Abbingdon Music Research DP-777 Thread
Mar 26, 2015 at 12:15 PM Post #511 of 571
Thanks Brian-
 
Certainly sounds like crappy shipping procedures…  and QC...
 
Anxious to hear more SQ reports as she breaks in !
 
David
 
Mar 26, 2015 at 12:43 PM Post #513 of 571
   
Brian, so there's no more switching from Classic DAC to Organic DAC when redbook and Hi Res Files are played - are all formats using the same DAC chips now?

No, no. There are still separate DAC paths. There is still a "classic" DAC path for Redbook and a 24 (32?) bit DAC for high-res playback. The chips' numbers are obscured, so I can't say what they are. Some of the improvements will affect both paths - the new output caps, the clock noise improvements, the new tubes. But Redbook also gets four DAC chips working as a "team" where there was only one chip before. By the way, I left all the settings in the default modes, because that's the way I last heard them with the old 777.
 
To answer your earlier question, I think the XLR output is simply in parallel with the RCA jack. John Atkinson said this in his Stereophile review: "Pin 2 of the XLR outputs appears to be in parallel with the RCA outputs; this is not a true balanced output." I saw nothing in the printed circuit board to suggest any changes there.
 
Mar 26, 2015 at 1:25 PM Post #515 of 571
I will say that I don't find it particularly worrisome that the XLR outputs are probably not truly balanced. To provide a truly balanced output they would have had to add more circuitry to make a negative phase, and this complication very likely would have detracted from the sound. The manual refers correctly to these outputs as "XLR", not balanced. I have both balanced and unbalanced inputs in my crossover but the balanced inputs involve more circuitry so I happily run the 777 to the crossover as RCA-to-RCA.
 
Mar 27, 2015 at 6:59 AM Post #516 of 571
I will say that I don't find it particularly worrisome that the XLR outputs are probably not truly balanced. To provide a truly balanced output they would have had to add more circuitry to make a negative phase, and this complication very likely would have detracted from the sound. The manual refers correctly to these outputs as "XLR", not balanced. I have both balanced and unbalanced inputs in my crossover but the balanced inputs involve more circuitry so I happily run the 777 to the crossover as RCA-to-RCA.


 
I agree with Brian.
When you look around some of the worlds best audio is not a balanced circuit this includes Kondo,Airtight,Reimyo these are all highly regarded products.
I personally think if it sounds good it sounds good whatever the topology.
 
Mar 27, 2015 at 8:00 AM Post #517 of 571
Right. It depends on the circuit topology chosen by the designer. Some circuits are inherently balanced, but most consumer products are inherently single-ended. Both kinds can work well in a home audio environment. There is no hard-and-fast rule on one being better than another. The only undisputed advantage to balanced is when running very long cables, such as in a studio or a concert hall where noise pick-up becomes a major problem.
 
I tend to think of four classes of equipment with regard to the balanced-SE question:
 
1.) Inherently balanced equipment: My Audio Research LS5 MkII line-stage is an example of this. The circuit is naturally balanced throughout by virtue of the differential "push-pull" topology chosen. It receives balanced inputs naturally, and drives them naturally. Aside from the long-cable noise issue, high-end manufacturers such as ARC sometimes use inherently balanced circuits (differential) to almost completely cancel even-order harmonics. My line stage can also receive single-ended signals and drive single-ended loads, with arguably only a very tiny loss of performance and a reduction in gain of 6dB (half).
 
2.) Inherently single-ended, but with true balanced inputs and outputs: My Apogee crossover is an example of this. The internal workings are single-ended, but provision has been made to receive balanced inputs with a balanced receiver circuit, and to drive balanced loads with a true differential driver circuit. But there has to be an internal conversion from balanced to SE, and then from SE back to balanced again. Additional circuits are required on both ends to accomplish those conversions. These kinds of devices often have both SE and balanced connectors. I use the SE (RCA) inputs and outputs, skipping the extra balancing circuitry altogether. Sometimes transformers are used to convert from SE-to-balanced or vice-versa, although active circuits can accomplish these conversions too.
 
3.) Single-ended throughout with "pseudo-balanced" connectors: Here the XLR connectors are driven by a SE signal, and the connector merely provides a convenient way to connect to a balanced preamp or power amp using an XLR-to-XLR cable. I think the 777 falls into this category for its analog outputs. There may be perceived marketing advantages for seeming to be "professional" or "balanced" (says my cynical side).
 
4.) Single-ended throughout with SE inputs and outputs: The vast majority of consumer equipment falls into this category. No apologies need to be made for this design choice. As you say, many fine pieces of equipment, most in fact, are made this way.
 
Mar 27, 2015 at 9:52 AM Post #518 of 571
Yup,  Like some of Nelson Pass stuff.  He makes some push-pull and some SE.  The SE sounds just as good or better than some of his push-pull stuff.  
 
Now when an amp is inherently balanced it doesn't matter if the signal from the DAC is SE or truly balanced, the amp will provide a balanced signal no matter what - correct?
 
Mar 27, 2015 at 10:13 AM Post #519 of 571
There are several possible scenarios in your question (as per my post earlier), but if you are referring to the case of a truly balanced power amp, generally having an XLR input, then you should be able to drive it with either SE or balanced sources  (with appropriate adapters), with little penalty, so long as the Common Mode Rejection Ratio (CMRR) of the amp is high. Well-designed truly balanced designs will have high CMRR. That is to say that the amp is able to recover its internally balanced signal from a SE signal with little degradation. Differential amplifier input stages (long-tail pairs) and transformers can have high CMRR. We are getting away from the main topic admittedly. Specifically, a 777 should be able to drive an XLR-input power amplifier through either its XLR or RCA connectors equally well since both appear to be SE-derived, but the 777's XLR connector provides a convenience if you're using XLR-to-XLR "balanced" cables, so that no adapters are required.
 
Mar 30, 2015 at 12:15 PM Post #520 of 571
Hi guys,
I´m still with you, but my one guy still hasn´t got his upgrade done. The other has not even started the process yet
The dealer claims for the second time that the PCB was broken and that he is now waiting for the third one to arrive.
One could say "s*** happens" or not believe this sad story.
My friend belongs to the first group, I to the latter.
 
Cheers
Kai
 
Mar 30, 2015 at 9:23 PM Post #521 of 571
I just  upgraded to a dp-777 this past Saturday from a Mcintosh D100 and I couldn't be more pleased.  With the mac I felt I couldn't enjoy classical (limited to bartok, stravinsky, part...) much and I had to turn my highs and low's down -3db on my legacy focus 2020 speakers with the switch on the rear.  With the amr they went back to their original positions.
 
Anyway, I'm enjoying symphonic music again and I'm just pleased as punch.
 
Just a few cons and they minor.  I was hoping to use both toslinks and both coaxials but that's not the way the dac designed, I ordered a switch box and problem solved.
 
No headphone jack.  I participated in the Lambert Headphone amp campaign on indiegogo so I'm another month out on that.
 
Lastly, my MC452 turned on remotely with my d100...whatever, I'm still really happy.
 
I was planning on a c2500 but I liked the price of the amr much more.
 
cheers
 
Apr 1, 2015 at 1:01 PM Post #523 of 571
Look what arrived today 
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   The NEW  AMR DP-777 SE.
 
The importer was nice enough to provide it for testing...  with my Eddie Curent 445 ( + LCD-X or TH-900)
 
Will it put my HUGO on retirement ?  (or I should say, on the road again)
 
 
 

 
Apr 1, 2015 at 1:18 PM Post #525 of 571
  Lucky you...  Looking forward to your impressions on the AMR and the Hugo..
 
Congrats!!!!!!!!!
 
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you will have to wait a little, the importer suggested I wait at least 300 hours of break-in before judging the SQ !
 

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