D-AOC PCBs - the building and help Thread

[Gold]

I put 10 turn trimmers is the Input and Output positions. I only brought Compression out to the faceplate. I use the input trimmer to get the thresholds matched and use the Output trimmer to match the gain.

 

[dagoose]

My guess is that you won't get the required accuracy by modding the device. Try Ian's "Neve Trick":take a 1k variable trimmer and put the hot leg of the 600 ohm transformer secondary to pin 1 of the trimmer, take the "wiper" or pin 2 as output and connect the TX 600 ohm secondary cold leg to pin 3. Do that on both L and R and set the trimmer to match gain.

That's a good one,  I will give that a try.  8)

 

[Holger]

Report back

 

[Gold]

I got the second Double DAOC done. I still need to dress some wires but I have both units pretty tightly matched. That's eight channels.

 

[[silent:arts]]

Paul, that looks amazing!

 

[Gold]

Thanks. It feels good to have them done.

 

[audiophreak]

WOW !!

 

[dagoose]

Report back

I just made the Left and Right level correct in a different, more simple but effective way. The difference was about 0.2db, so not that big and so the steps didn't have to be big.
I replaced R103 (R203) to a 44k + 10k multiturn trimmer instead of the 49k9. That way I could easily trim it to get the same gain on L an R.  8)

 

[L091c]

Does anyone have asource or part number for the PSU transformer?

Mine came from Don-Audio https://www.don-audio.com/g-pultec-power-trafo-sec-220v-9v-5V

 

[L091c]

I am finishing my D-AOC but I re-use a pretty case that already has a High Pass side chain switch in its front panel. I share Darius' concern that the HP should not happen using a passive capacitor (Cx04) before the vactrol because the resistance of the actual LED will vary by the signal (moving the cut off freq dynamically).

Would there be another way to introduce a switchable and stable HP side chain filter in the design? Like replacing/augmenting Cx04 with an active filter?

 

[KrIVIUM2323]

Hi,
put a buffer after c04 should do the trick..

 

[fragletrollet]

Can I use the 1N5170 instead of the 1N5171? 56V instead of 60v? I'm guessing it might not be crucial as it's in the meter circuit?

Also, I am thinking to install different vactrols and switch between them using relays, can normal small signal dip relays do the job or do I need high voltage ones? Would I just need to switch the diode part of the vactrols, will the vactrols that are out of the path on the diode side affect the signal on the resistance side, as they would be in paralell to the pair that is in circuit? (running the back to back vactrols kubi style, so 8 vactrols in total, 2 pairs for each side).

 

[L091c]

Hi,
put a buffer after c04 should do the trick..

Something like this Krivium? (Illustrating the before & after)

Not sure yet how to address the ref voltages though. What is the voltage swing here?

 

[KrIVIUM2323]

Hello,
Yes this is what i had in mind. ( the buffer could have been something different ( a jfet buffer, a tube as cathode follower - same as vx02a,...- but if there is already some +/-15v rail present opamp are easy to implement).

With the vactrols i used the cv voltage have never been an issue with typical +/- 15v rails. I've never used vtl5c2 (and don't really studied the schem of Daoc) so can't speak of it but i would be surprised if this was different. I would check for current capability of opamp but given the sidechain is driven by an ecc81 initially, i would expect a moderate needs in current so no needs for a 'special' opamp ). 

 

[L091c]

Yes this is what i had in mind. ( the buffer could have been something different ( a jfet buffer, a tube as cathode follower - same as vx02a,...- but if there is already some +/-15v rail present opamp are easy to implement).

Thanks Krivium for thinking with me!

The thing is, there is no +/- 15V rail, and even then, the voltage swing here could/should be over 200V (yay tubes!). The LED in the vactrol does not care about high voltage, it only cares about current. With an opamp as follower I will need to restrict the current to protect both the LED and the opamp, think I will finish the build first without the HPF, measure in-situ before adding modifications and think a bit longer about how to implement the buffer (preferably without adding another tube).

Love to hear other/better/safer approaches, please do share. Did anyone actually measure the original dynamic HPF that happens due to 100nF + R of Vactrol? Or did anyone add their own HPF to the D-AOC?

 

[justinheronmusic]

Starting to gather momentum for this build, before I get started, I have some questions.

Can this fit in a 2U case from Collectivecases?

What are my options for PSU transformer these days? Does Rondo Mueller have options? Or is there anything in the USA?

 

[shabtek]

can fit in 2u but tight, don't know about c.cases--if they make one for this than it should fit


external power supply can fit anyhing, send fused raw dc to main unit for filtering

 

[Potato Cakes]

Starting to gather momentum for this build, before I get started, I have some questions.

Can this fit in a 2U case from Collectivecases?

What are my options for PSU transformer these days? Does Rondo Mueller have options? Or is there anything in the USA?

I have mine in a 2U and it wasn't bad. Power transformer I ordered from don-audio.com.

Thanks!

Paul

 

[justinheronmusic]

I have mine in a 2U and it wasn't bad. Power transformer I ordered from don-audio.com.

Thanks!

Paul

Relief! The Power xfrmr was my bigest concern and if I can get it through Don-Audio then I can get a few other tidbits from them! Thank you!

 

[L091c]

Hi all, during building we found a pretty big deviation from spec'ed voltage. And we are not sure if we should be worried about it or trace the origin of this error. Two independent builds show: ~236V on the plate of ECC81/12AT7 instead of Volker's 109V. My heater is at 6.44V. Here are all my voltages (in green) next to Volker's (red):