Long answer
I asked the speaker question, because in my listening experience much of the "amp" sound is really just a by product of the speakers.
Over the years I have had a chance to listen to some pretty exotic stuff. Is there a sound difference? Everybody differs, but I say, YES, but, with a big BUT, just with certain speakers.
Back at the dawn of digital (early mid 80's), a local dealer let me practically live in his showroom in the evenings and on the weekends. I was a real customer. Had spend more than a few bucks. But basically I had upgrade disease, and was a live body that kept his showroom appearing busy. He should have been paying me
Spent hours listening to different combinations of speakers, amps, pre-amps, phonographs and CD.
I hooked up a NAD & Yamaha Receiver into their entry level speakers Fisher speakers from one of those "$500 rack systems" and there was no sound difference. Both sucked. It was the speakers. Nothing was going to sound good.
Tried the NAD and Yamaha Receivers on one of those small entry level brands of speakers that are long gone from this market. Both sounded pretty good, but there seemed to be a bit of mello sound from the Yamaha, as if the treble was turned down just a wee bit.
Moved up to Klipsch Heresey's and there was a sound difference. Both brands sounded bright, caused by the horn tweeter for sure, but the Yamaha sounded brigher, as if the treble was turned up a wee bit.
Notice with one brand the Yamaha sounded warm, and the other brand the Yamaha sounded bright?
Of course one could have argued that the Yamaha was sounding correct, and it was the NAD that was actually sounding "off".
Moved up to the bigger Klipsch Cornwall's and both units again sounded a wee bit bright, but I could not tell the difference between the receivers. Spend hours, days, trying to find a difference. Never could.
The same NAD or Yamaha Receivers hooked up to Infinity RS-6(?). Damn good. Both pieces of equipment. But the NAD seemed to have deeper bass.... just more umphf. No real sound difference in the mid and treble. Just a bit more bass. Everybody was always saying that I had the volume higher on the NAD and that was causing the deeper bass, but......
I also hooked up the NAD separates on the RS-6(?). The NAD separates were clearly better than the receivers from either company. An even bigger umpf to the bass, and there was another difference. The separates has less background noise. The preamp was better isolated and didn't have to contend with the noise being generated by a tuner unit.
Moved up to some bigger Infinity RS-5 Speakers and the receivers started to run out of steam, with the Yamaha really starting to struggle. A modest sized listening room, that was a bit dead acoustically, and the Yamaha was clipping on Dire Straits Money for Nothing at just moderate volumes. UGLY. At low volumes, the NAD receiver sounded better, but was that a better power supply? Or a better sounding receiver? If it was a better power supply, that could explain the difference with the RS-6(?)'s.
Moved up to the even bigger Infinity RS-4 Speakers, and the NAD receiver was gasping. But the NAD separates sounded wonderful. Difference between a low powered receiver and a moderately big amp.
So maybe power supply is the issue. But then again, NAD had that nice soft clipping circuit.
Oh, we could make the NAD separates go into panic mode.
There were some BIG, BIG Infinity RS II's (?). My car cost less than those babies. The NAD just could not hang with those speakers. Even trying the NAD in mono-block and biamping the speakers, nothing was working. Now, those big monoblocks (from another company long since departed from the audio scene), sitting over in the corner, they had no problem with those speakers. No wonder, those big monoblocks were like 400w into 8ohms.
Then one day, the Bang & Olufsen's showed up. Big bucks, fancy artful units. Real Pretty. And Expensive. Grabbed the speakers and hooked them up the NAD receiver and then the NAD separates. Sucky Sucky. Can't say it any other way.
The B&O speakers sounded great when powered by their own receiver. But combine the B&O speakers with the NAD, and things were not good.
Put the B&O speakers with the Yamaha, and the Yamaha almost sounded as good the B&O receiver.
Hmmmmm
What is going on here?
It is gotta be the speakers that are the real issue with the sound of the amps and receivers.
Now, the one exception to all of this was the Nakamichi separates. The amps were OEM from Threshold. Who knows who actually made the preamp.
I feel in love with the Nak stuff when it arrived. I already had a Nak cassette recorder (remember those?). $800 for a cassette recorder (in 1985!!). The darn thing weighed more than my NAD amp.
And the Nak separates were BEAUTIFUL. Clean simple lines. Solid Black. Not Black plastic. Shiny Black METAL. Even the buttons on the preamp were metal disks.
And the Nak stuff sounded smmmmmmoooooth on EVERY speaker in that store. Clean, powerful, and smmmmmmoooooth. Even tamed the bright sound of the Klipsch speakers. Sounded better than the B&O receiver with the B&O speakers. Could drive the Big Infinity's without breaking a sweat. Made my favorite Infinity RS-4's just sing as loud as any human could want, and the sound was perfect. Solid deep bass, clean even highs. Just plain and simple the best, "relatively" low price preamp and amp I ever heard, if you call almost 3K in 1985 low priced.
At various times in my life I have had a chance to "live" in other Audio stores. The brands change. Equipment improves. But every experience is been about the same. Some amps, or receivers, just do not sound good with certain speakers.
Is the fault of the speakers? Or the amps? Or just wishful thinking? I don't know.
But I would try the Yamaha and Denon units with another brand of speakers and see if the sound difference remains. By the way, I love the Denon.
