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$500 amplifiers to test and review?

SIY

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OTOH how much should one spend for an amp? What are the threshold of measurements at which amps differences are inaudible?

Depends on the speaker. If you have something that doesn't have bizarre impedance swings and power requirements (i.e., the majority of speakers), maybe a couple hundred bucks will get you something good enough for blamelessness. If you have electrostatics or speakers with incompetently designed crossovers (cough, Wilson, cough), plan on adding another zero at the end of the price tag.

As for thresholds, that's where things can get complicated, but if the output impedance is low enough to not cause frequency response deviations of more than 0.1dB, you're likely more than safe. The days of engineered amps having distortion high enough to be audible are many decades past.

Note, "engineered" rather than "designed." Pick the latter and all bets are off.
 

andreasmaaan

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@Xulonn, is this the amp you're talking about?

If so, Hypex has published quite detailed measurements on the board (and I believe this is just the Hypex board, which already includes a PS, in a box). The published measurements look extremely good.
 

Xulonn

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@Xulonn, is this the amp you're talking about?
Yes, Andreas. As a retiree with lots of spare time, I spent hours recently browsing the internet, looking at current offerings in tube, Class AB, and Class D amps - just for fun." Hypex kept popping up as the apparent leader in modern Class-D amplification, and that module really appeals to me as a key component for a modestly priced high-fidelity stereo system in a small to medium-sized room.

I hadn't participated at audio forums for several years and wanted to see what was being marketed and sold, and what was happening with technology. I have a history with Tripath Technology, and I like the way Hypex is carrying on and further refining Class-D amplifier technology, so I started a new thread here today titled "Digital evolution - some audio electronics history." LINK
 

Wombat

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Crown XLI 2500 @ $399,00 Amazon
View attachment 14287View attachment 14288
Class A/B
500 watts into 8ohm
750 watts into 4ohm

Specifications
Frequency Response20 Hz - 20 kHz, +0/-1 dB (at 1 watt)THD<0.5%, 20 Hz - 20 kHz
Intermodulation Distortion=/ <0.35% (60 Hz and 7 kHz at 4:1 from full rated ouput to -30 dB)
Slew Rate>10V/usVoltage Gain33 dB
Damping Factor(8 ohms, 10 Hz to 400 Hz) >200
Signal To Noise Ratio (A-weighted)>100 dB
Crosstalk (below rated power) 20 Hz to 1 kHz-75 dB, -59 dB
Input Sensitivity(for full rated power at 8 ohms) 0.775V or 1.4VInput
Impedance (nominal balanced, unbalanced)20kΩ, 10kΩAC
Line Voltage and Frequency Configurations Available(+10%) 120V~60 Hz; 220V~50/60 Hz; 230-240V~50/60 Hz
Dimensions19" x 3.5" x 12.4" (48.3cm x 8.9cm x 31.5cm)
Weight 29.7lbs (13.5kg)
IEC Power Connector15A

Good suggestion.
 

Wombat

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Talisker

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Hi Folks,
It will be very interesting to have some independent measurement of leaders of Class D : IcePower, Hypex NCore, Anaview and Pascal ...
Theses companies are selling amplifier modules that are used by many audio manufacturers ...
It's also a good idea too to compare different technologies to measure their progress one versus another ...
 

andreasmaaan

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Just re-posting here from another thread, as I realise it is a lot more relevant here today than it was there yesterday:

Here are some specs from a 2x75W Hypex that can be bought boxed with connectors and onboard power supply for under €400.


index.php



index.php



Full spec sheet here.

NB: I haven't seen independent measurements of this unit - these measurements come from the manufacturer.

Would love these measurements to be verified independently by Amir here :)
 

Talisker

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@andreasmaaan : You right, this company use it as well 3D Lab, and maybe Jeff Rowland. Minimum order to Pascal is 16 units for 240$ or for testing purpose it's one unit at 300$ (power included)
Anyway it's still interesting to compare ...
 
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restorer-john

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Crown XLI 2500 @ $399,00 Amazon

Class A/B
500 watts into 8ohm
750 watts into 4ohm

Specifications
Frequency Response20 Hz - 20 kHz, +0/-1 dB (at 1 watt)THD<0.5%, 20 Hz - 20 kHz
Intermodulation Distortion=/ <0.35% (60 Hz and 7 kHz at 4:1 from full rated ouput to -30 dB)
Slew Rate>10V/usVoltage Gain33 dB
Damping Factor(8 ohms, 10 Hz to 400 Hz) >200
Signal To Noise Ratio (A-weighted)>100 dB
Crosstalk (below rated power) 20 Hz to 1 kHz-75 dB, -59 dB
Input Sensitivity(for full rated power at 8 ohms) 0.775V or 1.4VInput
Impedance (nominal balanced, unbalanced)20kΩ, 10kΩAC
Line Voltage and Frequency Configurations Available(+10%) 120V~60 Hz; 220V~50/60 Hz; 230-240V~50/60 Hz
Dimensions19" x 3.5" x 12.4" (48.3cm x 8.9cm x 31.5cm)
Weight 29.7lbs (13.5kg)
IEC Power Connector15A


I'm sorry, those rated specifications aren't remotely high fidelity.

Frequency response is terrible. Clearly, for a 0.5% THD limit on a 1watt FR, things must be bad at frequency extremes.
IMD spec is the worst I have ever seen in a specification sheet and I've seen a lot of spec sheets.
Slew rate is poor.
S/N at 100dB with respect to 500w@8ohms means it has a residual of roughly 0.6mV. Consider most decent amplifiers has residuals in the low 10s of microvolts.
The input impedance is so low on a normal unbalanced inputs that it will seriously affect some preamplifiers and/or sources. It could not be used successfully with any passive 'preamps'.

It's a tough and cheap, sound reinforcement amplifier.

Bear in mind, it was the 1950s when Harold Leak established 0.1%THD (the Point One) as essentially the start of High Fidelity reproduction.

By way of comparison I have 1980s power amplifiers with 120dB+ A weighted S/N ratings, THD at 0.002%, IMDs at 0.0015%, Frequency responses of 1Hz-300Khz and slew rates of +/-400V/uS. These were specifications that were frequently bettered in actual testing.
 
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amirm

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restorer-john

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Well hopefully Dr. Floyd Toole will respond to your post that the Crown XLI is not remotely high fidelity.

It may turn out to be High Fidelity when tested, but as I said, the rated specifications certainly are not, and I'm sure the good Doctor will agree.

I'm sorry, those rated specifications aren't remotely high fidelity.
 

FrantzM

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You are right, here is Crowns email answer to my question :



Hi Steve,

Our Crown amps have a great sound, but wouldn’t be classified as high fidelity like our Mark Levinson amplifiers.
High Fidelity amps usually lie within a much higher cost range.
This isn’t to say that you wouldn’t like the Crown amplifiers.
Maybe check with some local dealers to see if you can hear what one sounds like before you buy it.

Best Regards,
Tony Smith

Technical Support Engineer
Harman Professional Solutions
I have no experience withe Crowns as HiFi amps. This answer however is exactly what I should expect from an Harman employee. a bit OT.
 
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