Monday, March 31, 2014

4580 IC's in Onkyo RDV-1

I was greatly relieved to find the Onkyo RDV-1 does indeed accept 96kHz inputs (in either coax or toslink, it turns out).  I run all my digital processors at 96kHz.  When I first opened the box I checked the manual, it said it only accepted up to 48kHz.  Despite my lack of time on Saturday, I quickly hooked up my new Black Lion Micro Sparrow ADC (mk1) to the Onkyo, and found it handled 96kHz fine and even shows a message saying it is doing 96kHz.  The Onkyo does not accept digital inputs higher than 96kHz, when given such inputs it displays the LCD rate, either 44.1 or 48khz.  I did not listen to see what those did.  But 96kHz in several tests over the weekend appears to be rock solid and sounds fine through the "stereo" outputs (not the same as the "front" outputs on this player…the "front" outputs sound very thin as subwoofer use is assumed--UPDATE, this may not be true with digital input--all were measured to be flat).  I measured the Stereo outputs with pink noise (which is random, so always fluctuating and never perfectly flat) and it looked as good as it gets with random noise measurements:

I've been pouring over the service manual schematic to see what the circuitry is like.  The output board has each output channel going through a 4580 opamp, then a 47uF capacitor, a small resistor, a number of shunt muting devices, and then the output.  Not wonderful but not too bad either.  I'd like to replace that electrolytic cap with a Teflon.  But what is a 4580 opamp?

Apparently it's similar to 5532, a higher current bipolar amp.  The 4580 is said to be much better than the 4558's used ubiquitously in "mid fi" audio equipment, maybe even some not so mid fi.

While researching this, I found the quotation from John Curl himself, as of 2009 his CD player uses 4558's (!!!)

Trevor, the 4558 is the IC that I have to listen through to compare SACD to DVD to CD. I can't afford an expensive player, because I don't design them.

I also found this objectophile blog saying essentially that 5532's are good enough.

I just checked photographs inside the Behringer 2496 DCX and guess what chips it uses?  4580's!  Somehow that still gets to about 0.1% distortion at full (just below 10v rms) output.  The problem with the DCX may be mainly that it insists on driving the outputs to 10v RMS at 0dB digital, and the only way you can attenuate that is by reducing the digital numbers, which is losing resolution and linearity.  And also that the DCX doesn't really have good enough power supply to drive the chips to 10vRMS with low distortion either.  To really do the 10V output well, it either needs better power supply, better chips, or both.

Meanwhile, my friend Tim is planning a significant chunk of work to add the best sounding of all IC's according to him and other sources, the OPA211, to our Kenwood L-1000T tuners.  That sounds good to me, so I won't be bugging him with links saying all good chips sound alike.  In fact I plan to address the psychology of those claims in a future column.  Tim analyzed a set of top opamps and decided which ones were actually most linear, the OPA211 on top, just as in the list he started with.  Here is the list he started with (not sure from where):


Compared with 4580's, Tim says OPA211 have 20dB more gain (which is good for opamp circuits, particularly ones with equalizing feedback) 80Mhz vs 12Mhz bandwidth for 4580, and distortion of .000015% vs .0005%--a factor of 30.  He says these specs (gain, bandwidth, THD) correspond generally to better sound quality (as determined in tests by him and a professor of engineering he collaborated with).

He generally doesn't respond when I talk about sighted tests, statistical significance, and the like, so I'm not going there.  It's not like even "white hat" audiophiles blind test everything to statistical significance.  The develop rules of thumb which extrapolate from blind tests, and then follow those rules of thumb.  But there's no telling whose extrapolation is actually better, without actual evidence.  All we really know from serious audio science is what the minimums are for good fidelity.

1 comment:

  1. Hello Charles, Audio Investigator, I have a Interga RDV 1.1 that has a intermittent issue with playing disc's, authorized service will not work on the unit, any ideas as to where to have it serviced maybe someone extremely knowledgeable or someone who can make his own parts. Thank you in advance. Joe