Flagship phono preamps create their own power supply from the mains, like a mains regenerator. This is critical to a well-designed phonograph stage. Without this, you will have a hard time amplifying the signal without additional noise. This is why the phono preamp presents the "hiss" so annoyingly. Unusually, the ZEN Phono has its own high-tech clean power supply. Create a 1.2MHz power supply (20,000 x 60Hz mains frequency). In this circuit, a 10 µF filter capacitor = 200,000 µF at lower audible frequencies. With serious levels of noise filtering, it performs at the level of vintage LC filter circuits found in vintage tube amps. On its own "island" PCB, it is isolated so there is no noise pollution from the analog stage. Simply super clean ±12V DC power supply.
Apart from the much lower signal levels in a phono preamp than general line-level audio? 30 to 60dB lower, so you need care and attention to preventing line noise (or any other source of noise) getting into the input. MC preamps see signals of 500µA ballpark level, so even a few µV of breakthrough might be clearly audible - I'd suggest one wouldn't normally expect a SMPS to work silently with a phono- or mic- preamp unless carefully engineered for the purpose, whereas a linear regulator supply is likely to work out of the box.
Its not uncommon to use a buck converter into a linear regulator to get the best of both worlds in sensitive analog applications (efficiency and clean supply rails).
Hi,
Mark, the common highender hasn´t got a tight set of understanding about transformer supplies .... let alone about the more recent switching supplies.
If it were different, how come we hear countless snakeoil theories in forums and see ridicolous cap-overkill in ´UpTuning´ power supplies?
jauu
Calvin
Mark, the common highender hasn´t got a tight set of understanding about transformer supplies .... let alone about the more recent switching supplies.
If it were different, how come we hear countless snakeoil theories in forums and see ridicolous cap-overkill in ´UpTuning´ power supplies?
jauu
Calvin
You don't do it only for a phono preamp unless you want to sell a million of them...Here's 1980's equipment...typical sony resonant converter...simillar technology to the later 90's sony tv sets...
http://www.thevintageknob.org/sony-TA-AX6.htmlhttps://elektrotanya.com/sony_ta-ax6_sm.pdf/download.html
http://www.thevintageknob.org/sony-TA-AX6.htmlhttps://elektrotanya.com/sony_ta-ax6_sm.pdf/download.html
I've used linear and SMPS extensively. Both have their places.
I have two designs for powering my phono design. One uses a 12V SMPS (or linear) and a DC-DC boost converter to make 400V, the other uses a transformer. Both designs run into a linear regulator. Both designs are quiet. One design weighs 5kg and cost more than 100$ to build, the other weighs about 1kg and cost about 40$ to build.
I have two designs for powering my phono design. One uses a 12V SMPS (or linear) and a DC-DC boost converter to make 400V, the other uses a transformer. Both designs run into a linear regulator. Both designs are quiet. One design weighs 5kg and cost more than 100$ to build, the other weighs about 1kg and cost about 40$ to build.
When there are no arguments, mockery appears.
The intelligent man always has an open mind to continue learning new things.
If you look at the article it shows that the switch mode power supply is only for the power amplifier - the blurb about the preamp unit says:
Though of course the phrases "zener diodes" and "virtually noiseless" don't sit well together(!)
I'd like to find a listing of all the linear regulated wall warts that have ever been made. Ebay is full of linear wall warts but you can't tell from the label whether regulation was employed. Often no technical documentation can be found.
I do note that a dirt cheap TC-750 phono preamp is very quiet using either a linear regulated, or switching wall wart.
I do note that a dirt cheap TC-750 phono preamp is very quiet using either a linear regulated, or switching wall wart.
I measured Jan Didden's "Silent Switcher" -- and it is, indeed, silent +/-15VDC @150mA.
If you want to DIY you can use the ADI/LTC chips -- parametric table: https://www.analog.com/en/parametricsearch/11497#/
or
see how Linear Tech did it (control the slew rate) in the datasheets for LT3439 gate driver etc.
If you want to DIY you can use the ADI/LTC chips -- parametric table: https://www.analog.com/en/parametricsearch/11497#/
or
see how Linear Tech did it (control the slew rate) in the datasheets for LT3439 gate driver etc.
It may be quiet with some switching supplies, but devil is in the details, some switching supplies generate much energy in the audio band, some less so, and it can be a dramatic difference. Lower power and more modern switching supplies tend to use higher frequencies, typically reducing the problem significantly - an old ATX computer supply by comparison is probably a poor choice for the TC-750!!
As I said above "I'd suggest one wouldn't normally expect a SMPS to work silently with a phono- or mic- preamp unless carefully engineered for the purpose" - ie you have to either check this, or be lucky. The TC-750 probably has some good PSU filtering, it would have been designed with a switching supply in mind (and may well have a linear regulator internally).
In electronics being cheap doesn't preclude good engineering! Only Audiophools think high price is required for performance!
Not mockery, humour; apologies if you misunderstood. I'm all ears (oops another pun!). How the does the power supply contribute to hiss in a phono preamplifier?
If a phono preamp is good enough it doesn't need any special regulator.The best solid state phono preamp i've heard of had a 6 transistor simple regulator for both rails and the next best one enjoyed an even simpler capacitor multiplier and there's not a single engineer on Earth that can prove those simple solutions didn't do the right job as those preamps specs left unmatched for 4 decades.
If your phono preamp needs special regulators, don't touch it.The preamplifier's PSRR and CMRR themselves need to be high enough in order to give the right sound before any filtering is needed.
My old engineer's 2 pennypost are in!
If your phono preamp needs special regulators, don't touch it.The preamplifier's PSRR and CMRR themselves need to be high enough in order to give the right sound before any filtering is needed.
My old engineer's 2 pennypost are in!
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There's one here who does just that routinely (in the "Type" box, select "phono"): Audio Electronics Review and Measurements Index
If the link didn't work correctly (it does for me) or you are looking at banner advertising inserted by Google, here is the site home page: Audio Science Review
Click on 'Review Index' → 'Electronics', then in the 'Type' box select 'Phono Preamp'
Click on 'Review Index' → 'Electronics', then in the 'Type' box select 'Phono Preamp'
I don't have a 'best' phono preamplifier that was reviewed there. I do have a Vincent Pho-8, and as Amin found here is a design fault with the erthing layout. I have modified mine to correct that problem and the excess mains frequency in the output. I haven't looked at the RIAA compliance which he found lacking. Other than that I concur entirely with his comments and findings. The Pho-8 is not high end, but very good value for money and damn good in absolute terms with the above caveats.
If you start to read the reviews you will soon see that designs are far from perfect and are still evolving. (Choosing a couple of models that you have heard of might make it more relevant to yourself, or just pick some at random.) I think by implication this invalidates your claim "there's not a single engineer on Earth that can prove those simple solutions didn't do the right job as those preamps specs left unmatched for 4 decades". In the past 4 decades THD+N in SOTA electronics has dropped by a couple of orders of magnitude.
For fun you can send Amir one or all of your cherished phono preamps for testing, I am sure he'd love to do that because that's how almost every review he does starts. But be prepared to be disappointed at how vintage phono preamps compare to the best contemporary designs.
If you start to read the reviews you will soon see that designs are far from perfect and are still evolving. (Choosing a couple of models that you have heard of might make it more relevant to yourself, or just pick some at random.) I think by implication this invalidates your claim "there's not a single engineer on Earth that can prove those simple solutions didn't do the right job as those preamps specs left unmatched for 4 decades". In the past 4 decades THD+N in SOTA electronics has dropped by a couple of orders of magnitude.
For fun you can send Amir one or all of your cherished phono preamps for testing, I am sure he'd love to do that because that's how almost every review he does starts. But be prepared to be disappointed at how vintage phono preamps compare to the best contemporary designs.