Re: The Carver Challenge
Yet that was the end result in a much more difficult test.
The results are right there, one tough customer Mr. Fremmer by his own admission could not sonically distinguish.
I never said frequency response match was anything other than necessary. I never said anything about sufficient. With cables the characteristics would tend to be more constant with level but the Carver style null test would tell for them as well as it did for amplifiers. I also never said all cables sound the same, in fact the opposite is true. I think in some cases the difference is obvious, I just don't subscribe to he theory that some folks have esoteric knowledge about some unknown physical properties of metals.
BTW 20yr ago someone gave me a Carver "Sonic Hologram" preamp to reverse engineer. What a collection of junk parts! I have no reason to believe he used other than the most ordinary components in the challenge. This does not get stated in the results one way or the other.
thetubeguy1954 said:
Yet that was the end result in a much more difficult test.
The results are right there, one tough customer Mr. Fremmer by his own admission could not sonically distinguish. I never said frequency response match was anything other than necessary. I never said anything about sufficient. With cables the characteristics would tend to be more constant with level but the Carver style null test would tell for them as well as it did for amplifiers. I also never said all cables sound the same, in fact the opposite is true. I think in some cases the difference is obvious, I just don't subscribe to he theory that some folks have esoteric knowledge about some unknown physical properties of metals.
BTW 20yr ago someone gave me a Carver "Sonic Hologram" preamp to reverse engineer. What a collection of junk parts! I have no reason to believe he used other than the most ordinary components in the challenge. This does not get stated in the results one way or the other.
A while back I did a SPICE simulation to see what kind of frequency response differences would occur for different cables with a "typical" loudspeaker as a load. I looked at the data from the audioholics.com article I posted earlier and found two cables that were at the extremes of L and C. One was some Goertz cable and the other was simple AWG10 zip cord. The data for the two cables were as follows:
Goertz:
L=0.021 uH/ft
C=327 pF/ft (!)
R=3.13 mOhm/ft
AWG10:
L=0.191 uH/ft
C=16.9 pF/ft
R=2.93 mOhm/ft
To model the cable, I used the LTRA model, which implements the Telegrapher's equations directly, assuming R, L, C and G are independent of frequency. For the speaker model, I used the one from Stereophile. I assumed a cable length of 20 ft. Below is a plot of the two cases, scaled to be both equal to 0 dB at 20 Hz:
The differences look pretty small to me. There was supposedly an Audio Critic article that showed similar computations, but with much larger differences. Does anyone know where that is, and if there's enough information given to duplicate it?
The LTspice simulation file that generated this is attached below. It's a zip file, as the Stereophile speaker load is in its own subcircuit, requiring separate files.
Goertz:
L=0.021 uH/ft
C=327 pF/ft (!)
R=3.13 mOhm/ft
AWG10:
L=0.191 uH/ft
C=16.9 pF/ft
R=2.93 mOhm/ft
To model the cable, I used the LTRA model, which implements the Telegrapher's equations directly, assuming R, L, C and G are independent of frequency. For the speaker model, I used the one from Stereophile. I assumed a cable length of 20 ft. Below is a plot of the two cases, scaled to be both equal to 0 dB at 20 Hz:
An externally hosted image should be here but it was not working when we last tested it.
The differences look pretty small to me. There was supposedly an Audio Critic article that showed similar computations, but with much larger differences. Does anyone know where that is, and if there's enough information given to duplicate it?
The LTspice simulation file that generated this is attached below. It's a zip file, as the Stereophile speaker load is in its own subcircuit, requiring separate files.
Andy C,
If you modify the voltage source to look more like a real power amp's output (output resistance of a few tenths of an ohm at higher frequencies; quite a bit more for non-FB SETs and the like) you get on the order of a half dB difference or more at HF.
edt: oop, sorry I was confusing phase and mag curves. Though now that I think of it, I dont' see why differences appear when all are driven from the same point.
edit again: ah, the scales are changing. Never mind!
Looks like a little over a tenth dB with 0.2 ohm source resistances in each separate line. Not huge, true
If you modify the voltage source to look more like a real power amp's output (output resistance of a few tenths of an ohm at higher frequencies; quite a bit more for non-FB SETs and the like) you get on the order of a half dB difference or more at HF.
edt: oop, sorry I was confusing phase and mag curves. Though now that I think of it, I dont' see why differences appear when all are driven from the same point.
edit again: ah, the scales are changing. Never mind!
Looks like a little over a tenth dB with 0.2 ohm source resistances in each separate line. Not huge, true
I Think You Missed A Point I Was Making
Hello Once Again Scott.
You seemed to have missed a point I was making! Let me try to remake it by laying some ground work.
1) 2X Bob came back to the listening panel of reviewers ---{ FYI Mr. Fremer wasn't one of them}--- completely convinced that his model 1.0 was now sonically indistinquishable from the Conrad Johnson Premier Four. One can conclude that:
a) The first 2X Bob was satisfied that the results of his measurements "proved" the amps were now sonically identical.
b) Either Bob himself couldn't hear a difference between the two amps or Bob didn't bother to listen and took comfort that the results of his measurements told the whole story about their sonic differences.
2) Both times the listening panel of reviewers were still clearly able to differentiate between Bob's model 1.0 and the Conrad Johnson Premier Four. Thus it's seen that:
a) The results of Bob's measurements were insufficient for determing when the amps were sonically identical.
b) The listening panel could hear a difference between the two amps even when the results of Bob's measurements "proved" they shouldn't be able to!
3) Although after 3X Bob was finally able to make the two amps sound indistinquishable from each other ---{to this listening panel}--- it was done with the help of the listening panel telling Bob what differences they heard.
So Scott it's my contention that Bob only made the two amps indistinquishable from each other for this listening panel! Furthermore I believe it's quite possible if I or someone else suddenly walked into the room where this test was done, that we'd be able to still be able to differentiate between Bob's model 1.0 and the Conrad Johnson Premier Four!
Afterall if the listening panel could still distinquish one amp from the other when Bob couldn't who's to say that I or someone else couldn't continue to distinquish one amp from the other when listening panel couldn't? As I told Sy previously when I was speaking about ICs I use Steely Dan's Aja for determining differences. I find this song to be invaluable, especially if I'm attempting to discriminate between two ICs ---{or other audio components}--- I might be having difficulty with. When this happens I'll listen specifically to when the drummer stops his solo and hits his drumsticks together (4:56-4:57) into the song. I've found transients are often where ICs and other audio components sound uniquely different and the striking of these drumsticks often helps me to deteremine if the IC has been changed or not! Perhaps I could have told the two amps apart with my test?
Speaking scientifically and objectively the ONLY thing this test proved was Bob Carver and this listening panel couldn't distinquish the two amps from each other after Bob used his methods and the listening panel gave their input to Bob after listening to Bob's 3 different attempts.
We really don't know if Bob could have made the amps sound identical or indistinquishable "if" the listening panel only told Bob they could hear a difference and nothing more and provided no clues as to what those specific differences were! Surely you'd have to agree from a scientific and objective POV that in the end all Bob was doing was eliminating the specific differences the listening panel told him they were hearing, right?
Although I am still amazed at what Bob did. A much better test would have been for Bob to make the amps sound identical based soley on tests and measurements without input about the sonic differences between the two different amps from the very people who ability to differentiate between the two different amps he was trying testing...
Thetubeguy1954
scott wurcer said:
Yet that was the end result in a much more difficult test.
Hello Once Again Scott.
You seemed to have missed a point I was making! Let me try to remake it by laying some ground work.
1) 2X Bob came back to the listening panel of reviewers ---{ FYI Mr. Fremer wasn't one of them}--- completely convinced that his model 1.0 was now sonically indistinquishable from the Conrad Johnson Premier Four. One can conclude that:
a) The first 2X Bob was satisfied that the results of his measurements "proved" the amps were now sonically identical.
b) Either Bob himself couldn't hear a difference between the two amps or Bob didn't bother to listen and took comfort that the results of his measurements told the whole story about their sonic differences.
2) Both times the listening panel of reviewers were still clearly able to differentiate between Bob's model 1.0 and the Conrad Johnson Premier Four. Thus it's seen that:
a) The results of Bob's measurements were insufficient for determing when the amps were sonically identical.
b) The listening panel could hear a difference between the two amps even when the results of Bob's measurements "proved" they shouldn't be able to!
3) Although after 3X Bob was finally able to make the two amps sound indistinquishable from each other ---{to this listening panel}--- it was done with the help of the listening panel telling Bob what differences they heard.
So Scott it's my contention that Bob only made the two amps indistinquishable from each other for this listening panel! Furthermore I believe it's quite possible if I or someone else suddenly walked into the room where this test was done, that we'd be able to still be able to differentiate between Bob's model 1.0 and the Conrad Johnson Premier Four!
Afterall if the listening panel could still distinquish one amp from the other when Bob couldn't who's to say that I or someone else couldn't continue to distinquish one amp from the other when listening panel couldn't? As I told Sy previously when I was speaking about ICs I use Steely Dan's Aja for determining differences. I find this song to be invaluable, especially if I'm attempting to discriminate between two ICs ---{or other audio components}--- I might be having difficulty with. When this happens I'll listen specifically to when the drummer stops his solo and hits his drumsticks together (4:56-4:57) into the song. I've found transients are often where ICs and other audio components sound uniquely different and the striking of these drumsticks often helps me to deteremine if the IC has been changed or not! Perhaps I could have told the two amps apart with my test?
Speaking scientifically and objectively the ONLY thing this test proved was Bob Carver and this listening panel couldn't distinquish the two amps from each other after Bob used his methods and the listening panel gave their input to Bob after listening to Bob's 3 different attempts.
We really don't know if Bob could have made the amps sound identical or indistinquishable "if" the listening panel only told Bob they could hear a difference and nothing more and provided no clues as to what those specific differences were! Surely you'd have to agree from a scientific and objective POV that in the end all Bob was doing was eliminating the specific differences the listening panel told him they were hearing, right?
Although I am still amazed at what Bob did. A much better test would have been for Bob to make the amps sound identical based soley on tests and measurements without input about the sonic differences between the two different amps from the very people who ability to differentiate between the two different amps he was trying testing...
Thetubeguy1954
Andre Visser said:
Thanks André.
bwaslo said:
I just re-ran it in an attempt to crudely model a solid-state amp. I assumed its output impedance would be dominated that of its parallel R-L network. I assumed 2 uH in parallel with 4 Ohms. This gave a bit less than 0.12 dB difference worst case. I guess if one were to model a SET, the differences would be much bigger, but I haven't tried it.
all these recent posts are looking at what the transmitter reaction is to variable reactance of the cables and the receiver's reaction to the non zero source impedance that the reactive cables present to it's input.
This is not a cable sound effect. This is a speaker and/or an amplifier distorting the signal due to cable reactance that upsets a badly designed output/input stage.
This is not a cable sound effect. This is a speaker and/or an amplifier distorting the signal due to cable reactance that upsets a badly designed output/input stage.
AndrewT,
All amplifiers, well designed or not, have a non-zero output impedance. And the series resistance of a cable will never be zero ohms either. These are factors that should be leveled when cables of the same L,C,R characteristics are matched.
All amplifiers, well designed or not, have a non-zero output impedance. And the series resistance of a cable will never be zero ohms either. These are factors that should be leveled when cables of the same L,C,R characteristics are matched.
AndrewT said:
Andrew,
To be sure, even if your amp had a perfect, flat, zero Zout output stage, you would still have the effects from cable parameters on whatever the speaker 'sees'.
Jan Didden
AndrewT said:
For those who don't have LTspice, I've posted below the schematic used to generate the graphs shown in my earlier post. The "amplifier" was modeled as an ideal voltage source, so the effect that's plotted is only an interaction between cable and speaker effects. The speaker model, shown as a box, is identical to what Stereophile uses in their amplifier reviews.
Attachments
SY said:
Found it, thanks. Unfortunately, he doesn't show the model used for the speaker, and the cable parameters are in a Hi-Fi News article that I don' t have. Too bad, as it would be nice to be able to reproduce his results.
Andy: I found that quite annoying, but one of his editorial tics was making a big deal out of something technically simple, then leaving it out with the excuse, "It would confuse the benighted."
I bet if you dropped him a note, he'd provide it.
I bet if you dropped him a note, he'd provide it.
Re: I Think You Missed A Point I Was Making
I understand, nobody said this wasn't work. I would think building and listening with a subset of your intended audience would be part of any reputable manufacturers process. I would think a couple of days hard work to replace $42,000 cables with $100-$200 in generic wire would be time well spent (probably even covers SY's per diem).
Frankly, if Mr. Fremmer was happy I sure I would be.
This stuff could could all be a bunch of fun rather than all this arguing. Unfortunately too much to lose on both sides.
thetubeguy1954 said:
I understand, nobody said this wasn't work. I would think building and listening with a subset of your intended audience would be part of any reputable manufacturers process. I would think a couple of days hard work to replace $42,000 cables with $100-$200 in generic wire would be time well spent (probably even covers SY's per diem).
Frankly, if Mr. Fremmer was happy I sure I would be.
This stuff could could all be a bunch of fun rather than all this arguing. Unfortunately too much to lose on both sides.
Unfortunately, my company doesn't pay as well as Analog, so I have to be more money-grubbing than you.😀
andy_c, if you really want some fun model the more punishing speaker loads like the electrostats from Martin Logan. 1-2 ohm @ 20 kHz from memory.
Re: Re: I Think You Missed A Point I Was Making
Scott
Isn't that the problem with a lot of interesting topics?
BTW sorry for being OT, any progress on the SWBT?
Cheers
scott wurcer said:
Scott
Isn't that the problem with a lot of interesting topics?
BTW sorry for being OT, any progress on the SWBT?
Cheers
I was referring to his challenge to Stereophile, where he matched a tube and a transistor amp. IIRC, the tube amp was a big, expensive C-J. The transistor amp was, of course, a Carver.
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