All Amps Sound the Same....

Most of my friends believe that all amps and CDPs sound the same (it is only about power while digital sounds always the same). Interestingly, they believe that speakers make big difference. 33% success rate ain't bad.

Jeff_jones - it is not that simple. SS designs 50 years ago were horrible with huge negative feedback and a lot of TIM distortions. Sanity is slowly coming back but amplifier design is not a trivial thing especially with budget constraints. The fact is that even for $1500 today you can find very decent and very horrible sounding amps. We tend to prefer the first kind.

"but if you want to electronically reproduce music, then the measurements should be the dominate method of understanding."

Onhwy61 - In order to get pleasant sound from SS amplifier you need to elimnate TIM (transient intermodulation) distortion that enhances odd harmonics and cannot be easily measured. This TIM is created by negative feedback - same feedback that makes wide bandwidth, low output impedance, low THD and IMD. If you see extremely good measurements - run away.

Onhwy61 - Rowland amps sound great because of Jeff Rowland and not any measurements.

Atmasphere amps measure quite bad (THD=1%, DF=1) but sound great.

I don't want to go into details why "feature massive use of negative feedback, outrageously good measurements and supposedly outstanding sound quality" isn't possible, but if you think of soulution 710 amplifier then you're mistaken. This particular amplifier has zero feedback:

http://www.axissaudio.com/amplifiers/710.htm

It is also mentioned in 6 moons review that 700 amps have zero feedback. Anything can be designed. The issue is cost ($40,000).

Icepower that you mentioned measures average. Popular 1000ASP module has only 38kHz bandwidth, 60deg phaseshift (20Hz-20kHz) and 0.2% THD

Onhwy61 - I'm only saying to avoid products that measure too well for the price, because something has to give and often it is sound. Soulution monoblocks look very impressive but I'm more withing Rowland 625 range.

I agree, that some kind of dynamic test would help not only designers but also buyers to make right decisions, but so far I can see many key specifications missing or without reference point. We all learned, one time or another, that equipment tested with sine or square waves behaves completely different with music. Often not a good specification but rather company name is wort paying for. I ended up buying small Rowland amp knowing that Rowland for over 20 years produced only very good amps. My next amp is likely to be Rowland.

I'm all for better testing, being frustrated with trial and error while pieces are often not available for trial (heavy or expensive). To add insult to injury some dealers start charging for in store demonstration. Well, it is what it is.

Frogman - nobody is talking about complete picture but rather about step in right direction.

As for the wire and interference. Lets for a moment assume that we're talking about speaker cables. Interference, usually high frequency, can be capacitively or electromagnetically coupled. In either case length of the wire makes difference. Let assume further, that we're dealing with electromagnetic pickup. At very high frequencies output of the amp has high impedance being also an input since feedback i connected there. Cable becomes an antenna. Antenna becomes practically ineffective when it is shorter than 1/10 of the wavelength. Let assume that we're dealing with 10MHz radio station nearby. Tenth of the wavelength is about 10ft. Using cables longer than 10ft exposes your amp to electromagnetic pickup of everything below 10MHz. It is not big help for very common 10ft cable since there are many radio stations above 10MHz, but at least eliminates a lot of mid and shortwaves. It can also eliminate other sources.

Reverse situation. Imagine that your class D amplifier is polluting speaker cables with 0.5MHz frequency. In order to effectively radiate it cable would have to be 200ft long. Your ICs can still pick it up capacitively but most likely they have shield and are in some distance.

I don't know of any positive effects of making cables longer. It will only introduce more interference by extending bandwidth increase capacitance and inductance. Unless you believe, that cable "enhances" sound longer cable is worse cable. 0.5m IC is better than 1m IC in spite of what dealer tells you (he has 1m in stock). Exception is digital cable when you want it either very short (few inches) or at least 1.5m long (but not much longer) to avoid first reflection on impedance boundary to interfere with the edge that is producing it thus affecting clean transition thru threshold point causing jitter (noise in time domain).

Even shielded cables are exposed to electromagnetic pickup. Non-magnetic shield (aluminum foil, copper braid) in reality does not protect against electromagnetic pickup but picked up signal, being high frequency travels on the outside of the cable - shield, because of the skin effect. Effective field in the center (where wire is) is zero. Skin effect is diminished at lower frequencies but they won't be picked up unless your IC is long enough to be 1/10 wavelength antenna. That's why even shielded cables should be kept short.

To be more clear:

Instead:
"Using cables longer than 10ft exposes your amp to electromagnetic pickup of everything below 10MHz"

should say:
"Using cables shorter than 10ft protects your amp from electromagnetic pickup below 10MHz"

My logic had better days. Russ69, sorry for posting on this thread. Just wanted to help.