Sunday, November 15, 2015

Krell FPB 300 back, now with Emotiva phono stage

It was cool all day Sunday, and by late afternoon I started playing the Krell FPB 300.  All the harshess and glare disappeared, leaving beautiful music in 3D.  I should listen to the Krell always, but have problems with my air conditioning when I do.  I need to get remote thermostat in different room than living room, but contractor has been reluctant to do that with my 12 year old system.

The Krell is 1.14 dB louder than the Aragon 8008BB I use during hotter months, so I increased the bass level from -11.7dB to -10.7dB and the  super tweeters from -1 to 0dB.  Using new Keithley 2015 meter the first time, reading seemed more stable than with Fluke 8060.

Somehow the bass is more authoritative too.  But before I had switched to the Krell I had increased the left and right notches at 45Hz and 66Hz by another dB.  At 45Hz they're now -6 and -7.  Going back years, I had notched to -9 or even -11 at 45 Hz, but while it makes the room less boomy, the sweet spot begins to sound thin.  In most recent adjustments I reduced the notches to -5 and -6, but that now seems inadequate.  Playing Jessy J it needed this adjustment.  Funny as I recall I had decreased the notches while listening to Jessy J also.

All Sunday I was playing the turntable with the Emotiva XSP-1 preamp I set up late Saturday night after going to the Symphony.  I decided it sounded best from the Processor Output into my Sonos uncompressed Line In, and thence to the living room or wherever.  From the unbalanced main outputs into Sonos Line Input, it was very very transparent but also, I feared, slightly harsh.  Just one inconclusive A/B test was performed after I first thought I hear the harshness, but then I decided I didn't need the volume control for just feeding the Sonos Line In, so I went with the Processor Output, which is a more direct path anyway.  (The "slightly harsh" finding was at best ambiguous if not totally dubious, and most noticeable actually when taking signal from the Alesis Masterlink playing a hybrid RCA Living Presence CD, which was harsh sounding either way, just somewhat harsher when being played through the unbalanced Main Outputs than through the Processor Output, I thought.)

Meanwhile I felt the main balanced outputs were just fine, wonderful actually, and I continue to use those for driving the balanced inputs to the Masterlink digital recorder, which was really the only reason I needed a "preamp" (instead of mere source switcher).  I made a quick test recording and it was perfectly transparent.

This must be my imagination, because published measurements show the XSP-1 to have remarkably low distortion through both outputs, including the unbalanced outputs.  But I just had this feeling, and anyway it can hardly be argued that the processor outputs would be worse--they do have less processing after all.  While using the Processor Outputs I also run Direct (no Tone Amplifier) and sometimes also Proc On (no signal running in output section) to get the best sound of all and the Processor Outputs.  But I need to do Proc Off to get output to the balanced main outputs, when doing a Masterlink recording.)  So it meets all my requirements if not as I had intended, by using processor output to drive Sonos and balanced outputs to drive Masterlink.  I found Sonos works OK with Nakamichi and XSP-1 phono straight into Sonos line input at max level, sometimes boosted one for low level recordings when max straight-thru gain isn't loud enough.  The XSP-1 MC phono, loading my Dynavector 17D3 to 100 ohms, is giving me the best sound I've ever had with the Mitsubishi LT-30 table, and perhaps the best sound ever.  The 100 ohm loading soaks up all the remaining resonances, some of which still had a speed instability sound.  Now the sound is rock solid, perfect pace, and sounds clear and less sibilant, more fully balanced.  Under optimal circumstances, such as a heavier arm with electromagnetic damping, the Dynavector might shine better just above 100 ohms, say 150 or 200.  Unfortunately the Emotiva gives me only 3 choices, 100, 500, and 1k, but 100 works fine under present circumstances anyway, possibly even better than the oft recommended 200 ohms because of too light arm and too little arm damping.  I'm loving the phono preamp, possibly the best part of the whole deal.  Previously my dB systems preamp had a fixed 1k ohm load, I think.  Possibly that preamp could be improved with loading and better caps, and the Classe repaired and juiced up (how about relay inputs straight to tape output, no buffering, pure).  Then I might have a pairing that would beat the XSP-1.  But right now the XSP-1 works and is working for me.  Even the processor outputs are at least muted if not buffered, and the muting works without relays, as does the volume control.  I wonder if all relays used for these tasks wouldn't be better.  That's my audiophilia nervosa.

Archimago did detailed measurements of the Emotiva through balanced and unbalanced outputs.  The technical quality of the balanced outputs is stunningly superb.  The unbalanced outputs are just a tad worse, definitely not as good, there are lots of tiny spikes rising from the noise floor, but still should be good enough for audio purposes.  Too bad he didn't also check out the processor output I am using, which I believe is better.

But those little spikes in the Unbalanced output are a bit worrisome, and especially if you think they might be induced by chassis EMF and RFI.  Another little tweak I did was to pull up on the shielded portion of the Ethernet cable so that the unshielded last-foot jumper I use does not come close to touching the Emotiva chassis.  I used a velcro tie to hold the unshielded jumper cable several inches above the Emotiva.

John Johnson of Secrets of Home Theater and High Fidelity tested the XSP-1, and the measurements are stunning, but note that he tested ONLY balanced input to balanced output.

I chose the XSP-1 precisely because of the precise digital volume control, which because of typically audiophile prejudices tend NOT to be found on high end preamps.  Other than the Emotiva, the only others I can think of are Classe and Mark Levinson at far higher prices.  And though I often scan ebay and Audiogon for Levinson preamps in the 38/38S/380/380S series, those are quite old products now and even when they were new many audiophiles didn't like them.

While I was at first inclined to be suspicious of the volume control on the Emotiva, I've moved on to another fear.  I think it may be asking too much of such a preamp to have both balanced and unbalanced outputs.  Likely the unbalanced output is taken from the balanced path in the end.  So if you are running an unbalanced input to unbalanced outputs, you are going through these conversions:

unbalanced to balanced
balanced volume control
balanced line amplifier
balanced to unbalanced

So if you are really intending this for purely unbalanced use, you are getting two extra conversions which likely do no good.

A cost no-object way to do this correctly would be essentially to have both balanced and unbalanced preamplifiers working in the same box.  Then unbalanced would stay unbalanced all the way through, and likewise for the balanced.

Now I loved the sound of my Classe CP-35 which was in some ways similar to the Emotiva.  The CP-35 had digital volume with balanced and unbalanced inputs and outputs.  But here's the difference.  I measured approximately 0.05% distortion with the CP-35, which is much higher than the Emotiva, but when looking at the spectrum it was all noise, not actually distortion.  There were no little spikes poking up through the noise floor, just a relatively high noise floor for a line amplifier.  As long as you don't actually hear the noise, noise is much more pleasant than distortion because it seems to be uncorrelated to the original signal.  We are correlation detectors par excellence (or run amok).

My current plan is to do my line source switching with an external switch box which will feed both Sonos Line Input and Emotiva.  Then just use the Emotiva to drive the balanced inputs of my Masterlink.  Balanced output is what Emotiva does best (and pretty much state of the art).  The unbalanced output should be good enough, but if you are perfectionistic or obsessive, "should be good enough" never is.

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