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Digital amps, and upgrading from Q5 Pro; V200?

mk2

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Hi everyone, I'm new here; enjoying reading some of the analysis of amplifiers and the approach taken.

My interest was piqued a while ago by the idea of Class D "Pure digital" amplification; specifically going straight from a digital signal to speaker voltage without analogue intermediate. I'm a digital audio (software) guy, so this feels natural to me.

On that basis I thought I would try an SMSL Q5 Pro. For a while I used it with some small Dynaudio 2/6 speakers on stands. Now I've swapped them for floorstanders for better low end; Dynaudio Audience 62.

There are many plusses about this amp for me; USB input; coax input; an analogue input for phono preamp; EQs; small size; everything in one box; low power. In practice I ignore its quirks; there's s spark when you plug in the DC; I already had to replace a tiny resistor on the power input side which burnt out; very coarse volume control; very coarse EQ. It's always sounded a little 'soft' for my preference, so I have the treble EQ set to +1 or +2. If I could have everything, a good internal phono and PSU would be nice.

Now I'm wondering if it's really just too low powered for these low sensitivity speakers.

I'm considering I.AM.D V200, for having no analogue intermediate (if I understand correctly), comparable features but more power (150W vs. 45W). Is it worth it if I'm not hearing any clipping or distortion? Or am I just wasting my time and money here trying to partner budget 'innovative' amps with these speakers.

Also interested in dodging the amp's matching external PSU. Is there any evidence of the improvement of an old-style "LPS200 Linear Power Supply" or would a modern switchmode PSU deliver just as well? There seems to be an interesting contradiction in driving something as precise as an amp with pulses, and then going back to a traditional PSU.

Thanks! And looking forward to reading more around here.

Dynaudio Audience 62 specs:

Sensitivity (2.83 V/1 m): 86 dB
IEC Long Term Power Handling: 150 W
Impedance: 4 Ohms

Listening distance is 3m, at low/medium volume.
 

Prana Ferox

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'Class D' has nothing to do with 'pure digital'. They're analog amplifiers. They're called 'class D' because it was the next letter after 'class C'. There's still a DAC in the Q5, you're just using the one in the box instead of one upstream.
 
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mk2

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Don't worry, I'm not under any illusion what Class D is. But my understanding is that some amplifiers, like the Q5 Pro do not internally have a traditional DAC, and that they drive a PWM signal directly from a digital source. Hence my clarification of my interpretation of "pure digital" and that I am probably interested in a subset of class D products.
 

Matias

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mk2

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They have average sensitivity. I would expect that little SMSL amp (I didn't see what technology it actually uses) will struggle power wise though.

Thanks, that's good to know.

I'm interested... when we say an amp would 'struggle', from an electronic/scientific point of view, what's going on there? Specifically with class D. I can intuit that when one of these amps hits its upper limit it generates a square wave -- no more voltage available. But I can't hear anything like that. And since this amp is a match to 4 ohm speakers, how does the 'struggling' manifest itself electrically in the waveform and what does more power actually fix?
 

RayDunzl

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how does the 'struggling' manifest itself electrically in the waveform

Distortion.


what does more power actually fix?

Raises the power output before distortion sets in ( due to lack of voltage swing/current starvation )


But I can't hear anything like that.

Opinion:
Additional distortion hides from the ear, as, in my world, "music" is a multiplicity of pre-distorted sines piled on top of each other.

I think we are accustomed to hearing distortion and not specifically noticing it.

It can be easily heard in a pure sine of the same amplitude (above the point where appreciable distortion sets in).
 
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Frank Dernie

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Thanks, that's good to know.

I'm interested... when we say an amp would 'struggle', from an electronic/scientific point of view, what's going on there? Specifically with class D. I can intuit that when one of these amps hits its upper limit it generates a square wave -- no more voltage available. But I can't hear anything like that. And since this amp is a match to 4 ohm speakers, how does the 'struggling' manifest itself electrically in the waveform and what does more power actually fix?
I had a 55 wpc into 8 ohms/110 into 4 ohm amp into speakers with 86dB sensitivity speakers.
It clipped on loud bits playing at live symphonic levels (oscilloscope on speaker input) but was fine when not playing that loud.
 
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mk2

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NAD M32 Pure Digital converts digital inputs to PWM and straight to the amplifier.

https://nadelectronics.com/product/m32-directdigital-amplifier/

Although I would choose their new M33 with traditional Sabre DAC, Purifi module amps and included room correction. Should be a killer all in one.
https://nadelectronics.com/nad-mast...purifis-ultra-quiet-amplification-technology/

Ha, thanks for these, though I don't think I even need to look up the price :) Though I have seen their D3020; I see now they do some others as well. That C238 looks interesting feature-wise; but only at 50W 4 ohm. I wonder if it omits the analogue intermediate stage. It's priced a little more than I had budgeted for.
 
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mk2

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Opinion:
Additional distortion hides from the ear, as, in my world, "music" is a multiplicity of pre-distorted sines piled on top of each other.

I think we are accustomed to hearing distortion and not specifically noticing it.

It can be easily heard in a pure sine of the same amplitude (above the point where appreciable distortion sets in).

Well, I may agree. I've spent a bunch of my working life deliberately applying distortion to audio to 'excite' it in some way, too. I never really thought to start testing my hifi with sine waves though(!) but perhaps it's worth a go for an experiment in exploring this amp, if I check my neighbours are out first.
 

RayDunzl

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With adequate power, you are more likely to be hearing distortion from the transducers before hearing distortions from the amplifier.

REW's tone generator allows you to specify levels of harmonic distortion added to a sine wave, with which you can test at otherwise non-distorting levels, to see what they sound like.

1581885194943.png
 
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mk2

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There was a review of the Q5 Pro posted recently.

So, it sounds like I'm basically interested in how far along this graph I am running. I don't have anything to measure with, but probably not that high most of the time. With my listening levels I must be 1W and 2W at most (though that would be virtually the peak for distortion, on one of the channels). If each doubling in W is +3dB I can visualise in my minds eye (ear) how much louder I need to go to work up the graph.

Fascinating to see the differences in the two channels. Also given the level of quality control on this amp, it wouldn't surprise me if my specimen differs completely from the review as well.

But if I'm listening at reasonable volumes then is a more powerful class D a red herring? And should I really be looking for a similarly-powered amp which has less distortion.


SMSL Q5 Pro USB DAC and Stereo Amplifier USB In Power 4 Ohm Audio Measurements.png
 
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mk2

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So, a brief update. I did upgrade from my Q5 Pro, but chose a Denon PMA-50 which I bought second hand for ~£200.

I concur with a review of the PMA-50 posted here, which is it's a nice little amp and none of the quirks of the cheaper class D amp.

If I understand correctly, these amps are both technically similar (digital signal driving the pulses to the class D amplifier, not an analogue intermediate). But the Denon does much better for distortion in the graphs (none of the crazyness and asymmetry) and with approx 2x the power, which seems to be plenty for my floorstanders. Feature wise the Denon has bluetooth.

Whether I could actually tell the difference between the old and new amps is yet to be tested. I'm certainly enjoying my music more today :O) Some of that has to do with just smoother functionality of the Denon; a change from the coarse volume and tone controls of the cheaper amp , which means I can just tune it a bit more. Though I'm happily listening with "source direct" right now, which has the right amount of treble -- not the softer sound of the Q5 Pro set to 0-0.

So, in a way I bottled it. Instead of the 'adventurous' option of something from AliExpress I went for a mainstream brand. But I think I've got what I was looking for.

Aside from the size, which is larger than I expected. I suppose I took my scale from the headphone socket; I assumed all 'micro' amps use 3.5mm jacks these days! I'm pleased with the integrated PSU, but the amp is still a lot bigger than the Q5 Pro -- it's roughly a full height amp, half width.
 
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