The IsDAC

Isaac Sibson said:
Different implementations of a DAC chip may sound very different indeed. A Marantz CD85 does not sound like a Naim CD1 does not sound like an Arcam Alpha 5 does not sound like a rotel RCD-955. They all use the same Philips TDA1541 DAC chip though.
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I dont doubt that, but to my ears the EMU is doing a really, really impressive job for me, for the miserly sum of £70 :)

Have you had much interest in it yet?
 
id be interested in one if i can get enough inputs on it (two coax inputs for my nad 521bbe and nokai mediamaster ondigital box and a coax for eater my dab tuner or minidisc)
 
When I a full time job hopefully before next christmas I would be interested in somthing like this. If I did I would want the PCB fully soldered and maybe DILs would be better than surfice mount because you can easily replace the ICs if somthing was to go wrong.

Also the power supply would be an issue as I would not be confident of soldering my own connections to the PCB. The box would not be a problem as I can create drill my own boxes. I could then build a switching unit in a matching seperate box to switch between inputs. I am hoping to spend at least £1000 on my system within the next two years including a new turntable and speakers so I should be able to afford a new DAC.

All I would need from the PCB is a soldered co-axial input, phono anologue outputs, and wholes to screw the PCB onto a chasis.
 
lordsummit said:
I think I'd probably want just a couple of coax and 1 optical, but to be honest. I can't see why I'd need more than one input.
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I think I would need about 2-3 inputs depending on the frequencies this DAC could lock onto. For example I think my digital freeview box digital signal is 33Khz, my CD is 44Khz, and my DVD 48Khz. Would it be much harder work/more expensive for it to have a multi frequency clock?
 
Right...

I've managed to source the ICs at reasonable cost. The AK4117 DIR is very cost effective, and the 4395 has dropped in price somewhat since I last bought one. I will calculate a BOM cost soon for suggested components. This will be a "basic" but good set, which can be tweaked.

Currently plan is for Rubycon ZA (their top low ESR cap since the demise of the black gate) caps, AD825 op-amps (no, not the latest and greatest, but good and more easily available and more reasonably priced). Regs aren't yet decided... Linear tech are good but expensive. I intend to set up for case-mounted socketry for greater flexibility in case work. Power and DAC boards will be separate, possibly even separate supplies for digital and analogue sections.
 
I have been furthering the design somewhat more.

For the rabid (yes, that's you WM), I am considering separating L/R channel power regulators, although I have a designed-in option that allows you to run both channels off a single pair of regs should you not be rabid.

I've also been working on the board layouts with reference to how the devices are pinned, and have come up with a pretty clean layout in my head. Translation to PCB isn't a problem, although I've not looked at the digital part of the PCB yet. However simplicity is good.

Something that may surprise people when I finish up the design is how small the main DAC board will be. This is a very deliberate design feature to keep all paths short, and keep any track or plane resonances to extremely high frequencies.

I also thought I might make clear the design concepts here.

1) Scalability. Build this DAC how you want it... you can have separate power to each channel, unbalanced and balanced outs, loads of ins. Or you can have one input and one output, with shared power not only between channels but between digital and analogue sections.

2) Performance. I am designing this in such a way that if you go for the full monty of specification, performance should be very good indeed. If I can improve significantly (note: subjective) on my best modded superDAC (Will's) then I'll be happy.

I can see that the utterly insane can end up with a 4 box DAC (3 psus and the DAC). You can put everything into the same box if you want, but I'd go for at least two boxes.
 
I have now begun on actual design work for the DAC. This process may take a while as I have to create symbols and packages for the more complex devices.

Then, once I've got the schematics together, the fun starts... Layout!
 
Many universal players have digital outputs for SACD and DVD-A but need suitably equipped AV amps to use it. Stereo Hi-fi users have to make do with analogue connections. May be one of these days someone will write some code that can be burnt into an EPROM for use in a DAC!
 
The AK4396 DAC chip can take a DSD input. However, I do not intend to implement this.

DVD-A is catered for by 192kHz capabilities if the transport has dual coax outputs for this.
 
Very interested. Especialy the concept of starting simple (ie. cheap) (eg. single input, simple regulators) up to multi-inputs, fully modded. I'd be most interested in a core kit; I can add cases, psus etc myself; but it's always helpful & convenient having someone else buy bits on your behalf.

My desire is for at least 3 inputs

Some quick questions (but not necessarily quick answers):
- any idea of outline costs now? still £200? was that budget for the bits form you or for a complete DAC (inc. transformer, case etc)?
- so I assume from the spec of the DIP it would still respond to quality/stability/clocking on transport?
- why the AK4395? is it becuase of your favourable experiences of the superdac?

Thanks

Chris
 
For what you want, ie a board and three chips, it will be less than £100. Other expense you decide from there on.

Yes, although the PLL means that this is limited, but as much as any other DAC which is similarly clocked.

Yes. The superdac with the 4393 sounds very good. The 4395 has a much higher spec filter on it (120dB attenuation vs 85dB) so should improve matters over the 4393 for a given implementation. Also, the AKM chips are well priced and their distributor is not so far up their own ... that they won't sell to individuals, unlike distributors of certain other similar parts.

Coming back to costs, £200 should build a two box, middle of the road spec, depending on how I break things down in terms of boards. For fancy specs I can see it being easy to spend £400+. Very basic single box single psu spec would come in around £150 or so.

All prices currently approximate. They're a rough idea.
 


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