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-   -   Metrum Octave Dac - What are the Chips used (http://www.diyaudio.com/forums/digital-line-level/208325-metrum-octave-dac-what-chips-used.html)

bencat 7th March 2012 01:59 PM

Metrum Octave Dac - What are the Chips used
 
This NOS Dac which is causing something of a stir is getting soem very glowing reviews including in Hi Fi Critic. In all the threads and reviews I have read up to now there has never been a mention of the manufacturer or chip number that is actually used. It is often mentioned that it is not an audio but an industrial one used for other things. However it should still be easy to get the chip number and who made it ?

I mentioned this Dac to my audio repair engineer and he sent me an e-mail that they were using TDA1543 chips which I would find pretty hard to accept as these are nothing like what is being described and are just cheap replacements for TDA1541 chips.

Does anyone have one of these Dacs and have you looked at what chip is installed . Would be interested if anyone can shed any light on this.

qusp 7th March 2012 03:45 PM

no, it is not TDA1543, ive seen inside pics in a review and they look nothing like them. its described as a very high speed industrial Dac chip and it is voltage out. its a NOS dac, but i think that is where the similarity to the TDA ends, so I would wonder a bit about your engineer, maybe he hoped you wouldnt do something like this.... sorry i dont know the part #, they have been tight-lipped about it. you would need to come up with some sort of uC or glue logic to use it for audio though

Sonaj 22nd March 2012 02:08 PM

Hm, while the chips don't look anything like regular TDA1543's they do look similar to the 16-pin package TDA1543T. I'm not saying that this is the chip they're using but from the photos I've seen it could very well be.

abraxalito 23rd March 2012 03:58 PM

Digital to Analog Converter - Precision DAC (=<10MSPS) - DAC8581 - TI.com

qusp 23rd March 2012 04:13 PM

yep, that looks right, not a TDA =D not even close

abraxalito 23rd March 2012 04:30 PM

Here's the back story as reported on 6moons:

...we subsequently attempted to design a DAC which would not be based on the regular AKM, Burr Brown, TI, Crystal and Wolfson chips which are ubiquitous in consumer audio. Instead we wanted an ultra high-speed part such as you'd find in industrial applications. After many years of experimentation we finally identified an extremely fast chip that's useable for 16 or 24-bit audio but handles sampling rates up to 15 Megahertz.

If you read the datasheet you'll notice there are a few things here which don't quite ring true - the claimed sample rate achievable is '15MHz'. Contrast that with the maximum data input rate of 50MHz - 16bits need to be fed in per sample, giving 3.125MHz flat out. The settling time (to 15bits) is quoted as 1uS giving a practical limit of 1MHz. I could mention further that its most definitely a 16bit DAC only...

<edit> There's a subsequent laugh further down the same article - Because our DAC chips are relatively expensive. TI's price is $1.85 each, 1k.

qusp 23rd March 2012 06:03 PM

they are running several in parallel though arent they? could they not interleave the samples on half for higher speed and parallel for higher bit depth?

the pricing..well.... not much to say there

Tam Lin 23rd March 2012 07:08 PM

Quote:

Originally Posted by qusp (Post 2957470)
yep, that looks right, not a TDA =D not even close

Actually, it is comparable to the TDA1543.
THD -75dB vs. -72dB
SNR 96dB vs. 108dB
Settling time .5us vs. 1us

abraxalito 24th March 2012 02:02 AM

Quote:

Originally Posted by qusp (Post 2957580)
they are running several in parallel though arent they?

Yep - 4 per channel.

Quote:

could they not interleave the samples on half for higher speed and parallel for higher bit depth?
They could use a DSP to oversample but it looks like they don't - the impulse (and square wave) response is devoid of any filtering effects. Paralleling doesn't increase the bit depth, oversampling might to a small degree.

qusp 24th March 2012 02:53 AM

Quote:

Originally Posted by abraxalito (Post 2958128)
Yep - 4 per channel.

thought i remembered that, didnt look at the article you linked, but i read it when it was released and i remember thinking using these chips was simply a way of having a unique selling point; rather than presenting any real performance advantage. I generally prefer to see an actual external i/u convertor designed for audio...ie. I prefer current out dacs

Quote:


They could use a DSP to oversample but it looks like they don't - the impulse (and square wave) response is devoid of any filtering effects.
ahh, was just a thought experiment, i think its as much hogwash as you

Quote:

Paralleling doesn't increase the bit depth, oversampling might to a small degree.
I meant only by way of lowering noise vs signal and thus presenting an apparent bit depth increase, however small. you know hifi, small becomes large


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