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

[BigTony]

Ok, credit where its due.

My amp has arrived, and I've poped the hood before powereing on.

All the Opams are in the correct locations, including the HDAM unit, and there is a distinct smell of 'used' amp about it, meaning that I'd have to agree that this has been tested and for some time, prior to shipping.

Now to turn it on (once I find a cable of course!)

Doh ..RTFM..

Ok everything sounds fine, will let it run for a day or so.

[Currawong]

I've updated my FAQ, btw, to distinguish the two "upgraded" versions available. I need to get some more 3-pin power plugs to test my theory that a lack of grounding is bad for the Zero -- causing hum and the HDAMs I'm currently burning in to get hotter than usual.

[BigTony]

Actually I was just about to ask if the Zero really wants a ground or not, I have both a grounded and un-grounded lead, but I went grounded first.

[dario]

Originally Posted by JohnnyLightOn

dario, are you using the Zero's built-in headphone amp? (if I understand the use of 3 HDAMs, that would be two in the amp section and one in the dac section?)

If so, how do you like the Zero's headphone amp with the HD650?

Yes, I'm using the zero's amp, I have 1 earth in the dac and 2 sun in the amp, I think that the 2xsun are quite better than 2xlt1364, I don't know if they can do better with external power or similar (probably would be a better idea buy a dedicated amp), but I have them, they are better than lt1364, than I use them...when I have time I will leave the 2xlt1364 to re-compare them with the 2xsun....

I think that zero's amp with the hd650 is a good combination, the volume is quite good to give ear damage in the long term, I would only get bigger soundstage and little more power for some songs and little better middle-low frequencies, but I have never tried standalone headphone amplifier to judge if using a standalone 200-300€ amp would be a real and ever justifiable cost...but I think in the near future I will buy one to try if there is a real and quite big step up..

Originally Posted by Pricklely Peete

Hi Dario,

Generally speaking the 650's take anywhere from 250 - 350 hours to give there all....the last 50 hours or so the changes are quite noticeable. They get even better from 200 hours on (maybe you'll be lucky and they will be fully burned in at 250).

Peete.

I have read that, I hope they will improve with time, but every time I listen them is a real real pleasure....

P.s Peete after my first hdam cap mod "failure" (I have soldered the cap to wrong pins...desoldered them and verified that would be all ok) I will re-try to do the mod in the near future with the real mod photos this time...

[MadMan007]

In order to further assess the problem I'm having I want to get some opamps for the DAC section to test. I haven't ordered anything yet and am looking to get LT1364's for the headphone section anyway, I'd like to try LT1469 in the DAC section. I think I can guess based on the LT1364 recommendation but can someone please advise me which exact LT1469 version to get? And will it be a direct plug-in to the DAC board socket without a brown-dog adaptor?...it is called a 'dual opamp' on the LT page. Linear Technology - LT1469-2 - Dual 200MHz, 30V/μs 16-Bit Accurate AV ≥ 2 Op Amp LT1469-2

If it cannot be used without an adaptor I'd like other suggestions of opamps that plug directly in to the socket, especially if they're from LT as well. The OPA2604 is one I know will work, if there's not a better alternative which exact version of that do I get? http://focus.ti.com/docs/prod/folder...t/opa2604.html

[Myriad]

X-Fi XtremeGamer -> Zero w/Lawrence HDAM DAC, LT1364 AMP -> Grado SR225

I performed the cap snipping mod. It now sounds noticeably more forward (almost annoyingly so), and some of my songs give me headaches listening to them. Some of the smoothness it had also seems to have dissapeared. I did only bother snipping one leg of each of the caps, which, given my limited knowledge of circuits, should be fine (I made sure there was no contact between the snipped ends). Is this normal and I'm just not used to the highs?

[DaMnEd]

Well, the point of sniping those is to get the highs killed by the sniped caps, so, I'd say it is very normal, but you may not like the effect on your setup, that is a different issue.

If you really dislike the effect id say solder the legs, you get the "old" sound back again.

[Myriad]

Yeah, definitely. I should've said I'm really more curious about the more forward, less smooth sound. Maybe it's just caused by my bad reaction to the highs, but it was mentioned a few pages ago that there aren't any negative side affects to the mod, so I just wanted the make sure I didn't bungle something. Though snipping two caps (didn't bother with the RCA caps since I don't use the output) really doesn't leave much room to mess anything up.

[Currawong]

Originally Posted by dario

I would only get bigger soundstage and little more power for some songs and little better middle-low frequencies, but I have never tried standalone headphone amplifier to judge if using a standalone 200-300€ amp would be a real and ever justifiable cost...but I think in the near future I will buy one to try if there is a real and quite big step up..

If you're looking for improvement, down the track an amp is worth it. My take on it is, if I'd never heard better, I would've been happy with just the Zero and the MB Quarts I'd had for 10 years. I've heard some very high-end hi-fi systems, so I'm ruined for life unfortunately.

Originally Posted by MadMan007

In order to further assess the problem I'm having I want to get some opamps for the DAC section to test. I haven't ordered anything yet and am looking to get LT1364's for the headphone section anyway, I'd like to try LT1469 in the DAC section. I think I can guess based on the LT1364 recommendation but can someone please advise me which exact LT1469 version to get? And will it be a direct plug-in to the DAC board socket without a brown-dog adaptor?...it is called a 'dual opamp' on the LT page. Linear Technology - LT1469-2 - Dual 200MHz, 30V/μs 16-Bit Accurate AV ≥ 2 Op Amp LT1469-2

If it cannot be used without an adaptor I'd like other suggestions of opamps that plug directly in to the socket, especially if they're from LT as well. The OPA2604 is one I know will work, if there's not a better alternative which exact version of that do I get? Precision Amplifiers - Wide Bandwidth - OPA2604 - TI.com

I think it's the PDIP package you want. If the opamp is a "dual" you don't need an adaptor. If it's a "single" then you do. A "dual" opamp has two channels, which are used in the Zero (and much else) for left and right.

Originally Posted by Myriad

X-Fi XtremeGamer -> Zero w/Lawrence HDAM DAC, LT1364 AMP -> Grado SR225

I performed the cap snipping mod. It now sounds noticeably more forward (almost annoyingly so), and some of my songs give me headaches listening to them. Some of the smoothness it had also seems to have dissapeared. I did only bother snipping one leg of each of the caps, which, given my limited knowledge of circuits, should be fine (I made sure there was no contact between the snipped ends). Is this normal and I'm just not used to the highs?

You could well not be used to the highs. I haven't ever tried a pair of Grados, only read that they are very bright cans, so this isn't a surprise.

[ScottieB]

Originally Posted by Currawong

You could well not be used to the highs. I haven't ever tried a pair of Grados, only read that they are very bright cans, so this isn't a surprise.

I'm pretty sure this is it. I actually wouldn't recommend that snip mod for Grados (at least the 80s and 225s - the only ones I've owned) because it puts the already bright headphones over the top (to my ears). It did a lot of good for my Senns though.

[Pricklely Peete]

Originally Posted by powertoold

Thanks for your input. My initial thought was whether the EM field generated by the transformer may be causing a hum on my right channel. To answer that question indirectly, I asked whether the side of the amp board closest to the transformer controls the right channel. It's a simple yes or no answer. I'm sure people who have modded the amp know which side of the amp board corresponds to a channel.

I wasn't thinking of buying a new transformer at all.

Sorry about that...I thought you were ignoring the answers you were being provided with, hence my terse response. I do have one question though...if you weren't going to buy a transformer that response you posted certainly leaned heavily in that direction.....did it not ?


The EM field is pretty small...lots of people put their HDAM modules right next to it with no SQ issues. I have rested an HDAM (temporarily) on top of the toroid and also had no issues, so it's safe to say that isn't the problem...although new supplies of transformers could have an issue...My Zero is over 7 months old now so who knows if they are still built with the same OEM toroidal. They do look the same. Part no on mine is HB-100/1852. I could find no brand name on it. FWIW.

Peete.

[MadMan007]

Originally Posted by Currawong

I think it's the PDIP package you want. If the opamp is a "dual" you don't need an adaptor. If it's a "single" then you do. A "dual" opamp has two channels, which are used in the Zero (and much else) for left and right.

Yea I know the PDIP is the right package after looking at the schematics. The LT1364 is 'dual and quad' but there are two needed for the headphone amp section, while LT1469 is 'dual' I guess if hte OP had shown a picture of something other than OPA627 in a brown dog I'd know OK before posting that I've gone through schematics on the various opamps, OPA627 schematics only show a single diode (? diode symbol at least) within the opamp package while the LTs show two and based on the pinouts of the LT1469 versus the OPA2604 the former should plug right in. *edit There are two 8-pin PDIP LT1469's: LT1469IN8#PBF and LT1469CN8#PBF the 'C' and 'N' are different. I'm not sure what that means, going by the LT1364 the 'C' would be the correct one but can someone verify that? *edit2: ha, ok I keep answering my own questions. C= commercial I = industrial and they refer to temperature ratings as seen in Section IV here: http://www.linear.com/purchase/ordering_info.pdf

I'm still not sure why the DAC uses one dual opamp and the HA uses two but maybe that's just up to the circuit topology or output requirements of the HA.

[StratCat]

Originally Posted by MasZakrY

Amazing. The bloated bass that the LT1364 originally had is gone and sounds better then ever! Only racked up ~30 hours on the Zero so far

I swear, I never believed in semiconductor burn-in 'till I upgraded my Zero's HPA from the stock NE5532's to LT1364's. Too many of us have independantly had the same sonic experience for this to be a coincedence, IMHO. Or, we all go thru the same psychoacoustic adaptation to the new chips; I might give it that.

But either way, *something* of similar perception amongst us definitely occurs: Bass becomes more solid and articulate with better imaging; upper mids and highs develop clarity and resolution, resulting in a slight increase in timbre and detail, and the mids and highs become less "decongested" for lack of better words. Pretty wild experience, and I don't know how to explain nor account for it.

[StratCat]

Originally Posted by helicopter34234

Where does everyone get their LT1364s? I got mine as a free sample (habit I picked up from doing grad school research), is that what others are doing or is this taboo? Hopefully I don't get buried in Linear Technology advertisements.

Quite a few peeps have gone the sample route...nothing taboo about that I'm aware of. I went thru Newark piggy-backing another order I was doing and didn't want to wait on samples (LT1341's were 4 bux/ea, IIRC).

Whatever works for you.

[StratCat]

Just thought I'd share something I found after some poking around, and will include in my upcoming Newark order:

A Vpot knob upgrade

I mean, comon, two bux? How could I resist?