[Erickq]

The OPA2604 is placed in a socket. You can just remove it by pulling it out and replacing it with another OPA. This guy posted some picures of it:
 
http://www.flickr.com/photos/lars-schenk/2915827446/in/photostream/
 
I also recieved my ZERO yesterday! I'm totally new to this high quality audio stuff, and I really like this setting. I use it with a sennheiser HD650 which I also received yesterday. It seemed a nice way to start listening to audio in good quality, and I am truly amazed.
 
Unfortunately I cannot compare it with anything else because this really is the first head-amp and headphone I own. Anyway, I read this forum very thoroughly, and all the comments on this forum were very useful for me. I'm sure I will enjoy this for a long time!

 

[eimis]

Quote:

My Zero is an OK device, but the Gain is wrong for my headphones, This is my work set up. Its the "09" version and it has too much gain for my Sennheiser HD 485 a high efficiency low resistance at 32 Ohm headphones 110dB, this is particularly annoying as the range on the volume control tracks especially badly.
 
I have to adjust the gain should we make a Wiki pages from this thread? Its to big to read in complete.
 

I imagined their has been come posts on this subject in this thread, 

 

I imagine setting the op-amps gain is trivial, and will only take two resistors per channel has anyone done this and what did they do? 

I've got denon ah-d1001 (32ohm) and I also think that Zero gain is bad for low impedance and sensitive headphones... IMO sound is distorted at low volumes and too harsh/loud at volume that distortion is not as presented.

 

[owenhamburg]

Quote:

I've got denon ah-d1001 (32ohm) and I also think that Zero gain is bad for low impedance and sensitive headphones... IMO sound is distorted at low volumes and too harsh/loud at volume that distortion is not as presented.

 
I did not have enough low watt resistors to do a final job this weekend, but I did reduce the gain for my Zero 09 DAC slightly, as a headphone amplifier for HD 485.
 
In the duel op amp in the zero 09 headphone amp, one channel set up as a non inverting buffer with 100% feedback, driving the volume control. The other half of the duel op amp seemed on my brief look to be part of the transistor drive circuit of the headphones, so the side effects of changes seemed to require more understanding of the circuit and some re-engineering, I took the option to reduce the volume rather than reducing the amps gain after the volume control.
 
I changed the output resister from the non inverting buffer output to the volume control. The original value was 1K in series with a 100K volume control. I changed this to 15K 1/4 Watt, (the PCB holes are small) resistor in series with the 100K volume control. I will probably letter try some higher values including 22K, 47K, 100K, 150K and 200K. With the 15K series resistor, the gain is not significantly changed, but for me the volume range I listen too at work is now outside the volume controls poor tracking range, so it was worth the effort.
 

Increasing the load the inverting buffer has to drive, should have no negative effects, I would even suggest that driving a higher load would improve the performance since the op amp should be driving the load in Class A. Provided you don't reduce the System gain too much and thermal noise becomes an issue. This should be no issue with the relatively resistors I suggest testing to match your system.
 
The total cost of this modification is in the area of 0.10 Euro, yes ten cents, and will make my work listening volume a little lower and more comfortable, If you are having issues with the volume control this might be the change you should start with.
 
I used a cheap 19 Euro soldering iron, with a thermostat (thermostats improve your soldering), a cheap solder removing tool, (About 5 Euro which is recommended to anyone who has a soldering iron) some multi core solder, and I also used a resistance meter (as a contact tester) to track components (The resister is next to the op amp) on the board (checking that I had followed the track correctly which is hard to do just by eye), and a simple screwdriver to take the zero apart.
 
For my use I suspect I will buy at least 10 of each value of resistor for my stores, I would suggest 22K, 47K, 100K, 150K and 200K resistor low watt 1% tolerance resisters with thin leads suitable for this job. If none of these reduce the volume range enough for me, I will then look at replacing the potentiometer, with a 10K or 50K Log values and keeping the load between 100K and 300K. This is the series resistance, or the resistance for the potentiometer plus your changed resistor. I expect I no lower than 100K for fear of loading the op amp (moving out of class a), or higher than 500K for fear of thermal noise.
 

Owen Hamburg
 

 

 

[Intuvati]

so after about 50 or so hours of burning in, this unit is really starting to sound great. However, I really do need some more bass, and from what i've heard, the 627 is the way to go. Its my understanding that i need the AP and NOT the AU model. previously, i was under the impression that the 627 went in the DAC part of the unit, but it seems this is not the case, in which case i would need two... just so i know, is this the right unit? so i need two of these, and what about the DAC section? What i'm looking for is something that will compliment my sources, most of which are orchestras, movie soundtracks, etc. on my old x-fi forte, i turned the bass knobs and treble knobs all the way to the right, and when the opening drums started to go (eg, "A Far Cry" from Escaflowne ost2), my phones quite literally shook (just a lil bit). If I have to sacrifice some of that for a more natural sound, so be it.
 
 
anyways, from page1 of this thread, the LT1364, LT1361, and LM4562 DACs are listed as being great with the 627... any ideas for the kind of music i listen to? i tried reading this whole thread but that idea soon went down the pooper

 

[ads2]

Hi there,
I have bought the Zero more than 2 years ago, so I dob't have the 2009 version. I have a version with Lawrtence HDAM.
So a few questions :
How does Lawrence HDAM compared to GDAudio Discrete OPA (moon earth, Sun) ?
What is the best OPA for the Amp part that go well with the HDAM ?
 
I ear a background noise, that increase while increasing volume.

Could this come from the "original" rotary potentiometer ?
The only mod I have is the HDAM, what else do you suggest ? soldering is not an issue, use to make DIY stuff...
Regards
 
Armindo

 

[Intuvati]

After some research (thanks google) i've decided to go with the audio-gd discrete opamps, earth/moon/sunV2 (i'll buy one of each, just so i'll have them all handy ) and i would like to know as well, which chips work well in the head amp section? I'm not really ready to buy a dedicated tube-amp yet, so I want to make this zero a great one. on the first page here, (for example) the 627s in the dac and the LT1364 are both said to be great, but does that only apply when they're used together like that? or am i an idiot and would the LT1364 be good with any DAC?
(most likely i'm an idiot)

 

[Fantasysage]

Which is the correct ebay store to get one of these from?

 

 

[DemonicLemming]

I picked mine up freom wsz0304 (Shenzhen Audio Store) recently, and it took exactly 5 days from me hitting the "Confirm purchase" button to it showing up at my front door.  No issues at all, and he was very quick to shoot me an email asking about color and voltage choice (I had forgotten to put them in at the payment details).
 
Quote:

Which is the correct ebay store to get one of these from?

 

 

 

[Kusari]

Hi, everyone!
 
Bought my own Zero Dac two years ago (got the original model without USB), because of this review. It was cheap and had a good sound quality. I used it with AKG K701's and thought it was a great pair!
 
Sadly couple of days ago my Zero died. Couple of weeks (maybe months?) it had a weird problem that sometimes while I was listening to music the sound started cracking terribly. It always got solved after I closed the iTunes (used computer as a source for this setup) and started it again and it worked again, didn't have to touch to the Zero DAC. Then on one nice morning the Zero was completely dead

The lights go on (so it has power), but there's no sound. Doesn't matter if I'm using phones or the line outs, completely dead. When it worked if used the phones and turned the volume all the way up (with no input) I could hear pretty loud hissing. Right now this is also gone. So it has power, but it doesn't give any output. Is there any good ideas where I could start to solve the problem? Do you guys think this is fixable ? The PCB and all the components look fine and anything doesn't look burned or damaged.
 
Thanks

 

[Fantasysage]

Quote:

Hi, everyone!
 
Bought my own Zero Dac two years ago (got the original model without USB), because of this review. It was cheap and had a good sound quality. I used it with AKG K701's and thought it was a great pair!
 
Sadly couple of days ago my Zero died. Couple of weeks (maybe months?) it had a weird problem that sometimes while I was listening to music the sound started cracking terribly. It always got solved after I closed the iTunes (used computer as a source for this setup) and started it again and it worked again, didn't have to touch to the Zero DAC. Then on one nice morning the Zero was completely dead

The lights go on (so it has power), but there's no sound. Doesn't matter if I'm using phones or the line outs, completely dead. When it worked if used the phones and turned the volume all the way up (with no input) I could hear pretty loud hissing. Right now this is also gone. So it has power, but it doesn't give any output. Is there any good ideas where I could start to solve the problem? Do you guys think this is fixable ? The PCB and all the components look fine and anything doesn't look burned or damaged.
 
Thanks

Sounds like your PC is the broken part there mate.
 

 

[Kusari]

Quote:

Sounds like your PC is the broken part there mate.
 

I tried the DAC on my other computer with same results. I don't have anything else to test if the PC is broken, but I don't think that's the case, because the DAC didn't work on the other computer either.
 
 

 

[notoriousmatty]

So I just bought one of these from wsz on ebay. I needed a DAC with optical as well as usb.  Going to add a Valhalla to the mix soon for my 880s.  Hope I made a good choice!

 

[sebmtl1]

i dont mean to hijack, but im new to this dac/amp thingy. Im willing to buy a new headset (hd650) but i am very confused what to do next. I have a macbook pro and im confused weither i have to get a DAC or an amp or something that can do both. Is the ZERO a dac and an amp at the same time, meaning that i only have to buy one piece instead of 2 (dac + amp)? Also, whats the better thing to do, get a zero or get a udac2 +little dot mk or get a headroom micro amp?? Sorry but i am SO confused lol!
 

 

[DemonicLemming]

DAC stands for "digital to analog converter" and that's what it does, by converting an optical/coaxial/USB input to an analog signal output to the amplifier.  By running USB, optical, or coax into a DAC, you bypass any internal amplification or the like (as my understanding of it is) from your computer's sound card; it's basically nothing but a raw signal output into the DAC.  Conversely, if you ran a 1/8" to RCA converter from a headphone jack to a discrete amp, you'd be sending the internally-amplified signal out to the amplifier, instead of a raw signal; this is typically a bad thing.
 
The Zero can act as a stand-alone DAC for an amp daisy-chained to it, or it can function as a DAC and an amp.  For the price, it's not a bad all-in-one combo, but I couldn't comment on it against the Headroom or uDAC2, since I haven't heard either of those.  I'm not sure what type of outputs a Macbook has, but you wouldn't be ill-served to buy a DAC/amp combo like the Zero, or a discrete DAC and amplifier combo, like the uDAC and the Little Dot, for the reasons given above.
 
tl;dr version (was a bit verbose above): a DAC converts a digital output signal from a computer into an analog signal that an amplifier can use.
Quote:

i dont mean to hijack, but im new to this dac/amp thingy. Im willing to buy a new headset (hd650) but i am very confused what to do next. I have a macbook pro and im confused weither i have to get a DAC or an amp or something that can do both. Is the ZERO a dac and an amp at the same time, meaning that i only have to buy one piece instead of 2 (dac + amp)? Also, whats the better thing to do, get a zero or get a udac2 +little dot mk or get a headroom micro amp?? Sorry but i am SO confused lol!
 

 

 

[sebmtl1]

Thanks man thats really appreciated. Can i ask you what dac and amp or dac/amp combo would really be my best buy for a 400$ budget? I have a 2011 macbook pro and senns hd650