D-AOC PCBs - the building and help Thread

[druu]

Finally somewhat finished my D-AOC. Thanks to those who gave assistance, very helpful.

A bit of level mismatch between channels in link mode but will sort that with the trimmer on the vactrol. Pretty happy with the sound!

 

[dagoose]

nice!

 

[druu]

Panel here if anyone's interested:

http://www.amnet.net.au/~amunday/d-aoc/D-AOC%20FRONT%20PANEL.pdf
http://www.amnet.net.au/~amunday/d-aoc/FRONT%20PANEL.dwg

 

[dagoose]

Just noticed the limit switch. What is it?  8)

 

[dipfrik]

Nice! Where do you get these knobs?

Cheers, Sven

 

[druu]

The Limit switch basically enables the slopes, otherwise it runs in 'analag' mode.

Knobs from Banzai.

 

[rock soderstrom]

Thanks for posting the panel data!

 

[druu]

So has anyone tried putting the 500R trimmer for stereo link balancing at the switch itself? I have +/-0.1dB throughout the whole compression range when not linked but stereo link just throws it out about 2dB

 

[protools]

Very Nice!

 

[druu]

Anyone find inconsistency when using the NE2 halogens? I've noticed they flicker sometimes and wondering if the ZD is better to use.

 

[dagoose]

Anyone find inconsistency when using the NE2 halogens? I've noticed they flicker sometimes and wondering if the ZD is better to use.

same here. Just try a couple of different ones and use the best. Worked for me, but i accidentily ordered 20 bulbs... 

 

[druu]

Hmm, do you think the diode would work ok instead?

I had to order those lamps from Israel, took over a month to receive!

 

[Nescafe]

MODDING THE SLOPES (& THRESHOLD)

Hi,
could somebody explain to me how to take measurement like this and what software to use, my purpose is trying to match between 2 channel.

Thank You.

 

[[silent:arts]]

You are on the right way exchanging the Edcors for mastering.

 

[alexc]

As well as having the desired sound and compression character, mastering generally is about  precise control, matchable across both channels.

So first up is to minimise sources of mismatch - here that means, as well as tube selection and matching, making sure the input, compression and output controls track as closely as possible for 2 channels.

That means rotary switches and hi precision resistors. No real problem, but it takes some care.

Then there is the sidechain matching - you would have to ensure the vactrol assembly responds as closely as possible across the channels.

That means measuring and selecting vactrols/leds and what not. Vactrol selection is not easy, needing some kind of test jig and lots of measurement time. And vactrols themselves are not cheap, as well as reputedly varying quite a bit in characteristics.

So, vactrol selection probably has potential to  make a positive difference, depending on your tolerances.

All this would really start to show up as precision in each channel as well as across both.

There are some other resistors here and there that should probably also checked for tolerance, but I found the d-oac to be remarkably similar across both channels with generally no special selection of anything.

---

Next up, the transformers should be good quality/premium - hopefully the manufacturing will ensure the transformer performance is reasonably the same. This is *not* always the case for cheaper traffos!

After that, it is a question of what 'character' the traffos impart. I've only really been able to tell much difference between 'premium' traffos and 'value' traffos, like Edcor xsm/wsm. This is not a slight on Edcors, in many ways they have a performance which is great at the price.

So any of the premium traffos should be reasonably transparent, low distortion etc. I'm no fan of transformer-less outputs - noise is an ever present and insidious problem in the overall audio system. Traffos, if not picking up psu noise, are your friend in preventing noise issues downstream ..

I would certainly recommend shielded traffos all round to help in noise rejection.

If you don't have a toroidal psu traffo, then ... not so good but not necessarily the end of the world.
But probably, yes.

So - please. Shielding. Please. And check before final placement, the best place for stuff to be aligned.
This makes more difference than all other everythings combined and x 10.

----

THEN, assuming the basic wiring, mechanicals and components are not detracting from the potential performance, as can most definately be the case for non-optimised positioning of (worse still, unshielded) signal transformers, you SHOULD be good to go.

To know for sure you are meeting the criteria for mastering basic performance, some skill and tools in measuring the unit performance is required.

Evaluate freq resp, distortion, gain structure and finally but most difficult, measure the gain reduction characteristics.

That means manually measuring the resultant range of output values for a defined range of input values at lots of different control settings. Then plotting them to give you the family of 'transfer function' curves of the unit.

Just like the reposting of that graph above.  How cool was that work as described, all the way back then

You might have access to a high end test tool that auto generates transfer functions, or maybe you write your own!
Thus you can demonstrate you have a unit you can safely think of as 'mastering quality'.

SO - somewhere between that and nothing, is the place you will find the things you might want to look  at .



Cheers

ps - I think of all the diy dual compressor/limiters I have done, the d-oac has the most potential as a mastering unit. And that includes the gssl.

pps - I would probably never master in the analog domain, but I'm not a professional  8)

 

[abbey road d enfer]

today I did some more measuring for this post:

Just one question, that you may have answered already... what software have you used to produce these graphs?

 

[[silent:arts]]

Just one question, that you may have answered already... what software have you used to produce these graphs?

Neutrik AS04 Software with Neutrik A2

 

[abbey road d enfer]

Just one question, that you may have answered already... what software have you used to produce these graphs?

Neutrik AS04 Software with Neutrik A2

Thanks.
I should have known, having been NTI's distributor for many years. I fact I used the A1/A2 as stand-alone instruments most of the times.

 

[alexc]

Hmm, do you think the diode would work ok instead?

Ya - ditch the neons. They suck. And 'ping'.

Get some zeners - 68V, 1W or something like that, if I recall.

Check the detail and get the nearest.

I used neons once. Then tossed them.

 

[mitsos]

I think I've said this before, but I'm finally going to get to mine..  :

couple of questions..  Has anyone done one with 12V heaters?

also, as far as the input level/threshold, has anyone use higher gain tubes either in position one or the sidechain?  I know people used higher ratio input trafos, which I would think would be the same as swapping V1?  But I read some comments that it would be better to swap the sidechain tube, hence the question. 

thanks!