Toroidal Transformers V HF Switch Mode Power Supplies

Knowing nothing about power supplies and transformers I was intrigued to spot this on a hifi manufacturers web site

. Separate the *****
PRE from amplifiers
using toroidal transformers.

I understand that Naim use toroidal transformers for better audio quality. So why would another manufacture recommend that there hifi is kept away from them?
The other manufacturer uses HF Switch Mode Power Supplies. If they consider these better for audio quality then it makes one wonder why Naim does not use them?
I ask these questions from a point of complete ignorance on the subject matter.

It’s probably interesting to read the explanations of other manufacturers. For example under the ’ TECHNOLOGY’ tab on Benchmark audio’s page for the AHB2, or Technics on the SU-R1000.

Seems the main advantage is a lack of ripple that needs to be rectified and that the switching freq. should be outside of the audible band.

I suspect it’s, as everything, a compromise with both having advantages and disadvantages that need to be dealt with. All depending on the implementation instead of one being inherently better.

It’s a complex issue, but Toroidal transformers are more efficient than traditional transformers (Why Naim use them) and as such they have a lower source impedance… however because they are more efficient they can more easily saturate . A saturating toroidal transformer produces noise on the mains in the form of harmonics. Some Hi-Fi equipment can be sensitive to this mains noise from these sort of linear power supplies.
Efficient transformers not saturating can produce harmonics as well, but I am not aware of these normally being problematic… although large reservoir electrolytics with very low ESR can push the linear power supply mains harmonic noise up. However toroidal transformers can act as a HF filter across transformer so they can also help impede hf noise including what they create…

As far as what is best, there are pros and cons in most technologies. Personally I think we’ll designed high frequency switch mode power supplies are what I would opt for when given the choice, albeit I realise there is more to fail over an extended period of time.


Some persons replaced the SMPS inside the Chord Dave with a big linear ps from Sean Jacobs. Apparently the uplift is staggering.

Interesting, it could be they have a high amount of mains noise, and toroidal (assuming that is what they are using) filters their mains noise… as I show above toroidal can be good at filtering noise, especially a toroidal with special circuitry.
I think in the Hi-Fi (consumer audio) world many don’t appreciate the potential noise issues and mitigation’s associated with efficient linear powersupplies… and many of these considerations don’t work in isolation. Mains noise can be very involved… and what works well in one house won’t necessarily be the same in somebody else’s… but the key thing is experiment and use what you like best.

What I do know is in my music production equipment, it all uses (I believe) quality switch mode powersupplies.
My Hi-Fi equipment is a mixture.

I guess if the Dave owners found noticeable improvements in sound when replacing the SMPS with the linear ps , the noise has dropped.
It’s not possible to observe a better sound if noise has increased.

I’m sure lots of different things contribute, including Sean’s rectifier design…

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Using switch mode power supplies in audio is like using global negative feedback: both have their pro and cons.

Like many things, and from an engineering point of view, it is the implementation that matters the most.

Using a switch-mode power supply has many advantages when well implemented, just like introducing global negative feedback in an amplifier design (the latter being a far more significant challenge to implement)

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Not necessarily true… but I know what you mean… adding noise (dither) to a digital signal can improve its rendering quality.
In fact I have been writing masters this evening, and I have added triangular dither to the PCM…

Feedback is interesting… it’s when you use stage feedback along with global feedback you can really some good performance benefits in terms of distortion, linearity and transient response. Seemingly interesting developments here in recent years in amplifier design. I find D Self’s book on the subject really interesting … well worth a read if you are interested in amplifier design and developments.

But is that purely because of it being linear, or just a better implementation?

Good question. But I have no response.
The DC4 costs 7k. But already the DC3 improved considerably, if I read some comments elsewhere.

DC4 next to Dave

One thing we can say for sure is that size was less of a constraint than for the original PSU :slight_smile:


Hi @Simon-in-Suffolk

Thank you for your responce.
It would appear that, as with other things in life, there is no straight forward answer and there are grey areas.

Hi @frenchrooster

That is an interesting outcome.


Hi @Thomas

Thank you for your answer.

That looks suspiciously like a quote from a Chord Electronics manual. I currently have two of their boxes sitting on my rack, with a Naim box (NDX2) sandwiched between them. It still seems to work pretty well, although it’s on my to-do list to try putting a bit more distance between them if I ever get round to it. When I spoke to Chord about this they said it was probably nothing to worry about in my setup. Maybe it would be different it I had a stack of big Naim PSUs.

Yep… it makes it interesting… some would really like everything to be easily categorised…

Or user has prevalent mains harmonic noise that is better filtered by filtering toroidal transformer.
Powersupply noise is a complex thing, and linear ones certainly can introduce their own issues, just like switchers can.
One thing is probably fair to say however cheap switchers are probably more noisy than cheap linear PSU. The frequency harmonics may tend to verge into higher frequencies with switch mode PSUs compared to linear PSU… however i am wary of the electromagnetic field from large transformers… i tend to large place transformers mounted well away from very sensitive electronics such as sensitive radio equipment, however one balances that with for best DC performance one typically wants to keep load as short as possible from PSU and use thick conductors.

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