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Review: ZERO 24 BIT/192KHz DAC/Headphone Amp/Pre-Amp - Page 617

post #9241 of 9372

Mine ZERO never had this pop. But I heard about someone with this issue and I think he didn't solve this issue. 

post #9242 of 9372

I just received a ZERO DAC. Using Grado SR-80 I can hear a hiss when the amp is supposed to be silent. It's noticeable at very low volumes, right from the start and just turning the pot slightly. Even more noticeable at 9 o'clock, and there is a loud hissing when pot is at 12 o'clock.


As I understand, this is due to Grados low impedance.


Is there a simple way to modify the headphone amp for low impedance headphones?
Or should I try to sell the Zero and look for something else? TY!

post #9243 of 9372

Press "Preamp" button (LED under "phone" goes off) - is hiss still there?

post #9244 of 9372

Yes. A little less, but yes the hiss is still here.

post #9245 of 9372

The thing is that this tiny difference is DAC noise (which is quite low). But bigger part of noise is caused by head-amp itself.


Just chcecked my old measurement and noise at 9 o'clock is ~70uVp (with SR80 it makes ~32dB SPL) and at 12 o'clock it is ~450uVp (with SR80 it makes ~46dB SPL which is very audible).


You can try some low noise OA, but I don't think it will be very helpful.

The ultimate solution is changing whole amp. I'am changing old amps for amps of my design (see signature) and at 12 o'clock the noise is only 12uVp (with SR80 it would be ~15dB SPL)

post #9246 of 9372

Great, tnx for helping me out!


Any recommendations for low noise OAs?


Anyway, I'm gonna send you a PM.

post #9247 of 9372

For examlpe NE5532 (generic low noise OA) and LME49720 (high performance and also low noise).

post #9248 of 9372

People... THIS is a MUCH better value.

post #9249 of 9372

Hi Guys,


I have a brand new Zero 09 with USB with approx 40 to 50 hours use.


been trawling through this post, lots of excellent stuff.  But can someone please help me select a reseller for a set of LT1364 & a set of LME49720's?  Lots for sale on ebay, but my problems are


1. Picking ones that are genuine

2. picking the right options!  Most have 3 different lots of suffixes to choose from and I am a bit clueless.


Sorry if the answers are on here somewhere, buy over 600 pages are a lot to get through.


I have been very impressed with the sound straight from the box, and I'm running it through a pretty decent rig - perreuax power amp, Polk RTA-15TL's...  I mainly use the DAC section through my amp/power amp combo, but with a wee child on the way I might find a bit more use for the headphone section.


The main reason for changing the headphone OP-Amp is that out of the box the output was clean through my AKG K240's (not the best HP I know - ex my DJ rig), now I am hearing a definite hiss and distortion on the higher frequencies and it is very distracting.  This hiss is only present when the input source is being played.  With no music the HP/Preamp out is clean even when increasing the volume.  I have tried with both USB and coax input from different sources - laptop, PC, CD etc and the hiss does not change.  I have also tried with different headphones - same hiss.  


The direct analog output is fine - no hiss.  If the headphone or preamp output is used there is hiss.


As this sound wasn't present to begin with I am seeing about return, or if the supplier will provide a replacement Headphone amp PCB.  If I cannot get a good return option that doesn't cost the earth I was thinking swapping out the headphone OP_amps might help, hence the question on what style.  


Any idea if this might work?  Anything else I can check?  There is nothing looking burnt or odd on the PCB and I can find not loose bits of solder viewing from above.  Remember I am trying to keep this pristine in case of return, if return isn't an option I have no problems ripping into it!


many thanks



post #9250 of 9372

I would rather buy those OA from Mouser, Farnel,... than eBay.

That hiss/distortion is on left, right or both channels?

post #9251 of 9372

Hi,  thanks for the reply.  Looks like Farnel has a local representative in NZ and I can see good pics of the options, thanks!


This hiss is both channels...In fact describing the noise it would be closer to the distorted higher frequencies I mentioned, everything at the top seems to be distorted and "hissy"


I was planning on changing out the AMP OPAmps anyway for sound quality and fun, but your help is trying to diagnose is appreciated.  Following the same route with the DAC Opamp also, and have an OPA_moon on it's way :)





post #9252 of 9372

So...I haven't read through all 600+ pages of this post but I have purchased a used Zero from another head-fi member and I am more than happy with it.  I have a small selection of op-amps and I have been playing around with the Audio-GD Earth (came with it as part of the sale) in main slot and playing with various options in the headphone amp slots.  It came with LT1364s in the headamp section and I really like that sound paired with the Earth or 627 in the main slot.  I had an extra 627 on an adapter so I plugged the 627s in both headamp slots and I am really digging the sound.  Anyone else try this combo with success?


Most of my gear is a little bright so the Audio-gd Earth/627 combo seems to be very easy on the ears while still imparting plenty of detail/instrument separation.

post #9253 of 9372

Greetings to you all.


I have only one question and didn't find the answer for it in this thread.


I consider buying the new 2012 edition Zero dac with OPA637U. I have AKG K550, which are low impedance.


So my question is, would that be a good buy? Considering the problem with a hiss mentioned earlier?


Just to mention, I am on a very tight budget.



post #9254 of 9372

AKG K550 are less sensitive than Grado SR80 (mentioned by Butherowski few posts before), so the hiss problem should be smaller.

post #9255 of 9372

Any one find that the Zero Amp is too powerful?

I'm using a zero dac/amp connected through optical to PC, powering hd650s. To be able listen to music comfortably, I need to play music at 1% on winamp, and volume control at the 1oclock knob. I know for a fact that my HD650s are not easy to power because i tried powering them on my portable rig, and I needed to nearly max out my stepdance2 to be able power the 650s to a 'reasonably' loud level.


Any ways on reducing the volume that doesn't involve the PC would be greatful! :)



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