Are there Class D amps that eliminate the original treble complaints?

[davide256]

Wondering what the current state of Class D amps is? A year ago I replaced my aging  class AB amp with Orchard Audio GaN mono blocks, which

was a major improvement in bass foundation and low volume resolution. After living with these for a year still pretty pleased but have realized that in high treble

they could be improved on, as they can accentuate irritants causing me to keep a tube pre to smooth them out. Reading reviews in the past, this seemed to be the

one criticism of class D. I'm wondering if any newer technology has emerged for class D that resolves this?

[davide256]

2 hours ago, Cormorant said:

I've had a pair of the new Hypex Nilai 500 monoblocks in my system since the beginning of January.

 

I find the treble to be superb -- extended, very clear, and tonally excellent.  The smoothness really makes one appreciate low distortion in the treble range.

 

I have not heard any Purifi amps in my system to compare.

hmm, ASR likes them. But of course they only measure without opining on sound quality :<}

 

https://www.audio “science” review/forum/index.php?threads/hypex-nilai500diy-amplifier-review.41669/

 

[davide256]

45 minutes ago, Miska said:

 

I would try something with Purifi modules. Like for example recent more expensive NAD models. These don't have as much output impedance issue at high frequencies, so they are less sensitive to speaker pairing. Class-D amps are a bit like tube power amps, where the speaker pairing plays bigger role.

 

Two things however to take into account. First the Hypex/Purifi models are not particularly great for low impedance difficult loads. So if a speaker impedance dips below 4 ohm or has low EPDR impedance, those amps can collapse. Second thing to pay attention to is the kind of DAC / filters paired with the DAC. So I would avoid running leaky filters or R2R at low NOS rates, because class-D amplifiers can alias the high level images down to audio band.

 

 Magnepan's do dip to 2 ohms above 6khz.  The treble issues with current class D amp are actually at their worst playing LP's vs my digital solution{s} with same music.

Would hate to give up the resolution of class D as its so much better than my prior tube and class AB amps from the lower treble down,

but somethings  got to change so I don't cringe at Enya, choral music and "Close Encounters of the Third Kind"

[davide256]

Something that also creates confusion/complexity with class D choices is the input section.  PS Audio talks about their "analog cell" input, even uses a tube buffer

in their most powerful class D amp. Apollon offers OPA 1612 as standard or offers Sparkos, Sonic Imagery OP amp choices, if you step up to their premium line

you can get Weis OP2-BP op amps.

 

Its been a while since I dabbled with op amps but my experience  then was that OP amps on a chip were just "flavors", that if you wanted more articulate sound

discrete component OP amps were what made a difference. The Hypex Nilai mentioned above says its input buffers are "fully discrete" but not sure if

that is saying the same thing.

 

Anyone able to opine on the input section and how to weigh choices in selecting a class D amp?

[davide256]

On 3/9/2023 at 10:25 AM, Miska said:

 

LP will spit out lot of harmonics beyond 20 kHz, because the cartridge THD near 20 kHz is pretty high. It already begins to increase from about 6 kHz. Probably not high enough to cause aliasing in the amp, but enough to cause increased power draw at higher frequencies. But that is not likely the main issue. More likely main issue is the output impedance increase near 20 kHz. When that is accompanied by drop of loudspeaker impedance, it makes causes variations to the frequency response. This is very typical for older class-D implementations. It will cause accentuated sibilance and such, in particular with LP. NAD also had a separate manual EQ compensation for this in their older amplifiers. Purifi modules shouldn't be as bad in this particular area, so worth checking out. It could be what you are looking for.

 

However, electrostatic and magnetostatic speakers are usually not the easy loads. Electrostatics also have impedance falling as function of frequency, since they are essentially just capacitors. Magnetostatics can be tricky too, so current class-D may not be best option to drive Apogee Scintilla's!

 

Magnepan included two 1 ohm 10 watt resistors with 1.7's for  tweeter attenuator jacks, using them bumps the tweeter path resistance up to 3 ohms

which has helped reduce the treble irritants from the GaN mono blocks. Its still there to some degree but better. Yea!

 

Phono cartridges don't have to have an inherent THD problem at 20khz.  I have observed that the atrophy of stylus manufacturing scale has caused

bushing mounted elliptical stylii to dominate for cartridges below USD $500 vs the sub $50 price in the 80's.  A nude mounted

hyperelliptical or other better geometry stylus that provides clean sound tracking above 10khz should take care of most of that issue,

more reason to upgrade to something like the shibata tipped Hana SL from the elliptical tipped Dynavector 10x5

[davide256]

Touched so far on 2 parts of a class D amplifier, the input circuit and the class D amplifier board but what about the 3rd, the power supply? After living with a heavy toroidal transformer + big caps in a class AB amplifier, the SMPS like bricks that came with the GaN amps were a bit surprising. Wondering at this point, how do you know if your class D amp has an appropriate power supply to get the best out of the electronics it powers?