X-Bosoz Finished

[AR2]

I am finished with my 6 channel balanced preamp. It's all started when I decided to do three way active speakers. Than I compiled various amps, that I changed in a meantime. Here is my original link for the speakers:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=21523&highlight=
It turns to be very complicated project since all speakers are with different sensitivity, amps are different - vacuum tube and solid state. I also wanted to do mods on digital crossover. So one after another it lead to this latest combination:
DCX2496 was moded to exclude circuitry all together after DA converters. Wires are bypassing signal directly to XLR connectors.

 

[AR2]

And this is whole output board of DCX 2496

 

[AR2]

On the preamp side I decided to go with separate case for PS since there was no room for everything in one case. The big transformer is 2 x 55v 300VA and for the negative rail I have two smaller ones 18V each. Besides two power supply boards I have soft switch and start circuit board that I got from some earlier group buys designed by Maxhawk
http://www.diyaudio.com/forums/showthread.php?s=&threadid=61653&highlight=

 

[BobEllis]

Looking forward to more pictures, since I am startting the same sort of thing with an analog active XO.

What did you use for the power umbilical? (connectors, cable)

 

[AR2]

Based on my various gain needs, in my design X Bosoz is separated from DA converters by Lundahls 1674 transformers. They are ether 1+1 : 2+2 or 2+2 : 1+1
They are ballanced and they completely kill 2.5 V DC that is coming out of DA converter. I am using Lundahl in front of XBosoz for low and high channels. For mid I am having only Lundahls without XBosoz. XBosozs are used all in ballanced configuration. Before the output I am using 6 channel ballanced Apex relay volume control.
For both cases I milled appropriate aluminum plate to serve as double bottom where everything is attached as well as to serve as a shield against noise. Power supply lines are routed underneet the plate and holes are surounded with rubberized material in order to prevent wire cuts.

 

[AR2]

Lundahls at home nicle tucked in.

 

[AR2]

Just to make sure they do not leave their places... I clamped them.

 

[AR2]

Boards all together assembled - 4 XBosoz boards and 3 Apex Boards.

 

[AR2]

And one more view.

 

[AR2]

Rear panel with XLRs and single ended option with switch and RCA plugs. Black round connector is 9 pin connector that is used to connect power supplies and grounds. One wire is for chasis ground, directly connected to earth from power plug, and signal grounds are connected to power supply grounds that are further connected over thermistor CL-60 to the chasis ground.

 

[AR2]

I made mistake and attached wrong image in one of the first posts. Here is the correct one - whole DCX board bypassed.

 

[AR2]

And finaly here is the front side without the front panel. Still waiting for the order of some milling bits in order to finish. For now here is the view of underside of front panel.

 

[AR2]

I will post final pictures next week when I completely finish front panel. And just to conclude:
X boards are from Kari's group buy, parts are provided from Anthony, Apox Boards are from Apox Controls that I got from Tyler on trade board, cases are as well from the trade board, all the knowledge I gained is from here, DIY audio, the design is by Nelson Pass, and pleasure is all mine. Thank you all.
Sound is absolutily perfect. I just recently completed Aleph 30 which I am using for the ribbon tweeters. http://www.diyaudio.com/forums/showthread.php?s=&threadid=70037
For the mids I have 2A3 vacum tube and on the bottom class AB amp. Pure haven.

 

[Coulomb]

Project looks good.

Anthony

 

[AR2]

Thanx Colomb.

 

[jleaman]

It looks good, BUT weay to crowded. I think if you changed the chassis and layout it might be a better idea. There is so much crammed things in there.. How come ?

 

[JoshK]

When your done, you want to make me one?

nice job, I've been considering doing something very similar.

 

[AR2]

It looks good, BUT weay to crowded. I think if you changed the chassis and layout it might be a better idea. There is so much crammed things in there.. How come ?

Think in the terms of 3 separate ballanced preamps. Than think how much wiring is needed which is never too good. I purposedly wanted to make it as close to each other in order to avoid extra signal routing. I used very good silver - teflon wire which is maybe thicker and add to the overal busy look. Ideally I should use PC mounted XLRs and do all of the routing from there which could also house Lundahls. That would be much better but that would be phase 2. Temperature wise everything works well, no excessive heating at all. Case cover has enough slot openning on the sides and there is quite enough circulation. Beside heat which is not an issue I do not see any reason for boards not to be close to each other. Trannies are in a separate box, and power distribution is bellow thick aluminum plate. Only 5V regulator board is in the case for volume control, which has to be as close to electronics. The case is already big it is standard 19" size. Only other option would be one more case which you would agree would not make it very practical to have three cases. Please let me know if you see any other issue beside esthetics.
Thanks for the opinion.

When your done, you want to make me one? Sure
nice job, I've been considering doing something very similar.

Please let me know if you need any help.

 

[Ryssen]

Loking good!!If you short out the output board you lose the filtering from the DAC´s as well,righ.Good or bad?So you can use LL1674 balanced,if I only use the DCX singlended,is it enough with 3 transformers then?In the LL1674 data I cant see how to use it as 1:1,how?Lundahl have some digital transformer,is it good to change the DCX input trafo with,or any other sugestions?

 

[AR2]

You cannot combine separate channels on one transformer. You have to present ballanced signal to the Lundahl in order to canncel DC coming out of DCX. Lundahls provide filtering by their natural roll off at around 50 KHz. I was wrong on 1:1. it is only 1:2 or 1:4, but 1:4 is really not recomennded. If ypou need 1:1 you will need different one - do not remember exactly what was the number. You could get all info and buy Lundahls from Kevin at K&K audio.
http://www.kandkaudio.com/