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Old 19th December 2011, 06:01 PM   #21
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Originally Posted by Ken Newton View Post
Hogwash. Central, don't you believe a word of that. Sonic is taking what is his own listening preference and making blanket claims about what will be the preference of others. All passive (meaning, a simple resistor from the current DAC output pin to ground) i/v implementations may sound worse than a "good" op-amp to sonic, but they may not all sound worse to you. In fact, you might find that you have a great preference for passive i/v, depending on the specific implementation. Not all, or even most, current output converter (DAC) chips are suitable for passive i/v, but some most certainly are. In fact, some of the most acclaimed commercial conversion stages utilize passive i/v, such as those from Audio Note, Ypsilon (I believe), BAT, and others.
I guess ALL the DAC manufacturers are stupid because they ALL recomend OpAmps as I/V (with virtually zero impendance on DAC outputs). Their engineers are smart enough to design a whole DAC, but they cannot figure that a resistor is a better choice for I/V? Or is a world-wide conspiration?

If resistor was sounding better, it would be in the datasheet. I guess the "do-it-on-the-knee" companies and users on the net are the true specialists...

Last edited by SoNic_real_one; 19th December 2011 at 06:05 PM.
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Old 20th December 2011, 01:13 AM   #22
Jay is offline Jay  Indonesia
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Yes. It is related to Signal to Noise Ratio (SNR). This is intrinsic to the chip so not much you can do with external components.
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Originally Posted by SoNic_real_one View Post
I guess ALL the DAC manufacturers are stupid because they ALL recomend OpAmps as I/V (with virtually zero impendance on DAC outputs). Their engineers are smart enough to design a whole DAC, but they cannot figure that a resistor is a better choice for I/V? Or is a world-wide conspiration?

If resistor was sounding better, it would be in the datasheet. I guess the "do-it-on-the-knee" companies and users on the net are the true specialists...
In this imperfect audio world, we have to accept compromises. Our decisions should be based on knowledge. I cannot see anything wrong with passive approach or opamp approach.

When the DAC has low dynamic range, of course passive I/V tends to give trouble, but not so if we take that into account in designing from source to speaker.

One way to improve dynamic is by using opamp instead of resistors. But opamps have their own problems. But may be not if the opamp has high slew rate and a good power supply. I prefer passive approach than using less than 10V/us opamp (It was even very difficult to beat OPA2134 (20V/us) with passive I/V). So I think I will not go the passive route as I have the money to buy parts and have sufficient knowledge, skill and ears to build a good sounding system.

So again, it is all about implementation. If money is not a problem (to buy better parts), imo it is always easier (and I think better) to go with active. And hey, you can choose from the many discrete opamp designs out there.

Successful passive implementation requires careful attention and matching from start to end of the audio chain

N.B. I wanted to edit the SNR with THD+N in previous post but for a reason I don't have an edit button so
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Old 20th December 2011, 05:37 AM   #23
CENTRAL is offline CENTRAL  Greece
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Originally Posted by Jay View Post

N.B. I wanted to edit the SNR with THD+N in previous post but for a reason I don't have an edit button so
Yep! makes more sense that way!!!
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Old 20th December 2011, 07:46 AM   #24
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It's all very well discussing ten thousand ways to skin a cat....why exactly should they all sound different again?
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Old 20th December 2011, 10:25 AM   #25
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It's all very well discussing ten thousand ways to skin a cat....why exactly should they all sound different again?
You basically just answered your own question. Sound improvements can also be made that are unrelated to the DAC chip sets. Take the analog output stage for example. I have a Denon 2900 with a new ZAPfilter installed. It sounds way better than stock, yet the DAC chip set has not been altered.
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Old 20th December 2011, 02:41 PM   #26
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Originally Posted by Jay View Post
In this imperfect audio world, we have to accept compromises. Our decisions should be based on knowledge. I cannot see anything wrong with passive approach or opamp approach.
That would make sense if the resistor I/V would be MORE EXPENSIVE than an OpAmp one. Since the cost is superior, obviously, there was no "compromise" when manufacturers selected OpAmps as the required output stage.
Good OpAmps today have more than 20V/uS and THD+N at -110dB. They are way better than the OpAmps used in '80's DAC's. What was "high-performance, audiophile quality" in 1985 (for example LM833), is "low-cost, general use" now.

Some people didn't get the memo yet.

Last edited by SoNic_real_one; 20th December 2011 at 02:49 PM.
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Old 20th December 2011, 11:23 PM   #27
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[QUOTE=SoNic_real_one;2827054]I guess ALL the DAC manufacturers are stupid because they ALL recomend OpAmps as I/V (with virtually zero impendance on DAC outputs). Their engineers are smart enough to design a whole DAC, but they cannot figure that a resistor is a better choice for I/V? Or is a world-wide conspiration?


That is such a specious argument.

The question of what sounds best is not a function of smarts. If some people find a different solution to sound better it doesn't make them smarter than the DAC design engineers assuming those engineers tried alternative solutions and listened to them. It is merely a matter of preference.

The engineers who designed the DAC may not even be the same guys who designed the I/V stage for that matter.
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Old 21st December 2011, 12:05 AM   #28
Jay is offline Jay  Indonesia
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Originally Posted by SoNic_real_one View Post
That would make sense if the resistor I/V would be MORE EXPENSIVE than an OpAmp one. Since the cost is superior, obviously, there was no "compromise" when manufacturers selected OpAmps as the required output stage.
Good OpAmps today have more than 20V/uS and THD+N at -110dB. They are way better than the OpAmps used in '80's DAC's. What was "high-performance, audiophile quality" in 1985 (for example LM833), is "low-cost, general use" now.

Some people didn't get the memo yet.
A decision to use passive I/V is like a decision to use the shortest signal path, single ended design then to work out the related issues like putting massive inductors in power rail, etc. The external work may be more expensive (and time consuming) than the I/V itself.

If I/V is used but there is opamp in the signal chain, then that would be against the philosophy.

All in all, I'm against the passive I/V myself. I believe that those with good ears will know why.
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Old 21st December 2011, 12:18 AM   #29
Jay is offline Jay  Indonesia
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Originally Posted by ssportclay View Post
Sound improvements can also be made that are unrelated to the DAC chip sets. Take the analog output stage for example. I have a Denon 2900 with a new ZAPfilter installed. It sounds way better than stock, yet the DAC chip set has not been altered.
Sure, even passive I/V can be followed with discrete buffer. There are many ways to make a DAC to sound good, even with a cheap DAC like TDA1453.

That's why I stated that DNR is one important parameter that defines a signature of a DAC. Because no matter what you do with the auxiliary circuits, it will never sound like what it is intrinsically incapable of. It doesn't mean that high DNR DAC design will always preferable soundwise than low DNR DAC. It depends on the design. But "dynamics" is audible, and it is a positive characteristics. Have a good listen.
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Old 21st December 2011, 01:38 PM   #30
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Originally Posted by Jay View Post
Sure, even passive I/V can be followed with discrete buffer. There are many ways to make a DAC to sound good, even with a cheap DAC like TDA1453.

That's why I stated that DNR is one important parameter that defines a signature of a DAC. Because no matter what you do with the auxiliary circuits, it will never sound like what it is intrinsically incapable of. It doesn't mean that high DNR DAC design will always preferable soundwise than low DNR DAC. It depends on the design. But "dynamics" is audible, and it is a positive characteristics. Have a good listen.
Thanks Jay. I am having a very good listen. The clarity and dynamic slam that the ZAPfilter brings to the table is very addictive like a drug habit that can't be kicked. I think differences in DAC chip set are generally overrated and the analog output stage gets generally overlooked.
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