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Old 24th November 2011, 09:14 PM   #1
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Default HA INFO NG94 ver1 op-amp change

This is my first post so bare with me

I have a NG94 ver 1 dac and I would like to tryout different op-amps. They are rollable which is good because I don't have any electronics skills so I can't make any other mods to the dac. The problem is that I'm not sure which op-amps would be suitable for this dac. I've read that some work in different places and because I don't have any knowledge about these things I thought it would be best to ask first before doing anything stupid

So what I have gathered is that the dac uses pair of opa2604 at the I/V section (whatever that is) and one opa2604 for the output buffer. Then there are two BUF634's and one opa2604 for the headphone amplifier. So these are the ones I assume I can change. There isn't really that much of information about the first version of this dac around the net so I haven't found that much help. I found one post at the head-fi but it is over two years old and there wasn't really that much of a conversation.

HA NG94 Desktop Dac This is some Chinese page that has at least some information about the dac. I already ordered a few op-amps, OP275, LME49860 and LM4562 so if I can usen them good but it doesn't really matter. If you need more information or some pictures of the dac please ask.
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Old 30th November 2011, 03:11 AM   #2
Previously: Kuei Yang Wang
Join Date: Nov 2002

Originally Posted by subballo View Post
I have a NG94 ver 1 dac and I would like to tryout different op-amps.
Make sure that the Op-Amp's you roll are really suitable.

For example, it may not be possible to replace a Fet Input Op-Amp with a bipolar one (the reverse is often possible and beneficial, if the Fet Input Op-Amp has low enough noise), one would need to know the precise circuit to be sure.

If the Op-Amp fitted is unity gain stable, it is best to stick to unity gain stable replacements, unless you have the full circuit diagram available and can confirm that your Op-Amp's will be stable.

Given that the DAC is most likely a usual CKM (CKM = Chinese Kopy Mao) cut & paste job the PSU decoupling may be poor, so stay away from very fast (Video) Op-Amp's, even if these can give some of the best sound quality available from generic Op-Amp circuitry, unless you can apply the neeed modification to ensure stability.

Originally Posted by subballo View Post
HA NG94 Desktop Dac This is some Chinese page that has at least some information about the dac.
The information is scant, most is bad advertising copy, bad even before google translation makes complete doggerel out of it.

Some high resolution close-ups may help with a quick attempt at analysis...

Funny thing about the Model ID. In Anglo-American usage among engineers and the military NG has a very definitive and pejorative meaning...

Ciao T
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Old 30th November 2011, 03:14 AM   #3
Pano is offline Pano  United States
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NFG, is what we used to say.
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Old 2nd December 2011, 06:15 AM   #4
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What DAC chip is used in this device ? Receiver is mentioned: DIR9001.
It's only audio. Member of the non modular PCB design committee
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