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Zhaolu DAC - a good value DAC?
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Old 4th March 2008, 02:54 AM   #331
billnchristy is offline billnchristy  United States
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I have no idea what I am doing either...at least we are on the same page.

It is on the DAC board. Look at the bottom Op-amp...pass the resistors to its right...see that purple cap? Right next to it is a 2 pin jumper set.

Thats the one.
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Old 4th March 2008, 03:00 AM   #332
kevinkr is offline kevinkr  United States
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Zhaolu DAC - a good value DAC?
Quote:
Originally posted by C37
Hi Kevin,

Thanks for the fast answer! In my pic posted right before= the center tap goes to the 4th connector from the left too, if I cut the bottom trace ( which I havenít yet) as well as the top ( that one I did: the one that goes to the cap), then the center tap is not connected to anything???
Or are there some hidden connection beneath the plastic conn1?

Regards,
Thomas
Hi Thomas (C37),
Hope you understood the intent, there is one trace that goes from pin 4 to the mecca between the two 3300uF caps as shown in post #317 that does not get cut.. Top trace and 4 tiny whiskers on top and bottom of pin 4th from left (center tap) are only ones cut...
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Old 4th March 2008, 03:52 AM   #333
jholtz is offline jholtz  United States
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I'm curious if anyone has tried the Burson Discrete opamp? I thought about trying them before I bought the Zapfilter but didn't. I'd be interested in user feedback.

EDIT: I just remembered why. They're almost as expensive as the Zapfilter.

Thanks!

Jim
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Old 4th March 2008, 05:13 AM   #334
kevinkr is offline kevinkr  United States
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Zhaolu DAC - a good value DAC?
Quote:
Originally posted by billnchristy
I have no idea what I am doing either...at least we are on the same page.

It is on the DAC board. Look at the bottom Op-amp...pass the resistors to its right...see that purple cap? Right next to it is a 2 pin jumper set.

Thats the one.



I guess the best thing to do is set it to whatever sounds best with the source hardware you are using. I'm assuming 96kHz is probably fast enough. I've noticed that 24/96 reproduction in my 2.5A is just ok - it seems that the dac really performs much better at the lower sample rates.
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Old 4th March 2008, 11:49 AM   #335
C37 is offline C37  Belgium
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Hi kevin, yes i figured it out, thanks. That conn1 is pain somewhere to resolder... Anyway, I am still recovering from the audio shock, this mod rocks!

I have a modded 2.5 with zapfilter, and these few tweaks to the psu really make the stock psu unit sound like broken...Cheers!
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Old 4th March 2008, 02:52 PM   #336
kevinkr is offline kevinkr  United States
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Zhaolu DAC - a good value DAC?
Hi Thomas,
I delighted to hear that it worked as well for you as it did for me. The really unfortunate thing about all of this is the engineers at Zhaolu could have and should have done all this work - there was so much potential that could have been unlocked right from the get go and for no really significant increase in cost.

This would have pushed it from: "Zhaolu - a good value DAC" to "Zhaolu - an unbelievably good sounding DAC." Sad really...
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Old 5th March 2008, 02:10 AM   #337
kevinkr is offline kevinkr  United States
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Zhaolu DAC - a good value DAC?
Exclamation Servo

I spent several hours implementing the servo shown in post #302 and I would recommend that you NOT use this circuit.

While it worked exactly as predicted on the bench and the output offset settled to less than 1mV after a couple of minutes, in actual use bursts of distortion started to occur on musical crescendos that were not previously present.

I suspect because of the physical size of the film caps used and some lead lengths required by this mod that the integrator was not really stable.. It was an extremely kluggy implementation and the LM4562 might not be the best low frequency integrator due to stability considerations.

Funny that it took over an hour to implement the mod and just a few minutes to remove it..

The servo was definitely the source of distortion - as I listen to it now it's back to being clean.

This is probably the end of the line for me and the Zhaolu.. I've ordered a pair of COD pcbs, an IVY pcb, and an assembled and tested spdif module based on the Wolfson WM8804 from Twisted Pear.

The Zhaolu will continue serving in my system until the Twisted Pear stuff is tweaked enough to surpass its performance. In the mean time it sounds very good and I will probably reapply it somewhere else.
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Old 5th March 2008, 05:22 AM   #338
DcibeL is offline DcibeL  Canada
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Quote:
Originally posted by BobM
I took a look at the diodes in my 2.5C and decided to not upgrade them. They are actually fairly high quality, fast Vishay diodes (2A if I remember correctly).
If they were BYV28 as marked on the PCB then they would be good diodes, but the diodes themselves clearly say BY228 on them, which is a slow high voltage diode. I'm replacing them with MUR210.

My parts arrived today (haven't picked them up yet), so I'll be modifying over the weekend. Wish me luck.
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Old 5th March 2008, 12:30 PM   #339
BobM is offline BobM  United States
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Default Re: Servo

Quote:
Originally posted by kevinkr
I spent several hours implementing the servo shown in post #302 and I would recommend that you NOT use this circuit.

Which version did you implement in post #303? Was that the servo or non-servo changes described?

And if it's the servo version then what to change to avoid the problem you describe?

Bob
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Old 5th March 2008, 01:40 PM   #340
DcibeL is offline DcibeL  Canada
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Default Re: Re: Servo

Quote:
Originally posted by Kevinkr
I spent several hours implementing the SERVO shown in post #302 and I would recommend that you NOT use this circuit.
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