Good morning everyone. Happy new year 2022.
I haven't been on the forum for quite some time.
I have built several phono preampli diy of the well-known ones and not so much. VSPS300, VSPS400, Muffsy PP3, P06 ESP, Solidphono by TNT.
My question today is if these phono pre can be powered by switching source + 15v 0 -15v.
The question arises after I have seen the Cambridge Alva Duo fed that way.
It would be a lighter source, more economical and may not introduce noise of 50 / 60hz.
Greetings to all.
I haven't been on the forum for quite some time.
I have built several phono preampli diy of the well-known ones and not so much. VSPS300, VSPS400, Muffsy PP3, P06 ESP, Solidphono by TNT.
My question today is if these phono pre can be powered by switching source + 15v 0 -15v.
The question arises after I have seen the Cambridge Alva Duo fed that way.
It would be a lighter source, more economical and may not introduce noise of 50 / 60hz.
Greetings to all.
Technology does not matter. Execution does. Yes, you can make a very very clean SMPS. For bigger loads it is economical. For the tiny loads of a phono amp, it may be cheaper to use a linear. Cascade a handful of regulators etc. The same level of quality in a small SMPS may cost more.
SMPS ARE routinely used in audio. Even high end. For example the Benchmark amp is one of the best at any price. New Topping PS5 is unbelievably clean. There are many published post supply filters for DIY. Some markets may select a linear for advertising reasons claiming some magic superiority. I don't use them because I am not competent to do so. I know linear. Not an excuse for a comercial product.
SMPS ARE routinely used in audio. Even high end. For example the Benchmark amp is one of the best at any price. New Topping PS5 is unbelievably clean. There are many published post supply filters for DIY. Some markets may select a linear for advertising reasons claiming some magic superiority. I don't use them because I am not competent to do so. I know linear. Not an excuse for a comercial product.
At low power levels like preamp supply linear regulators are simpler and cheaper from both design costs and implementation.You don't care about switching noise, emi...they are simply put cleaner in a smaller envelope, there's no need for additional inductors with linear supplies either nor very low esr capacitors so it's basically cheaper to manufacture too while efficiency don't matter for audio preamplifiers.It may count for sattelite or orbital telescope equipment where saving weight and efficiency is a must, but on Earth...100mW or 10mW is the same thing.
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Just curiosity arose after I saw the interior of the Cambridge Alva Duo, where you can see the power source that is switched.
I think the Cambridge Alva Solo has it too.
All my pre DIY phono are powered by conventional sources, but on the advice of RJM from VSPS and Solidphono from TNT, they have a 50w toroidal transformer.
According to them the difference in dynamics is noticeable.
That is why I thought that when using switching sources it is easier to reach 50 watts or more.
Greetings
I think the Cambridge Alva Solo has it too.
All my pre DIY phono are powered by conventional sources, but on the advice of RJM from VSPS and Solidphono from TNT, they have a 50w toroidal transformer.
According to them the difference in dynamics is noticeable.
That is why I thought that when using switching sources it is easier to reach 50 watts or more.
Greetings
Regular Linear supplies are WAY cleaner and at those minuscule power levels, small and light.
Why put a switching noise factory near a sensitive preamp is beyond me.
Edit:
as of:
Preamp needs are MINUSCULE (milliWatts) and to boot , 99.999% of them are Class A and driving a high impedance load so current consumption is constant, WHAT "dynamics"?
Why put a switching noise factory near a sensitive preamp is beyond me.
Edit:
as of:
Nonsense.
Preamp needs are MINUSCULE (milliWatts) and to boot , 99.999% of them are Class A and driving a high impedance load so current consumption is constant, WHAT "dynamics"?
A non solution for a non problem.
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The only preamps you get cheaper by using some sort of switchers are tube preamps where you can obtain the anode voltage through a very simple resonant inverter from the fillament supply as tube preamps ate class A so their consumption is very predictable, avoiding thus buying a dedicated transformer with both high voltage for anodes and a low fillament voltage.Yet that is debatable too if you can find a suitable r-core transformer source on ebay.
And low esr capacitors aren't long lived capacitors, switching supplies in general living a lot less than a simple linear regulator unless it's oversized which defeats a switcher purpose... Rezonant power supplies are a bit longer lived but you need real experience to build a good one.Every single LCD or LED display is nowadays supplied with a resonant supply yet their usual life is less than 3...5 years...
And low esr capacitors aren't long lived capacitors, switching supplies in general living a lot less than a simple linear regulator unless it's oversized which defeats a switcher purpose... Rezonant power supplies are a bit longer lived but you need real experience to build a good one.Every single LCD or LED display is nowadays supplied with a resonant supply yet their usual life is less than 3...5 years...
FM Fahey:
Nonsense.
Preamp needs are MINUSCULE (milliWatts) and to boot , 99.999% of them are Class A and driving a high impedance load so current consumption is constant, WHAT "dynamics"?"
I cannot refute this argument. I am simply a doctor who is fond of audio and DIY. I have no theoretical knowledge, I just look at circuits, assemble them and then enjoy them.
I have simply followed the advice of the aforementioned.
But I have seen for example the power supply of the LEHEMANN Black Cube and it adjusts to give power sources to preamps.
Nonsense.
Preamp needs are MINUSCULE (milliWatts) and to boot , 99.999% of them are Class A and driving a high impedance load so current consumption is constant, WHAT "dynamics"?"
I cannot refute this argument. I am simply a doctor who is fond of audio and DIY. I have no theoretical knowledge, I just look at circuits, assemble them and then enjoy them.
I have simply followed the advice of the aforementioned.
But I have seen for example the power supply of the LEHEMANN Black Cube and it adjusts to give power sources to preamps.
Some switchmode chips under light load change to lower frequency operation - this can be an issue for audio as even if the switcher is nominally well into the ultrasonic range in frequency, without a significant load it may drop to a lower frequency, or to a sporadic burst mode, both of which may be slap bang in the audio band and hard to filter out.
And for a phono preamp you have the issue of RFI getting into the preamp input (such as switching noise), and there's a limit to how much RF you can filter out with capacitance if the cartridge loading capacitance is a couple of 100pF, some of which is already taken up by the cable.
And for a phono preamp you have the issue of RFI getting into the preamp input (such as switching noise), and there's a limit to how much RF you can filter out with capacitance if the cartridge loading capacitance is a couple of 100pF, some of which is already taken up by the cable.
Interesting to hear that comment from RJM and Solidphono - as it complements what Mike Kontor (who made the 'Phantom Audio' phono stage 10 years ago) told me. He said he always used a much larger VA transformer for the (linear) PS powering the phono stage than what the current draw suggested - as this made the phono stage have better bass. So he used 150VA traffos!
Andy
Hi,
I understand the concern about HF switching artefacts.
This is the one area where the quality of a switcher supply obviates.
But switchers are essentially noisefree below their switching rate.
What I don't understand is why the noise and switching noise of a trafo supply shouldn't matter at all?
The artifacts of those are right in the listening range from 50/100Hz up.
Getting rid of those artifacts requires way more bulky and tendentially lower quality parts.
I'd think that dealing with artifacts well outside the listening range would be prefferable to dealing with artifacts directly interfering within the audio band.
Besides when I have a look into measurement gear, the most advanced and most sensitive analyzers built from the 80s to recent all seem to employ switcher supplys ... why?
jauu
Calvin
I understand the concern about HF switching artefacts.
This is the one area where the quality of a switcher supply obviates.
But switchers are essentially noisefree below their switching rate.
What I don't understand is why the noise and switching noise of a trafo supply shouldn't matter at all?
The artifacts of those are right in the listening range from 50/100Hz up.
Getting rid of those artifacts requires way more bulky and tendentially lower quality parts.
I'd think that dealing with artifacts well outside the listening range would be prefferable to dealing with artifacts directly interfering within the audio band.
Besides when I have a look into measurement gear, the most advanced and most sensitive analyzers built from the 80s to recent all seem to employ switcher supplys ... why?
jauu
Calvin
SMPS's used to be noisy, and got a bad name in high end audio. But that is not the case anymore today. But as the hifi scene is quiet conservative on technology it's still a tricky marketing thing to use SMPS's. Linear psu's sell easier, and can be sold at higher price.
And for low power use, and linear is cheaper to build than a good smps.
But technically there are no reasons why a smps couldn't power a phono stage. It has to be done right to avoid switching noise, but it can be done. Some, like Manley Labs even start to build tube amps with smps's, and that is way trickier due to the high voltages needed than phono stages running from 12v to 24v...
And for low power use, and linear is cheaper to build than a good smps.
But technically there are no reasons why a smps couldn't power a phono stage. It has to be done right to avoid switching noise, but it can be done. Some, like Manley Labs even start to build tube amps with smps's, and that is way trickier due to the high voltages needed than phono stages running from 12v to 24v...
Not sure where you got that piece of information from, Calvin?
I tend to experiment - ie. try things out, rather than just read about them.
What I can say is that once when I tried powering a head amp (ie. a gain stage which takes LOMC voltages and produces an MM-level output) with a 12v SMPS ... the noise from the spkrs was unacceptable. (I tried this to see whether I could use a $50 Meanwell instead of a $500 Sbooster for my head amp.
)So I had to continue to use an Sbooster to power the headamps.
Andy
Hi,
sorry to hear that you felt enforced to invest 450$ more.
Well I tested and used -and not just once- Meanwell, XPPower and Hypex ac/dc converters, XPpower, Traco, CUI and Murata dc/dc converter as well as discrete dc/dc switcher solutions (LTC8582 et al) from phono-MC stages over highlevel stages to power amps and always had very positive results.
Admittedly all switchers require at least some passive post filtering, but often this suffices already.
When used in conjunction with those modern fast regulator chips (LT304x/309x, TPS3x/7x series) the performance is certainly top notch in every aspect.
jauu
Calvin
sorry to hear that you felt enforced to invest 450$ more.
Well I tested and used -and not just once- Meanwell, XPPower and Hypex ac/dc converters, XPpower, Traco, CUI and Murata dc/dc converter as well as discrete dc/dc switcher solutions (LTC8582 et al) from phono-MC stages over highlevel stages to power amps and always had very positive results.
Admittedly all switchers require at least some passive post filtering, but often this suffices already.
When used in conjunction with those modern fast regulator chips (LT304x/309x, TPS3x/7x series) the performance is certainly top notch in every aspect.
jauu
Calvin
Wel some of the better measuring cheaper phonostages, the Cambridge Duo, has a SMPS and is basicly noisefree as tested by ASR. The precestor, the Cambridge CP2 is the one that is on my rack and is also with a SMPS and is by far the best phono stage i've ever owned and as good as the one in my old (1982) and at that time very expensive Luxman C-02 preamplifier. That C-02 is not better but costed about 4000 Deutsche Mark (2045€) in 1982, in today's value of money that would be +/- 10K€.Not sure where you got that piece of information from, Calvin?
I tend to experiment - ie. try things out, rather than just read about them.
What I can say is that once when I tried powering a head amp (ie. a gain stage which takes LOMC voltages and produces an MM-level output) with a 12v SMPS ... the noise from the spkrs was unacceptable. (I tried this to see whether I could use a $50 Meanwell instead of a $500 Sbooster for my head amp.
So I had to continue to use an Sbooster to power the headamps.
Andy
But like said, it all depends on the implementation. There are many bad SMPS's arround, and a few wel build ones. And before 2010 none of the SMPS's were fit for things like phono stages or preamplifiers in general i think, but technology moved on...
Sounds like hocus pocus to me - if the supply is stiff and handles the actual max current, you're good for bass (or DC come to that, if its a DC-coupled amp).He said he always used a much larger VA transformer for the (linear) PS powering the phono stage than what the current draw suggested - as this made the phono stage have better bass. So he used 150VA traffos!
Under-sized coupling caps (particularly if there are several in the signal path) are what usually limit the lower octave. Typical roll-off frequencies for coupling caps should be a couple of Hz or lower to prevent bass response droop adding up like this, but often people skimp with this (sometimes to avoid electrolytics). Having 3 coupling stages each with a 5Hz rolloff gives nearly a dB of droop at 20Hz, using 1Hz roll offs and its 1/30th of a dB droop at 20Hz for the three stages, and the voltage across the capacitors is 26dB down at 20Hz reducing their ability to distort the signal by that factor (allowing cheap electrolytics to be used with good performance).
Roll-offs significantly lower than 1Hz lead to annoying start-up delays and transients though.
No amount of extra PSU grunt can compensate for a mediocre frequency response of the circuit...
Agreed!
Sure, that's what the theory says! But Mike was in the position of building - and listening to - many of them. All I can assume is ... he started off using,say, a 20VA mains traffo - as that was all that was required. Then one day he used a 50VA traffo - as that was all he had on the bench ... and found he heard more bass. Then he switched to a 150VA traffo - and found he heard even more bass!
Agreed.
Andy