One SMPS500R can supply two TDA8950Th amplifier modules. the output voltage should be set to +-36V (+-34 to 38V range). if you prefer that each module to be supplied separately, should use two SMPS300R set to same voltage each. the advantage of using two power supplies instead of one, is that the channel separation is better.
Cristi,
I just received my SMPS300R; thanks for the fast shipment. Just one question: do you have a PDF or schematic for this unit yet? I ask because the mains terminals aren't labeled, and even though it looks like the positive is on the right and the ground in the center, I'd like to be certain before plugging in the unit.
Also - the unit I received has three DC output terminals (+, -, and GND) , even though I ordered single-voltage. Should I just ignore the negative terminal?
I just received my SMPS300R; thanks for the fast shipment. Just one question: do you have a PDF or schematic for this unit yet? I ask because the mains terminals aren't labeled, and even though it looks like the positive is on the right and the ground in the center, I'd like to be certain before plugging in the unit.
Also - the unit I received has three DC output terminals (+, -, and GND) , even though I ordered single-voltage. Should I just ignore the negative terminal?
I think Cristi is working on it
When you hold the psu with mains terminal in front of you, from left to right : Earth, Neutral, Live.
On single voltage version, "negative out" and "positive out" are connected together. Either one is V+. GND is 0V.
Hi Cristi,
Would it be possible to design a SMPS for running preamps (opamp circuits) and the like from? I would envisage something that could provide a clean couple of amps at 15V+ -0- 15V- and then maybe a clean couple of AUX voltages for running 5V+ and 10-12V+
Iv'e been using linear power supplies based on LM317/LM337 and then adding extra transformers and 750* regs for additional voltages. It gets a bit messy and I keep getting 50hz ground loops which I think could be avoided with a good SMPS.
What do you think, Is it worth while?
cheers,
col.
Would it be possible to design a SMPS for running preamps (opamp circuits) and the like from? I would envisage something that could provide a clean couple of amps at 15V+ -0- 15V- and then maybe a clean couple of AUX voltages for running 5V+ and 10-12V+
Iv'e been using linear power supplies based on LM317/LM337 and then adding extra transformers and 750* regs for additional voltages. It gets a bit messy and I keep getting 50hz ground loops which I think could be avoided with a good SMPS.
What do you think, Is it worth while?
cheers,
col.
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Connecting SMPS800R
Anyone see a problem in connecting the main output GND of SMPS800R to mains earth as its reference? Is that actually the correct way to connect it up?
Although the mains IEC socket's earth is connected to the board, the output ground seems to be isolated from it. I don't like the idea of using a floating GND as the main system ground (for amplifier etc.). Actually i tried it, and the results were a lot of noise/ hiss / buzzing.
Anyone see a problem in connecting the main output GND of SMPS800R to mains earth as its reference? Is that actually the correct way to connect it up?
Although the mains IEC socket's earth is connected to the board, the output ground seems to be isolated from it. I don't like the idea of using a floating GND as the main system ground (for amplifier etc.). Actually i tried it, and the results were a lot of noise/ hiss / buzzing.
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Output ground is floating on most if not all Connex SMPS.
You can reference output ground to earth via a 10R / 1W resistor. I had a terrible noise without it. The noise is completly gone with this resistor.
I just connected GND to mains earth and inserted an 8.2 ohm 5W resistor on the connection. The input shield ground and amplifier grounds are also connected to the same mains earth point, and.....the amount of noise is terrible! How can i ever get this to be silent?
I noticed when i touch the casework of the audio source preamp the noise reduces a bit.
I noticed when i touch the casework of the audio source preamp the noise reduces a bit.
For my smps800r GND connect for lowest noise I found was using alligator clip from output side mounting screw (floating not connected to any chassis) to IEC mounting screw. See photo.
Next smps800r I'm being sent from connex I'll try faraday shield and other ways to lower noise floor in addition to above grounding.
Next smps800r I'm being sent from connex I'll try faraday shield and other ways to lower noise floor in addition to above grounding.
Brubeck:
I measured the output ripple of SMPS2000R +-60V version, at 1A load, 38mV pk-pk on each rail. at no-load, the ripple is higher, about 83mV due to the fact that the power supply works in burst mode. it needs about 50mA to work in continuous mode.
Col:
SMPS800R has the aux. voltage regulated and diferential, the values can range from +-5V to +-15V. the aux. GND is isolated from main output GND to avoid any possible loops.
to design a smps specially to supply preamplifiers is not that hard as it is to convince someone that it could have better performances than a classic mains transformer plus rectifiers, filters, regulators. with a carefully designed layout, enclosed into a shielded case, properly filtered, can reach better performances.
mrvireless:
for low noise, all the power supply mounting holes must be connected together via chassis. due to the compact size of the pcb there is no physical space to route the Earth connection from one side of the board to the other without compromising the safety, and the power supply should only be used when is installed into a metal enclosure which provides conductive path for earth potential.
the GND to Earth connection can be done via one few ohms to 1K resistor, next to the output connector, and it's value should be chosen for minimum possible noise.
it is very possible that your signal source is grounded improperly, and there is the noise coming from. please read this article, it is well explained what and how. Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
also, try to keep the small signal stages away from the smps transformer, this is the highest source of noise from all the power supply, the noise decrease exponentially and at 10-15cm away is almost gone. shielding is a must if there are preamplifiers or radio receivers in close proximity. but before you do that, check again all the cables.
I measured the output ripple of SMPS2000R +-60V version, at 1A load, 38mV pk-pk on each rail. at no-load, the ripple is higher, about 83mV due to the fact that the power supply works in burst mode. it needs about 50mA to work in continuous mode.
Col:
SMPS800R has the aux. voltage regulated and diferential, the values can range from +-5V to +-15V. the aux. GND is isolated from main output GND to avoid any possible loops.
to design a smps specially to supply preamplifiers is not that hard as it is to convince someone that it could have better performances than a classic mains transformer plus rectifiers, filters, regulators. with a carefully designed layout, enclosed into a shielded case, properly filtered, can reach better performances.
mrvireless:
for low noise, all the power supply mounting holes must be connected together via chassis. due to the compact size of the pcb there is no physical space to route the Earth connection from one side of the board to the other without compromising the safety, and the power supply should only be used when is installed into a metal enclosure which provides conductive path for earth potential.
the GND to Earth connection can be done via one few ohms to 1K resistor, next to the output connector, and it's value should be chosen for minimum possible noise.
it is very possible that your signal source is grounded improperly, and there is the noise coming from. please read this article, it is well explained what and how. Earthing (Grounding) Your Hi-Fi - Tricks and Techniques
also, try to keep the small signal stages away from the smps transformer, this is the highest source of noise from all the power supply, the noise decrease exponentially and at 10-15cm away is almost gone. shielding is a must if there are preamplifiers or radio receivers in close proximity. but before you do that, check again all the cables.
For my smps800r GND connect for lowest noise I found was using alligator clip from output side mounting screw (floating not connected to any chassis) to IEC mounting screw. See photo.
I grounded all 4 mounting screws the obvious way at first. The resulting noise level was very audible through my speakers.
So I tried different configurations to lower the noise floor including some shielding. The configuration above made an audible difference and best low noise floor in my system.
I also use balanced AC power.
YMMV
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@Cristi
I've followed your advice and it still isn't right.
I connected the mounting holes together. One of them isn't connected to anything on board so i didn't bother with that one, but the other three are connected. So they are connected to mains earth via the IEC connector.
I inserted resistance between the output GND and mains earth (i didn't solder on board because i don't want to modify it). First 8.2 ohms and then added an extra 2.7 kohm. Neither made a difference.
In the photo you can see the setup. The smps is around 1 meter away from the preamp (Grace audio, not DIY....i think the grounding in that is properly done).
Ignore three of those power amp board mounted to the heatsink. I am using only one, the rest are disconnected. They are Optimos amplifiers.
I can say that with a linear psu they sound almost quiet except for a little buzzing. I wanted to get rid of that buzzing - by using this regulated smps, but in fact the noise is much worse. I really want to resolve this......
What am i doing wrong?
Is this likely to be due to the RFI from the smps?
Is it due to the amplifiers being used?...would using a commercial module help (Hypex etc?). Mine are class AB, well respected from a great designer (Randy Slone) and unmodified by me.
The noise from the speakers sounds like a speedboat, which sometimes speeds up a little and sometimes slows down a little!
I've followed your advice and it still isn't right.
I connected the mounting holes together. One of them isn't connected to anything on board so i didn't bother with that one, but the other three are connected. So they are connected to mains earth via the IEC connector.
I inserted resistance between the output GND and mains earth (i didn't solder on board because i don't want to modify it). First 8.2 ohms and then added an extra 2.7 kohm. Neither made a difference.
In the photo you can see the setup. The smps is around 1 meter away from the preamp (Grace audio, not DIY....i think the grounding in that is properly done).
Ignore three of those power amp board mounted to the heatsink. I am using only one, the rest are disconnected. They are Optimos amplifiers.
I can say that with a linear psu they sound almost quiet except for a little buzzing. I wanted to get rid of that buzzing - by using this regulated smps, but in fact the noise is much worse. I really want to resolve this......
What am i doing wrong?
Is this likely to be due to the RFI from the smps?
Is it due to the amplifiers being used?...would using a commercial module help (Hypex etc?). Mine are class AB, well respected from a great designer (Randy Slone) and unmodified by me.
The noise from the speakers sounds like a speedboat, which sometimes speeds up a little and sometimes slows down a little!
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So you have some grounding loops or shield problems in your amps, or your PSU is poorly designed. A well designed amp is dead silent when no signal in the input, only a little hiss when ears are close to the loudspeakers in the worse case. Hum or buzz can be the sign of some oscillation in the amp itself too. The purpose to replace a PSU by a SMPS is not to cure any amp defect. It is to bring a good supply for less cost and weight than a conventional transformer.
There has to be another problem over there. measure the resistance of the GND wires from the signal calbes, and the leakage current on GND to Earth. i had a similar problem some months ago, when i could not discover where the noise came from until i changed the signal cable. i used a cheap one, which had almost 5 ohms the GND wire resistance. that was enough to build-up few tens of mV under the leakage current flow tru the cable.
also, what is the amplifier idle current consumption ? is enough that the smps will work in continuous mode, not burst ? it needs about 50-60mA on each rail.
also, what is the amplifier idle current consumption ? is enough that the smps will work in continuous mode, not burst ? it needs about 50-60mA on each rail.
I had a "MyRef" LM3886 amp set up on my bench that has an on board linear supply. Running it at +-40V it was very quiet through a fairly sensitive ribbon tweeter.
I then hooked up my 41hz "Truepath" powered by an SMPS800R at +-60v to the same tweeter and to be honest I expected it to be a little more noisy but I was mistaken. It was at least as quiet, if not more so.
The inputs were both shorted and I did not have power ground connected to earth, nor any shielding of any kind for the SMPS.
About the only thing I did that would have any benefit to reducing emi was to braid the power wires to the amp module. Even that was only to keep it neat.
I've now decided to go all SMPS with my 4 way active project to keep the chassis smaller.
Cristi:
Can you tell me how to decide between the SMPS250QR, SMPS300R and A350SMPS? I want around +-40-45V and any of them would have plenty of power. It's to drive the mid and tweeter in an active setup. I'm not concerned with the price difference between them.
I then hooked up my 41hz "Truepath" powered by an SMPS800R at +-60v to the same tweeter and to be honest I expected it to be a little more noisy but I was mistaken. It was at least as quiet, if not more so.
The inputs were both shorted and I did not have power ground connected to earth, nor any shielding of any kind for the SMPS.
About the only thing I did that would have any benefit to reducing emi was to braid the power wires to the amp module. Even that was only to keep it neat.
I've now decided to go all SMPS with my 4 way active project to keep the chassis smaller.
Cristi:
Can you tell me how to decide between the SMPS250QR, SMPS300R and A350SMPS? I want around +-40-45V and any of them would have plenty of power. It's to drive the mid and tweeter in an active setup. I'm not concerned with the price difference between them.
@Cristi
I will do some tests and report back.
Actually when using my linear psu the amp is now dead silent. I disconnected the grounding wire from the signal input shield so that it is only grounded at the pre-amp side, and even the tiny (very tiny) buzzing noise i had vanished. Clearly that was a small ground loop.
However, switching to the SMPS is another story. Same amp, same wiring. Just the psu is changed and wired as advised. The noise is significant, very audible.
As i say i will do some measurements and get back.
On a side note i ordered +/- 15V aux supply and it has come with +/- 12V.
I will do some tests and report back.
Actually when using my linear psu the amp is now dead silent. I disconnected the grounding wire from the signal input shield so that it is only grounded at the pre-amp side, and even the tiny (very tiny) buzzing noise i had vanished. Clearly that was a small ground loop.
However, switching to the SMPS is another story. Same amp, same wiring. Just the psu is changed and wired as advised. The noise is significant, very audible.
As i say i will do some measurements and get back.
On a side note i ordered +/- 15V aux supply and it has come with +/- 12V.
@Cristi
OK i measured the idle current, it is about 71 mA on both rails.
With regards to resistance on the signal cable it is below 0.5 ohm ohm end to end. I have not connected it to earth at the amplifier side so there is no chance of a ground loop forming. Using a linear PSU the output in this configuration is absolutely silent except for some thermal noise if you put your ear right up to the speaker.
I don't think it is my setup because it works fine without the SMPS800R. I only change the PSU and the noise comes. Is it air borne? Is it induced on the ground wiring? I don't know. Does it sound like a faulty PSU? The sound from the speakers almost mimics the audible sound generated by the high frequency transformer. Listen to video link.
Idle current:
Aux voltage (order no. 271):
**Video Link**
OK i measured the idle current, it is about 71 mA on both rails.
With regards to resistance on the signal cable it is below 0.5 ohm ohm end to end. I have not connected it to earth at the amplifier side so there is no chance of a ground loop forming. Using a linear PSU the output in this configuration is absolutely silent except for some thermal noise if you put your ear right up to the speaker.
I don't think it is my setup because it works fine without the SMPS800R. I only change the PSU and the noise comes. Is it air borne? Is it induced on the ground wiring? I don't know. Does it sound like a faulty PSU? The sound from the speakers almost mimics the audible sound generated by the high frequency transformer. Listen to video link.
Idle current:
Aux voltage (order no. 271):
**Video Link**
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