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In Reply to: RE: The graph doesn't lie... posted by E-Stat on December 24, 2024 at 11:30:08
....and has nothing to do with component matching, impedance, room acoustics, and all the other distractions you're trying so desperately to inject into the mix. The Device Under Test is what is being discussed. And the DUT shows bass roll-off.The chart and math do not lie. That piece of ARC gear IS rolled-off in the bass region, noticeably so. Period. End of story.
Chart of your ARC preamp......
Rolled-off in the bass region. The chart shows it. The math proves it.
dB = 10 * log(P2/P1)rearranged to solve for P2
P2 = P1 * (10^(dB/10))
Edits: 12/24/24 12/24/24 12/24/24Follow Ups:
The graph shows me that the ARC preamp output impedance is probably high and incapable of driving lower impedance loads w/o severe roll-off. The graph shows exactly that. Many other preamps don't suffer in this area. Many are flat from below 10Hz to well beyond 20KHz regardless of what impedance they are driving.
ARC looks rolled off in the bass region of your graph and that is precisely what I've heard in many ARC products. It's their 'house sound': solid-state with a tube output buffer to veil and roll things off.
Some like their 'house sound'. Others don't. Nothing wrong with personal preferences.
The graph shows me that the ARC preamp output impedance is probably high and incapable of driving lower impedance loads w/o severe roll-off.The balanced output Z is 500 ohms. What fool would ever attempt to drive a 600 ohm amp? Contrary to your lack of awareness, matching gear is all about impedance. Hence multiple values tested - 600 and 100k ohms with vastly different results. What amps on the market today use 600 ohms?
ARC looks rolled off in the bass region of your graph
There is no *me* to this. I reference John Atkinson's measurements. Flat to 20 hz is *rolled off* to exactly what? Huh?
First column is 10 hz. Down about a tenth.
Edits: 12/25/24
> > Sanders Sound Systems ESL MkII Monobloc Amplifier < <
1,000Ω input impedance balanced, 100KΩ unbalanced. Amp is supposedly designed specifically for e-stat speakers and their sometimes difficult loads. I have a friend that just bought a pair of these amps. He loves them except . . . He's driving them with an ARC Ref something-or-other preamp in balanced mode . . . and experiences noticeable low-end roll-off. He's in the market for a new and more capable preamp.
because it really does matter. If using balanced, he made a poor choice given the 2:1 ratio. On the other hand, I agree with JA that 274:1 works fine!
The speaker to amplifier relationship is every bit as important. The Sanders hybrid electrostat has a Scream Machine roller coaster impedance curve and has special needs itself. Fortunately, my stats don't exhibit such a ride. Similarly, tube power amps work well driving them with their tame impedance curve. :)
You probably know that 600Ω is a "professional" standard and I'd assume that's one reason Stereophile tests with this loading.* It's unfortunate that a consumer needs to check for this type of compatibility in today's plug-n-play environment. It's not like this is some subtle sonic difference. ARC really should be more up-front regarding the (lack of) compatibility of their products with professional standards. At any rate, no ARC preamps for my friend - one lifetime.
*I've got old VOMs with dB scales where "0dB" is defined as the voltage that produces 1mW into a 600Ω load.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
600 ohms was used in telephone industry. No need for that today.
There have always been compatibility aspects to matching audio gear. I learned that as a teenager. Sorry your friend didn't.
BTW, Sanders doesn't understand cable interaction either. ;)
Posturing, the point remains: there are commercially available amps with very low input impedance, right or wrong. It's interesting to note that ability to drive 600Ω loads would seem irrelevant today esp for home equipment. And yet the ability to do so is claimed as an advantage or feature by some mfgrs. Even some modern (and vintage) "audiophile" grade opamps specify the ability to drive 600Ω loads at low distortion. So maybe 600Ω capability is somehow relevant in modern consumer equipment . . . Shorthand for "Will drive anything likely to be encountered".
.
Have Fun and Enjoy the Music
"Still Working the Problem"
while some inmates draw diagrams, argue and completely miss the point about using (abundantly found) high Z amps with tube preamps - which eliminates frequency based mismatching issues. :)
Edits: 12/26/24
From JA's measurement section:"With the volume control set to its maximum, the frequency response into 100k ohms was perfectly flat within the audioband and superbly well matched between channels (fig.4, blue and red traces). With the high output impedance at low frequencies, it came as no surprise that the output rolled off below 200Hz into 600 ohms (fig.4, cyan, magenta), reaching -3dB at 58Hz. With the volume control set to "73" (green, gray), the line stage's ultrasonic response was more rolled off than with the control set to "103," but the output at 20kHz was still down by only a negligible 0.5dB. "
Details do matter. Can you recognize cyan and magenta? One to which you pointed?
Edits: 12/24/24 12/24/24
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