Hello, Yojiunn,
Ackcheng is right: the supplies need a small minimul load, as with no load connected they are operating discontinuously, trying to keep the output voltage constant.
When the supplies are configured for lower voltage than nominal, as in your case (SPS80HV configured at +/-60V output), this is specially true.
We could have included this load in the board itself (and in fact it has a couple of resistors), of course, but it would be a waste of energy and dissipation as any practical load will stop that noise.
Hope to have answered your question,
Best regards,
Sergio
Ackcheng is right: the supplies need a small minimul load, as with no load connected they are operating discontinuously, trying to keep the output voltage constant.
When the supplies are configured for lower voltage than nominal, as in your case (SPS80HV configured at +/-60V output), this is specially true.
We could have included this load in the board itself (and in fact it has a couple of resistors), of course, but it would be a waste of energy and dissipation as any practical load will stop that noise.
Hope to have answered your question,
Best regards,
Sergio
SMPS vs Linear PS
I am a first time DIYer and ready to make the plunge into an amp. I appreciate everyones comments so far. I have narrowed down my choices to UcD 400ADs or Coldamps BP4078s. I am curious after reading this thread if someone could list the mods that could/should be done on the UcD 400s to get them to an appreciable level of listening. Also since Bqt and others have apparently done some direct comparisons, I would love to hear from them.
I am very interested also in which power supply would you more experienced DIYers recommend with these modules. I would like to use the SMPS from Coldamp, I just want to make sure that for an newbie like myself, I am not going to be overwhelmed just trying to get it to work. I have a solid Linear PS design that was given to me but as you all know, it takes up a lot more space. SQ is my primary goal.
I have built some DIY speakers composed of PHL 1240 midbass, and Scan Speak 9900 Revelators (Danny Richie's design). Current have a Z1 Yamaha Reciever from a couple years back which is being upgraded to either a Lexicon or Sunfire preamp for HT.
Thanks for all of your post and valuable input
Ark
I am a first time DIYer and ready to make the plunge into an amp. I appreciate everyones comments so far. I have narrowed down my choices to UcD 400ADs or Coldamps BP4078s. I am curious after reading this thread if someone could list the mods that could/should be done on the UcD 400s to get them to an appreciable level of listening. Also since Bqt and others have apparently done some direct comparisons, I would love to hear from them.
I am very interested also in which power supply would you more experienced DIYers recommend with these modules. I would like to use the SMPS from Coldamp, I just want to make sure that for an newbie like myself, I am not going to be overwhelmed just trying to get it to work. I have a solid Linear PS design that was given to me but as you all know, it takes up a lot more space. SQ is my primary goal.
I have built some DIY speakers composed of PHL 1240 midbass, and Scan Speak 9900 Revelators (Danny Richie's design). Current have a Z1 Yamaha Reciever from a couple years back which is being upgraded to either a Lexicon or Sunfire preamp for HT.
Thanks for all of your post and valuable input
Ark
Fortunately for you, the coldamp SPS80 is very easy to install, you only need to connect mains (with a switch in series), and connect the outputs to the modules. Nothing more. The module itself includes the soft start and filtering.
The BP4078 modules are also very easy to install, while still very flexible.
Of course if any help is needed you can always contact us for any question. We also suggest our customers to send us photos of their setups so we can validate the cabling and assemblying before they turn them on, and make suggestions. This way a lot of problems are avoided.
Best regards,
Sergio
The BP4078 modules are also very easy to install, while still very flexible.
Of course if any help is needed you can always contact us for any question. We also suggest our customers to send us photos of their setups so we can validate the cabling and assemblying before they turn them on, and make suggestions. This way a lot of problems are avoided.
Best regards,
Sergio
Hello,
The choke is enclosed with the supply just in case your cabling or layout is not optimal. In some cases, some customers have found that a very subtle noise was coupled, in which case we recommended to add those chokes in series.
They are often not required with BP4078 either. You can start by wiring all without them and, if you find any coloured noise (apart from the normal noise produced into the UcD400), you can easily cut the wires and insert them in series.
The choke is enclosed with the supply just in case your cabling or layout is not optimal. In some cases, some customers have found that a very subtle noise was coupled, in which case we recommended to add those chokes in series.
They are often not required with BP4078 either. You can start by wiring all without them and, if you find any coloured noise (apart from the normal noise produced into the UcD400), you can easily cut the wires and insert them in series.
In order to power 4 channels at their full power, 400W/4ohm (with BP4078, 600W/2ohm is also possible), you need two SPS80 PSUs.
In the case of BP4078, in order to maximize efficiency, you can provide separate gate-driver voltage, thus reducing the idle dissipation from 9.5W to around 6.1W per module. (at +/-60V supplies). The aux. output of the SPS80 can be used for this purpose, as described in the BP4078 application notes and SPS80 datasheet.
You can also maximize efficiency by reducing supply voltage if you don't require full power.
Best regards,
Sergio
In the case of BP4078, in order to maximize efficiency, you can provide separate gate-driver voltage, thus reducing the idle dissipation from 9.5W to around 6.1W per module. (at +/-60V supplies). The aux. output of the SPS80 can be used for this purpose, as described in the BP4078 application notes and SPS80 datasheet.
You can also maximize efficiency by reducing supply voltage if you don't require full power.
Best regards,
Sergio
Hello.
In case that your casse is bare conductive metal under the SPS80 PCB, we recommend to add a thin foil (<1mm) of isolating material such as plastic.
But please cover only the inner zone of the frame, so the frame metal is directly in contact with the chassis metal, or you will ruin thermal transfer from the frame to the chassis!
The board has a separator in its centre so it is impossible that the board touches the metal, and besides the chassis has to be connected to earth, so it's totally safe, but it is good to provide the extra isolation layer as described.
In case that your casse is bare conductive metal under the SPS80 PCB, we recommend to add a thin foil (<1mm) of isolating material such as plastic.
But please cover only the inner zone of the frame, so the frame metal is directly in contact with the chassis metal, or you will ruin thermal transfer from the frame to the chassis!
The board has a separator in its centre so it is impossible that the board touches the metal, and besides the chassis has to be connected to earth, so it's totally safe, but it is good to provide the extra isolation layer as described.
ssanmor said:
I'm late to this thread, but this caught my attention.
In a SMPS, the output capacitance is required for filtering at frequencies on the order of the switching frequency and its harmonics, which should be well above the audio range, but you don't need it as an energy reservoir at audio frequencies. With a high enough switching frequency, your feedback loop unity gain point can be high also, and so your controller can have significant gain and insignificant phase shift at audio. If so, the controller itself can respond to any power demands that vary at audio rates; you don't need the output capacitor to do that (and in fact a large cap just slows the controller down). You can get a supply that has ridiculously low effective source impedance from DC to 20KHz with quite small output caps that way.
And if you are using current-mode sensing on your switches, you can tolerate a lot of input ripple as well, and you don't need a very large primary-side reservoir either.
I'm wondering why you didn't take that approach. What am I missing...?
Hello, Garaje. Thanks for your comments.
We agree with you, and it's true that you don't need too high capacitance as long as you have a high controller gain. However, we preferred to have a compromise between loop gain and capacitance reservoir, in order to ensure stability under almost any possible load. Keep in mind that these supplies must be able to work ok in DC applications (industrial, etc), audio amplifiers of any kind (Class AB, D, valves, etc), etc.
The results we have obtained are: very very low ripple voltage (less than 1Vpp at full output), excellent load and line regulation (less than 1V difference between no-load and full-load), and a consistent ramp up voltage with no overshoot (linearly climbing in the same time with no-load and full-load.
It is true that we could have taken the low-capacitance / high gain approach, and it would have probably allowed a somewhat lower cost product, but our goal is flexibility and compatibility with any situation, that's why we chose this way. It is only a a compromise, design is full of them as you know!
We agree with you, and it's true that you don't need too high capacitance as long as you have a high controller gain. However, we preferred to have a compromise between loop gain and capacitance reservoir, in order to ensure stability under almost any possible load. Keep in mind that these supplies must be able to work ok in DC applications (industrial, etc), audio amplifiers of any kind (Class AB, D, valves, etc), etc.
The results we have obtained are: very very low ripple voltage (less than 1Vpp at full output), excellent load and line regulation (less than 1V difference between no-load and full-load), and a consistent ramp up voltage with no overshoot (linearly climbing in the same time with no-load and full-load.
It is true that we could have taken the low-capacitance / high gain approach, and it would have probably allowed a somewhat lower cost product, but our goal is flexibility and compatibility with any situation, that's why we chose this way. It is only a a compromise, design is full of them as you know!
OK I see. I was thinking you were designing the SMPS for your own amplifiers. I agree it makes good sense to go with a low-bandwidth loop if you don't know where the load poles and zeros are going to be.
And of course the high-gain approach has other headaches too. If you are asking the controller to respond to audio frequency power changes, you need to consider it as part of the signal path. High quality voltage references and op-amps may not be that hard to get (though it does open up a whole area to argue about what op-amps sound best) but if you have an isolated secondary, nice high-bandwidth low-noise linear optoisolators are.
I am looking forward to trying out your SMPS and class D amps in the near future, this is fun technology to play with...
And of course the high-gain approach has other headaches too. If you are asking the controller to respond to audio frequency power changes, you need to consider it as part of the signal path. High quality voltage references and op-amps may not be that hard to get (though it does open up a whole area to argue about what op-amps sound best) but if you have an isolated secondary, nice high-bandwidth low-noise linear optoisolators are.
I am looking forward to trying out your SMPS and class D amps in the near future, this is fun technology to play with...
ssanmor said:
Hi Sergio,
I just saw this thread... two days after I bought some large PSU caps! Could I attach these between the SPS80 and UcDs to provide more reservoir power?
The preamp will send +12V to the power amp for turn-on; could I use that to control the modules and avoid hassling with relays?
Thanks in advance,
Francois.
Yes, for sure, you can add them, provided that you don't exceed around 10000uF per rail.
About using +12V to turn on the amps, if it is ground referenced, that's ok, much cleaner than using relays. The modules will remain in "stand by", dissipating about half of normal when that signal is below 2V aprox.
Best regards
About using +12V to turn on the amps, if it is ground referenced, that's ok, much cleaner than using relays. The modules will remain in "stand by", dissipating about half of normal when that signal is below 2V aprox.
Best regards
ssanmor said:
Hmmm. So 35000 uF per rail is right out. Oh well, more items for the Trading Post. How about if I stick 0.3 ohm resistors between the supply and capacitors? It'll screw up regulation a bit, I know, but with parallel caps to reduce high frequency ESL that should also reduce residual HF noise.
I looked again at the preamp supply, and it's actually +15V. Any problems here?
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