[ArtVark]

My On/Off button died quite soon after I got my 2.5, now it's more or less permanently On. I don't really mind, except that the relays have a tendency to click off and on once in a while when there is no source signal. And that's irritating when I'm enjoying silence instead of music.
I've read somewhere about bypassing the relays, bu there were no details. I was thinking of getting some better RCAs and bypassing and removing the relays completely, which I hope will be a small improvement for the sound as well.
What would the disadvantage of this be? Is there noise when there is no source signal?

Ton

 

[Crow]

Quote:

Originally Posted by ArtVark /img/forum/go_quote.gif My On/Off button died quite soon after I got my 2.5, now it's more or less permanently On. I don't really mind, except that the relays have a tendency to click off and on once in a while when there is no source signal. And that's irritating when I'm enjoying silence instead of music. I've read somewhere about bypassing the relays, bu there were no details. I was thinking of getting some better RCAs and bypassing and removing the relays completely, which I hope will be a small improvement for the sound as well. What would the disadvantage of this be? Is there noise when there is no source signal? Ton

It seems curious to me that the relays click randomly with no signal. I leave my 2.5 on for long stretches without this issue. Perhaps your power is cutting in and out at times because of the faulty switch, causing the relays to click off then back on. You might try wiring up a new switch first, like a nice toggle or similar. You can find them at your local Ace/other hardware store...

 

[Crow]

Quote:

Originally Posted by ArtVark /img/forum/go_quote.gif What would the disadvantage of this be? Is there noise when there is no source signal? Ton

Whoops missed the questions. Relays are often used to protect circuitry/devices downstream (or up) from short-circuit damage, over current conditions etc. To me they indicate a thoughtful/safe circuit design in the 2.5. If you must replace them maybe you could go with those gold-contacted ones, but to me it's worth just keeping them.

There is nearly zero noise with no source signal on the 2.5 because the DAC chip goes into digital mute, sort of like it closes the door to all noise, even its own.

 

[audiohound]

Quote:

Originally Posted by d-cee /img/forum/go_quote.gif i don't think you emailed the right people... best to PM Ori here on head-fi or use the email link at the bottom of the OMZ website Oritek Audio - Zhaolu D2.5A DAC modifications page

Thanks D-CEE. Indeed I had the wrong e-mail address and got in touch with Ori by using the link you provided. Happy listening!

 

[d-cee]

Quote:

Originally Posted by ArtVark /img/forum/go_quote.gif My On/Off button died quite soon after I got my 2.5, now it's more or less permanently On. I don't really mind, except that the relays have a tendency to click off and on once in a while when there is no source signal. And that's irritating when I'm enjoying silence instead of music. I've read somewhere about bypassing the relays, bu there were no details. I was thinking of getting some better RCAs and bypassing and removing the relays completely, which I hope will be a small improvement for the sound as well. What would the disadvantage of this be? Is there noise when there is no source signal? Ton

what transport are you using? people had issues previously using PC as a transport...

 

[Kevin Sinnott]

Quote:

Originally Posted by Bobs /img/forum/go_quote.gif I also have the Rockna dac on order. I ordered it 5 weeks ago, and they told me last week i probably wont receive it before christmas. I`m getting a bit tired of these small companies, wondering if i should just go all the way and get a Stello DA220 or something.

I own the Rockna RD-2. It took awhile to get it, but it's worth the wait. I can't think of anything from a larger company that compares to its design and build.

 

[ArtVark]

D-Cee,
Sorry for the late reply. I've been checking out some different sources. The problem only occurs with my Sony SCD-XE670.
Using a computer USB source, some DVD players (including a Sony) and streaming media player there is no problem.

Ton

 

[d-cee]

Quote:

Originally Posted by ArtVark /img/forum/go_quote.gif D-Cee, Sorry for the late reply. I've been checking out some different sources. The problem only occurs with my Sony SCD-XE670. Using a computer USB source, some DVD players (including a Sony) and streaming media player there is no problem. Ton

some people were having issues because the transport switched off, or at least stopped outputting anything when there was no music coming through... hence it would detect no signal and start switching off

bypassing the relay is pretty easy, not sure which version of the Zhaolu you have but there's these little button/pads on the DAC - small silver box with black nipple on top, about 3 x 3 mm, one says OPTI the other says COAX

if you flip the board over. they both have 2 solder points directly beneath them, short the legs between coax with a short wire and it will default to coax

i am assuming you have a D2.0 since the D2.5 defaults to coax, in which case these little buttons are on the bottom right of the board when viewing the DAC from the top with the front facing you

 

[FarFromCentre]

Hey everyone, I haven't seen too much of the D3.0 around here (I wonder why?), I got one and I plan on modding it sometime the future. What is a good place to start?

 

[deuginthesky]

Change the op amps on the signal exit, the pair of OPA604 by better ones: OPA627, LME49710. No need to desolder anything, they are on a socket.

For more changes (resistors, bypass caps..), use a very hot iron solder, around 480°C. The solder on the PCB is really boring to remove, much more than on the 2.5.

 

[gregmorris]

I by-passed the large polyprop. input caps (closest to the volume pot.) on the upgraded discrete mosfet headamp. The built in dc servo takes care of the small dc coming in from the zhaolu's cap by-passed output. The dc offset from the headamp remains virtually 0.

I also increased the quiescent current of the headamp by adjusting the outter trimpots, near the heatsink. This will push the amp further into Class A operation. The original reading was around 21mV and I turned it up to around 27mV....the heatsink gets warmer but I can easily leave my hand on it. I adjusted the inner trimpots to get the dc offset as close as possible to 0 (with the servo opamp removed). I will probably try increasing the quiescent current further in the future to see what it sounds like..... Maybe turn it up until the heatsink is almost too hot to leave my hand on?

This amp is very very good for the upgrade price. I think the adjustments I made make it sound even better.

 

[d-cee]

Quote:

Originally Posted by gregmorris /img/forum/go_quote.gif I by-passed the large polyprop. input caps (closest to the volume pot.) on the upgraded discrete mosfet headamp. The built in dc servo takes care of the small dc coming in from the zhaolu's cap by-passed output. The dc offset from the headamp remains virtually 0. I also increased the quiescent current of the headamp by adjusting the outter trimpots, near the heatsink. This will push the amp further into Class A operation. The original reading was around 21mV and I turned it up to around 27mV....the heatsink gets warmer but I can easily leave my hand on it. I adjusted the inner trimpots to get the dc offset as close as possible to 0 (with the servo opamp removed). I will probably try increasing the quiescent current further in the future to see what it sounds like..... Maybe turn it up until the heatsink is almost too hot to leave my hand on? This amp is very very good for the upgrade price. I think the adjustments I made make it sound even better.

that's interesting, look forward to it. the upgraded, discete inbuild amp is certainly excellent for the price, surprised more hasn't been discussed about improving it

 

[Artemus GF]

somebody know if a Zhaolu 2.5a convert 88,2kHz or 176,4kHz without to resample it?

another question: whats a good replacement OPA for the AD-08? (i'am using 2x OPA2107 and one OPA2107 at discrete headphone amp, headphone: A900)
i have 1x OPA2107, 2x LT1057, 4x LME49720 (improved LM4562), 3x OPA2134 (2x JRC-G155B and one TL082CN) left

 

[nikongod]

As a very sweet mod for the 2.5c/discrete output stage, replace the pot with an alps blue. it will fit if you remove the input caps, move the 2 resistors slightly behind the cap to the bottom of the board, remove the input 4-pin connector (i soldered the wires to the bottom of the board. i didn't use Valhalla wire, and it looks like it might have come that way, so Patrick82 disapproves...) AND put the pot in on its side, wired to the bottom of the board. the stock pot is a pile of crap, probably WORSE than the stock input caps. mine had a pretty strong imbalance at ALL levels.

Quote:

Originally Posted by gregmorris /img/forum/go_quote.gif I also increased the quiescent current of the headamp by adjusting the outter trimpots, near the heatsink. This will push the amp further into Class A operation. The original reading was around 21mV and I turned it up to around 27mV....the heatsink gets warmer but I can easily leave my hand on it.

thats kind of odd (imho) on my 2.5c, the idle was set at about 150mV. it would not go lower than about 120mV. i had it running as high as 160mV, but returned it to 150 after looking up the datasheets for the output transistors. they seem a little "small" with regards to output power.

is it possible that there are 2 different discrete output boards? that would be cool. because of this possibility, i WOULD NOT use my voltages. if there are in fact 2 boards the numbers mean totally different things. taking an educated guess that the boards are made for whatever transistors can be bought by the pound for $0.25 this week there may even be more than 2... would you mind posting part numbers? i will update this post tomorrow with some of mine.

as a last bit: There are 2 jumpers on the board between the pots, and SLIGHTLY closer to the opamp. removing them removes the dc servo from the circuit. a little faster than pulling the opamp every time you want to bias.

 

[gregmorris]

thats kind of odd (imho) on my 2.5c, the idle was set at about 150mV. it would not go lower than about 120mV. i had it running as high as 160mV, but returned it to 150 after looking up the datasheets for the output transistors. they seem a little "small" with regards to output power.

is it possible that there are 2 different discrete output boards? that would be cool. because of this possibility, i WOULD NOT use my voltages. if there are in fact 2 boards the numbers mean totally different things. taking an educated guess that the boards are made for whatever transistors can be bought by the pound for $0.25 this week there may even be more than 2... would you mind posting part numbers? i will update this post tomorrow with some of mine.

QUOTE]

My discrete amp uses 2SK214 and 2SJ77 mosfets.... My previously stated readings where mistaken and need another 0 added. I was reading closer to 300mV last night. I had asked Eddie at diykits to turn up the bias a bit higher before shipping so thats probably why mine originally read 210mV (vs. 150mV). As I recall, Eddie said 1V was the upper limit..... That seems a bit high!

I'm currently using LM4562 for the DAC's left/right output opamps and a BB2107 for the center. The DC offset is 7.8mV in the right channel and a fairly high 26.9mV in the right.... I'm not sure the cause of the imbalance but it seems to be there in varying degrees with all opamps tried. The headamp's servo seems to take care of the offset. The headamp out is less than 1mV in both channels.