D-AOC PCBs - the building and help Thread

[weiss]

I have a question before ordering the frontpanel

I see a lot of guys using the term compression instead of threshold like in the schematic. does the volume actually change when turning this specific knob? can it be called threshold either way or what is the deal? 

 

[[silent:arts]]

I have a question before ordering the frontpanel

Don't put the power switch in the middle!
And it is compression, not threshold 

 

[weiss]

Don't put the power switch in the middle!
And it is compression, not threshold 

alright, thanks 

i don't plan to. I got this layout ready. but i also made a 2U version, can't decide yet 

 

[Pusch3l]

Don't put the power switch in the middle!

I am curious Volker... why?

 

[[silent:arts]]

I am curious Volker... why?

It is a massive design failure having that 230V Mains AC crossing all those wires carrying your sensitive audio signal.

 

[Pusch3l]

Hehe.. i put it in the middle of the Frontpanel... maybe i got lucky that the unit is dead quiet. But i have to say that the only cables crossing the mains are those for the VU. The whole audiopath is on the other side of the case.

 

[weiss]

Just setting up this additional slope mod pcb. I have already one vactrol installed on the main pcb but how would i wire the second vactrol on this pcb? maybe you could help me out here... 



thanks

 

[weiss]

When i wire the lundahl ll1540 reversed as 2:1 on the output, is it true, that pins 7 and 6 stay untouched (primary side)?
And to which pin does the ground connection of the bypass pcb need to connect?

i hope someone can answer, this thread seems dead 

 

[[silent:arts]]

I would wire the secondaries in parallel.
You know the LL1540 would be better at the input?

You can wire the Bypass PCB GND to your Chassis / star GND.

 

[weiss]

I would wire the secondaries in parallel.
You know the LL1540 would be better at the input?

You can wire the Bypass PCB GND to your Chassis / star GND.

hey thanks,
ah, i thought I'd use 2 for input and 2 for output..

i just don't know if this is correct ???

I'm using LL1540's for both input and output. Input I have wired as 1:1 as follows (please correct if I'm wrong) - Refer to here for pinout http://www.lundahl.se/pdf/1540.pdf :

Primary: pins 2+4 tied, pin 1(+), pin 3(-) - From Bypass board XLR
Secondary: pins 5+7 tied, pin 8(+), pin 6+pin E(-) - To PCB

For the output (also LL1540) I wanted to wire reversed 2:1. I have the following:

Primary: pins 8+5 tied as (+), pin E to ground - From PCB
Secondary: pins 2+4 tied, pin 1(+), pin 3(-) - To Bypass PCB

 

[weiss]

anyone? 

could i also use some audiophiler 20uf MKP capacitors (400v) instead of the solens?
i have 2 laying around..  ???

thanks

 

[rock soderstrom]

Yes, you can use them.  400V is enough. The double capacity will extend your bandwith somwhat. The lower cut-off frequency of the amp will be some Hz deeper.

 

[weiss]

Yes, you can use them.  400V is enough. The double capacity will extend your bandwith somwhat. The lower cut-off frequency of the amp will be some Hz deeper.

great, thank you thorsten!!  8)

 

[weiss]

months later and about 800 bucks less in my pockets i finished wiring up my DOTC !!
If you make out any obvious mistakes, i'd be happy to know . Tomorrow i'm gonna test that beast.

The guts:

 

[[silent:arts]]

I prefer shielded cables for wiring the pots & switches.
However, I can't see any obvious mistakes, fire it up and show us the front panel

 

[weiss]

My Dual Opto Tube Compressor is up and running  8)

- 4x Lundahl LL1540
- Fully stepped attenuators
- Kubis Mod with 4 Vactrols and slope mod adjustable through frontpanel rotary switch

I'm gonna check the audio now..  Could suddenly smell a lot of plastic when i opened the top, don't know if it's normal though.. No smoke, nothing seems to be burning, so.. ???

Bypass LED's and Output VU switch is not installed yet, waiting for some parts to arrive 

here's the picture for your collection, volker

 

[tony hunt]

Now, that is what I call a front panel! 

 

[weiss]

Now, that is what I call a front panel! 

thanks 
it was obviously not 100% my own idea, but i liked the look of it and made my own layout 

 

[weiss]

After about 3 min my fuse just blew... 
I turned the switch off on the back but the frontpanel switch was still on. When i turned it back on on the back the device stayed dark..
Was using a 250 mA 250V slow blow.
Nothing looks burned or anything.. i assume that's the voltage peak after powering the unit.. but after my calculation each tube uses 4W x6 makes around 24W so it should actually work with these fuses but i'm gonna try increasing the value..

EDIT: The "smell" seems to come from the slope mod pcb i use.. but still no idea if that's a problem or not..

 

[weiss]

Using 800mA fuse and it works until now.. Let's see.

Do i need to replace R126 & R226 with a trimmer in order to make the meters read zero dB?
At the moment they stay on the complete left side.
But the voltages Rx09, Rx05 Rx11 Rx27 and Rx28 are perfectly fine.