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Old 30th April 2008, 12:57 PM   #111
spencer is offline spencer  Hong Kong
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Bernhard,

For those chips measure relatively no so good, can we get better by doing trimmer adjustment as per the datasheet?

Yes I also prefer to buy used chips which more likely to be good.
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Old 30th April 2008, 01:53 PM   #112
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The adjustment of the PCM63 affects only near full scale, -6 to 0 dB.

For the 1000th time , this is why I use PCM56, it has MSB adjust for low level signals, that gets about 30 - 50% of chips to perform well.
Besides it has a smaller footprint which is important for paralleling chips, cost much less, is widely available in old CD players, allows large values of passive I/V resistors, performs very good at non os...
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Old 30th April 2008, 06:18 PM   #113
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Quote:
Originally posted by spzzzzkt

What I see as the main issue with A'afs chips is that he's charging a premium price on the basis they are a high performance chip - but what you get is a "lucky dip"....
If you pay for a BMW you expect all BMW not half BMW with the rest Trabant.
Indeed, for this money you should get all 4 DAC chips in premium quality. There is no any doubt about this.

I am sorry that I was not aware to the fact that A'AF is not proofing his Chips before mailing them to the clients. I was sure that this just happened to me once (as I was the first one to buy them).
Moreover: A'AF wrote to me at the time that it never happened to him before that someone complains about the PCMs (
). BUT, he send me then some more Chips so I was able to match them; I felt that he trusted my judgment and that he was all in all OK. I simply sent him back the rest / what I didn't like, and that was it.

I got one pair of great “Y”s for about US$ 125.- but also a bit of nervous tension. A good friend took the other 2 matched pairs of “K”s (1 of them was from the same PCM63K “military grade” line which have been good as well).

Quote:
People _are_ getting bad sounding chips, b_d's experience shows and the tests I've done bear out there is bad and good.
I feel somehow sad about what happened to some members here. However, A’AF did replace the Chips and I hope that things will be at the end OK for everybody here. It would surely be very nice to hear from A’AF that he is going to exchange the bad “Y”s for you and beauty_devine with no hassle.


Quote:
I'm not sure if I will send them back - i'll see how I feel about it tomorrow. It just hurts having effectively paid $250 for two good chips. Genuine or not that is just stupid money for a pair of DAC chips.
Paul, whatever you decide, please don’t send back the good sounding “Y”s. I trust your ears & measurements and I will gladly take them from you as a second pair / reserve for the future.

Conclusion: This should not be of a reason to consider going backwards to the “K” and surely not to the PCM 56

Greetings,

IY
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Old 30th April 2008, 10:18 PM   #114
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I don't think A'af does any quality control or checking - the "GB: for 2SK389 and 2SJ109" thread stands witness to that. But I guess the general perception is the Y grade must be better so people don't question that the performance will be good. Hopefully this thread has opened peoples eyes to the fact DAC grades don't guarantee good performance.

I've decided to hang onto the 2 better performing Y's as I doubt I'll easily find ones that measure this well. I will to talk with A'af one more time, to see if he is prepared to work something out to replace the chips that are clearly substandard.

I sincerely hope that A'af does decide to do grading on his chips if he continues to sell them at his current price. I guess he thought I was being a smart a**, but that was motivated me to offer him test data on the ones I sent back...
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Old 30th April 2008, 10:25 PM   #115
A'af is offline A'af  Indonesia
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Quote:
Originally posted by spzzzzkt
A'af has agreed to take the chips back and refund purchase price.

Looks like I'm back to running the PCM63K's for the moment...

Hi spzzzzkt,

Did we are agreed offline about the statement above?

If you have change your mind, please mail me with the "nice" sound please

Yes i know, those chips are premium price, so i will try to provide with premium service also

But no reply to your mail about 2 days and later mail me with tension and seems i want to run.... not my style....

and about overstating... if FAKES sound more better than excellent... so the result is a GREAT FAKES!!

from the first start i know this not a fakes, even IY know first!! (actually ) but yes i didnt realize some of those have a bad performance. How do i say, i dont have times to test them one by one for sure...

okay wanna hear from you in this first of May...

all the best,
a'af
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Old 30th April 2008, 11:05 PM   #116
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Only wanted to confirm again the finds of Bernhard and Paul.
After having redone the test shown earlier, with better resolution and more averaging, the pic got much clearer, and the spurs much more visible. And the best testing chips in my posession are the noname nostamp BBkorea ones from '98.. and the level differences are the same that had been shown.

A sidenote: if You think less spurs are the king, then try dithering:
my Rotel player measured so well because the dither was on, at level 7. [PMD100] This also forces somehow both channels more uniform.

Here it is again, dither level 7, and both channels looking like this:
(carrier level is -60db on the disc but measures like -65db here.)
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File Type: gif rotel-60nsrightdither7.gif (8.6 KB, 432 views)
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Old 30th April 2008, 11:07 PM   #117
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The same without dither:
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File Type: gif rotel-60nsright_nodither.gif (8.7 KB, 423 views)
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Old 30th April 2008, 11:14 PM   #118
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Also dither level 4 is similarly good.

Question to Paul: did You find a correlation between the sound and measurement level? I don't know, I would need more time to concentrate on it, but for me the better measuring korean chips did not sound better in the Dac, [apart from sounding horrible for the first couple hours.. though this had passed away later on]

Other point: Remember that PCM58 measured so bad earlier?

Here it is, before MSB adjustment: [actually there are only two pots implemented out of 4 for most upper bits]
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File Type: gif onkyoright-60dbns.gif (10.7 KB, 409 views)
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Old 30th April 2008, 11:16 PM   #119
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And after adjustment [and it's still only a first approach, only bit 18 bit 17 adjusted, should go on with bit16 bit15]

(Carrier is -63dB with this player, and notice also the ~10db lower noise in the floor, the spikes still visible here would be in the noise in the previous pic)
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File Type: gif onkyo-60dbnsrightadj2.gif (9.7 KB, 410 views)
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Old 30th April 2008, 11:19 PM   #120
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Default A friendly msg. to A'AF (Juang)

Quote:
Originally posted by A'af
from the first start i know this not a fakes, even IY know first!! (actually ) but yes i didnt realize some of those have a bad performance. How do i say, i dont have times to test them one by one for sure...
A'AF, a real friendly advice to you, and please allow me:

Try and find some method to proof things like the PCMs (“K" or "Y") before mailing them. It might not be an easy thing to do, but you will be the first to benefit from it. People here generally like your merchandise & working with you, but you also have a big responsibility towards all of us, especially as we are working in such a tricky and difficult subject as sound.

When you originally told me that there are no problems known to you with the PCMs, I felt quite embarrassed to tell you that “you are wrong”, especially as a novice on this board. Of course, I did not have any other choice as to trust my own ears, and they told me a simple answer which you also accepted. I appreciate your readiness to send me some other chips, a fact which enabled me to have what I truly enjoy nowadays, this excellent sound.

But it is exactly this topic of integrity which you should protect by all means, simply by keeping supplying your clients with the best possible products, while finding a way to pre test them before shipment.

All the best,

IY
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