Aragon 4004 mk2 vs Adcom 555 mk2

I have used amps with feedback switches too (like the Unison Simply 2 and 4 tube integrateds) and I didn't find the soundstage "clouds" up really when i go to high feedback. I would say that it is more of softer and slower sound instead but I could hear the same background details in both with no difference in level. It was more of a mood change IMO. I about wore the switch out going back and forth and came to the conclusion that the difference was overall quite subtle. My brother couldn't hear the difference in a blind test but I could albeit just barely. I think the switch went between 6 dB and 12 dB. Pretty cool - I would like to find other amps with a toggle switch like that and listen again. ciao - Arthur

Aball thats what I was trying to say in other words.It does seem a tad slower and softer.Which to my ears is slighlty cloudy.I really don't understand the reason for having these settings.When the designer states for the most transparency leave it on the lowest settings.Then again maybe it has something to do with matching the preamp or cd player gain to the amplifier.I don't know ..Aball your the engineer how about shed some light on this.

Yeah, this is driving me nuts. A friend of mine was nice enough to drop off his Pass Labs X350 amp again to compare to my Aragon Palladium monoblocks. Both put out very similiar power regardless of impedance, both are practically identical in SQ too from all the ABing I did tonight. The Aragon's are true differntial balanced monoblocks, the Pass Labs is a 0 feedback design supposedly which they advertise(Aragon doesnt state its a 0 feedback design)and is also a balanced design by nature if Im correct. And I cant tell the difference between the 2 for the life of me.

Ritteri here's an section of an article I came across done by Doug Blackburn of Soundstage.You can go to this address and read the entire article .Of course this is one persons opinion. http://www.soundstage.com/maxdb/maxdb101998.htm

Feedback in low-level gain stages – It is becoming increasingly clear that less feedback rather than more is musically desirable. However, there is a point where you have to stop removing feedback due to some element(s) of the whole presentation falling apart, like the quality of bass. Too little negative feedback is big trouble for bass quality. How much is too little and how much is too much? I’ve never been impressed with zero negative feedback in an amplifier. A little bit of feedback, even as small an amount as 2dB to 4dB in one gain stage (out of three) is enough to keep the bass in line while not enough to do harm to the loveliness of the mids and highs. Too much is easy to identify. Think sibilants. You hear too much emphasis on sibilants? Chances are the amplifier you are listening to has way too much negative feedback. In fact, a good portion of what at one time was known in high-end land as "solid-state sound" was strictly an artifact of silly-large amounts of negative feedback. It is not entirely inaccurate to think of amps using a lot of negative feedback as the uptight conservative businessman of the audiophile world -- too inhibited to ever have a really good time. They are too controlled, too unforgiving, too dry, too emotionless, too uptight. They are certainly lower in total harmonic distortion than low-negative-feedback amps, but what does it matter if the music is as crisp and colorless as fall leaves in winter?

While zero negative feedback is too little, 10dB of global or even local (within a single gain stage) is often too much. Think 2dB to 6dB of local feedback for most amplifiers to do their thing with high levels of musicality across the entire musical spectrum. You can do "stupid amplifier tricks" playing with less or more feedback, but in the end, they all eventually sound "tricky" while the very moderate amount of feedback sounds like music. It’s typical for solid-state amplifiers to have 20dB to 60dB of negative feedback. Are those guys actually listening to what they are building?

There may very well be some wailing about my pronouncement that 2dB to 6dB of local negative feedback with no global negative feedback is "enough" coming from the amplifier manufacturer/designer community. Don’t trust them. If they think they need more feedback than that to get good sound, they just aren’t listening, or they don’t know how to resolve the problems that will crop up (sonic problems) when they eliminate most of the feedback they are used to using. That doesn’t mean my concept of the right amount of feedback is incorrect. It just means that some manufacturers/designers aren’t going to know how to incorporate that small of an amount of feedback into their products. The manufacturers that can build great-sounding solid-state (or tube) amps with low amounts of negative feedback without suffering muddiness of sound and woolly bass have a major sonic advantage that you will/can recognize once you have heard it.

Is having adjustable negative feedback a good idea? I have seen several tube amplifiers which have user adjustable negative feedback. On the surface, this seems like quite a worthwhile feature. It certainly is educational to hear what happens as you change the amount of feedback. However, once you begin trying different discrete resistors that are soldered into a negative-feedback loop -- well.... Let’s just say that the resistors in the negative-feedback loop are impressively obvious when changed, either in value, manufacturer or material. I cannot imagine any potentiometer added to the feedback loop would do anything but sound really bad compared to a single properly selected high-quality resistor. In fact, having heard how critical the resistor in the negative-feedback loop is, I can’t imagine a worse place to locate a potentiometer than in the negative-feedback loop. Compared to a good resistor, the best potentiometers sound quite bad. Use of a stepped attenuator might eliminate a lot of problems caused by sonic limitations of potentiometers. However, the negative-feedback loop is a very sensitive area of the circuit, I’m not sure if mechanical contacts in the stepped attenuator could ever be good enough to be sonically inconsequential in this location.

Two things:

1. The feedback loop would not use a pot if the design is worth anything as the guy suggested. The switch, as a designers opinion, switches high-quality resistors in and out - doesn't use a pot so that argument is not worth reading. He is right - pots sound terrible, that is why they are rarely used or done so as to no affect the circuit.

2. The feedback switch is so that if you are using inefficient speakers, the amp will be stable with higher feedback. A zero/low feedback design can become unstable very very easily if the right (rather, wrong) conditions arise. So the switchable feedbacks are to match speakers - not correct sound. Arthur