helpful.


Paul

 

[Rocinante]

Hey all,
I'm wiring this up now but I still have a a few parts to collect.  Does anyone know if 400v 10 uf's are safe to use as opposed to the 600v that's called for?    I remember reading the output caps never get more than 350v but want to obviously be sure.
Thanks in advance.

 

[Potato Cakes]

Silvas,

Would you mind posting the resistor values you used for your stepped Elma switches?

Thanks!

Paul

 

[Rocinante]

Hey
I'm all wired up and failing over here.  As far as I know everything looks right but I got some problems;
First off I'm using the custom Edcor. Its definitely putting out 24, 9, 250.
But my R1 is hot. I smoked two 10 watt double 1ks. I put a 500 ohm power resiter rated at 50 watts and its still hot. Like hot to touch. My diodes look alright and ive checked the rectifiers which I put large heat sinks on and their running luke warm.
My heaters are running at 6.0
But my voltages arent lined up to everyone elses.
Sorry to rectify an old thread but ive spent months and im not much farther. Tubes light up but they're at a dramitically different brightness from one another.
Any help would really be great.
Thanks in advance.
Dylan

 

[rmaier]

Hi Dylan,
Contemplating this as my next build, so I'm curious about the Edcor power transformer. Regarding your problem with R1 470 2W, I've read that here that the 470R 2W resistors should be metal oxide. Is that what you're using?
Ralph

 

[Rocinante]

It smoked the 470 2w. It smoked the dual 1k in parrallel 5 watts.
I now have a 500 r 25w power resistor and its hot. Like hot to touch.  I orderred a 1k 50w power resistor hopefully that will bring it down.  Others have experienced the same thing.
As far as the edcor power xfmr, its definitely slick looking. My filaments were fine but several people experienced the colors being mislabeled.
I thought I had everything right but obviously something is amiss.

 

[rmaier]

Bummer.

 

[[silent:arts]]

If R1 is smoking there must be something wrong.
Does it burn without tubes inserted?

 

[rmaier]

Regarding the power transformer: I just noticed that Gustav offers a toroid with 9V 2A and 230V 35mA secondaries. Is 2A a bit too little for the heater supply (I'm aware that the schematic calls for 2.5)? I'd like to use a toroid if at all possible, and can't find anything from Antek that quite fits the bill.

Link: https://pcbgrinder.com/index.php?route=product/product&path=94_97&product_id=181

Thanks,

Ralph

 

[Rocinante]

If R1 is smoking there must be something wrong.
Does it burn without tubes inserted?

No but its Hot. To hot to touch. Maybe the xfmrs current is to high? They're reading 250v going in. Ive triple/quadruple checked.

 

[druu]

IIRC, R1 also smoked on mine due to a silly high (252V secondary on the transformer). I ended up using a large resistor as a voltage divider to bring it down before the board..

 

[Rocinante]

I've ordered some 1k power resistors, should that be enough?

 

[Unit-8]

Hi all,

I finally started to do tests on the d-aoc, but I have a problem.
The d-aoc does not compress.
The audio passes without problems in the circuit, but I have no action on the controls of threshold, input and output.
My idea is that vactrols not working, but it could be another cause that I did not understand so far.
I measured the voltages from test points and have these values:
CH1
R122 = 0V
R118 = 115V (instead of 133)
R105 = 84V (instead of 109)
R111 = 208V (instead of 222)
R127 = 68V (I'm using 68V zener)
R128 = 229V (sometimes I have 235)
Heater voltage = 6.3V
Same voltages on CH2 apart on R205 that I have 87V
The voltages are all lower then Volker readings shown on the forum.
Maybe I should replace the resistors R2 and R3 with a resistor 510R + jumper to elevate all voltages?
The transformer I have is the same used on Gyraf G9 from Don Audio and have this specs:
Pri. 2 x 115V - Sec. 9V - 2.5A, 5V - 0.5A and 220V - 0.1A
Mains in Italy is 220V.
Any help is appreciated. Thanks in advance.