Review: ZERO 24 BIT/192KHz DAC/Headphone Amp/Pre-Amp

[fl00r]

biglawhk

ZERO 24/192 DAC D A CONVERTOR , HEAD FI AMP , BRAND NEW - eBay (item 230224146851 end time Feb-25-08 03:31:48 PST)

[dantztiludrop]

Originally Posted by dsmudger

OK been away a couple of days so behind on reading the last few pages.. but just to say, I finally pulled the lever and ordered six OPA627s in metal TCO 99 package

I've just stuck two of them in the DAC leaving my LME49720s in the headamp section - and I do have to say I've had my socks blown clean off!

Bass is bigger than anything else I've tried so far (finally where I want it, nicely making up for the brightness of my Grados), nice integrated sound and not at the expense of detail.

Will try an all-627 setup later on, but wow - these 627s are a winner

I've been looking around online for the OPA627s at a reasonably decent price....where did you get yours' from?

[dsmudger]

Originally Posted by dantztiludrop

I've been looking around online for the OPA627s at a reasonably decent price....where did you get yours' from?

Ah, they were from Mr Wu at diykits - he even threw in a free browndog adaptor since I'd asked if he sold them - and it was the small type that fits the right hand side of the headamp section - just how cool is that?!

Pretty sure he's the cheapest source of metal 627s as well..

BTW I've now tried the all-627 setup - it's more musical, balanced and integrated, but lacks some of the relentless crisp detail of the 49720, and the amount of bass becomes almost a little excessive. So I think I like the sound better with 49720s left in the headamp section - trouble is you still get a bit of dip at certain frequencies (though actually it's only noticeable with certain tracks where there's a an instrument or vocal that sits right in that gap..) and overall it's clearly less detailed than 49720s all round

Very pleased with the sound overall (627s in DAC/49720 in headamp) - it's by leaps and bounds the best I've got out of it (the bass extension alone is nothing like any other combo I've tried..) and I'd definitely recommend others try it and see how it works for them, but it still just kind of feels like this setup isn't quite up to the full potential of my headphones - shame the amp can't take OPA637s as they seem to get described as being a lot like the 627 but more detailed :\

Perhaps there are some other fast crispy-sounding opamps out there that need trying in combination with 627s?

[edguetzow]

Originally Posted by dantztiludrop

I've been looking around online for the OPA627s at a reasonably decent price....where did you get yours' from?

Me too!

[Penchum]

Originally Posted by dsmudger

Ah, they were from Mr Wu at diykits - he even threw in a free browndog adaptor since I'd asked if he sold them - and it was the small type that fits the right hand side of the headamp section - just how cool is that?!

Pretty sure he's the cheapest source of metal 627s as well..

BTW I've now tried the all-627 setup - it's more musical, balanced and integrated, but lacks some of the relentless crisp detail of the 49720, and the amount of bass becomes almost a little excessive. So I think I like the sound better with 49720s left in the headamp section - trouble is you still get a bit of dip at certain frequencies (though actually it's only noticeable with certain tracks where there's a an instrument or vocal that sits right in that gap..) and overall it's clearly less detailed than 49720s all round

Very pleased with the sound overall (627s in DAC/49720 in headamp) - it's by leaps and bounds the best I've got out of it (the bass extension alone is nothing like any other combo I've tried..) and I'd definitely recommend others try it and see how it works for them, but it still just kind of feels like this setup isn't quite up to the full potential of my headphones - shame the amp can't take OPA637s as they seem to get described as being a lot like the 627 but more detailed :\

Perhaps there are some other fast crispy-sounding opamps out there that need trying in combination with 627s?

You should go back and re-try some of the LT's with your 627's. I still like the 627's with the 1364's in the headphone amp. Maybe that combo you would like?

[Ash]

I know this off topic for all of you talking about op-amp swapping. I have a very basic question about the functionality of this amp/dac.

I want to use it as a DAC/pre-amp to feed my A/v reciever - thru the analog out. In addition I want to use the headphone amp part on the front for occasional headphone listening sessions. Is this possible?
- What switches the output from the RCA - R/L to the headphone out?
- Is this amp capable of driving cans like the AKG 701s or Beyerdynamic 880s effortlessly?

Thanks folks!

[dsmudger]

Originally Posted by Ash

I know this off topic for all of you talking about op-amp swapping. I have a very basic question about the functionality of this amp/dac.

I want to use it as a DAC/pre-amp to feed my A/v reciever - thru the analog out. In addition I want to use the headphone amp part on the front for occasional headphone listening sessions. Is this possible?
- What switches the output from the RCA - R/L to the headphone out?
- Is this amp capable of driving cans like the AKG 701s or Beyerdynamic 880s effortlessly?

Thanks folks!

Haven't tried this myself but it's been reported that it's the presence of headphones in the front socket that switches it But yes, either way there is a phono out on the back you can use for this..

As for driving headphones I've never turned mine up above around the 10 o'clock position, so I really don't think you'll have any trouble even with hard to drive models.

[edguetzow]

shame the amp can't take OPA637s as they seem to get described as being a lot like the 627 but more detailed :\

Thanks for the update!!

So, have you read or heard if the OPA637's will work well in our Zero's Dac section?

[Fremen]

Originally Posted by RFL

Funny. Once I had ordered them by mistake [as I just recalled], and now I find myself with WIMA FKP2 10nF and 1nF caps ready to use in the Zero...


Unfortunately I'm missing the 560 pf value. I think I'll substitute that with 220 pf both in C9 and in C10 as in the AD1852 datasheet; and change the 10 ohm output series resistor to 100 or 200 ohms, leaving in the 10 nF parallel caps.

Here are some couples of values that would follow the AD1852 datasheet LPF behaviour (for C9=C10 and R20):
470pF, 10 ohms
330pF, 130 Ohms
220pf , 200 Ohms

[Fremen]

I received today the WIMA caps I ordered yesterday.
Here is the mod:
I replaced the two 560pF and 1nF caps of the DAC filter (C9,C10,C11 and C12 in the AD1852 datasheet) with 470pF caps to extand the bandwith and have the same response than the typical application filter (as I described in a previous post). At the same time I replaced the other caps with they equivalent in polypropylene.
The results are surprising. I have to listen further but for now I already changed my opamps config. I have been using the stock OPA2604 in the dac filter and 2 LM4562 in the amp section (because of the cleaner highs compare to the stock NE5532) for 2 weeks now. When I first switched my zero on after the mod, I found a complete change. Not surprisingly, the highs were ... lounder, too much for my taste with the LM4562. So I put back the 2 NE5532 in the amp and now I have the highs of the LM4562 before the mod with the basses of the NE5532 wich I prefered compare to the LM4562. I find the highs also much clearer after the mod.

Edit: I just put back the LM4562 in the amp and finally still like it better than the NE5532

[bada bing]

Originally Posted by Ash

I know this off topic for all of you talking about op-amp swapping. I have a very basic question about the functionality of this amp/dac.

I want to use it as a DAC/pre-amp to feed my A/v reciever - thru the analog out. In addition I want to use the headphone amp part on the front for occasional headphone listening sessions. Is this possible?
- What switches the output from the RCA - R/L to the headphone out?
- Is this amp capable of driving cans like the AKG 701s or Beyerdynamic 880s effortlessly?

Thanks folks!

The zero has a limited switch function. The head phone button on the front toggles the output from: volume control through the RCA + headphone jack off or; front headphone jack on with volume control + RCA out at line level.
So, yes it is usable as you describe.

The amp section is capable of fully driving any common cans. I use it with my HD650's and RS-1's (examples of high and low impedance common cans), it has more than enough drive for both. more than 10-11 o'clock is damaging with Senn's, with Grado you won't make it past 9:30.

[Ash]

Originally Posted by bada bing

The zero has a limited switch function. The head phone button on the front toggles the output from: volume control through the RCA + headphone jack off or; front headphone jack on with volume control + RCA out at line level.
So, yes it is usable as you describe.

The amp section is capable of fully driving any common cans. I use it with my HD650's and RS-1's (examples of high and low impedance common cans), it has more than enough drive for both. more than 10-11 o'clock is damaging with Senn's, with Grado you won't make it past 9:30.

Thank you. That was very helpful to know. This amp is one of my top two contenders at this point. The added DAC functionality will allow me to integrate my my rig.
From my limited knowledge in this area, as I understand it now - changing op-amps is akin to rolling tubes in a tube based system? Is this pretty complicated or doable?

[Henmyr]

Originally Posted by RFL

Congrats! Seems like a fine job.


Me, however, I want to stay "safe" and follow the datasheet indications. So I'll keep the same 1 nF values and just put in the 220 pF ones and 200 ohm resistors. I like the "analog" sound in digital stuff, which the stock Zero has.

Also with the 200 ohm resistors the better opamps shouldn't oscillate anymore, thus they should reveal all their potential.

Will this resistor make the sound worse in some way when using op-amps which works very well in the stock zero? I'm very interested in this mod if it works out very well. I wan't to try the LT1028 again but don't want to damage anything.

[bada bing]

Originally Posted by Fremen

I received today the WIMA caps I ordered yesterday.
Here is the mod:
I replaced the two 560pF and 1nF caps of the DAC filter (C9,C10,C11 and C12 in the AD1852 datasheet) with 470pF caps to extand the bandwith and have the same response than the typical application filter (as I described in a previous post). At the same time I replaced the other caps with they equivalent in polypropylene.
The results are surprising. I have to listen further but for now I already changed my opamps config. I have been using the stock OPA2604 in the dac filter and 2 LM4562 in the amp section (because of the cleaner highs compare to the stock NE5532) for 2 weeks now. When I first switched my zero on after the mod, I found a complete change. Not surprisingly, the highs were ... lounder, too much for my taste with the LM4562. So I put back the 2 NE5532 in the amp and now I have the highs of the LM4562 before the mod with the basses of the NE5532 wich I prefered compare to the LM4562. I find the highs also much clearer after the mod.

Edit: I just put back the LM4562 in the amp and finally still like it better than the NE5532

Did you do anything with the 47nF electrolytics on the DAC output ? They are outside of the area pictured. I wonder about those 47nF caps. The DAC application recommended circuit doesn't include any DC blocking at all. It appears like offset might not be a problem after the balanced to SE conversion ? Did you consider temporarily shorting the two 47nF caps and measuring the offset at the filter output ?

47nF are pretty big honky dirty electrolytics on a high impedance, low current line. I'm curious what the rational was ? I'm considering as RFL said - ordering hiQ film caps and implimenting the data sheet circuit exactly - sans 47nF electrolytic blocking caps.

[Penchum]

Originally Posted by Ash

Thank you. That was very helpful to know. This amp is one of my top two contenders at this point. The added DAC functionality will allow me to integrate my my rig.
From my limited knowledge in this area, as I understand it now - changing op-amps is akin to rolling tubes in a tube based system? Is this pretty complicated or doable?

Hi, I guess I answered another of your posts in a different thread just a little while ago! Changing Opamps to customize the output is very easy. They are just a chip in a socket. You pull out the old and push in the new. There is enough information in this thread to get anyone started, if they want too.

See my other post also. See ya!!