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franjam's κDCX build for non-engineers & the inexperienced


Re: franjam's κDCX build for non-engineers & the inexperienc

Postby franjam » February 25th, 2018, 8:43 am

Hi James thanks for the reply,, and it's obviously nice to know the stuff helps a bit.

I also did a lot of research on the various DCX mods out there and I felt and still feel that the AMB offer is the best value. A lot of the offers are very excessively priced and not as elegantly designed in my view . Also the o78/79 regulator and o1 clock are really good value aswell although I can't compare results with other offers . The price when you build them yourself however is unbeatable.

Having lived with the finished kDCX for a couple of weeks now, plus having finished the DSP part aweek ago, (coming up next ;-) ), I can only say that I have no regrets with this choice ; It was sometimes tough, a steep learning curve with soldering the smd's but overall very satisfying and the more I live with the sound the more I appreciate the difference, some of which is quite subtle. My sound has become incredibly refined and exquisite and musical in ways it was difficult to imagine before. I can totally lose myself in La Traviata without wincing at certain high notes as before for example.

So if you're halfway confident with a soldering iron, your eyesight isn't toooo bad and your a little bit brave I say that you won't regret the result :D :shock: 8-) :ugeek:
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby franjam » February 25th, 2018, 10:28 am

So here's a re-cap :lol: :roll: of the DSP section re-build mod and general finishing off..

First of all there's no way round it but desoldering the Behringer pcb is an utter BASTARD!! :twisted: You need heat, solder sucker, de-soldering braid and lot's of patience...; I say this with serenity and experience now :geek:, because I started without the de-soldering braid and the patience and made a real town halls of the job at first :oops: . It is very easy to damage the pcb tracks even with the bounce you get off the solder sucker, so if the the solder isn't all out first time, as it often isn't, move on to the soldering braid. And take your time ; A little more time but a better result for sure ;)

underside DSP pcb.jpg

My budget being way over whatever it was in the first place I had to do the recap with what I had to hand...

There are 2 sizes to the Elna 25v10uF's, I had the bigger size, they do fit, but it's a squeeze. For the two 47uF's I had a couple of Nichicon FG's at 63V so in they went. I had the 6 x 1uFs in Rubicon general purpose caps which left the power supply section.
For this I had Panasonic FR's in a mix : 4x 10uF/50V, 6 x 47uF at 25V and the 4.7uF at 25V. So not quite to spec but good enough I reckoned ; I decided to use the 47uF directly behind the voltage regulators, (just on intuition), and the others in the other spots.
I added the 2 o78 regulators last as they are the tallest elements.
here's a pic :)

DSP recap +regulators.jpg

So that left the o1 clock. Having already built one for my Marantz CD63 and going over the relevant section that Ti has posted for the DCX it was relatively straight forward. That said I can only re-emphasise the delicacy of the pcb as I managed to dislodge a track by just pressing a little too hard with the soldering iron tip trying to move the smd cap I was de-soldering. Again soldering braid is a good idea here. I used the two screws/bolts from the old Rs232 socket on the old analogue pcb for the standoffs, ;) they were just about ,if not exactly, perfect for the job, ie. the thread is close enough to do the job :) .

Time for a pic again :D

kDCX job done.jpg

I don't know if it was my imagination but kDCX casing seemed to be getting warmer than the original DCX. (op-amps?) Anyway I decided to glue a heatsink from my computer modding days on the Sharc chip which gets very warm,(I had no thermal glue to hand so I used thermal paste with a drop of Araldite on each corner of the chip and a weight on top for an hour or two). I also drilled a number of 5mm holes in the base and the top cover in a straight line from above the 2 voltage regulators on the PSU heatsink following the line of op-amps on the kDCX PCB, (not shown). As the original casing is completely closed I wanted the air to be able to circulate better : less heat, longer life :) at least that's the intention..

So there we go job done, DCX completely optimised, at least for me it's as far as I can or want to go. I still don't think my input ouput config is as good as it could be but I'll take my time with that...de-soldering the tiny resistors in the kDCX is also a challenge..

As I said earlier, I'm very happy with this job in all respects, fun, challenging, financially accessible, and the difference in sound is undeniable which is what in the end it's all about. Again, as with my CD63 I believe the o78 regulators brought an appreciable difference ; with a good recording depth, detail and texture have become exquisite, really, so I'm just made up, as the scousers say ;) .

I think that's it for my DCX, next up will be the valve mod on my cd player, I'm still waiting for the transformer :P. However that said, I'm getting my DenonDL103R cartridge back with a new paratrace diamond next wednesday, so it'll be interesting to hear how my setup now sounds with that, as it's not played any vinyl since the DCX rebuild, watch this space, :) and feel free to comment constructively on anything of course ;)
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby amb » February 25th, 2018, 11:34 am

Yes, the OPA1632s contribute to the higher heat, as they have higher quiescent currents and run hotter than the stock opamps.
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