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Class D
Amplifier comparision test
started on 17 July 2008, last update 8 September 2008
INTRODUCTION
In these last years there was a large diffusion of Class D amplifiers using the pulse width modulation.
from AES document High Fidelity Pulse Width Modulation Amplifiers based on Novel Double Loop Feedback Techniques (mirror)
The basic principle behind a PWMamplifier is shown in Fig. 1.The amplifier principle is also termed a digital power amplifier due to the digital operation of the power transistors or a class D amplifier. The audio signal is pulse width modulated by comparing it with a reference signal (carrier) which can be performed in either the digital or analogue domain. The resulting small signal PWM is converted to power levels by the power switch. Ideal switching elements operating either 'on' or 'off' is the secret behind the theoretical very high efficiency of the PWM based amplifier.
Many people have buy a T-Amp with Tripath chips and now they are happy.
So I have decided to build this complete test to compare many different technologies.
TECHNOLOGIES
photo | company | model | Power | Output current max | Input impedance | output impedence | size (mm) |
ICE Power by Bang Olufsen | 250A | 250W on 2.7ohm with +50v | 25A | 8Kohm | 5mohm | 69 x 75 | |
Tripath | MOKS Fenice 100 with Tripath TA2022 got from Audioskeggia | 90W on 4ohm with +-31v | 4.6A | 100k | 100 x 130 | ||
NewClassD | NCD04 | 400W on 4ohm | 28A | 5Kohm | 38 x 100 | ||
Hypex | UCD 180 OEM | 180W on 4ohm with +-45v | 10A | 100k or 1K8 | 20mohm | 67 x 73 | |
Hypex | UCD 180HG with HxR regulators | 180W on 4ohm with +-45v | 10A | 100k | 20mohm | 65 x 65 |
These modules have different characteristics like the power but this is not important because I will compare only the sonic performances as full-range amplifier in normal domestic use.
The Hypex 180OEM can be used without the input buffer stage to increase sonic
performances.
I have found on HiFifever forum the descrition to modify the common Hypex 180
modules, see
http://www.hififever.com/forum/viewtopic.php?t=1772 (mirror)
POWER SUPPLY DESIGN
The
power supply used is a classic configuration, 3 components: transformer,
diode bridge and capacitors. To get the best sonic performances and to have a true comparation test all the power supply use the same diode bridge and capacitors. As capacitors I have choices one of the best components in the market: Mundorf MLytic (snap-in 22000uF 63v). To begin soon the test as diode bridge as been used a 36MB160A by IRF but will follow tests with ultra fast diodes with soft recovery. All the amplifiers use Nuvotem Talema Encapsulated Toroidal transformers with different power and voltages buy from RS-Components 1 x RS 223-8904 0500P1-2-030K
for ICEPower |
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For the NewClassD modules I have used at the begin a 600VA 37-0-37V R-Core transformer and after two custom transformers 0-42V 0-42V 500VA build by Canterbury Windings transformers and designed on my specifications with:
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MEASUREMENTS
In all my recent projects I
insert some measurements
using the Clio system by
Audiomatica
but I don't consider these important in this test because I am sure that the
distortion of all these modules are very low and the frequency response is
perfect as declared so only the sonic performances are important. Probably it is interesting compare the residuals square wave of these modules but now I don't have a valid instrument for this measurement. |
SONIC PERFORMANCES TEST 1
In all my sonic performance tests I always
search to be sure of an objective result using many persons and these with
different experiences.
This mean that the result here is not my personal and it is not subjective like
many other test published online.
photo (click to enlarge) | environment | hardware | software | results (1 is the best) |
This is the system set-up for the
first test on August 24, 2008.
We were in my laboratory room.
Two of my friends with a lot of
experience on music reproduction were present at the test. They
always agreed on the grades given.
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As
digital source: - My laptop PC - Audiotrak Optoplay to create a valid 24bit toslink output - FireStoneAudio Spitfire DAC modified As analog source: Loudspeakers cables: |
Messiah (Dublin Version, 1742)
(Dunedin Consort)
Recit Comfort ye.flac
88KHz 24bit from LINN
Oreobambo
Blue Eyes Moon
Piano
CD
Porcupine Tree
We Lost the skyline
Drown with me
LP
|
1) NewclassD
2) Tripath
3) Hypex 180OEM
4) Icepower
The bad result obtain for the
Hypex in this test can be caused by 2 factors: The Tripath amp. have sufficient detail but a little metallic sound. |
SONIC PERFORMANCES TEST 2
In this second test the UCD180HG with HxR regulator have replaced the UCD 180OEM to increase performances.
The UCD180HG has been tested with 22000uF 63v Mundorf MLytic capacitors and with their original UcD supply HG Mono using high-speed rectifier bridge and Slit-Foil capacitors.
The dual power supply of the analog section for the IcePower has been upgraded with OS-CON and r-core transformer to try to increase performances.
photo (click to enlarge) | environment | hardware | software | results (1 is the best) |
|
This is the system set-up for the
test on 7 September
2008.
We were in my laboratory room.
Two of my friends with a lot of
experience on music reproduction were present at the test. They
always agreed on the grades given.
|
As
digital source: - My laptop PC - Audiotrak Optoplay to create a valid 24bit toslink output - FireStoneAudio Spitfire DAC modified with OP275 As analog source: Loudspeakers cables: |
Messiah (Dublin Version, 1742)
(Dunedin Consort)
Recit Comfort ye.flac
88KHz 24bit from LINN
Vivaldi
Porcupine Tree
We Lost the skyline
Drown with me
LP
Emerson Lake & Palmer |
1) NewclassD
2) Hypex 180OHG
3) Tripath
4) Icepower
The details ear with NewClassD amp. are excellent using the standard LM6172 op-amp. The test with the optional LM4562 give a more smooth sound but some details are lost and in this case there is less difference with the Hypex. The Hypex HG with both the power supply: Mundorf MLytic capacitors or UcD supply HG Mono is a lot better than Tripath and Icepower. To be sure of this result for the first two amps. I will schedule very soon another test with a different system. After these good results with Hypex and NewClassD I will continue to use these amps. until there is this hot season and I will wait the winter before to reinsert the vacuum tubes on my 845 reference amp.The The NewClassD amp will be tested soon with the power supply board using 8 x ultra fast recovery diodes. |
SONIC PERFORMANCES TEST 2 bis
photo (click to enlarge) | environment | hardware | software | results (1 is the best) |
|
This is the system set-up for the
test on 21 September
2008.
We were in my laboratory room.
Another my friend with a lot of
experience on music reproduction and owner of many electrostatic
loudspeakers and reference amps. l was present at the test and we
was
always agreed on the grades given.
|
As analog source: - Rega Planar 3 with Denon DL-103 - My Pre phono 2 considered in this test better than Bartolomea Aloia VTPA - DACT stepper attenuator 10K Interconnect cables: - SilverMIca Zero-One by Voodoo Cable Loudspeakers cables: |
Norah Jones Feels Like Home Blue Note LP |
5) Icepower
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SONIC PERFORMANCES TEST 3
In this test the best amplifiers will be compare on different loudspeakers.
photo (click to enlarge) | environment | hardware | software | results (1 is the best) |
Here the NewClassD in the chassie |
This is the system set-up for the
test on 28 September
2008.
We were in the hobby room of a my friend with a lot of
experience on music reproduction and owner of many electrostatic
loudspeakers and reference amps. l was present at the test and we
was
always agreed on the grades given. |
As analog source: - cartridge Supex sd900 super - pre-pre Supex sdt77 - turntable Pink Triangle - My Pre phono 2 considered in this test better than Bartolomea Aloia VTPA Interconnect cables:
Loudspeakers cables: Electrostatic loudspeakers Audiostatic ES-240 prefered by the owner to the Quad ESL57 and ESL63. |
various LP of my fiend |
1) NewclassD with original
LM6172
opamp 2) Hypex 180OHG To be
sure of the result has been connected some minutes a traditional
amplifier.
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