Just for information, a lot of the noise generated in PC's is not from the SMPS, it is generated by the circuitry switching, so adding a linear supply isn't realy gonna cleans things up. High speed fast switching digital circuitry is noisy.
Look at "simultaneous switching noise" for starters.
So adding the linear supply would be like making a chocolate fire guard.
Back in the days when I was a lad, there was still linear PSUs for computers, lots of 2N3035's in parallel, the size of a small car, excess heat blah de balh de blah.
Look at "simultaneous switching noise" for starters.
So adding the linear supply would be like making a chocolate fire guard.
Back in the days when I was a lad, there was still linear PSUs for computers, lots of 2N3035's in parallel, the size of a small car, excess heat blah de balh de blah.
Nowadays pure audio pcs should not require more than 40-70W. Mine uses max 70W during startup. So it should not be an issue any more. A couple of power transistors will make the job easily. I agree that regularors on the mainboard, the CPU & RAM will produce a lot of noise. This requires separated psus for the dirty components and peripherals. As my soundcard is external (rme FF400) and will be powered separately I think that it makes a difference in sq if using a smps or regulated linear psu. I've just ordered the components of my audio pc a second time in order to be able to make a-b tests with 2 pcs - smps vs linear. There are so many different opinions on the net - so I have to rely on my own experience
Shelby, although this was some time ago, I'd be interested in the results of your experiment.
I have been trying various ways of powering a dedicated audio PC - standard ATX power supply, Pico PSU, Pico PSU powered by linear and then a full linear psu with different rail voltages for P24 and P4 connectors. The latter is definitely the best in terms of sound quality (and I'm just outputing to a DAC through USB!!).
However, I've run into problems with the switching on/off of the linear supplies and have already gone through one motherboard. I believer that I need to create a solution using relays so that power is only supplied to the MB when the case power button is pressed (as opposed to when the linear supply is turned on). I'm not entirely sure how to go about this yet!
Cheers,
Crom
I have been trying various ways of powering a dedicated audio PC - standard ATX power supply, Pico PSU, Pico PSU powered by linear and then a full linear psu with different rail voltages for P24 and P4 connectors. The latter is definitely the best in terms of sound quality (and I'm just outputing to a DAC through USB!!).
However, I've run into problems with the switching on/off of the linear supplies and have already gone through one motherboard. I believer that I need to create a solution using relays so that power is only supplied to the MB when the case power button is pressed (as opposed to when the linear supply is turned on). I'm not entirely sure how to go about this yet!
Cheers,
Crom
Hi Marce, I understand your position and you have a point. I'm sure that I could send you some scope traces showing my RAM being fed by ATX SMPS and a directly connected linear PS and that the linear would be cleaner - I've tried this. However, this argument is really beside the point of this thread (and others that degenerate into this argument). The point is that some users have decided that a linear power supply provides a distinct audible improvement. Designing and building a DIY linear PS is a lot easier (in my mind) than doing the same for a high quality SMPS so it makes sense (for those users who are interested) to use linear (even though there are heat and inefficiency issues). So, it would be great to enlist your help in solving the issues so that we can move this project onto a more practical basis, if you are willing to help, rather than getting hung up on whether we are all mad and wasting our time.
PI agree that DIYers can build a cleaner linear than an SMPS, but the trouble with linears is noise in the lower frequencies that are harder to filter out.
SMPSs that are often supplied with PC's are made cheaply, the market demands low price. I still believe from what I have seen of the noise spectrums of PCs and similar circuitry that SMPS's are best, that is using well designed SMPS's, not cheep basic PC ones though.
For PC RAM you need a fast scope these days, and even on a good day the waveform would frighten most people...
For Linear supplies to get good filtering requires BIG components, not cheap.
SMPSs that are often supplied with PC's are made cheaply, the market demands low price. I still believe from what I have seen of the noise spectrums of PCs and similar circuitry that SMPS's are best, that is using well designed SMPS's, not cheep basic PC ones though.
For PC RAM you need a fast scope these days, and even on a good day the waveform would frighten most people...
For Linear supplies to get good filtering requires BIG components, not cheap.
Hi Marce, it's an interesting idea. I've used the hypex smps's with the nc400 power amp modules and the sound they produce is great so I'm not doubting their ability to produce good sound. I'm concerned about the high frequency noise that they seem to inject into everything (both the mb and the mains) but this could of course be, as you say, to do with the budget smps's. having a said that, I've used some serious atx power supplies and they've all been pretty noisy.
So, perhaps I'm hung up on a linear because I've tried it and I know it produces good results. My first question would be...how clean can the supply from a decently constructed switched mode ps be? Second q...what's the circuit diagram look like?
So, perhaps I'm hung up on a linear because I've tried it and I know it produces good results. My first question would be...how clean can the supply from a decently constructed switched mode ps be? Second q...what's the circuit diagram look like?
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