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Old 18th August 2005, 03:40 PM   #1
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Default My first DIY DAC, advice needed

Hi all

So I decided to build myself a DAC. First of all: this is my first DIY project of this kind.
After considering all the options I've come to the conclusion that... that I have no conclusion. Mind that a few weeks ago I haven't even thought about this, I was almost dead-set on buying a NOS filterless DAC w AD1865, so please forgive any really stupid stuff I may write. But long is boring so I'll skip to the subject.

1. I think I will go for NOS and filterless. Why? Just for the sake of it. Consider those "project requirements" Nonetheless, further tweaks are not only welcome, but planned. As for others "requirements":
- no tube I/V or anything scary like that. No no no, DIY tubes is not for me (yet), I'm not ready to take that step.
- I'd like both I2S and S/PDIF input
- less than (roughly) 300$ in parts
- balanced would be nice, my (future amp) has balanced in

2. AD1865 is much praised but there are some naysayers. Considering that I have the possibility of listening to this DAC http://www.rockna-line.com/diy/dac/dac.htm I though that I should go for something else, even just for comparing. What chip would the gurus recommend?

3. I lack the expertise and the time (at least now) for "designing" my own. All my personal touch will be the choice of miscellaneous blocks (oscillator, I/V, power supply, etc). I'm calling for the gurus to help me.
- I was thinking about using the discrete opamp by Mr. Pass (D1) for I/V, just to find out that I'm not the first one. Any opinions on this?
- other thing is the clock. I know about the Guido Tent clock, the Kwak-clock, anything else I should find about?
- power supply - things I read about 78xx regulators make my skin crawl, any other better chips or discrete designs out there?
- what input S/PDIF decoder?
- anything else I might have missed


Last, but not least, please note that this is not one of those "what is the best ... out there?". All I want is to be pointed to the right direction by the more experienced, just get me going
Elso Kwak, Jean-Paul, Kuei Yang Wang? (I appologize to any guru not included in the list, also I appologize for including non-gurus by accident. just kidding )


Regards,
Calin
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Old 18th August 2005, 04:02 PM   #2
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Quote:
NOS and filterless. Why? Just for the sake of it.

It's fashionable. It's also rebelious. Be damned all engineering But would it sound better to You?

I was in similar position at some stage. Tried lot's and lot's of different configurations using the darling little 1543. Separate PS for everything; top quality parts. It only got better and better. Just not good enough. I know, i should have tried Thorsten's sinc filter before giving up.


It may be worth looking at something less revolutionary like the Rakk Dac - and it's right within your price range.
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Old 18th August 2005, 04:16 PM   #3
dddac is offline dddac  Germany
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Have a look at my DIY-Site, I have projects described in detail on both non oversampling (8412-1543)as well oversampled dacs (PCM63/PCM1704-DF1704/SM5842). Also a solution for use with a PCM1738 with transformer output...

might help you decide....

good luck with your DAC !

doede

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Old 18th August 2005, 04:21 PM   #4
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Take a look at Doede Douma's DDDAC1543: nonos - 8*TDA1543 DACs (no balanced outs I'm affraid) with Tent's 01 clock; resistor load as I/V. All for EU115. This is the starter kit to be fed with a battery. You can tweak it as much as you want and it sounds very, very good. (no digital artifact here)

Maybe with 16*TDA1543 and transformer output you can make balanced outs

Good luck
Mauricio
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Old 18th August 2005, 04:23 PM   #5
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Default Hi Doede !

You wrote faster than me
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Old 18th August 2005, 04:50 PM   #6
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Quote:
Originally posted by analog_sa
It's fashionable. It's also rebelious. Be damned all engineering
Yup the hype got to me. God knows that first time I found about that I was like "whaaaat?"

Quote:
Originally posted by analog_sa
But would it sound better to You?
Dunno, AudioNote can't be all wrong.

Quote:
Maybe with 16*TDA1543 and transformer output you can make balanced outs
Ahh, let me think about this... Oops, I think I've blown a fuse
Other option would be to give up on the balanced. This is not a must, but it sounds cool And my amp has balanced in as said before.

As for batteries. Nah, I never liked the idea. But that's not an integral part of the DAC so I guess it's not an issue.

Btw Mauricio, don't you have an UCD180 also? I remember seeing you on the UCD180 Q&A thread, if my memory isn't playing tricks on me. Excuse me if so. Anyway, I have 2 of those, that's the amp I'm going to use.

One other short question: why resistor I/V? Do you think that a more complex scheme is overkill?

And one of those questions from the "which is the best" series (can't help myself): which part of a DAC do you see as the most important? Clock, chip, output block?

Regards,
Calin
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Old 18th August 2005, 05:02 PM   #7
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Quote:
Originally posted by analog_sa
I know, i should have tried Thorsten's sinc filter before giving up.
I missed that at first read. I guess it answers the latter questions. So Thorsten's sinc filter you say...

Regards,
Calin
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Old 19th August 2005, 02:21 AM   #8
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Default Hi mr_push_pull !

Good memory

Quote:
As for batteries. Nah, I never liked the idea
My 36Ah battery will last 36hrs if I didn't recharge it
And is humm free
Appart for the fact that it reduces/eliminates digital artifacts.

Quote:
Anyway, I have 2 of those, that's the amp I'm going to use.
Why don't you go active? I use a cheap Behringer active crossover that makes "servo-balanced outputs". I feed directly (without preamp) the amps with that balanced signal. (Someday I will have a HiEnd crossover). The dynamics of this configuration are overwelming (did I wrote this wright? )

Quote:
One other short question: why resistor I/V? Do you think that a more complex scheme is overkill?
How would I know?
Ask the wise. Ask Doede.
The philosophy is "simpler is better" everytime you add an active stage you introduce distortion. The best opamp is no opamp
The second best is OPA627, maybe.

Quote:
which part of a DAC do you see as the most important? Clock, chip, output block?
Hey, I'm only beginning with it! So far I would say:
Output coupling capacitor make a huge difference. Non polar BG 22uF parallel Wima 0.47 uF made the sound very warm and relaxing, with good dynamics but lack of HF extension.
BG non polar 4.7uF in super-E-cap configuration (antiparallel) is very, very transparent and extended but takes eons to burn-in!!! This DAC is up to down detailed.

Add independent regulated supply for Tent clock (even with 7805, said to be very bad, but is the only one that I know how to use) made a better soundstaging (depth) and "presence"
Even wiring makes a change

Good luck, Calin.

Mauricio
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Old 19th August 2005, 02:25 AM   #9
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Sorry. I forgot to mention that all my previous opinions were about DDDAC1543

A not so cheap option to a balanced DAC is modifying a M-audio superDAC (my other DAC ) based on the AK4393 DAC chip.

M
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Old 19th August 2005, 04:34 AM   #10
wa2ise is offline wa2ise  United States
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Quote:
1. I think I will go for NOS and filterless. Why? Just for the sake of it. Consider those "project requirements" Nonetheless, further tweaks are not only welcome, but planned. As for others "requirements":
- no tube I/V or anything scary like that. No no no, DIY tubes is not for me (yet), I'm not ready to take that step.
I/V circuits ain't that scary Anyway you could feed to an external preamp circuit the I/V signal. The preamp would be similar to a phono preamp except no RIAA equalization circuit. Your favorite circuit that would amplify a 100mV signal up to line levels, 1 to 2V is all you'd need. Could be tube, transistor or op-amp.

Anyway, take a look at my web page on modifying the analog section of CD players . The preamp circuit need not be in the same box as the rest of the CD player. For someone starting with tubes, it would be easier to have the tube circuits inside a separate box.
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