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Originally Posted by Pricklely Peete /img/forum/go_quote.gif
I'm thinking a true dual mono supply is the way to go but it would require a new chassis and quite a bit of money to complete properly. No doubt IMO that it would make a big big difference compared to the stock supply, not that the stock supply is inadequate for the current job it's just not an all out design. I'm hoping Bill's experiments are along these lines but he has not chimed in in quite awhile so I hope he's still thinking of doing something similar (he hinted at such several pages back).
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I have to wonder what benefit there would be to a dual mono supply on this board, its totally single ended with a passive I/V and all the dac chips are in parallel. it would seem to me to be a bit of a waste of time and money. using separate regulation and transformers for analogue and digital sections would work well, but the point of having a dual mono supply is to have separate grounds for physically separate channels, ie. galvanic isolation of left and right channels, this works well with dacs that have chips set up for each differential channel and separate active analogue I/V sections, but you have none of this here. now if you modified the dac so it used 8 chips for R and 8 chips for L, that might be different, but this would be pretty involved and would also require some digital tweaking. would be cheaper to buy a second dac and bridge them.
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I would likely split the PSU duties off further by dedicating another separate (PSU board and transformer, 15VA toroidal or R-Core if it can be sourced) low V supply to the receiver chip/clock boards. Getting these supplies (all three of them ) as clean and linear as possible should yield huge dividends. |
as above, just the 2 supplies should be enough, more discrete regulators would work well, but no real need for more power supplies
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The expense and size factor is the only limiting factor but it could be done for under 150USD including a half decent chassis I would imagine. Upgrade the DC lines to heavier jacks (like Mini XLR) and use either CC OFC 6N copper solid core (18 awg) or solid silver of the same gauge. Might as well build a decent mains cable for the PSU while your at it. A solid silver mains cable with tinned copper mesh shield could be built for a small outlay in cash. Maybe another 100USD or less depending on length and OEC/Plug choices. The entry level Wattgates are more than good enough. Of course all of these ideas are just suggestions and may represent a level of overkill that some may find unnecessary but I'm pretty sure limitations of this type are not a factor in this thread. What I mean by that is a basic mod rule I learned a while back WRT and it pertains to all audio gear, work on the PSU first, second and third and then move on to the other bits once you've maxed that PSU design out or have run into your budget limitation. It's a good rule that has worked with every mod/project I've managed to complete without blowing the piece of the gear up (I exaggerate of course about blowing stuff up but it happens to the best of us from time to time when attention to detail slips) Kind of an expensive reminder/lesson to be careful and precise and to take nothing for granted. |
actually with the right thinking and purchases the size does not need to be that bad, buy a nice piece of custom iron (or 2 if you must) from richard sumner (sumR), with multiple secondaries at the voltages needed to cover the voltage drop across each regulator, buy a slab of 10mm copper the same size as the profile of the DC30 and have the digital transformer and PSU on one side and the analogue section on the other, bolt the diodes or ICs to either side (isolated) to keep the temperature steady and even for more matched performance. this would keep heat down and save on heatsinking/space, as well as shielding one side from the other very effectively (ground the sink) use a discrete rectifier to feed the DC voltages to the regs. JSR01 from sjostromaudio.com would save you on space as its a jung super regulator made with discrete SMD parts, so is very small and thin.
contrary to popular belief around here high quality SMD is usually superior and mostly cheaper. crappy SMD is ....crappy of course, but so is crappy P2P wiring, worse even, especially for digital, the ground plane is of huge importance to noise levels and therefore dynamic range in a dac, you completely give away this benefit by airwiring stuff; in fact in many cases I would think that the small 'bypasses' often seen in here to avoid nothing but traces would introduce more noise than any benefit gained by the wire (please remember i'm an avid cable believer too) many DIYers are afraid of SMD though, its not as accessible as through-hole. this dac would benefit greatly from a discrete diamond buffer, mosfet follower or similar at the output IMO, seems many of you are running this into a preamp, with a nice buffer (with current gain) to drive the cables, you could avoid the pre. you can even combine a follower with a transformer in the feedback loop. i'm doing this with my dac was going to go completely passive with transformers, but found a great little circuit by mister jung that gives you the best of both worlds.
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The hard part is sourcing the right base PSU pcb, proto'ing a board would be too expensive unless some members here have access to such services for a decent price. That being said I'm weak on design but I'm trying to learn as fast as I can. |
its not hard at all, i've been collecting regulators and power supply PCBs for the last 6 months or so and i'm amazed (and dismayed, my poor poor wallet) at the shear number of them. sjostromaudio.com is a good source, thats where I got many of my different variants of super regulator, got heaps of different shunts as well. the DC30 has plenty of room for all you could need. house the iron, rectifier and power supplies in the DC30 and then use JSR01 or similar small discrete regs in place of the 3 pin variety close to the target. PSU wiring can be a bit longer, but the regs should be as close as is possible.
i'm playing around with eagle for PCB design as well, plenty of learning ahead there, but I cant wait for the possibilities. in fact getting small runs of PCBs made is quite cheap. you could get 5 FR4 boards large enough for a bipolar or dual regulator for 50-60 bucks and there is no shortage of designs available on DIYAUDIO, can often find blank PCBs in the swap meet section from people who bought too many or went another direction. or get involved in a group buy for a good design.
plenty of fun to be had. i fact i'm currently loving the look of the variable christmas tree lights of my latest power supply
LED references FTW. you will find that LEDs are great low noise references, so power supplies are often quite pretty
especially for lower voltages needed by DACs
yay back to the music