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

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

Postby franjam » January 12th, 2018, 8:30 am

Ok I'd like to start this thread as per the title for all the non-engineers & the inexperienced out there who'd like to have a go at this build. (There are so many highly qualified people on this forum its ridiculous :roll: ) So I'll try and see it thru to the end and ask all the daft and embarrasingly obvious questions that we are often too intimidated to ask. Having said that most people with knowledge are happy to share and educate others which is my experience on this forum so far :) . So if you are hesitating about this build for reasons of in-experience, read on, and I hope it allows you or encourages you to make the right decision.

I learn't to solder little more than a year ago, I've always been handy, I used to be a stonemeson, I've also been a social worker and today I am a manual therapist. I've always been into music ; I think I bought my first HiFi system at 13 years old ; my 1st live concert was the Clash when I was 14 years old in Manchester, England ,(so work it out ;) ). I've seen Zappa, James Brown, Van Morrison, the Stones, Bowie, Dylan, Santana among others, ( yes I'm boasting a little :D ), just missed Led Zep unfortunately :cry:

The point is that music and hiFi have always been an integral part of my life, but it was only after my divorce a few years ago that I pulled out my vinyls which had been boxed somewhere and started looking at improving my sound system. I won't go into ALL the boring details but in 2016 I built two Fane scoop based folded horn speakers with 15" 1974 GoodmansAudiom full-range drivers coupled with Hifax treble horns. At the same time I bought the Behringer DCX2496 active Xover after becoming convinced of its advantages., (I wasn't dissapointed). This was all set up using the UMIK 1 measuring mic and REW which is indispensable to get the best out of your drivers, the room and the DCX.

In 2017 I re-built and modded two A&R Cambridge A60 amplifiers which I'd had since i was about 18. This was a serious learning curve , made lots of mistakes ; blew up transistors, replaced parts I shouldn't have and spent probably far more than I should have done for the same result ; but I enjoyed it and the result was pretty good in the end. I then moved on and built the Elekit TU8500 valve pre-amp bought fom Victor Kung at VK.Music in canada, ( a great guy who gave great support by the way ), Fortunately the instructions were completely idiot proof and the improvement over the A60 pre-amp, even rebuilt, was world's apart.

At the end of last year I completely renovated and modded my Marantz CD63SE cd player, mostly using Thorsten loesch's tips at TNT audio but not only, (one does have to put up with his humour but he does seem to know what he's talking about most of the time :shock: ). Again I was very happy with the result which was basically day and night as we say in French, (I am half French on my mother's side BTW). I am about to bang the o1 clock on it, so I'm not sure what to expect as it sounds so good right now ; there is still a slight hardness in the treble on certain voices, Van Morrison's Angelou for example, so I hope it improves that...(see relevant topic if you are interested).

I've omitted all the steps/mods with my original Rega Planar 3 and my Nytech CT206 tuner, (very rare! look it up), but I'm now happy with that, so that brings me to the next obvious link in the chain which is the DCX and the point of this topic :D, I have to say that it is great fun improving one's sound system by increments and doing it yourself ; my hopes for the kDCX are high as it represents a fair investment for me. (luckily my fiancée shares my love of music and is very understanding, phew! I'm lucky in that department ;) )

So I now have a little experience with soldering but I don't pretend to know or understand why all these parts are chosen and put together in the way they are, Having said that I know a lot more than i did a year ago so..onward!
Having just received, ( and checked ), all the parts from Mouser, (I'm still waiting for the pcb's :roll: ), I can see that this is going to be micro-surgery compared to what I've done before so it's a little daunting at this point ; but hey, another challenge :)

Budget wise this build has so far cost me a third more than I guesstimated, I didn't count on all those very expensive transistors, (about 20), (read op-amps not transistors) which are about a third of the total cost by themselves, and I didn't calculate the parts cost before ordering the pcb's, ( all sounded so good ;) ). My own fault obviously, but a quick question Ti; are there cheaper alternative parts out there for the more budget strapped audiophile? A bit like the less powerful B24 amp kind of thing...too late for me of course but then I did always prefer the best if I can afford it.. :) , and even when I can't sometimes :D ).

Anyway, watch this space, I'm running out to the post box like a big kid every day at the moment :) hopefully building and more comments will start soon..
Last edited by franjam on January 13th, 2018, 3:56 am, edited 2 times in total.
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby amb » January 12th, 2018, 11:05 am

franjam wrote:...
Ti; are there cheaper alternative parts out there for the more budget strapped audiophile? A bit like the less powerful B24 amp kind of thing...too late for me of course but then I did always prefer the best if I can afford it.. :) , and even when I can't sometimes :D ).

Unfortunately there isn't anything you could substitute to reduce cost. The κDCX was designed to be a superior replacement for the stock Behringer analog board, and the parts selection reflects that. You should read the κDCX development thread to understand more about the design and parts choices.
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby franjam » January 13th, 2018, 2:30 am

I did read that and it helped me make my decision, I just wondered if there might have been compromise middle of the road transistors (edit I meant op-amps :oops: ) between the old version and the kDCX ; but I understand you were looking for a no compromise design.
Last edited by franjam on January 13th, 2018, 3:57 am, edited 1 time in total.
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby amb » January 13th, 2018, 2:45 am

The only bipolar transistors on the κDCX are a small number of MMBTA06 and MMBTA56, and these should be quite inexpensive. Then there are a pair of MMBTJ108 JFETs per output channel. These shouldn't be expensive either, so there isn't a way to reduce the cost by any significant amount with other transistors. The "costly" items are the opamps, relays, XLR jacks, etc., but the opamps have no suitable substitutes that are cheaper.
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby franjam » January 13th, 2018, 3:49 am

:D Yeah in fact the op-amps were what I was talking about.... :D It does occur to me now that a bit could be saved if one was prepared to salvage the XLR parts, RJ45 sockets switch etc from the old board.. (I didn't buy the RJ 45 sockets as I know I'll never be daisy chaining..)
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby amb » January 13th, 2018, 4:27 am

You can’t reuse the XLR or the RJ45 jacks from the stock analog board because they don’t have the exact same PCB footprints. The ones used by Behringer are unobtainium so the κDCX was designed to use similar but different parts.
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby franjam » January 13th, 2018, 6:04 am

Well there you go , now we know. :geek:

The pin headers arrived in their envelope this morning , still awaiting the pcb's though :? can you track from your end TI ? I can't get anything from my end :cry:
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby amb » January 13th, 2018, 1:46 pm

Contact me offline about order-specific questions or issues.
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby franjam » January 14th, 2018, 7:10 am

Ok no worries
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Re: franjam's κDCX build for non-engineers & the inexperienc

Postby franjam » January 20th, 2018, 4:44 am

Hi TI,
Despite sending 2 emails using the contact form at the bottom of the shop page regarding the tracking of my pcb order I have received no replies ; I realise this is not the appropriate place to discuss this but at least I am certain this will be read ; there must be some problem ; please indicate the correct contact address to contact you about this order, or contact me directly.
Thankyou.
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