Frequently Asked Questions
- Q: Can I use your amplifier modules and supplies for non-audio purposes?
- Q: I hooked up my UcD to an oscilloscope and I see some HF sine wave at about 400 kHz. Is this normal?
- Q: How do I connect a LED to the SMPS output?
Warranty / RMA
Cables / Connections
- Q: The UcD amplifier needs a balanced input signal. My preamp only has unbalanced RCA outputs. Do I just connect the ‘-‘ input to ground?
- Q: I would like to switch from XLR to RCA and vice versa without the need of pulling the unused cable out of the amp.
- Q: I have no preamp. My source is unbalanced and I would like to use the “RCA to XLR” cable method. Can I add a potentiometer and retain some of the benefits of this connection method?
- Q: Do UcD amplifiers work well with tube preamps?
Temperature / Implementation
- Q: I have a stereo UcD amplifier and one module gets warmer than the other. Both function properly though.
- Q: The blue heatsink on the module gets very warm and the output coil even gets warmer! I thought UcD Class D stayed cool at all times!
- Q: Do I need a heatsink to cool my UcD amplifier?
- Q: I need double the power in an 8Ohm load than a UcD amplifier can produce. Is there some way I can bridge two, for example, UcD400’s?
- Q: What is the purpose of the optional HxR regulators?
- Q: Does my UcD amplifier really sound better when upgraded with two of these?
- Q: How do I calculate the input sensitivity for my application?
- Q: Can I adjust the gain or buffer of the NCxxxMP module?
A: Our products are intended to be used for reproduction of audio. The use in any other application is not supported and at your own risk.Go up
2 Q: I hooked up my UcD to an oscilloscope and I see some HF sine wave at about 400 kHz. Is this normal?
A: Yes. The 400kHz signal you see at the output of the amplifier is the residue of the switching nature of class D amplifiers. This is completely normal and does no harm. For more information please refer to our EMI application note.Go up
A: You have a standard warranty of two years on a Hypex product (one year for OEM products). We consider ourselves to be very flexible when it comes to this subject. However, when we find extensive modifications made by yourself which prevents us from repairing the module or is even the cause of the failure itself, we may charge you for the repair or even decide not to repair the module at all.Go up
4 Q: The UcD amplifier needs a balanced input signal. My preamp only has unbalanced RCA outputs. Do I just connect the ‘-‘ input to ground?
A: Yes, but only as described here.
5 Q: I would like to switch from XLR to RCA and vice versa without the need of pulling the unused cable out of the amp.
A: That basically amounts to a source selector. Refer to this document for information of how to wire an RCA connector to the UcD module. Install a DPDT switch to connect the hot/cold inputs of the UcD module to either pins 2/3 of the XLR connector or to the signal and shell contacts of the RCA connector. Note that pin 1 of the XLR connector is not switched, but remains hardwired to chassis. The RCA shell contact also remains hardwired to the chassis. This means that when the DPDT switch is set to RCA, the cold input of the UcD module is grounded via the RCA connector. See schematic in this document.Go up
6 Q: I have no preamp. My source is unbalanced and I would like to use the “RCA to XLR” cable method. Can I add a potentiometer and retain some of the benefits of this connection method?
A: Indeed you can. There’s no good way of adding a potentiometer to a truly balanced connection, but in a “pseudo balanced” connection it is possible. You'll need to use microphone cable (shielded twisted pair). There are 2 stretches of cable. Cable 1 goes from the RCA terminals to the pot. Cable 2 goes from the pot to the UcD input.
1) Cable 1 (RCA end): shield and white wire to RCA ground. Blue wire to RCA signal.
2) Cable 1 (Potentiometer end): white to potentiometer "common". Blue to potentiometer "input". Shield of cable one is connected to shield of cable 2 AND TO NOTHING ELSE!
3) Cable 2 (Potentiometer end): white to potentiometer "common". Blue to potentiometer "output" (wiper). As said in 2) the shield connects to the shield of cable 1 and to nothing else. RESIST ANY URGE to connect the shield to the pot common. 4) Cable 2 (amplifier end): white to pin 1, blue to pin 3, shield to pin 2. So that means that the shield of cable 1 continues as the shield of cable 2, so you get a contiguous shield all the way from the RCA to the amplifier. Any circulating currents that go through the shield will never mix with the audio ground because the audio ground is kept separate (white wire) and sensed differentially by the amplifier.Go up
A: Fundamentally there is no problem of course. However, most tube preamplifiers are designed alongside tube power amplifiers which are always AC coupled. As a result, many tube preamplifiers lack precautions against turn-on/turnoff transients. Some are liable to produce the full anode voltage at their outputs during turn-on and turn-off. We find that a large proportion of repairs are due to tube preamplifiers discharging their output caps into the UcD’s input circuit. Note that most solid state amps dislike such treatment, not just UcD.Go up
8 Q: I have a stereo UcD amplifier and one module gets warmer than the other. Both function properly though.
A: Our modules are factory trimmed for best THD, not operating current. Operating current varies over a 20% range. The temperature difference is clearly noticeable but not a cause for worry.Go up
9 Q: The blue heatsink on the module gets very warm and the output coil even gets warmer! I thought UcD Class D stayed cool at all times!
A: Class D is “cool” in terms of how much power gets dissipated. If one were to heat-sink a class D amplifier like an equivalent class AB amp, they would remain utterly stone cold. The idea of course is to make the amplifiers more compact by reducing the heatsink. An idling UcD amplifier draws up to 2% of rated power. That’s 8W for a UcD400 amplifier. Whether that translates into a small or large temperature rise depends on the size of the heatsink. Please refer to the Thermal design application note for more information.Go up
A: Yes! Never operate the amplifier without a heatsink or you’ll risk overheating it. Even 90% efficient UcD700 running at full power dissipates as much as 70Watts. Simplest solution would be an all aluminium case to which the amplifier is mounted. When using a steel case a regular heatsink should be used. Make sure there is always some airflow through the case by means of venting holes. Please refer to the Thermal design application note for more information.
- Thermal Design (Application Note)
11 Q: I need double the power in an 8Ohm load than a UcD amplifier can produce. Is there some way I can bridge two, for example, UcD400’s?
A: You need to drive one of the modules 180 degrees out of phase by simply swapping the negative and positive input signal wires. Tie the loudspeaker between both positive loudspeaker outputs of the amplifiers and connect a 100n/200V capacitor across the loudspeaker terminals at the amplifiers’ side. This set-up is most applicable for 8 Ohm loads since each amplifier ‘sees’ 4 Ohms with an 8 Ohm load attached. A 4 Ohm load might trigger the current protection leaving you with not nearly as much power as you might have expected.
A: The HPR12/HNR12 are voltage regulators like the 7812/7912 IC’s. The difference is that they have a wider bandwidth, lower noise and lower output impedance. Additionally, they have kelvin-sense inputs so you can make a local regulator that doesn’t have to be physically close to the circuit being powered. Typical op-amp based circuits have a much greater sensitivity to power supply ripple and noise than the data sheet’s DC PSRR values would suggest.Go up
A: Clean supplies are part and parcel of good audio. The noise and rejection specifications of the HxR modules are unparalleled and as such make a great upgrade for any circuit using (or in need of) regulators.Go up
A: You can connect a LED with series resistor to the positive auxiliary output of the SMPS. You can use an online calculator like http://ledcalc.com/ to determine the value for the resistor.Go up
A: Input sensitivity is dependent on the desired output power, the impedance of the speaker and the gain of the amplifier. Naturally the desired output power cannot be higher than the rated maximum of the amplifier. In the example the input sensitivity for a 400W output in 4 Ohm is calculated. The gain and maximum output power is given in the datasheet. The speaker load is dependent on the user application.
A: The NCxxxMP modules are designed to be ‘quick-install' modules. The modules are intended to be applied in mass production environments. Therefore, we do not support modification of the modules. Hence, modifying the modules will result in voiding the warranty. Hypex has designed a buffer-less amplifier to be used in applications where the designer/manufacturer wants full control of buffer op-amp and gain. Please take a look at our NC500 OEM in combination with a SMPS1200A700.Go up