[audioneophyte]

Quote:

Originally Posted by Labtek Can you show me a picture of the Headphone amp stage? i.e. is it acting as a pre amp for the RCA as I really don't have clear picture of this amp in my head.

Sure, here are some high-res pics:

http://69.93.96.202/~stefan/

It has two different RCA outputs, one is volume controlled, one is not.

The non-volume controlled one is not affected by the noises at all.

See here:

http://www.ifiaudio.com/images/D2-detail1.jpg

If the headphone amp PCB is not securely attached with screws to the chassis exactly as it shipped all hell breaks lose... as in buzzing when you TOUCH the volume control, let alone turn it.

I'd take your advice about more earth ground.. but to what? I'm not quite ready to just short random parts of it with pieces of metal

EDIT: I really don't understand why that would occur though... is current supposed to flow through the potentiometer's turning dial?!

 

[Labtek]

Quote:

Originally Posted by audioneophyte Sure, here are some high-res pics: http://69.93.96.202/~stefan/ It has two different RCA outputs, one is volume controlled, one is not. The non-volume controlled one is not affected by the noises at all. See here: http://www.ifiaudio.com/images/D2-detail1.jpg If the headphone amp PCB is not securely attached with screws to the chassis exactly as it shipped all hell breaks lose... as in buzzing when you TOUCH the volume control, let alone turn it. I'd take your advice about more earth ground.. but to what? I'm not quite ready to just short random parts of it with pieces of metal EDIT: I really don't understand why that would occur though... is current supposed to flow through the potentiometer's turning dial?!

Run a wire from the cassis or heat sink to the earth post on the inside of the amp i.e. the post on the right as you look power socket at the back of the amp. There is current running through the chassis lick the chassis after previously touching it and you will see what I mean. It may hurt a little but not alot. This current is causing the hum and noise which fluctuates when you earth it tries to get to earth through your body. All the current wants to do is get to earth so let it through the power lead. Just hope some of your transistors havn't blown in all this curfuffle. There is nothing wrong with the potentiometer. Do the tongue test with the amp on. Try it first with a finger. Tongues are more sensitive. By the way I want that amp how much was it and where do I get one, it's a beauty.

 

[audioneophyte]

I see the Zhaolu is so irresistible even when broken it still attracts new buyers ...

I got it from Wei at www.ifiaudio.com, most people here seem to get it from Eddie Wu at diykits.co.hk

Anyway, thanks for the suggestions. I tried:

A) Chassis to ground on power socket.
B) Heatsink to ground on power socket.
C) Screw on headphone amplifier PCB to ground on power socket.

No real discernible effect, in the best case scenario it was the same as in the beginning.

At this point I'm pretty much convinced that my upgraded headphone amp is broken. So I'll have to try to get another to replace it. I'll see what Wei says.
Anyone have a spare Zhaolu dedicated headphone amp?

This really sucks because it sounds absolutely awesome, but the static/noise is killing it for me. I even ordered a pair of Sennheiser 580s to go with it but it looks like I won't have anything to plug them into when they get here.

 

[Labtek]

Quote:

Originally Posted by audioneophyte I see the Zhaolu is so irresistible even when broken it still attracts new buyers ... I got it from Wei at www.ifiaudio.com, most people here seem to get it from Eddie Wu at diykits.co.hk Anyway, thanks for the suggestions. I tried: A) Chassis to ground on power socket. B) Heatsink to ground on power socket. C) Screw on headphone amplifier PCB to ground on power socket. No real discernible effect, in the best case scenario it was the same as in the beginning. At this point I'm pretty much convinced that my upgraded headphone amp is broken. So I'll have to try to get another to replace it. I'll see what Wei says. Anyone have a spare Zhaolu dedicated headphone amp? This really sucks because it sounds absolutely awesome, but the static/noise is killing it for me. I even ordered a pair of Sennheiser 580s to go with it but it looks like I won't have anything to plug them into when they get here.

I could swear to the heavens that if you tried swapping the transistors you'd be very suprised how easy it is just make sure you put them all in place before you fire her up. Try it you will not be miserable and if it breaks I'll buy it off you for £150 if you ship it. As it will cost me £20 for the transistors. They may look complicated but they really are the simplist of electronic equipment. Transistors crackle pop hiss hum and generally go crazy when you touch the pot because your trying to put current through them when they can't handle it. Although you've earthed the amp one of the transistors is constantly chucking current in the mix as well. Please believe me you won't regret it. And then its just a question of ordering the replacement and listening to one channel in the meantime poping it in and away you go. It can be fun you know.

 

[audioneophyte]

Does anyone know what the four blue Trimming potentiometers on the headphone amp are supposed to be set to?

Comparing with this picture: http://www.erji.net/attachment/Mon_0606/2_147534.jpg

The 3rd one (from bottom to top) on mine seems to be set at a different angle.. (same as the 2nd and 4th)

 

[Sinwerm]

Quote:

Originally Posted by audioneophyte Hi guys, It appears I spoke positively way too soon on the Zhaolu D2 unit. I have the CS4398 unit with the "upgraded" headphone amp. Everything was going good until I noticed a slight buzzing/static noise on the left channel with my headphones. Well, I ignored it for a few hours but it got worse, and then I noticed touching or tapping the volume control would cause the static/noise to get a lot worse. I opened it up but couldn't really notice anything visibly wrong ... the static is still there, and I also hear a pretty nasty hum whenever I turn the volume pot past 1/4 maybe. Also touching it or having your hand near it (the pot) causes the buzzing to increase. I'm stumped on this. Did I just get a lemon? I sent an email to iFi about this but I'm hoping I wont have to send it back, because I really liked the sound quality, but these issues are killing it.

I have a stupid question , you say you have the upgraded headphone amp , is this the whole amp unit that you had to put in or did it come with the "upgraded" unit installed ? I think it is referred to as discreate head amp ? Im just wondering if you could switch them out and try the stock one. You bought it from Eddie in Hong Kong or ifaudio ? I feel for you , great unit for sound as a DAC , I just don't trust the amp section myself.

 

[audioneophyte]

I bought it with the factory installed discreete headphone amp unit from iFi as stated previously

HELP!: New theory

I started "blindly" tweaking the settings on the four blue trimming potentiometers on the headphone amp PCB.

See this picture: http://www.erji.net/attachment/Mon_0606/2_147534.jpg

Touching the top one (rightmost) caused similar static sounds to appear in RIGHT channel. So I turned the 2nd one (from left) a little bit, maybe about 10 degrees, it's closer to being horizontal now (parallel with the transistors) and the static in the left channel seems to be REDUCED immediately, if not eliminated.

<EDIT>NM about temperature, it gets very hot anyway.</EDIT>

How do I measure, what voltage are they supposed to be set to?
Edit: I guess I should have paid more attention in those E&M 101 classes

 

[Gone4T]

Quote:

Originally Posted by audioneophyte I started "blindly" tweaking the settings on the four blue trimming potentiometers on the headphone amp PCB.

Here's a photo of the discrete headphone amp and the trimpots and their orientation.

 

[audioneophyte]

Thank you very much, here are mine after making the adjustment I detailed in the first post:



I will monitor what happens but so far the results are excellent, no more static!

I'm not sure if this is merely covering up some other fault though.

EDIT: Yours seem to be at pretty different angles ... I'm afraid of changing anything more just by orientation. Is there a more "scientific", quantitative way of doing this? (Multimeter perhaps?)

 

[Labtek]

Quote:

Originally Posted by audioneophyte Thank you very much, here are mine after making the adjustment I detailed in the first post: I will monitor what happens but so far the results are excellent, no more static! I'm not sure if this is merely covering up some other fault though. EDIT: Yours seem to be at pretty different angles ... I'm afraid of changing anything more just by orientation. Is there a more "scientific", quantitative way of doing this? (Multimeter perhaps?)

Check the tracks, but those pots feed the transistors. You probably caught it in time. I'd listen to another amp though just to check quality. Well done!!!

 

[adhoc]

trimpot orientation does not really matter that much in my experience.

ie. a particular trimmer angle does not always equate to a particular result.

 

[n_maher]

Quote:

Originally Posted by audioneophyte I'm not sure if this is merely covering up some other fault though.

If tapping the volume control or the trim post made an audible difference in noise (as well as adjusting the trimpot) I'd say it's likely that you've got a different issue besides whatever the trimpot was set at. While trimmers like that may tend to drift over time the problem you first desribed sounds like a grounding issue to me. And I can't see how that would be effected by adjusting a trimpot.

 

[audioneophyte]

You raise a good point.

I was actually not entirely accurate in my original description.

The tapping on volume control noises ocurred after I first removed the headphone amp PCB from the chassis and then put it back... I must have not attached it properly. There is defintely some sort of grounding issue but if the headphone amp is in the chassis attached with all four screws it goes away, but not otherwise.

Anyway, this looks to be it. There are no more noises of any sort that I can pick up, channel balance seems okay, bass response is good, I think I'll leave it be for now.

A big thank you to everyone (esp. Labtek) for all the helpful suggestions, you saved my Zhaolu and my sanity.

One last clarification:

The issue that started this all was static noise in left channel, along the way I also started having trouble with the volume pot, most likely due to grounding issues. Both seem fixed, static noise was definitely fixed by changing the setting on the trim pot until I could no longer hear any noise.

LAST EDIT:

Just for the record, Wei / Ifi offered to replace the headphone amp, or the entire unit, or whatever it takes to fix it. So even if the Zhaolus are not prefect, a good dealer certainly goes a long way. YMMV, as always.

 

[Labtek]

I wasn't sure at some points which was more important your sanity or that beautiful amp. However I appear to have outstripped a DAC in sound although it takes a bit of work for me. See post- "Digilogue+ Digital/Analogue single stream" But with your DAC if you split a digital signal and pass one spur through the DAC and the other through a controllable preamp such as an LDII and combine again before entering the amp you will have the same result. You'll just have to listen to the phones on the main amp, sorry.