Can the PCM1794 better the PS1's sound? (or: alternative DAC w/ simple output stage?) - diyAudio
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Old 22nd January 2012, 01:22 PM   #1
sfasf is offline sfasf  United Kingdom
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Default Can the PCM1794 better the PS1's sound? (or: alternative DAC w/ simple output stage?)

Could anyone comment on how the PCM1794 sounds in relation to the PS1's AKM4309AVM??

I am asking because I am looking to build an affordable DAC unit-- the PCM1794 has been recommended. However, it requires a relatively complex output stage to fullfill it's potential. The Playstation 1's DAC however, just requires a couple of resistors.. and i've heard it and I like the sound. This DAC is out of production, however.

So, would the PCM1794, with proper I/V output stage sound significantly better?? (can anyone reccomend an I/V stage??), or is there a good (in-production) alternative which has a simple output stage like the AKM4309, whilst remaining affordable and sounding as good or better?
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Old 22nd January 2012, 07:12 PM   #2
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Is this a real question?? Of course is better. And yes, it needs quality OpAmps to achieve the maximum from I/V conversion, if you look for "direct output" you need some voltage output DAC's - like the PCM1793 or PCM1781 (this one has really simple output).
AKM4309 is a nice simple DAC, but it's just a modest performance, delta-sigma DAC. Regardless what fans say - THD @ -84dB, S/N A weight @ -90dB are nothing to be excited for - especially in a delta-sigma DAC. I even listen one (they are cheap here in CashConverter stores) but was nothing special.

Last edited by SoNic_real_one; 22nd January 2012 at 07:31 PM.
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Old 23rd January 2012, 12:07 AM   #3
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The PCM1794A does not require an op-amp I/V circuit to obtain excellent sound. In fact, there are several high-end digital audio component vendors who sell very highly regarded non-opamp I/V units based on T.I.'s PCM179x series of DAC chips. Among them are; Audio Research which utilizes a passive resistor I/V, Neko which utilizes a Jensen transformer I/V, and Yamamoto which utilizes a zero-feedback grounded base PNP transistor I/V.
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Old 23rd January 2012, 12:42 AM   #4
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Note to mention Ayre's QB-9 which (from eyeballing a PCB pic) has passive resistor I/V followed by discrete transistor amplification.
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Old 23rd January 2012, 12:42 AM   #5
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Yet, again, none of those is listed in the TI datasheet. Those "solutions" are nothing more than gimmics ment to find a niche suitable for their marketing and pushing high prices.
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Old 23rd January 2012, 01:31 AM   #6
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by SoNic_real_one View Post
Yet, again, none of those is listed in the TI datasheet. Those "solutions" are nothing more than gimmics ment to find a niche suitable for their marketing and pushing high prices.
Have you actually heard any of these "gimmicks," some of them actually work remarkably well IMLE. (I've experimented with them all, although personally I think the resistor IV is not a great idea with this chip, unless the resistor is tiny.) I'm currently using mono mode 1794As driving TI THS4131 for IV conversion into transformers (for balanced to unbalanced conversion) and am a big fan of the 1794A.

An interesting aside is that the THS4130/4131 were originally developed as DSL line amplifiers, when TI noticed people using these for audio and for driving ADCs they rewrote their datasheets and application notes to reflect this note. Just because it is not mentioned in an app note does not automatically invalidate a given design approach.
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Old 23rd January 2012, 07:33 AM   #7
sfasf is offline sfasf  United Kingdom
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Sonic: I haven't heard the PCM1794, and i haven't read any direct comparisons, so I can only know how they compare by asking. I assume you listened to the correct version (100x or 5xxx)? I thought it sounded very good (as do lots of people, apparently), but i have not had a 'proper' DAC so i'm sure there is room for improvement still.

Anyone else have an opinion on how they compare??

Everything i've read on the I/V stage has suggested that avoiding OP amps (ie discrete I/V stage) is the way to go. This is my starting point... can anyone suggest a better alternative??
I'm looking for unbalanced.

Is there anything worth considering that is similarly priced that allows for much simpler output stage implementation? ..or are there other chips i should consider? or any cheaper ones worth considering?
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Old 23rd January 2012, 07:40 AM   #8
wwenze is offline wwenze  Singapore
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Hmm, PS1 and PCM1794 seem to be designed with different goals in mind. Stereophile has measurements of the PS1, if measurements are of any importance to you.
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Old 23rd January 2012, 08:39 AM   #9
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Quote:
Originally Posted by sfasf View Post
Could anyone comment on how the PCM1794 sounds in relation to the PS1's AKM4309AVM??

I am asking because I am looking to build an affordable DAC unit-- the PCM1794 has been recommended. However, it requires a relatively complex output stage to fullfill it's potential. The Playstation 1's DAC however, just requires a couple of resistors.. and i've heard it and I like the sound. This DAC is out of production, however.

So, would the PCM1794, with proper I/V output stage sound significantly better?? (can anyone reccomend an I/V stage??), or is there a good (in-production) alternative which has a simple output stage like the AKM4309, whilst remaining affordable and sounding as good or better?
1794 is a perfect candidate for passive I/V with close to 8 mA of differential current swing. Add a transformer for I/V & dif-to-single-end conversion, all at the same time -> and you're done. Simple.

Properly implemented OP I/V stage in a low-noise environment will sound consistently (not dependant on the rest of the audio system) excellent AND neutral …. so… to a priori disregard OP’s is a mistake. .. many are actually not ready for such solution –> it can sound too realistic; almost frightening in a good system….. so transformer / resistor solution might be preferable choice.

Anyway – with 8mA of current swing, you can rest assured that you picked the best contender for passive I/V, so have fun!

Boky
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Old 23rd January 2012, 02:29 PM   #10
sfasf is offline sfasf  United Kingdom
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So, i think you are suggesting i use the transformer? If so.. i have no idea what transformer i would want.. [e: .. and it seems they can get very expensive so as stated.. i want to avoid that. Is the transformer solution still the best given a requirement for affordability?]

And why this over the op-amps, since you seem to rate them highly??

You think this would be better than the type of circuit i posted?..

Am currently getting very bogged down and confused reading many posts regarding 1794 output / i/v stages..

Last edited by sfasf; 23rd January 2012 at 02:39 PM.
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