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Review of the Audio-gd DAC-19 DSP & C2 amp - The ACSS connection - Page 3

post #31 of 981
4/19/10 at 9:40am
Thread Starter 
Quote:
Originally Posted by kunalraiker View Post
I wouldn't agree with slim.a on the post for noise floor, the C-2 is not the quietest I've heard,with my Grado 325is even with no DAC connected the complete darkness disappears at about 2'o clock and same on high gain, I do have cx300 will test and advise later.
What you are saying is no different from I have said. If you re-read my post, you will find that I have said the following "With the far more sensitive cx300, I start hearing the noise floor when I got past 2-3 o'clock."

The reason you start hearing the noise when you turn the volume so high is that the C2 can output as much as 10v. (See the specs here: н¨ÍøÒ³ 1).
The reason you don't hear the noise floor with something like the emu0404 usb for example is that it has very limited output. The headphone output is limited to around 2v.

The C2 was made so that it could drive difficult cans like the HD650 and K701 with ease and a lot of headroom. That is why I suggested to SoupRKnowva to ask Kingwa for a modified version (if he accepts doing so). By lowering the gain/maximum output, it will be probably possible to lower even more the noise floor but it will cause it to lower the headroom with low sensitivity cans.

BTW, kunalraiker, how high do you turn up the volume with the Grados? Even with the HD-650, I rarely go past 2 oclock ...
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post #32 of 981
4/20/10 at 5:52am
Thread Starter 

More on the gain of the C2 ...

I did a little bit of experimenting yesterday with the CX300 and the C2 and got disappointed by the limited usability of the volume when connected with the ACSS (The high/low gain switch work only when the C2 is connected through RCA). The problem wasn't noise level but rather a slight channel imbalance at the lowest settings.

I asked Kingwa by mail and he said that they can lower the gain if needed. But I wonder why they don't offer 2 versions: one with high gain (for the hd650, K701...) and another with low gain (for the very sensitive headphones).
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post #33 of 981
4/20/10 at 7:37am
slim.a: It could be the amount of wiring that would be required. It's not as simple with ACSS altering the gain. If the C2 is anything like the C2C, then to install a gain switch would require a lot of extra wire inside the unit.

The problem with the channel imbalance is probably the result of the Alps pot. They aren't always great at the lower end of the range.
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post #34 of 981
4/20/10 at 10:30am
Thread Starter 
Quote:
Originally Posted by Currawong View Post
slim.a: It could be the amount of wiring that would be required. It's not as simple with ACSS altering the gain. If the C2 is anything like the C2C, then to install a gain switch would require a lot of extra wire inside the unit.

The problem with the channel imbalance is probably the result of the Alps pot. They aren't always great at the lower end of the range.
I understand that it might be complex (or it might reduce the sound quality) to add a gain switch for the ACSS path since the gain is variable anyway ...

That is why I was suggesting is to make a second version of the C2 where the maximum gain will be lower than what it is currently the case.

In my personal case (with the hd-650) the gain is perfect, but I was thinking about those who use higher efficiency headphones and would never go past 9-10. In that case, they would be stuck using the alps volume pot on its worst range (the lower one).
Perhaps a better pot would solve the problem at the lowest settings?
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post #35 of 981
4/21/10 at 9:02am
I am struggling between DAC-19 DSP + C2 and Meier Audio StageDAC + Concerto.
How does Wolfson WM8741 do compared to PCM1704UK, are they same class chips?
I really like amount of features that Meier's gear have, like crossfading, balanced ground, volume control and superior(I think) power circuit.
Also Concerto comes with better stock OPAs, than C2. They are changable as well.

To be honest, I could have had Audio-gd stuff delivered long ago if only not problems between Hong Kong and customs of my country. So while when both sides come to some solution I bumped into Meier Audio...
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post #36 of 981
4/21/10 at 9:11am
Quote:
Originally Posted by slim.a View Post
What you are saying is no different from I have said. If you re-read my post, you will find that I have said the following "With the far more sensitive cx300, I start hearing the noise floor when I got past 2-3 o'clock."

The reason you start hearing the noise when you turn the volume so high is that the C2 can output as much as 10v. (See the specs here: н¨ÍøÒ³ 1).
The reason you don't hear the noise floor with something like the emu0404 usb for example is that it has very limited output. The headphone output is limited to around 2v.

The C2 was made so that it could drive difficult cans like the HD650 and K701 with ease and a lot of headroom. That is why I suggested to SoupRKnowva to ask Kingwa for a modified version (if he accepts doing so). By lowering the gain/maximum output, it will be probably possible to lower even more the noise floor but it will cause it to lower the headroom with low sensitivity cans.

BTW, kunalraiker, how high do you turn up the volume with the Grados? Even with the HD-650, I rarely go past 2 oclock ...
I e-mailed Kingwa about the noise and the cross talk,I've quoted his reply

The C2 can let two RCA input without cross-talk and without any costly, we can design the un-available input short to GND, but we are applied this in our other preamp amp, a lot people ask us why their source feed to the preamp and other gear at same time, only our preamp can work, other gears can't work?
So we don't use this design in C2.
About the noise, The C2 has high gain and high input impedance, if you don't connect any source to C2, the input will received some RF disturb and output to headphone.
If you connect the C2 to source, the source output noise will through C2 and have gain, output to headphone.
The standard test the noise of C2, you can short the input to GND let it can't receive the RF disturb, or connect a 600 ohms resistor at C2 input, this time test the noise is the real C2 noise.

As for your question slim.a I listen to Grado's on low gain at 10:00pm and the newly acquired K701's at high gain at 9:30
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post #37 of 981
4/21/10 at 9:37am
Quote:
Originally Posted by Gwarlek View Post
I am struggling between DAC-19 DSP + C2 and Meier Audio StageDAC + Concerto.
How does Wolfson WM8741 do compared to PCM1704UK, are they same class chips?
I really like amount of features that Meier's gear have, like crossfading, balanced ground, volume control and superior(I think) power circuit.
Also Concerto comes with better stock OPAs, than C2. They are changable as well.

To be honest, I could have had Audio-gd stuff delivered long ago if only not problems between Hong Kong and customs of my country. So while when both sides come to some solution I bumped into Meier Audio...
The PCM1704UK is better than the WM8471, I've built and experiemented with a lot of DAC's and nothing beats the R2R's. If you want something like the Meier DAC and have DIY skills it can be put together for a few hundred bucks, I can point you to what you need to buy, just PM me. The DAC19 is beyond most anyones DIY skills with their current domain zero NFB analog stage, it is truly a well engineered piece.

As far as the amp, understand that the beauty of the AudioGD amp is with the ACSS connection there are no opamps any where in the signal path. Tell me this isn't better than having a cmoy in your audiochain.
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post #38 of 981
4/21/10 at 10:20am
Sadly, my DIY skill aren't going any further than cable making.
But okay, you convinced me. I guess, I will just sit and wait until shipping becomes possible.
Thanks for input.
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post #39 of 981
4/21/10 at 10:26am
Quote:
Originally Posted by Gwarlek View Post
To be honest, I could have had Audio-gd stuff delivered long ago if only not problems between Hong Kong and customs of my country. So while when both sides come to some solution I bumped into Meier Audio...
Does Audio GD actually ship from Hong Kong though? Their address is actually in Foshan, Guangdong province ... Audio GD and everyone else have a bank account in Hong Kong probably because the mainland has currency conversion controls (they leave the money here, invest it in financial or property assets, or maybe Kingwa sends his kids to international school ). (edit) That said, Foshan is really close to HK and they might ship from here too... transfer of goods definitely not my specialty in law.
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post #40 of 981
4/21/10 at 10:38am
Ypoknos, you are actually right! "China Postal" mentioned on the site. Gonna call in the post office and ask if customs' blackout spreads on continental China as well.
Thanks for the notice!
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post #41 of 981
4/21/10 at 10:44am
I believe it ships directly from Guangdong province. I will check when I get home. I have bought a couple of items already from Audio-gd and it normally takes 7-8 business days I believe. Expect to wait about two weeks from the time you order it...unless of course you order your device custom/ask for modifications.
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post #42 of 981
4/21/10 at 3:16pm
Quote:
Originally Posted by kunalraiker View Post
I e-mailed Kingwa about the noise and the cross talk,I've quoted his reply

About the noise, The C2 has high gain and high input impedance, if you don't connect any source to C2, the input will received some RF disturb and output to headphone.
If you connect the C2 to source, the source output noise will through C2 and have gain, output to headphone.
The standard test the noise of C2, you can short the input to GND let it can't receive the RF disturb, or connect a 600 ohms resistor at C2 input, this time test the noise is the real C2 noise.
Does this mean using RCA Shorting plugs on the unused RCA input will eliminate the RF disturbances?
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post #43 of 981
4/21/10 at 8:54pm
With all the (appreciated) effort you put into this review- you are going to have to get yourself into the higher AGD balanced gear to really be impressed I feel. The HD650 balanced with a AGD balanced DAC/amp is another sizeable step towards immersion into the music.
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post #44 of 981
4/23/10 at 3:54am
Quote:
Originally Posted by tim3320070 View Post
With all the (appreciated) effort you put into this review- you are going to have to get yourself into the higher AGD balanced gear to really be impressed I feel. The HD650 balanced with a AGD balanced DAC/amp is another sizeable step towards immersion into the music.
I second that.

I would only add that, while amps are excellent, the PCM1704 DACs are the real stars of the show.
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post #45 of 981
4/23/10 at 6:52am
I finally got my dac19DSP a few hours ago. First impression, it's a great dac. I don't have enough time to listen to it, so I can't say much about it right now.

But there is a small problem, I requested a bnc version, but it seems they send me a rca version. Is it worth to send it back to change the rca input to bnc input? Since I ordered m2tech hiface bnc + Oyaide DB-510 BNC (sending it to me, not receive yet). I can think of 3 different ways to solve the problem:

1. send it back
2. buy a Oyaide DR-510 RCA
3. buy a BNC to RCA adaptor

The easiest way is to buy a BNC to RCA adaptor, but will it affect the sound quality a lot?

I attached a pic of my dac, I think it's a rca input.
LL
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