DCB1 Build

Terrific job!!!

How dare you knot the power cord twice??? It's now turned into an inductor. :eek:hyeah:

Valuable point! I wanted to prevent tension on the cord joints (between transformer primary and power cable) on both ways (push & pull). As the power requirement is very low, I am not sure if it would make any adverse affect or not! But I will think of some alternate way.
 
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No wonder that Sachin asked me to upload lots of picture on this project, as he alone do not have to take all the classes. Now Keith, what about this picture? Isn't it more satisfactory? IEC socket was taken from broken SMPS of a PC.

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No wonder that Sachin asked me to upload lots of picture on this project, as he alone do not have to take all the classes. Now Keith, what about this picture? Isn't it more satisfactory? IEC socket was taken from broken SMPS of a PC.
:clapping::clapping:
 
Recently, in an effort to try and reduce the low level noise that's been plaguing my DCB1, I decided to rewire the internal cabling with proper shielded twisted pairs. Since magma's DCB1 had the same issues, we decided to tackle his buffer first. I used Helusound AES DMX balanced cable because that was what I had at hand. This cable has wound, multi strand copper outer shield with aluminised Mylar foil inner shield. The two cores are 24 AWG silver coated copper multi strand. This cable replaced the old CAT 6 solid core wires from RCA sockets to board, and board to pot. I also replaced a DPDT switch which was used to switch between the two sources, with a 3-pole 4-way rotary source selector switch. Using a third pole allows one to route the return wire with signal wire. Earlier, I ended up separating the signal and return leads as a DPDT supports only making-breaking one lead. The current one is much better as the twisted pair need not be unwound.

After rechecking DC offset voltage at the output and ensuring that it was within safe limits, I fired it up. Noise had reduced very substantially, though there was still a vestige of it.

What struck me was the sudden jump in clarity, with much better focused imaging and specific placement of images, better resolution, and most unexpectedly, a relaxed and airy presentation. Tone had also changed, especially in the upper bass and mids. I liked the new tonality.

Some days later I tried the same changes on my DCB1 too, but using a different brand and model of twisted balanced cable. This cable has only wound, multi stranded copper shield. And not very dense winding either.

I've used this cable as an interconnect and like it a lot, but as internal wiring it wasn't anywhere near the Helusound DMX. It had lower resolution, and just doesn't have the unforced and relaxed air. Even after a few days worth of burn in, there wasn't any perceptible improvement.

So I ended rewiring my DCB1 too with the Helusound DMX. I could hear the same things I heard on magma's DCB1, proving that it wasn't a fluke.

What seems to matter most seems to be how good is the shielding. I'm guessing that besides reducing induced hash, it is also reducing channel cross talk (which could explain the pinpoint imaging). Also, when I hear the two cables side by side in IC duty, the Helusound is quite a bit brighter than the other cable, and the brightness was not much to my liking. In fact if to be used as IC I much prefer the other cable. So these cables can shine in one application, while not doing so well elsewhere.

So changing your internal wiring to a good shielded twisted pair seems to be a cheap - if tedious - way to greatly improve the sound of your DCB1.

Another cable with lots of promise is the Gotham GAC2 as it has one of the finest shielding I've seen on audio cables.
 
Some pictures:

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Unusual location of source selector knob is to avoid long run of cabling:

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In case anyone's keen, this is the switch for source selection:

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I would like to thank fellow member saheb11123 for the rotary source selector idea:thumbsup:
 
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yeh josh
the new modded dcb1 sounds phenomenal
good we did that 2 core shield

(what was also important was the ground drain wire we added and that source selecter switch that ensures all running lenghts are same with no uneven breaks)
we should now call this the DCB1 - mk OJ )
( OJ for joshua OM )

though we still need to dive a bit in the "grounding" well as i suggested
lets do it on mine first using lugs
so we can figure out what works best

one of the best preamps ive heard period ( branded ones included) - ( and ive heard quite a few )
 
The green wire - is that collecting all ground's and then running them to a common ground? Looks like it.

Edit: Can you explain the wiring of this connection both at this end and the destination end?
 

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Yes, that's the "rail" for the shield of the internal cables at the source end. Destination end is kept floating.
 
Yes, that's the "rail" for the shield of the internal cables at the source end. Destination end is kept floating.
That is perfectly correct. I always do like that.
BTW don't you get pop or click when you change input while source grounds are also shifting? Because by this switching ground I have got MOSFETs exploded in output of class T power amplifier . Since then I let go grounds directly from sources merged and non-switched. Though l try to isolate left and right ground.
 
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Josh
Did you do the wiper and ccw connections as I said
Wiper - cold and ccw - ground ??

Also
You've not grounded the iec
Or introduced that diode ckt yet

Any humm??
 
Josh
Did you do the wiper and ccw connections as I said
Wiper - cold and ccw - ground ??

Also
You've not grounded the iec
Or introduced that diode ckt yet

Any humm??

Yes, pot connections are done. The ALPS R27 Blue Velvet (50kOhms) is good. I'm awaiting the DACT-type pot (10k). Will try as and when I receive it.

For grounding I need to buy components from market.

The hum is now very very low. Can hear only if one literally presses ear to tweeter. And zero on woofer. So for now I consider it as good as gone.
 
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