AMP A / B COMPARISONS

[Skylab]

That ranking of third is only true if you look at the very largest of US cities only. If you include in "cities" places like International Falls MN, Chicago doesn't even come close to the top 10.

 

[micmacmo]

According to wikipedia, International Falls competes with Fraser, CO for the title of Icebox of the Nation. I think they should both hire new tourism/marketing consultants.

Sorry, way off topic.

 

[jeffreyfranz]

Thanks for the great review. Regarding your quoted text, below, I believe John Dunlavy (not positive it was him) once said anything over about 300pF capacitance may result in treble roll-off. Generally, however, I would agree with you that a 2-Ohm output impedance should be able to give quite a wideband, flat frequency response. Thanks again for doing the amp comparisons and for your forthcoming DAC comparisons. 

 
 
Thoughts:
Due to the physical layout I've got, the analog signal has to go through moderately long RCA cables from the NFB-10ES to the Beta 22.  Maybe these are rolling off the upper treble a little bit?   In the past 11 tests, the analog signal from the DAC Magic went through these cable to feed BOTH amps, so it was a constant. Here, the signal goes through this RCA cable for the Beta 22, but in the NFB-10ES it's DAC is directly connected internally to it's amp.  I measured the capacitance of those RCA cables at 500 pF, with a  2 ohm output impedance for the NFB-10ES DAC outputs, this should be flat into the MHz. 

 

[BobSaysHi]

Quote:

Yes, it could be used for an A/B switch but there's simpler ways.
 
There's really no need to use an op-amp etc to drive the relay in an A/B switch.  For delayed turn-on and DC offset protection - which is the epsilon's intended use, yes, you need something to do the delay function and something to sense the presence of dangerous DC and drive the relay coil when needed.  But for an A/B switch, you can use an actual DPDT switch to select which of two amplifiers drives the load, or if you have balanced circuits you can use a 4PDT switch.  Instead of a mechanical switch you can always use a relay -  making a 4PDT A/B box for balanced amps using a pair of DPDT relays is easy, perhaps easier than  finding a nice 4PDT switch.  I haven't made one myself, but I do have some A/B boxes I made using relays- I built one to A/B phono preamps, and this box switches the phono cartridge between the two preamps' imputs, as well as selecting which output of the two phono preamps drives the listening amplifier.  This has relays in it, which are energized by some rechargeable AA batteries. There's a switch which sends the DC from the batteries to all the relay coils, so that one simple switch controls the all the action. Using batteries eliminates any ground loops or other signal pollution that using some kind of AC power supply might introduce.  The batteries  can keep the relays in the energized state for 5 hours, long enough for any kind of A/B test session.  This box can also be slaved to another relay - for example, the USB-actuated relay of my prototype computer-operated A/B/X tester.  This interface to my notebook PC uses optical isolation to make sure the PC's chassis / power ground is totally isolated from the audio switching boxes.  All the relay-operated A/B boxes I'm building work either manually by a switch on their front panel or by means of a jack they can be "slaved" to the isolated computer interface.  (Computer interface etc not completed yet.)
 
I'll be posting my phono preamp A/B tests elsewhere, but when I do I'll mention it here in case anyone wants to see it.  I'm comparing a few lower-cost phono preamps.

Yeah, I felt it was an overly complicated way of doing it too, it just reminded me of this thread so I figured I'd share it here.

 

[milosz]

Quote:

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No, but they were probably Canadian.... could have had frostbite damage to their ears. 

Careful. Might I remind you that Chicago has the third coldest winters of all cities in the continental US. Glass houses being what they are. Black pots and kettles suffering inferiority complexes. etc.

Yeah that's true.  And here, because we spent all our money on headphones and amps we've none left to buy health insurance.  So our frostbitten ears will go untreated, and fall off.  At least in Canada they have national health coverage...
 

 

[chesebert]

OP, I am being brutally honest here, your comparisons are worthless, except for the obvious conclusion: if you own a $400 source don't go spend $2,000 on an amp. 
 
You should use at least a PSA PW or Ayre QB9 if you are using PC-based audio. Preferably, it would be best if you can take source quality out of the equation by using, for example, Esoteric D01, dSC Puccini or MSB Plat IV.

 

[sphinxvc]

Subscribed.  Excellent work so far.  Looking forward to your DAC comparisons.  And a comparison of the Beta22 vs. the M3 using the NFB-10ES as the source.  If the difference is more noticeable than the last round, it will only re-validate the upgrading axiom "source first."
 
 

 

[upstateguy]

Quote:

OP, I am being brutally honest here, your comparisons are worthless, except for the obvious conclusion: if you own a $400 source don't go spend $2,000 on an amp. 
 
You should use at least a PSA PW or Ayre QB9 if you are using PC-based audio. Preferably, it would be best if you can take source quality out of the equation by using, for example, Esoteric D01, dSC Puccini or MSB Plat IV.

That's a pretty harsh thing to say.
 
I also disagree with you.
 
USG

 

[chesebert]

You are right about one thing, the comparisons were worthwhile to demonstrate this: "if you own a $400 source don't go spend $2,000 on an amp and $1500 on a headphone"
 

 
Quote:

That's a pretty harsh thing to say.
 
I also disagree with you.
 
USG

 

[Mad Lust Envy]

Quote:

OP, I am being brutally honest here, your comparisons are awesome, and I've come to an obvious conclusion: if you own a good source, don't waste your money buying overpriced amps.

Fixed.

 

[chesebert]

I don't understand what you mean.
 
Quote:

Fixed.

 

[Paganini Alfredo]

I think he disagrees with what you said

 

[zenpunk]

So do I...

 

[kite7]

Quote:

You are right about one thing, the comparisons were worthwhile to demonstrate this: "if you own a $400 source don't go spend $2,000 on an amp and $1500 on a headphone"

 
Can you explain why all equipment must be equal or greater value for a comparison to be valid when not all equipment contribute to the same amount of improvement or difference in sound?

 

[chesebert]

Can you explain why it doesn't make sense to test for any performance differences between a 911Turbo and 911GT on a track when you are using some $50 tires you got from Bell Tire?   Can you think of atleat 1 reason why this is stupid?

Quote:

 
Can you explain why all equipment must be equal or greater value for a comparison to be valid when not all equipment contribute to the same amount of improvement or difference in sound?