[audiohound]

Quote:

Originally Posted by unbiased /img/forum/go_quote.gif You can order them from www.digikey.com. I just ordered a pair from them about 3 weeks ago and they had them in stock. Other sources for op amps and electronic parts are Mouser Electronics and Newark Electronics. I just ordered a Zhaolu D2.5C with optional discrete amplifier module upgrade from Audiomagus. I have no idea how this unit is going to sound and was wondering if anyone else here has heard it or compared it to the stock and/or Ori modded headphone amp module? I think I am going DAC/amp crazt as in the past couple of weeks I bought 3 DAC/amps... an iBasso D1, a ZERO 24/192 (Zhaolu clone?) and now a Zhaolu D2.5C with discrete headphone amp. I only have the ZERO 24/192 DAC/amp in hand now and amp burning it in. I did try some op amp rolling on it initially and I think I liked the OPA627 op amps in place of the OPA2604 DAC amp that came with it. For now, I am running it with all of its original op amps to give it a chance to smooth out/burn in. Can't wait to get my other DAC/amps to compare them.

Thanks, I found them on the Digikey site. Is this the right part: "IC OPAMP AUDIO DUAL HF 8-DIP" and is it 2 that I need?

 

[joe_cool]

Quote:

Originally Posted by audiohound /img/forum/go_quote.gif Thanks, I found them on the Digikey site. Is this the right part: "IC OPAMP AUDIO DUAL HF 8-DIP" and is it 2 that I need?

The part you want is LM4562NA (or the newer part number LME49720NA). It has two amplifiers in the chip so you probably only need one part.

The Zhaolu 2.5 uses two dual opamps on the analog filter board.

 

[unbiased]

Quote:

Originally Posted by audiohound /img/forum/go_quote.gif Thanks, I found them on the Digikey site. Is this the right part: "IC OPAMP AUDIO DUAL HF 8-DIP" and is it 2 that I need?

Yes as JoeCool had already answered your question, that is the part number and description. I don't know if you need two or not as I don't have my Zhaolu 2.5C DAC/amp to look at yet. I am sure someone else on this forum can tell you for sure though. I personally don't like this op amp though. I think it is kind of bright sounding in the headphone amps I have tried it in which is the Practical Devices Xmoy2 penguin tin can style amp, ZERO 24/192 DAC/amp and an iBasso D1. YMMV of course!

 

[pompon]

Any way to have headphone output on oritek zhaolu 2.5a ?

I own Citypulse DA7.2x + txco clock .. good idea to upgrade with Oritek Zhaolu 2.5a ?

 

[d-cee]

D2.5 has 2 dual opamps in analog output section, 1 dual opamp in the power supply section and 2 dual opamps in the stock headphone amp. the upgraded discrete headphone amp has 1 dual opamp

D2.0 has 3 dual opamps in the analog output section, 2 dual opamps in the stock headphone amp. the upgraded discrete headphone amp has 1 dual opamp

 

[d-cee]

Quote:

Originally Posted by pompon /img/forum/go_quote.gif Any way to have headphone output on oritek zhaolu 2.5a ? I own Citypulse DA7.2x + txco clock .. good idea to upgrade with Oritek Zhaolu 2.5a ?

maybe... i dunno about OMZ D2.5 but my OMZ D2 has a bit of spare room at the front.

it'd probably take a bit of re-wiring though i dunno...

best to contact Ori about that one

 

[Ori]

Quote:

Originally Posted by pompon /img/forum/go_quote.gif Any way to have headphone output on oritek zhaolu 2.5a ?

Please contact me directly via email regarding a headphone option for the OMZ.

 

[d-cee]

Quote:

Originally Posted by Ori /img/forum/go_quote.gif Please contact me directly via email regarding a headphone option for the OMZ.

is that a fore gleam of things to come!?!

 

[audiohound]

Quote:

Originally Posted by jholtz /img/forum/go_quote.gif Hi, I'm new to Head-Fi. I've been following the Zhaolu mod thread with great interest. It looks like an inexpensive DAC with great potential. Thanks to all that have done such a superb job of documenting the mod process. My question is, there is a Dc offset as I understand it that is related to the AD1852 DAC and can't be trimmed out. Does the CS4398 also have a DC offset issue? I'm curious why the blocking caps are causing a significant degradation in sound quality. Blocking caps are quite common in electronics. I've installed Blackgates or Muse KZ caps in the past with good success. That doesn't seem to be an option here. I do remeber reading that it had to do with being on the input side rather than output. Could the caps be moved to the output side? If these are newbie questions, please be gentle. I don't have the technical skills of many that post here. Thanks for the feedback! Jim

I'm another newbie still learning how to understand specs, and in fear of frying my system. Purchased the Zhaolu D2.5C and, after some easy op amp rolling, I plan to perform this more challenging bypass mod recommended by Ori below, but fear DC Offset issues:

"You might consider is the famous "cap bypass mod". You should understand that it increases the DC offset on the RCA outputs. I measured 50-60 mV and in some extreme cases you might see over 100 mV. If your amp has a capacitor at the input, then this is not an issue. Most tubes amps do. You may want to use a multimeter to check the DC offset at the RCA output after the mod, just to verify it's within the reasonable limits. The procedure is quite simple: red probe to inner part ("tip") of the RCA jack and black probe to the outer part ("barrel"). Turn on the unit when measuring but you don't need a source or an amp."

So...I'm ready to perform this mod but I can't get definitive info from NAD on whether my NAD 304 Integrated (used as Preamp, only) is DC Coupled or what my B&K ST125.5 amp can handle (although B&K confirmed the power amp is not DC Coupled). I'm still learning about specs and I'm not yet up to speed on this.

I have the NAD spec sheet here (and there's a link below), It says line-level input sensitivity is 165mV. Once again, the DC Offset from the modded DAC will be 50-60 mV. Doesn't this suggest that it would be safe since the DAC is offsetting less than what the Preamp is rated to receive?

Does anyone have the willingness/patience to open (or repaste) below user manual links showing equipment specs and make a reasonable inference or recommendatation regarding the safety of increased DC Offset in my set-up?

See page 2 for NAD specs:
http://207.228.230.231/info/NAD_304.pdf


See page 13 for B&K specs:
http://www.bkcomp.com/fileadmin/cont...2_1_manual.pdf


Thanks, Audiohound

 

[Ori]

The potential DC offset is 50-60 mV. You may find much smaller levels after you mod your Zhaolu.
The NAD spec says clearly that it will tolerate up to 10V input. That gives a lot of margin. It's a modern solid-state amp with some provisions to cancel DC on the speaker ports, so I'd say it's safe to run even with 60 mV offset.
The B&K is not as clear, but it likely would be the same conceptual circuitry as the NAD.
I'd mod the Zhaolu without removing the caps, then measure the offset on each channel. You can swap opamps around (make sure to plug them in the correct orientation!) and see which combination gives you the lowest offset.
Good luck!

 

[unbiased]

Quote:

Originally Posted by audiohound /img/forum/go_quote.gif I'm another newbie still learning how to understand specs, and in fear of frying my system. Purchased the Zhaolu D2.5C and, after some easy op amp rolling, I plan to perform this more challenging bypass mod recommended by Ori below, but fear DC Offset issues: "You might consider is the famous "cap bypass mod". You should understand that it increases the DC offset on the RCA outputs. I measured 50-60 mV and in some extreme cases you might see over 100 mV. If your amp has a capacitor at the input, then this is not an issue. Most tubes amps do. You may want to use a multimeter to check the DC offset at the RCA output after the mod, just to verify it's within the reasonable limits. The procedure is quite simple: red probe to inner part ("tip") of the RCA jack and black probe to the outer part ("barrel"). Turn on the unit when measuring but you don't need a source or an amp." So...I'm ready to perform this mod but I can't get definitive info from NAD on whether my NAD 304 Integrated (used as Preamp, only) is DC Coupled or what my B&K ST125.5 amp can handle (although B&K confirmed the power amp is not DC Coupled). I'm still learning about specs and I'm not yet up to speed on this. I have the NAD spec sheet here (and there's a link below), It says line-level input sensitivity is 165mV. Once again, the DC Offset from the modded DAC will be 50-60 mV. Doesn't this suggest that it would be safe since the DAC is offsetting less than what the Preamp is rated to receive? Does anyone have the willingness/patience to open (or repaste) below user manual links showing equipment specs and make a reasonable inference or recommendatation regarding the safety of increased DC Offset in my set-up? See page 2 for NAD specs: http://207.228.230.231/info/NAD_304.pdf See page 13 for B&K specs: http://www.bkcomp.com/fileadmin/cont...2_1_manual.pdf Thanks, Audiohound

Audiohound, you must be careful with the DC offsets when bypassing output capacitors (of any equipment). Even though the reported offset voltages reported here are in the 50mv to 60mv range, you should always check your particular offset voltages to make sure it is very low. Even 50mv to 60mv might be enough to upset the ciruit equilibrium (biasing) of upstream preamps, amps or other devices, if they are DC coupled inputs and are very sensitive. If your upstream equipment is not DC coupled (meaning it has input capacitors in its circuit path) then you should be okay and no harm what-so-ever will occur even if your DAC/amp offset voltage were to go wild and swing up to 1 volt or more.

Now, as for your particular NAD 304 amp, it is capacitor coupled (not DC coupled) so it would be safe for you to plug in your caps bypassed DAC/amp into the line inputs of the NAD 304. On the schematic of that amp they show a .1uf capacitor in series with the line level inputs after a 20K volumn control. So you are good to go from this stand point.

If B&K said for sure that the particular amplifier that you have is not DC coupled, then you should be good to go plugging the D2.5C directly into the power amp too!

Have fun, but be careful! I just got my Zhaolu 2.5C with upgraded discrete headphone amp module and am burning it in. Weird that it finally makes me like my AKG-701 headphones now! This thing is sound great out of the box and can only improve with the burn-in...!

 

[audiohound]

Quote:

Originally Posted by unbiased /img/forum/go_quote.gif Audiohound, you must be careful with the DC offsets when bypassing output capacitors (of any equipment). Even though the reported offset voltages reported here are in the 50mv to 60mv range, you should always check your particular offset voltages to make sure it is very low. Even 50mv to 60mv might be enough to upset the ciruit equilibrium (biasing) of upstream preamps, amps or other devices, if they are DC coupled inputs and are very sensitive. If your upstream equipment is not DC coupled (meaning it has input capacitors in its circuit path) then you should be okay and no harm what-so-ever will occur even if your DAC/amp offset voltage were to go wild and swing up to 1 volt or more. Now, as for your particular NAD 304 amp, it is capacitor coupled (not DC coupled) so it would be safe for you to plug in your caps bypassed DAC/amp into the line inputs of the NAD 304. On the schematic of that amp they show a .1uf capacitor in series with the line level inputs after a 20K volumn control. So you are good to go from this stand point. If B&K said for sure that the particular amplifier that you have is not DC coupled, then you should be good to go plugging the D2.5C directly into the power amp too! Have fun, but be careful! I just got my Zhaolu 2.5C with upgraded discrete headphone amp module and am burning it in. Weird that it finally makes me like my AKG-701 headphones now! This thing is sound great out of the box and can only improve with the burn-in...!

Thanks very much....I really appreciate the very specific info you provided. I also purchased form AudioMagus and I'm glad to hear you like it right out of the box. And you're right, it only gets better! Wondering if you or anyone can recommend the type of wire and solder to use for the bypass mod.

Regards, Audihound

 

[audiohound]

Thanks, Ori....I really appreciate it. After all, you're the King of Zhaolu mods so I value your advice a great deal.

 

[joe_cool]

Quote:

Originally Posted by audiohound /img/forum/go_quote.gif Am I safe with 50-60 mV DC Offset after modding the Zhaolu DAC?

On my Zhaolu 2.5C I measured 8mv offset on each channel with the Nichicon ES caps bypassed (shorted with solid wire). On my Entech 205 (which has no coupling caps to begin with) I measured 1mv on one channel and 15mv on the other.

If you aren't confident that you know what you're doing then please don't try to modify equipment with dangerous power levels.

 

[udo]

Any knowledge about a NAD C320BEE being capacitor coupled?