Meridian Explorer DAC/Amp Stream of Consciousness Review (WARNING: Not Good) - Page 4
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Got one from Todd the Vinyl Junkie too measure the output impedance----Thanks Todd!
Using a 1kHz tone with 0.410 Vrms output into an open circuit
With 32 Ohm lod voltage dropped to 0.167 Vrms for a 46.56 Ohm calculated output Z
With 150 Ohm load voltage dropped to 0.312 Vrms for a calculated 47.12 Ohm output Z
Wow... so it's official then, purrin does NOT have a busted unit.... oh well.
It means that the amp essentially applies a headphone-dependent tone control (equalization curve) to the sound you hear. In many cases, this will mean the sound is more "midrangey" and with rolled off highs than an amp that is accurate. The effect will be more pronounced on low and medium impedance headphones, and most pronounced on low impedance IEMs with multiple drivers and crossover networks.
Also, it means that the bass will be poorly damped (wooly instead of tight). Some people perceive this as a more "bodacious" bass that they find pleasing, but it is not particularly accurate.
It also means that Purrin has much better hearing than Computer Audiophile's Chris Connaker, Audiostream's Michael Lavorgna, the Tone Audio reviewer, etc. Not bad at all Purrin! I wish there was some way to tag a user as having "good ears".
Lavorgna did most of his review with line out, amp, and, speakers, not headphones, on which he defers to Hertsens. He did this with Dragonfly and iDAC, too. More of a DAC-only evaluation. Connaker did more headphone evaluation, but some of it was with HD-600 (300 ohms), which should be less affected by the output Z. He also used some other 'phones that may well have been adversely affected by output Z that he didn't notice or report.
Still dismayed to hear these results, even though my HD-650 should be more impervious to the ill effects--and of course this issue goes away when using the line out and separate amp. Not that I'm letting Meridian off the hook; it's a pretty bad decision not to disclose such a consequential design trade-off.
Edited by Aerocraft67 - 2/27/13 at 5:31pm
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It would be fairly disingenuous to review a portable dac/amp as a dac only. Defeats the purpose of having such a device if you have to carry another portable amp around.
Not quite sure what you mean by that, but ML and I communicate very little. Just see him a shows and stuff. Generally, we each do what we think is right for our respective readers and really don't worry about cross-over of product.
Valid point for sure. But having shopped this subsegment carefully, I found that it's actually hard to find a current-generation DAC-only device at this price point. Dragonfly, iDAC, and Explorer all come with amps. Even though iFi sells an amp designed to pair with iDAC. You have to move over to Modi or Halide at different price points to get DAC only. And all accounts are that these are all competent DACs.
What I was getting at (and aero seemed to imply as well) is that it would makes sense for Lavorgna not to focus on headphones as that seems to be your area while you would let him focus on something like digital downloads and DACs. At least that's what it seems from reading both sites.
Ah. Yes we're both aware of each other. For example I'll be doing fewer desktop speakers, and when I do they'll be compact low-cost ones because I know ML would cover the bigger more expensive ones. I know that JA sends headphone inquiries my way a lot. So we work together in a loose sense. Something like the Explorer may get covered by all three, and that doesn't bother us as there will be some naturally occurring editorial slant for each.
I gotta say when I heard the Explorer today it with Senn Momentums (a 22 Ohm headphone) that it sounded remarkably loose and uncontrolled.