[joe_cool]

Well, it's Saturday night and the heavy rollers are off-line, so I decided to post a mini-review on the DR DAC2 which I recently bought from Korea via eBay. It was delivered via UPS in less than 48 hours.

This is a small unit with a lot of built-in functions. It has 24/96 USB input (no driver required) as well as Toslink SPDIF, coax SPDIF, and analog stereo inputs. There are Toslink SPDIF (AC3 pass-through supported) and line-level stereo analog outputs as well as two headphone outputs with low-gain and high-gain configurations. All analog outputs are controlled by the front-panel Alps potentiometer.

Included is a small 15VDC switching power supply rated at two amps and good for 110 or 220 volts AC input. Also there is a 5-foot USB cable (A-B) with a donut choke on the peripheral end, a multi-language instruction manual and some small adhesive-backed silicone bumper feet.

My first impression was about the small size of the unit relative to the weight of the box. The power supply is very light so most of the weight is in the main unit. Some will wonder if sonic improvements could be gained with a linear DC power supply, but in my mind this is doubtful as the internal power supply is obviously a switcher with multiple output voltages.

My areas of interest in this unit are the USB interface, the headphone amplifier and of course the DAC itself, which is a BB1798 with differential current outputs. The DAC analog section includes 3 dual op-amps so there is an I/V converter for each output and a converter/filter for each channel. After a quick listen I replaced the stock 5532 op-amps with 3 x LM4562NA which improved the resolution considerably.

The line output (after the volume control) uses an OPA2134 and the headphone amp uses an OPA2604 driving a complex discrete-transistor array. I didn't attempt to trace the circuit but there appear to be 32 discrete transistors on both sides of the PCB including the 4 larger output devices.

In general I would rate the USB input as very good. I noticed no obvious jitter when driven by the USB2 ports on my Asus P4P800SE using several high-grade cables.

The DAC section I would rate excellent (at least equal in comparison to my M-Audio SuperDAC with considerable enhancements). There was no problem with 192kHz data but this was tested via coax using my M-Audio Revo5. No testing of the TOSLINK input or output was attempted.

The headphone amp I would also rate very good when driving AKG K701s. The low-gain jack gave the best sound but head-bangers will want to use the high-gain jack for dangerous volumes.

Improvements in the line-out and headphone amps are likely possible with better op-amps. I would consider the BB OPA2107, 2x OPA627, 2x AD825 or AD8620 for the line-out. Higher gain-bandwidth may be required for the headphone amp and I would recommend 2x AD825 or AD8620. The analog PS is +/- 12VDC.

I will try to post pics and further impressions when time permits.

 

[joe_cool]

The case is a little different than what I saw on their web site:

Here is a shot of the pcb with different opamps:

As I expected the resolution and tonal accuracy of the line output and headphone amp improved considerably. I will do more testing of the USB interface as compared to the coax SPDIF and post results.

<edit> No problems were encountered with USB input up to 24/96 using DVD-A as source. Using a Belkin Pro 3-meter cable there was no noticeable difference vs. the coax SPDIF input. ASIO4ALL works fine but so does Direct Sound with Foobar 2000. <edit>

 

[joe_cool]

After a few days of burn-in and testing IMO the best sounding amp for both the headphone and line-out was also the LM4562. The original OPA2604 headphone amp sounded good but I didn't like the original OPA2134 line-output amp in this application. I also tried the AD825(2x), AD8620 and OPA627(2x).

I was not sure the BJT-input amps would work in these positions so I did some circuit investigation. The selected input (line or dac) feeds a 10K-ohm volume control, then a 2.2uF Wima cap, then a 50K-ohm load resistor, so the DC impedance seen by the (selected) line-out or headphone amp is 50K-ohms, and this does not vary with changes in the volume control. Roughly estimating, 10na bias current plus 10na offset current (20na) X 50Kohms = 1mv. I measured three different op-amps in the headphone circuit (set on high gain, 10X or 20dBV) and all were below 10mv offset at the headphone output. IMO this is an acceptable offset. Some FET-input amps have greater offsets due to input offset voltage.

 

[Currawong]

Nice work. I've often pondered trying the DR.DAC2, but the price has been just over what I felt like spending for the purposes of experimentation.

One correction: You can't hear jitter. Jitter causes SQ degradation, it doesn't have a sound of its own.

 

[joe_cool]

OK, I'm convinced. The LME49720HA is just excellent. The original NE5532 amps were quite good in the DAC section, but the HA chips on BD adapters put the preamp and headamp sections a notch above the LM4562NA chips.

 

[DarKu]

i had the Dr.DAC2 which is absolutely the same as DX version minus the Optical out.
It is a good source i can tell, the Pico i have now is considerable better in almost every aspect, except that it doesnt have all the inputs and outputs.
I had my Dr.DAC2 for one year and i would say that it is a good source at 300$ not more not less, the strangest thing is that you like the LM4562 with your K701, LM4562 was the brightest op-amp i tried and it did a pretty bad job driving my Grados, also LM4562 decreases the bass which for K701 it is just a "NO way" thing,...strange you like them. I would choose some warmer op-amps if i was you

 

[joe_cool]

Quote:

Originally Posted by DarKu /img/forum/go_quote.gif i had the Dr.DAC2 which is absolutely the same as DX version minus the Optical out.

absolutely......except for the case
Quote:

Originally Posted by DarKu /img/forum/go_quote.gif It is a good source i can tell, the Pico i have now is considerable better in almost every aspect, except that it doesnt have all the inputs and outputs.

Your opinion is respected. Headamp is a strong competitor.
Quote:

Originally Posted by DarKu /img/forum/go_quote.gif I had my Dr.DAC2 for one year and i would say that it is a good source at 300$ not more not less, the strangest thing is that you like the LM4562 with your K701, LM4562 was the brightest op-amp i tried and it did a pretty bad job driving my Grados, also LM4562 decreases the bass which for K701 it is just a "NO way" thing,...strange you like them. I would choose some warmer op-amps if i was you

Well, some people don't like accuracy. The OPA2134 for instance has a fat tubby bass and the top end sounds like a plastic instrument. But it's spec's are good and it costs more than an NE5532 so it must be good....?

 

[leeperry]

the bass is flabby on the 4562, don't you think?

 

[ROBSCIX]

Quote:

Originally Posted by joe_cool /img/forum/go_quote.gif OK, I'm convinced. The LME49720HA is just excellent. The original NE5532 amps were quite good in the DAC section, but the HA chips on BD adapters put the preamp and headamp sections a notch above the LM4562NA chips.

The LME49720 are very good provided you have a good circuit. You should try the dual LME49710HA module. They take the sound of the LME49720 a bit further. Usually TO-99 versions (HA-metal can) are a step above the chip based version of the same chip.
How do you like the overall sound of this DAC now you have the HA opamps installed?

 

[joe_cool]

Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif The LME49720 are very good provided you have a good circuit. You should try the dual LME49710HA module. They take the sound of the LME49720 a bit further. Usually TO-99 versions (HA-metal can) are a step above the chip based version of the same chip. How do you like the overall sound of this DAC now you have the HA opamps installed?

I feel this DAC (using the USB input) is very good, but the synergy with the line-out and headphone-out is excellent, even with K701s on the headphone output.

 

[joe_cool]

Why do some people reject the sound of the LM4562NA, LME49710NA or LME49720HA amps as "too bright"? I have the opinion that it sounds like live music.

 

[leeperry]

to me the bass on the 4562NA is just AWOL, something in the low end is missing...the trebles are bright and the bass is on the light side.

the 49720HA is almost perfect, great bass/trebles but something lacks in the mids...something that the OPA2132P has a great deal of! details, "grain"...that the 49720HA simply lacks

but well, there's no perfect IC op-amp anyway

 

[ROBSCIX]

Quote:

Originally Posted by joe_cool /img/forum/go_quote.gif Why do some people reject the sound of the LM4562NA, LME49710NA or LME49720HA amps as "too bright"? I have the opinion that it sounds like live music.

I think they seem to forget their cans are also part of the equation.
Here is a pic you might like:

The bottom ones are LME49720HAs but the top one is a dual LME49710HA which has better sound then the 720HA module. May be one you might want to test out

 

[jojo_b2]

I can't really chime in on op-amp characteristics.

But I have tried a DX 2 here in SG by a local retailer. For the price and size of this amp DAC. It's very good. Still cannot buy due to recent big ticket purchases. =(

I tried it with a HD800, ultrasone Pro 750 and my ESW10. It sounded very good on all three specially on the Pro750s. the HD800 was driven ok but not as good as my full rig. =)

This one a person can consider for a small office rig due to it's size and also having a functional DAC.

@OP

Can you post a pic of the unit besides a CD so people can see how SMALL it is. =)

 

[joe_cool]

Well I do have a camera...