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Hypex UcD180HG HxR amplifier module analysis and review

pma

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Hypex UcD180HG HxR module analysis and review

After buying and testing AIYIMA A07 amplifier (based on TPA3255 class D chip) in January 2021 I was quite disappointed with the frequency response modulated by speaker complex impedance and its audible consequences. This is, unfortunately, inevitable for the class D design with output LC filter outside the feedback loop, because the LC filter response damping not only depends on load resistance, but also LC filter impedance interacts with connected speaker complex load impedance, which may modify the frequency response even more. This was confirmed by measurements of A07 frequency response into various speakers and into speaker dummy load.

So I was seeking for a different class D topology (and not only hysteresis switching with PFFB) that would have affordable price and would be free of the mentioned frequency response modulation by the complex load. Yes there are Ncore and Purifi modules that are close to amplifier perfection, but they are quite expensive, NC400 module would cost 349.00 EUR (incl. Tax), without a power supply. So I started to review another options and turned my attention to the older UcD design, namely UcD180HG HxR, the latest datasheet [1] link is here:

https://www.diyclassd.com/img/upload/doc/ucd/ucd180hg/Documentation/UcD180HG_datasheet_R5.pdf

I ordered the module from Audiophonics France at the following price:
UcD180HG HxR module at 115.96 EUR, 4-pin Hypex signal cable at 8.97 EUR, shipping 13.71 EUR, total price 138.64 EUR incl. tax.

Hypex UcD180HG HxR description and analysis

Block diagram of the UcD180HG is shown in Fig.1 (from [1])

UcD_blockdiag_Fig1.png

Fig.1. UcD 180HG block diagram

We can try to make a circuit analysis in MicroCap circuit simulator, starting with a circuit diagram as shown in Fig.2 which is based on information published in paper [2]
UcDsim_schematics_Fig2.png

Fig.2. MicroCap UcD simulation

It is a self-oscillating circuit with phase-shift control using the reconstruction filter L1,C1 and phase lead network R3,C2. The frequency of the self oscillations would be at the point where loop gain phase shift is 180°, see plots in Fig.3.

UcDsim_selfoscill_Fig3.png

Fig.3. Simulation of UcD oscillating frequency by loop gain analysis

The feedback is taken from the load, behind the output LC filter. This results, in simulation, in low output impedance and frequency response almost independent of load impedance. The manufacturer states in [1]:
  • Flat, fully load-independent frequency response
  • Low output impedance
  • Very low, frequency-independent THD
  • Very low noise
  • Fully passive loop control
and
  • Runs on unregulated +/- rail
  • Pop-free start and stop control
  • Differential audio input
  • No compromise components
  • LM4562 buffer OpAmp
  • HxR12 ready
  • Improved on-board buffer supply
  • Overcurrent and overvoltage protection
  • Weight: 90gms (3.1oz.)
HxR stands for high-performance voltage regulators developed by Hypex. They are based on transconductance amplifiers and have very low noise and very good ripple rejection, far much better compared to usual voltage regulator ICs. This should contribute to excellent CMR and power supply ripple rejection of UcD180HG HxR module.

Parameters as declared by the manufacturer

UcD_parameters_manufacturer.png

Now it will be my goal to measure what I get from the module in my amplifier setup.

Amplifier setup

The amplifier was built in one of my prototype cases (Fig.4).
casework_Fig4.JPG

Fig.4. Test case for the UcD180HG module

It has side heatsinks and pre-drilled holes for speaker binding posts, XLR input connector and 230Vac input plug with switch and fuse. Case dimensions are 376 x 216 x 70 mm. Wiring can be seen in Fig.5.
case_top_UCD_wires_Fig5.png

Fig.5. Wiring diagram of the amplifier

Transformer Tr is 230V~/2x32V~/100VA and it will, unfortunately, restrict the maximum power of the amplifier. DRC is a bridge diode rectifier with capacitor bank 2 x 11500uF. 230Vac input plug is 3-pin with PE pin connected directly to the metal case. XLR input connector has pin 1 connected via 47nF/1kV foil capacitor connected to the metal case. I know it would be optimal if it was directly connected to the case, however only if all audio components in the chain were properly built this way. This is unfortunately not the case and the DACs and soundcards used have pin 1 connected to PCB analog ground and in case of 2 class I components interconnected the balancing ground current flows between 2 different PE plug pins and in my case it makes as much as 30mA between 2 rooms. Then, CMR of the audio components plays a considerable game. As the amp has only one signal connector, no further PCB ground current is created except for that through the transformer stray capacitance and this current is low enough to create any issues. The photo below (Fig.6) shows the real amplifier layout and wiring. The detailed photo of the UcD module is in Fig.7.

P1040564s_Fig6.JPG

Fig.6. The amplifier assembled

P1040553s_Fig7.JPG

Fig.7. UcD180HG module

Measurements

Switching frequency


was measured as 422kHz with 372mV amplitude, see Fig.8

P1040570s_Fig8.JPG

Fig.8. Switching frequency output residuals

Frequency response (Fig.9)

UcD180HG_freqresp_4R_8R_Fig9.png

Fig.9. Frequency response into 4ohm and 8ohm

Frequency response was measured from 20Hz to 40kHz and is almost independent of load impedance, as stated correctly by the manufacturer. And there is no peaking.

THD and THD+N

Distortion plots vs. power are shown below, measured at 20Hz, 1kHz and 6kHz. Please note they are almost independent of signal frequency. Maximum power is limited by the 100VA transformer in the linear power supply. The amplifier gave 130W/4ohm/1kHz with THD+N = 1%.

UcD180HG_thdampl_20Hz_4R_Fig10.png

Fig.10. THD and THD+N at 20Hz

UcD180HG_thdampl_1k_4R_Fig11.png

Fig.11. THD and THD+N at 1kHz

UcD180HG_thdampl_6k_4R_Fig12.png

Fig.12. THD and THD+N at 6kHz

SINAD at 5W

SINAD at 5W/4ohm is 76dB and at 5W/8ohm 82dB.

UcD180HG_1k_5W_4R_Fig12.png

Fig.13. 5W/4ohm

UcD180HG_1k_5W_8R_Fig13.png

Fig.14. 5W/8ohm

@Matias you can use the values for your SINAD chart.

CCIF intermodulation distortion 19+20kHz
was measured 0.024% at 20W/4ohm

UcD180HG_CCIF_19+20kHz_4R_Fig14.png

Fig.15. CCIF IMD 19+20kHz

Thermal management

In a long term continuous sine test 45W/4ohm the side heatsink remained almost cold to touch and the module heatsink was mildly warm to touch. No thermal issues with the case and heatsink used.

Conclusion

Hypex UcD180HG HxR module is an older class D circuit solution which cannot compete in distortion parameters with Ncore or Purifi, however it has several very interesting features. It is a simple circuit, price is about 1/3 of NC400, it has frequency response independent of load impedance and nonlinearity almost independent of frequency. These are features I appreciate much and I have to say I like this module.

Literature:
[1] Hypex UcD180HG_datasheet_R5

[2] Putzeys, B.: Simple self-oscillating class D amplifier with full output filter control. AES 118th convention, 2005
 

Matias

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Nice, thanks for all the detailed measurements and walkthrough.

Power at 1% THD+N 4 ohms 1kHz is what, about 130W?
 
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pma

pma

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Nice, thanks for all the detailed measurements and walkthrough.

Power at 1% THD+N 4 ohms 1kHz is what, about 130W?

Yes, 130W/4ohm/1% with my 100VA transformer, however it looks quite similar like in the Hypex datasheet

1636138235118.png


Edit: please find my measurement below as a comparison
UcD180HG_thdampl_1k_4R_1%.png
 
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pma

pma

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pma

pma

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Most components are placed from the bottom side of the module. Nice job. See LM4562.

UcD180_bottom.JPG



BTW output noise voltage measured as 72uV, 20Hz-22kHz unweighted, no filter to remove switching residuals used. When A-weighted, the noise was 37.5uV.
 

Tangband

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Pma - would you say that these Hypex modules are as good as the class A/B chip amp lm3886 ?
 
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pma

pma

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Pma - would you say that these Hypex modules are as good as the class A/B chip amp lm3886 ?

Hi, thank you for asking, though it is a difficult question. In a simplest datasheet circuit implementation of LM3886, I am not sure. But Hypex designs (Bruno) are at the top so let's take @tomchr LM3886 implementation, Modulus-86
Regarding price, Modulus-86 is sold as a bare PCB at $79. I am not sure if there is an assembled module for sale, maybe Tom would reply, with price.

Modulus-86
Pros: much lower distortion
Cons: lower power, 1/3 - 1/2 of UcD180. Price?

UcD180HG HxR
Pros: higher power quite considerably, 2x - 3x
Cons: considerably higher distortion

So it depends what you are seeking for.
I have never measured Modulus-86, but I expect it is also load invariant as is UcD180HG HxR.

FYI, I measured the LM3886 in a "datasheet circuit" 12 years ago with the result as follows:
1636191519734.png
 
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pma

pma

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Modulus-286 (125W/4R) assembled module is $360, and Modulus-186 (65W/4R) is $290.
Thank you Klaus.

Modulus-286 measured by @amirm, 95W/4ohm and then shutdown. I would say that UcD180HG HxR is a more robust amplifier and has minimum load impedance of 1ohm.

 
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pma

pma

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I made some critical listening, mainly with classical music.
To name one, Beethoven violin concerto in D major, Anne-Sophie Mutter and New York Philharmonic directed by Kurt Masur, Deutsche Grammophon 471 633-2.

P1040575s.JPG


The CD layer is ripped to PC and played through Focusrite 2i2 Gen3 balanced output directly to UcD180HG balanced input. The sound file converted to mono and played through one Quadral Ascent 90, 3-way floor standing speaker:

ascent90-2.JPG


The result is very positive. The sound is very good, with excellent bass control, balanced tonality, very good resolution of instruments, no sound melting, no coloration. More than enough power to play very loud and the amplifier remains, of course, cold under any conditions as also verified in the post #1.

I am very satisfied and I plan a level matched test with my A250W class AB amplifier.
 

voodooless

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I’ve been running a UCD400 for quite a few years now. Never felt a reason to “upgrade”. It’s a non HxR version, but it has been modified with external voltage regulators as well as one for the bias. Does it perform better? I have no idea, but it does look cool :cool:.
1636280496571.jpeg
 
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pma

pma

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I’ve been running a UCD400 for quite a few years now. Never felt a reason to “upgrade”. It’s a non HxR version, but it has been modified with external voltage regulators as well as one for the bias. Does it perform better? I have no idea, but it does look cool :cool:.
View attachment 163803
Looks good. Good wiring!
 

voodooless

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Looks good. Good wiring!
Little secret: it’s even pure silver :facepalm: (well, some of it). Back then I could get it really cheap, so I though: why not. It also has some protection that is not in the signal path, it saved me a few times.

The major bad thing is the toroids that occasionally hum with DC.
 
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pma

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To complete the mission, I am attaching the inevitable oscilloscope measurements:

1kHz_sq_response.png

Large signal 1kHz square response into 4ohm


10kHz_sq_response.png

Large signal 10kHz square response into 4ohm

10kHz_sine_wideband_spectrum.png

Large signal 10kHz sine wideband spectrum with carrier frequency modulation

carrier_residuals_time.png

Switching frequency residuals in time domain

carrier_residuals_spectrum.png

Switching frequency residuals in frequency domain


UcD180_step.JPG

Step response (added 12/1/2021)
 
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tomchr

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Modulus-286 measured by @amirm, 95W/4ohm and then shutdown.
That was because of the power supply used in that specific build. The Modulus-286 provides 125 W into 4 Ω if the power supply can provide enough current.

Also note that Hypex uses the 1% THD point in their spec of the output power. I use the last point before that nearly vertical part of the graph.

Tom
 

Attachments

  • Modulus-286 R2.0_ THD+N vs Output Power (1 kHz, 4 ohm, 20 kHz BW).PNG
    Modulus-286 R2.0_ THD+N vs Output Power (1 kHz, 4 ohm, 20 kHz BW).PNG
    47.1 KB · Views: 42

tomchr

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Most components are placed from the bottom side of the module. Nice job. See LM4562.
Neat. Also note that one solder joint that hasn't flowed correctly. Some components are frighteningly close to the mounting screws.

Tom

UcD180_bottom.png
 

tomchr

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Just to be clear: If you want a Class D amp, I'll recommend Hypex or Purifi any day of the week. But they are cost-optimized devices.

Tom
 
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