A friend of mine has an Adcom 555 mk2 and he brought it over to my house a couple months ago because he wanted to hear it power my Paradigm Reference 100.2 (his stereo got piece-mealed when he moved and is still that way). He just had it checked out and it was ready for a test. I took my McIntosh MC7100 out and put his amp in. We listened to the same music on both and the Adcom was definately lean, a little bright, and somehow not as extended in either direction as my McIntosh. We were both surprised. It also started clipping at the same point as my amp desite the Adcom power being rated much higher (gain is similar). He left disappointed and last I heard, it is up for sale.... Anyway, depends on the type of sound you like and your system synergy, but in our test and in our opinion, the Adcom failed. Audition if you can. I don't know the 4004 but I auditioned the 2005 with a Stage One and it sounded very good with Definitive Tech speakers. Good luck! Arthur |
One point I want to make (I have done research in this) about bipolar vs. MOSFET is that the notion "bipolar to mosfets because of inherently better distortion characteristics" isn't quite right. Distortion (due to nonlinearity - not noise which is design related) is lower in BJTs than in MOSFETs. This is why most makers today only use BJTs in output stages. In the near future, with recent developments in lateral MOSFET doping, this may not be the case anymore but for now, the BJT is the undisputed champ for linearity. One of the main advantages of going wtih MOSFET is that you can lower the amount of feedback before instability ensues. Design is a matter of weighing the trade-offs....
As for Class D, there is still some work to be done before all digital kills off analog IMO. There are many issues still to be resolved and talk about non-linearities!! I will stop here because I will get carried away with this one. Arthur |
I like the two following quotes together:
"It sounds like Mcintosh tried to make this amp sound like tubes.Which was not a very good idea. " AND "somewhat resembles tubes (more "musical")."
Personally, I would rather have music than sounds. To me and my friend, McIntosh was more appealing than the 555. I guess we just like music. I was simply reciting my story, as you did.
As for the Carver, I don't know it. There are several amps in the $600-900 range I would like to hear but haven't yet. I am not permanently sold on McIntosh but for now, it is the most musical I have heard - and that is what I am in this for. Cheers! Arthur |
Gmood1: Your McIntosh MC7106 did not have autoformers. Sorry to break the bad news for your argument.
Also, don't forget about system synergy when you compare amps. The system you tried the component in is as critical to the sound description as the component itself. |
Gmood1 - Ok, here is another argument for you - LOL! ;)
I read a McIntosh white paper on the power guards and the distortion sensing circuit has a super high input impedance (order of 1 Gohm) which effectively takes it out of the circuit. Very clever use of JFETs.
The smooth, thick sound that McIntoshes have is probably due to fairly high negative feedback IMO. The Mc guys are all true electrical engineers so NFB is a requirement in their book (and mine too to some extent). The newer designs use less NFB than the older ones like our amps due to BJT improvements but nonetheless, it is a type of sound you have to like to appreciate, I realize. The upshot is that they are indestructible (especially with autoformers but I digress...) and have lower distortion than most amps out there.
Anyway, good system matching is most critical for hi-fi sound regardless of the equipement used. The best sound I have ever heard was a McIntosh MC602 (and C42) with Martin Logan Prodigys. Wow - I will never forget it. One day I will have Mcs and electrostats as the synergy was obvious in the first 3 seconds of music - it sounded like 600W of crystal clear tube amps.
Cheers and enjoy the music! Arthur |
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 |
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 |
Yep, anything in excess is bad, feedback included. Yet, I don't understand the hang up that audiophiles have with feedback. When I say feedback, I mean GLOBAL feedback. It has a zillion advantages that any engineer can name off for you because in the rest of the electronic world, feedback is absolutely critical in just about every circuit I can think of. In audio, I don't think feedback causes any detriment to the sound per se. I have looked this up several times and the post Gmood pasted above has too many inconsistencies to be reliable IMO. Local feedback is present in 99% of amps. I talked to Nelson Pass and what he calls "zero feedback" means he has local feedback but no global. This is fine however no one ever seems to complain about local feedback sounding poor. Kind of funny that guys who buy zero feedback amps for the name are actually listening to high local feedback designs and proclaiming its benefits. An amp with no feedback at all, will crash and burn with most speakers. I guarantee it. I have seen it in the lab many many times. So, before complaining about feedback sounding bad, consider what I have said. There is probably an exception out there somewhere (meaning no NFB at all) but we probably wouldn't buy it due to audible oscillatory reactions with the speaker's reactance. Arthur |
Hey
The Macs have some global feedback, yes. That was the source of my argument. But so does most Mark Levinson and Jeff Rowland gear although they try not to say so openly; I asked them and they told me. There are many others, I am sure - especially BJT designs. I bet most bomb proof designs have NFB and I agree with Eldartford about the "negative" name being poorly suited.
I am not sold to McIntosh forever and ever (surprised? LOL!) and want to try different things to compare. This is just my 4th system but I have been financially crunched lately. I have a list of all kinds of amps once I can save some money to rotate at least one added piece. I will add the Monarchys to the list!
Going back to Eldartford's comments: I have a mathematical proof I did for one of my classes comparing local and global feedback effects and most terms drop out in equal cascaded op-amp stages to where there is no difference. However, if the stages are unequal, problems can arise - but those hifi engineers are smart people and they naturally balance the system. I admit however that the proof probably didn't cover all variables and the human ear may be able to clue in on something that was deemed mathematically "negligible" thus far in the formulation. The more I am in school, the more I realize that we actually don't know much about how the world around us works and so each one of us here may be right, or wrong. Either way, we know what each of us likes to hear and that really is the important part. The rest is pure fun in experimentation! Enjoy -
Arthur |
