Saturday, June 24, 2017

Master 7 thumping and then channel dies

On my 70 foot coax connection to the Tact, and AES after that, the Audio GD Master 7 Singularity sometimes makes thumps up to -20dB, but more typically only up to -60dB, when tracks change, when the Oppo is turned off, etc.  I suspected this what happens when the digital signal clock from the source gets off the beat in some way and the PLL servo follows for a while before deciding there is no PLL lock and then it cuts off entirely.  Before cutting off entirely, the thump occurs.

DVD-Audio discs are the worst for this kind of thing.  HRx discs seemed less affected.

I played a great HRx disc over and over, and zero thumping at all.  The spectrum of the input to the DAC (shown on one DEQ) was matching the spectrum of the output of the DAC (shown on another DEQ).

Then, the next day, it appeared on the DEQ spectrum display that over 20 hours there had been a -20dB thump from the Master 7 going down to very low frequencies, while the Oppo had been turned off.  I turned on the Oppo and now it seemed the Master 7 was not picking up 24/96 originating from the Oppo at all.  I cycled through inputs on the Tact, and sometimes it would pick it up, and sometimes not.  This was the first clear sign of a serious problem from the Master 7 since I had hooked it up using AES.

Checking it out on my Fluke 8060 meter, I noticed that the left channel, still working, did make "thumps" up to 0.2V when I was changing sources on the Tact, though usually only 40mV.  And when those thumps occur, they only slowly, over seconds, return to 0V.  The DC servo is set to a very low frequency.  For practical reasons, I'd prefer a faster return to 0V, otherwise DC is being pumped out into my speakers.

But the left channel was no longer working at all, no longer putting out signal, though it was still thumping.  Perhaps it got 'locked up' somehow.

I've taken it offline.  I need something extremely reliable.  Will retest later.  Now I'm thinking the whole episode since Master 7 arrived has been enormously frustrating.  Now I'm again beginning to worry it was behind other problems like the shutdowns, though I actually don't have any clear evidence, other than the thumping, and now the apparently dead channel, that it had been doing anything wrong after I connected the DAC itself using AES.  I'm don't know what I'm going to do with the Master 7, can I get it fixed, can I get as much as half of my money out of it???

Hooked up my Denon DVD-9000 as DAC.  It is very sweet sounding, but I fear not as magically transparent as the Master 7.  I suspect the Denon could be much better with a better analog output stage and balanced outputs.

Back when I ordered Master 7, I was thinking of Kingwa as a sort of latter day James Bongiorno, a charismatic and uncompromising designer making legendary products.  But Kingwa is apparently doing much better, as it seemed James left company after company and finally his two signature companies GAS and Sumo failed, whereas Audio GD has continued for more than a decade now.  So maybe Kingwa got it right.

There was a downside I know of.  GAS equipment was not the most reliable.  I 'failed' a Grandson amp once merely by power cycling it too fast, it was killed by its own servo loop.  Later I had endless RFI issues with my own Son of Ampzilla, which I was never able to fix (I still have it in storage many decades later).  Seeing the way it was built with lots of plug-in boards made me wonder how robust it was.

Perhaps what was missing was better production engineering.  Perhaps Bongiorno had taken on and/or delegated too many things to people who were not qualified.  There is something to be said about a company with more than one good engineer, good enough not to always be a yes man.

Now I'm wondering if Audio GD doesn't indeed follow suit.

A friend of mine, reading about the Master 7 Singularity, thought it might better to use the standard SPDIF receiver chips, custom receiver programming is work for a team of engineers, checking each other out, beta testing, and so on.  I told him custom digital receivers were nothing new, Levinson and others were doing that long ago, the Levinson 360S also uses a custom programmed receiver.  Recently I've been wishing I had bought one of those instead, I'm thinking it wouldn't have issues like I've seen, and it was fully tested and looked fantastic in test by John Atkinson.

Update: I connected the Denon DVD-9000, which never had a hitch reading the signal through all my digital stuff from the Kitchen Oppo.

But it has a large latency, over 300 ms, that I can't correct for with my DEQ.  I'll need another DEQ, that still seems to be the best option.  That will give me more parametric filters too...

I learned to like the sound of the 9000 after some changes.  But the latency makes it useless.  I heard the latency right off, but I didn't measure it until much later, after coming to think for awhile it wasn't there anymore--but on speaker pop it was like two separate sounds, bouncing back and forth.  But for some of the day before learning to like the 9000 I had been listening to the DAC 19 again.

I found the SpeakerPop sound to be a good way of setting the alignment by ear.  I think I can do that within 0.2 ms or so, though I actually set it to 3.79ms, a little lower than before.  I need to measure it of course but that requires either the Tact setup or REW or a scope.  I tried a new scope app and it wasn't much use for lack of triggering.

But there was a problem doing the 88 kHz with the Dac 19 again.  But I then found I could fix it by re-tightening the F connector that connects to the cross attic RG6.  Perhaps that was why the Master 7 hadn't been picking up the Oppo signal well, though that didn't explain the channel dropout: I'm thinking that was caused by me flipping through the Tact selector a few times, making those little thumps I described before (and if they stayed little, I could live with that, and it was seeming that normal DVD-Audio track changes and that sort of thing were only -60dB or so LF thumps.  But when I got home, possibly some noise on the line had caused the -20dB thump clearly visible on the peak hold spectrum, and then the Oppo connection wasn't working on the Master 7 reliably, possibly explaining that.

BTW both the Dac 19 anniversary and the Denon are completely thump free.  On the Denon there seem to be endless relays clicking for this and that.  But there is never a thump.  The Dac 19 has no relays but is still thump free, even when I was messing with the F connector aformentioned getting 88kHz to play, it was a live line going in and out until I finally got it tighened correctly but no thumping--a very difficult case (the very case that had probably caused the -20dB thump on the Master 7).

I'm now hoping Master 7 "fixes itself" like the Krell did simply by being powered off long enough.  We'll see.  Otherwise, I'll have to see if I can get warranty repair before trying to sell it.

At it's best, the Denon DVD-9000 is nearly there, and it clearly has more resolution than the Dac 19, but more closed sound which is actually quite nice and sweet and helps you enjoy the music.  I'd be playing it right now, overall I consider it better than the DAC 19, except the midrange delay muddies up everything, and even 300 + 3.79 ms adjustment isn't quite enough to fix it, and that's more important than anything.

I realize now the Denon DVD-5000 on the super tweeters probably has a similar delay, meaning that I would be better simply delaying the bass line.

But if I can get the Master 7 going again, and weird problems don't come back, I could put the Dac 19 on the tweeters, which had been the plan (though, when the Oppo line wasn't working, I was thinking of putting the Dac 19 into my analog resampling group).

I've been listening to straight through digital, and I think because of finally getting the polarity correct, after who know how long, loving it more than ever.  I even made it through the 2017 Grammy collection just now.

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