DAC designs

richardcooper2k · Post by **richardcooper2k** » Sat Mar 29, 2008 11:46 am

dac shoot out as well then

i've been thinking about building a dddac but i can have a listen first now !

Andrew · Post by **Andrew** » Sat Mar 29, 2008 1:00 pm

So what modules did you for then Nick, I'm getting curious....

Post by **Nick** » Sat Mar 29, 2008 1:11 pm

One of the sp/diff to i2s boards, and one of the tower 1543 boards. I thought the i2s would be a good place to strat with for any other designs as its a easy way of getting a i2s feed. Its got a tent labs relocker on as well.

http://www.dddac.de/ma_dac31.htm

Andrew · Post by **Andrew** » Sat Mar 29, 2008 1:14 pm

Must get down to yours for a play....and a listen.

Post by **Nick** » Sat Mar 29, 2008 1:18 pm

You know where I am

Post by **Nick** » Sun Mar 30, 2008 4:08 pm

I have been reading this months HiFi world, in Noel's colum he comments on the problems with filterless DAC's, and remarks that the problem is one of aliasing frequencies being generated. Am I missing something, isn't aliasing a problem when a ADC is used without a filter limited input, not a DAC?

SimonC · Post by **SimonC** » Mon Mar 31, 2008 7:42 am

Andrew wrote:Must get down to yours for a play....and a listen.

I'd be interested in coming out to play as well, especially now you've got a dddac set-up. I'd be really interested in hearing the stacked 1543's alongside Ian's 1541, and maybe we can borrow a couple of other toys (anyone with an isodac?)

Simon C

Post by **Nick** » Mon Mar 31, 2008 7:56 am

I'd be interested in coming out to play as well, especially now you've got a dddac set-up. I'd be really interested in hearing the stacked 1543's alongside Ian's 1541, and maybe we can borrow a couple of other toys (anyone with an isodac?)

I think the plan is to do some of that at Owsten, but as always you are more than welcome, but you will have to talk nicely to Ian about the 1541.

How is the 6c33c going?

SimonC · Post by **SimonC** » Mon Mar 31, 2008 8:30 am

I can't make Owston

plus I can't help thinking that you need to live with dac's for a while as some of the differences are subtle, and I'm not sure that the hustle & bustle of Owston would be the best enviroment for a proper listen.

I can try bribing Ian with more of my wife's soup, plus there's always the trump card of homemade chocolate espresso cake...as far as I can work out it involves mixing dark choc, a shot of espresso, double cream and alcohol. Always a winning combination.

The 6c33 has moved on slowly since your last visit, (family pressures and house DIY), I've had HT on the 6c33's but needs tweaking, its about 40v overvolted, and have the psu built for the c3g's. Maybe get power on these this week as the family is away for a couple of nights.

Simon C

Andrew · Post by **Andrew** » Mon Mar 31, 2008 11:23 am

Nick wrote:I have been reading this months HiFi world, in Noel's colum he comments on the problems with filterless DAC's, and remarks that the problem is one of aliasing frequencies being generated. Am I missing something, isn't aliasing a problem when a ADC is used without a filter limited input, not a DAC?

I think he means "imaging" which, is a problem, and is kind of the reverse, I think.

-- Andrew

Neal · Post by **Neal** » Mon Mar 31, 2008 11:47 am

Well I'll have my bu**erd, sorry modified

Beresford and an interesting portable battery powerd DAC from iBasso...

Post by **Nick** » Mon Mar 31, 2008 12:02 pm

I think he means "imaging" which, is a problem, and is kind of the reverse, I think.

Have you got any references to that, I have forgoten far too much theory about sampling

ed · Post by ed » Mon Mar 31, 2008 3:43 pm

I posted this up a long time ago. I wasn't sure if it was relevent then, and I'm still not sure now....but here it is again, IMO the best description of what audio bits get up to.....

http://www.tnt-audio.com/clinica/convertus1_e.html

Post by **Nick** » Mon Mar 31, 2008 3:59 pm

Ah, ok, so without filtering you get a image between Fs/2 and Fs of the difference signal. But given that Fs/2 is > 20k, then assuming this signal has no unwanted effect on the folowing amplifier its benign.

I can see though if slew rate limiting or IM was generated thne it could cause a problem.

Think this justifies my amp rolling off signals above 20k, its just being a large reconstruction filter

Andrew · Post by **Andrew** » Mon Mar 31, 2008 8:21 pm

Nick wrote:
I think he means "imaging" which, is a problem, and is kind of the reverse, I think.
Have you got any references to that, I have forgoten far too much theory about sampling

I'll dig something out, as soon as I can.

audio-talk

DAC designs

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