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Any reason to upgrade amp from Denon X3600?

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chych7

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In case anyone is still reading... I did perform some additional testing with the AB switcher I built.

My first test here was to compare the Denon X3600 output to a Nobsound Mini amp I had laying around. The Nobsound is a bargain basement class D amp, about 30 WPC, and only $34. Surely I'd hear some difference from the Denon X3600, which got a commendable review from Amir. Speakers are Philharmonic BMR. The Denon was set to "Pure Direct" mode, which disabled the subwoofers and any room correction/DSP. PC was the source, using HDMI.

The Nobsound's gain was too low for the Denon's pre-out output, compared to the Denon amp's output. To boost the gain, I used a JDS Lab atom (also well reviewed) as a preamp to the Nobsound. Now I could do some level matching:

fresp.png


From the frequency response plot, there is about a 2 dB low/high frequency roll-off from the Nobsound. This is probably because the amp has lower bandwidth than the Denon, so it would be expected.

For the blind listening test, I recruited my wife to control the AB switcher. She did not know which setting corresponded to which amp, so she was blind to it. I did not see the AB switcher, so I was blind to the setting. The AB switch was instantaneous; one click and the amps were toggled. The listening volume was 75-80 dB, which was on the loud side for us. We played various music, both lossless and streaming, and our conclusions can be summarized:
- For myself, I could not tell any difference whatsoever. Every time the amp switched, I struggled to hear any difference. I also saw the frequency response plots beforehand (my wife did not), and was looking for a high frequency difference, but couldn't hear it.
- Surprisingly, my wife was able to hear a distinct difference between the two amps. She was able to hear the attenuation in the high frequency of the Nobsound (which I told her after the test was over), that I was not. I presume she has more sensitive hearing than me.
- My wife's preference was for the Nobsound, because the high frequency roll-off made the highs less harsh. She also described that amp as sounding slightly more fuller in bass. The frequency response plots don't explain that, but I'm guessing it's a psychoacoustic effect where rolling-off the highs allows us to perceive lower frequencies better. This had me thinking - some amps, like tube amps, roll-off at high freqs, and give a "warm" or "tubey" sound, as described by some audiophiles. This seems to just be equivalent to a tone control. If an amp's undesirable traits (HF roll-off) are being used to compensate undesirable traits of a speaker (brightness), then that seems like a backwards way to achieve a desired tonal response. Better to use a DSP or a preamp with tone controls, I'd think.

So there you have it. My limited pseudo-scientific test found that there was a difference between a bargain basement $34 class D amp, and a well-measuring AVR, and the former had a slight preference subjectively. Ok so the next step is to get a better amp like a Hypex/Purifi. I may consider this later (after I'm back from some well-earned vacation). But given the law of diminishing returns, I suspect I won't hear a difference. I also suspect my wife will prefer the amp that has the HF roll-off, which a higher-end amp may not have.

One additional comment - I also tried the listening test and switching amps in "stereo" mode, which enables the subwoofers and Audyssey XT32 room correction. In this configuration, the Nobsound would occasionally make clicking/popping noises during certain parts of a song, and was repeatable (the same part of a song would always make the noise); the amp was probably clipping/distorting. This could suggest that room correction can decrease headroom on an amp, so one with higher power is needed; or, the room correction has dependence on some specific characteristics of the amp. I could have rerun Audyssey with the Nobsound to further explore that, but that's more work than I want to sign up for.
 

Jlm86

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Well then, time to build a ABX switcher and evaluate this myself, since no one here seems to have anything to say. Good thing amps and things from Amazon have a trial/return policy, in case I don't find any difference. The science of audio can't avoid addressing the role of the observer; audio, by nature, only exists in our minds.
What did you end up doing? I'm in same situation and asking similar question..
 
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chych7

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What did you end up doing? I'm in same situation and asking similar question..

I did end up getting a Hypex NC252MP (the Audiophonics one that was reviewed here). Used the ABX switcher and compared it to the Nobsound. Couldn't really hear much difference except for a very slight high frequency roll-off on the Nobsound. Played at fairly loud volumes too. End result was disappointment. I kept the Hypex anyway for the "jewelry" aspect, but it's really not necessary. The money spent on amps is better spent on things like room treatments.
 

Jlm86

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Looking for upgrades to my HT/music sound system, I've gone through the major hitters already for my budget (speakers - Philharmonic BMR, subwoofers - 2x HSU ULS15.2, room treatments, bass integration/DSP) and am now looking at amplification. Running everything off a Denon X3600, which has good measurements from the ASR review. I'm primarily looking at any improvements to audio quality for stereo music listening, so am considering some kind of stereo amplifier in the <$1k range, like a Hypex type of amp. Currently the Denon sounds great to me, plenty loud, no audible distortion.

What I can't figure out is how to interpret all the conflicting information on this forum. Do amps matter? Yes, no? Is a nice Hypex amp audibly different than a good receiver's amp (and not just audibly different, but enough to actually matter to show a subjective improvement)? There seems to be a lot of effort here to discern the different electrical characteristics of various amps (i.e. the "science"), but not a lot of effort to show what that means in the subjective experience (something "science" tends to avoid, but in the end, this is what really matters for the consumer of such products). Especially when considering that speaker distortion and psychoacoustcs can greatly mask any differences between great/good amps. Are higher end amps just jewelry, somewhat equivalent to fancy high-dollar cables (clearly pooh-poo'd on this forum)? Or do they really make an audible and scientifically provable improvement to the subjective experience? What do I do with ~$1k?
Have asked the same question in last few months..
Setup new pair of JBL 580s../530 cntr

X3600
HSU Vt15
 
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