[HumanMedia]

Tweaks installed:
*TXCO oscillator upgrade - across the board improvement with warmer bass and midrange and finer treble
*Neutrik 75 ohm BNC female isolated chassis connector for digital connection - more airy and clearer than RCA or optical connection
*ERS cloth glued to right hand inside top and side of chassis - took a small amount of grit from the treble
*Bussman ceramic fuse (1A 250V Fast Blow 20mm) - Ceramic fuses do sound better, but dont use HiFiTuning fuses they make this DAC sound worse.
*Cleaned internal connectors with Isopropyl achohol and applied Quicksilver Gold contact enhancer (fuse, power connectors, red amp modules, socketed oscillator, socketed firmware(?) chip, opamp at front of unit (headphone?). All combined, the cleaning, contact enhancement and ceramic fuse made a noticeable improvement, firming up the midrange.

I also noticed that tapping the chassis even very gently vibrated the oscillator and 6 large caps way more than it really should. There is probably much scope for vibration control on these components in particular and the chassis overall. I Bluetacked over the TXCO temporarily to help dampen this delicate component.

My next step will be the rectifying diodes. There is a small potential for problems with changing the type of diode, so Im going to get an opinion from someone who knows what they are doing before jumping in.

The 7.2x is sounding much better. Going back and forth with the Zhaolu, I now cant return, despite the 7.2x still being flawed in the high frequencies (a little coarse). Its pros far outweigh its cons.

 

[pojen_h@hotmail.]

update later (checking fuse on my unit 120v? 250v?)

Update

Hi HumanMedia,

I double check my unit and find mine also have 250v fuses. (good!) The fuse is "F1AL250V" "A009662".

Is this one you refer to?
http://www.itcelectronics.com/prodDisplay.asp

I also want to upgrade my RCA plug on my fix out. However, I found the plug are rest in some red box housing. I think I can remove the red box, but should I use write to connect the RCA plug to the PCB board? (run a short length of soler or should I get a wire to connect?) This is what I want to place with the stock RCA plug.

There are a lot of screw to unscrew. I don't think I would like to open it up that often. XD

 

[pojen_h@hotmail.]

Got e-mail from Eddie,

First Step

Second Step

Quote:

from Eddie: Third : make sure the DIRECTION OF OCCILATOR to insert ! You should CLEAN UP the PCB after soldering. Check up the high and low and you will find something ! Wu.

from the picture Eddie just send me, the 3 "33" cap must be removed before install the TXCO.

 

[HumanMedia]

Mine had the socket preinstalled so the caps werent there. If you have the socket installed, then the notch at one end of the black plastic under the TXCO should match the position of the notch at the end of the socket.

There is an interesting jumper on the board. Marked Hardware/Software As shipped the jumper is enabling "Software". Wonder what this could all be about?

 

[HumanMedia]

Quote:

Originally Posted by pojen_h@hotmail. update later (checking fuse on my unit 120v? 250v?) Update Hi HumanMedia, I double check my unit and find mine also have 250v fuses. (good!) The fuse is "F1AL250V" "A009662". Is this one you refer to? http://www.itcelectronics.com/prodDisplay.asp I also want to upgrade my RCA plug on my fix out. However, I found the plug are rest in some red box housing. I think I can remove the red box, but should I use write to connect the RCA plug to the PCB board? (run a short length of soler or should I get a wire to connect?) This is what I want to place with the stock RCA plug. There are a lot of screw to unscrew. I don't think I would like to open it up that often. XD

F1AL250V simply refers to Fast Blow, 1 Amp, 250V.

I could only find glass fuses on that site. They need to be ceramic in a white tube (not glass). Bussman and Littlefuse are great. You can probably get them locally. And you need 20mm x 5mm not 3AG (1.25" x .25")

 

[HumanMedia]

Quote:

Originally Posted by pojen_h@hotmail. I also want to upgrade my RCA plug on my fix out. However, I found the plug are rest in some red box housing. I think I can remove the red box, but should I use write to connect the RCA plug to the PCB board? (run a short length of soler or should I get a wire to connect?) This is what I want to place with the stock RCA plug. There are a lot of screw to unscrew. I don't think I would like to open it up that often. XD

On replacing RCA's.

You should use proper hookup wire to connect RCA to PCB. I would recommend 22awg single stand copper with Teflon dialectric/insulation. The Homegrown audio silver stuff is good. Personally I prefer copper VHAudio Chela speaker cable which I pull apart into individual strands. 1ft of Chela will go a long way for hookup wire (48 x 1ft strands).

Note that the holes in the chassis are quite close together so those connectors you linked to may not fit in easily as the plastic collars would overlap. You may need to move the connector holes or at least widen them with a reamer.

Also my gut feel is that silver/rhodium may not synergize with the 7.2x sound and that gold/copper may be better. This is all system dependant though.

 

[pojen_h@hotmail.]

Quote:

Originally Posted by HumanMedia Mine had the socket preinstalled so the caps werent there. If you have the socket installed, then the notch at one end of the black plastic under the TXCO should match the position of the notch at the end of the socket.

No, I have to install the socket myself. Eddie ship me both TXCO and socket to do the work.

Quote:

Originally Posted by HumanMedia F1AL250V simply refers to Fast Blow, 1 Amp, 250V. I could only find glass fuses on that site. They need to be ceramic in a white tube (not glass). Bussman and Littlefuse are great. You can probably get them locally. And you need 20mm x 5mm not 3AG (1.25" x .25")

Thanks for the reply. The link is not working.

I did a serch on froogle with keywords, "20mm 5mm fuse 1a" It seems the only one that is available is from Bussmann. However, I am a little confused on which to get. They have
- Bussman GMA
- Bussman GMC
- BUssman GMD
- Bussman GDA
- BUssman GDC
- Bussman GDB

It seems they are all have glass tube. Click me

Quote:

Originally Posted by HumanMedia On replacing RCA's. ... Note that the holes in the chassis are quite close together so those connectors you linked to may not fit in easily as the plastic collars would overlap. You may need to move the connector holes or at least widen them with a reamer..

That is what I am worried. It seems like replacing RCA plug is not going to be a easy task. I am going to postpone the RCA plug upgrade plan. (or hope that I can find a way to do it, next time I open it.)

 

[HumanMedia]

Try here:
http://www.mouser.com/search/Product...76-24111000021


Also Littlefuse have offices all around the world. Check with your closest office and you may find a reseller very close to you.

 

[Spare Tire]

Hum... What is this bizarre frequency...

I was going to give it a go but i'm completly out of cash, with my McAlister amp coming and some stax i want on ebay, will have to postpone this. Hope the price doesn't go up any further as this gets more popular, like the zhaolu.

 

[Meyvn]

Quote:

Originally Posted by Spare Tire Well yes, i know i need a balanced amp, but about electrostats being balanced, i thought that because the stators push and pull at the membrane that it meant it was balanced. Maybe there's a big mixup in my head but then what is balanced?

I don't think the push-pull nature of electrostats is the same as the push-pull nature of balanced sources and amplification; electrostatic stators will push and pull regardless of whether or not the signal coming into them is balanced. And dynamic drivers won't work that way regardless as well, yet they can be driven balanced. The push-pull of electrostatic stators has nothing to do with the push-pull of balanced audio. It's a coincidence of name.

 

[HumanMedia]

How are people going with the TCXO?

The TCXO and a few small tweaks, plus a stiff 350 hour burn-in, certainly has transformed this DAC. Detail that even RogerWilco would be happy with.

How are other people faring with it?
Any other tweaks?

 

[RogerWilco]

Quote:

Originally Posted by HumanMedia How are people going with the TCXO? The TCXO and a few small tweaks, plus a stiff 350 hour burn-in, certainly has transformed this DAC. Detail that even RogerWilco would be happy with. How are other people faring with it? Any other tweaks?

I have been so busy here lately --have not had much time for audio.The citypulse does seem like a nice dac--i wonder if it has the same great imaging the zhaolu has.I would also hope it has the detail of the zhaolu.

 

[pojen_h@hotmail.]

I just received my soldering iron and solder. I am planning to work on it this weekend. Any suggestion before I start play with the unit?

P.Huang

 

[HumanMedia]

Quote:

Originally Posted by pojen_h@hotmail. I just received my soldering iron and solder. I am planning to work on it this weekend. Any suggestion before I start play with the unit? P.Huang

Make sure to get a solder-sucker to desolder the existing bits. I prefer the pneumatic type you press down with your thumb.

 

[Spare Tire]

Quote:

Originally Posted by pojen_h@hotmail. I just received my soldering iron and solder. I am planning to work on it this weekend. Any suggestion before I start play with the unit? P.Huang

Did you ask him specifically to get the kit and do the assembling yourself or does it happen randomly that he sends out units with sockets and units without like that to unsuspecting customers?