Toroidal vs. Non-toroidal Transformers

Toroidal s are generally considered to have superior performance; at least in solid state gear. When I had some custom gear built years ago I used them. I knew more about them then than I do know so I won't try to reconstruct what I thought but I believe that the magnetic fields they create are less obtrusive and they have a superior weight to performance ratio. However, I have had some very good gear that did not use them so not having them would not disqualify a component.

Is the 'other' transformer you're alluding to an R-core? Is so, they are appropriate for low power applications like preamps, DACs and CDPs. They're about 4 times more expensive than traditional toroidals and are good for suppressing AC hash and radiate less interference, or so I'm told.

I don't think it matters much as to the type of power transformer used. I am sure there are "cheap" and "better" forms of either type, but, how would you be able to tell. Both kinds will do the job effectively.

There is a bit more of a tendency for toroidal power transformers to hum or buzz (the transformer itself vibrating and creating noise, not noise injected into the output signal) if there is crap on the powerline, but that hardly happens.

If the only obvious difference that you can see between the two, in terms of build quality, is the choice of power transformer, I would call it a tie.

I have no experience with the Denon SACD player. I've heard various Marantz players and they sounded pretty nice for the money.

I have often wondered the same thing. Sooooooooo

Toroidal transformers are more efficient than the cheaper laminated E-I types for a similar power level. Other advantages compared to E-I types, include smaller size (about half), lower weight (about half), less mechanical hum (making them superior in audio amplifiers), lower exterior magnetic field (about one tenth), low off-load losses (making them more efficient in standby circuits), single-bolt mounting, and greater choice of shapes. The main disadvantages are higher cost and limited power capacity (see "Classification" above). Because of the lack of a residual gap in the magnetic path, toroidal transformers also tend to exhibit higher inrush current, compared to laminated E-I types.

Ferrite toroidal cores are used at higher frequencies, typically between a few tens of kilohertz to hundreds of megahertz, to reduce losses, physical size, and weight of a switched-mode power supply. A drawback of toroidal transformer construction is the higher labor cost of winding. This is because it is necessary to pass the entire length of a coil winding through the core aperture each time a single turn is added to the coil. As a consequence, toroidal transformers are uncommon above ratings of a few kVA. Small distribution transformers may achieve some of the benefits of a toroidal core by splitting it and forcing it open, then inserting a bobbin containing primary and secondary windings.

Here is a cut-and-paste from an article written by Ken Stevens of CAT in 1998 (w.r.t. to AC power it should be relevant even today):
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The EI transformer’s superior handling of DC offset in the primary is certainly part of the story. Also the EI transformer handles the DC current imbalance in the secondary better as well (this caused by non-exact matching of diodes in a full-wave bridge or even more so by mismatched halves off center-tapped secondaries).

I believe, however, that the main reason for the better sound with the EI transformer is its vastly superior rejection of RF noise from the power line. Toroidal transformers have two major problems regarding noise. The first problem is the extremely low leakage inductance of even a sloppily wound toroid. I am not exaggerating to say that this leakage inductance will be more than 10 times lower in a toroidal transformer than in a simply wound EI transformer. Indeed, it may approach 100 times lower. Normally, because low LI yields wide bandwidth, one would assume that this is a good thing. Unfortunately, in the case of a power transformer, this gives the toroid an extremely wide passband for differential noise (i.e. noise which is on line but not on neutral) to get through to the equipment.

Some add-on line-filtering devices attempt to shunt this differential noise to neutral (converting it to common-mode noise) and/or "ground" (supposedly eliminating it). These devices can be somewhat effective on equipment that is extremely bad in this regard (i.e. those with toroids), but their effectiveness is limited in two major ways. First is the fact that the inductors and caps used have self resonances that make them ineffective beyond that frequency. Typically a good film cap will be limited to a megahertz or so and likewise for a similar-quality inductor -- totally ineffective for FM or CB. Of course you may use a tiny cap with a higher resonant frequency, but this will be a very small cap which will be less able to "short" the noise to the other side at any given frequency. For example, a 100pF ceramic cap may have a resonant frequency of 50 to 100 meg, but its impedance at 10 meg is about 160 ohms, not a very good "shunt" to ground at all. Bypasses don't solve this problem at all -- in fact, they make it worse because the parallel combination of two low-loss caps will have an extremely high-impedance resonance between their two low-impedance resonances, making the majority of the "in-between area" worse than if the bypass weren’t used at all.

The second major problem with using a network to shunt the noise to ground, or neutral, is that the ground wire in your wall socket is not a good ground at all for radio frequencies. The problem is that the length of wire running from your socket to ground is substantially greater than a wavelength at FM frequencies and therefore is disconnected from ground at those frequencies. Indeed, your home wiring is more of an antenna, actually picking up RF signals quite well. Of course you can't dump RF noise from line to a ground, which is just as dirty.

The next problem with toroidal transformers is their very high capacitance between primary and secondary windings. This high capacitance is due to the much larger surface area between adjacent layers of winding on a toroid versus a similarly sized EI transformer. Of course, you could put extra insulation between the primary and secondary layers of a toroid to reduce this capacitance, but the same amount of insulation would yield an even greater reduction in the capacitance of the EI transformer. All things being equal, the EI transformer wins big. Of course, this high capacitance creates a lower impedance path for common-mode noise -- noise which is the same on line and neutral (and ground also). At high frequencies, like FM, the noise is mainly common-mode because of the fact that the three conductors -- line, neutral and ground -- travel side by side through your house acting more like antennae for RF than anything else.

There are numerous advanced tricks for further reducing the two problems mentioned above, although one must be careful not to overdo it. If you went crazy with increased leakage inductance, for example, the resonance set up by the transformer and the caps after the full-wave bridge could drop too low for good regulation, resulting in boomy bass and dynamic compression.
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Personally, I've heard a few Denon CD players (used as CD players & as transports) & I seem to find them ALL to be rather "screechy" in the upper freq delivery. IMHO, of course. YMMV.

These responses are very informative. I, too, think exactly that: Denon players are a tad "screechy" in the highs. This term, "screechy," is an excellent way to describe it.

I have very sensitive ears, and I have posed this question because I already have the highly-regarded SA-15S2. I have had it for a week now. At first, I was very impressed with its performance--lush, dynamic, smooth. In the last couple of days, though, I am a bit puzzled by its sound. I cannot listen for more than 45 minutes or so, and I am trying to figure out why. It is bothering my ears some, and I am wondering if there is some type of problem in the highs. I am now taking a break from listening to it, as I am trying to rest my ears.

Also, the drawer opened once unexpectedly. I am 99% certain I did not hit the remote (or other button), and so I was puzzled by that, too. My previous unit, the SA8004, did not seem to bother my ears, and I do not remember the tray coming out unexpectedly.

I don't think it matters much as to the type of power transformer used. I am sure there are "cheap" and "better" forms of either type, but, how would you be able to tell. Both kinds will do the job effectively.

There is a bit more of a tendency for toroidal power transformers to hum or buzz (the transformer itself vibrating and creating noise, not noise injected into the output signal) if there is crap on the powerline, but that hardly happens.

If the only obvious difference that you can see between the two, in terms of build quality, is the choice of power transformer, I would call it a tie.

I have no experience with the Denon SACD player. I've heard various Marantz players and they sounded pretty nice for the money.

The DAC and analog output design will have much more impact on sound than will the type of transformer. You are looking at lower end processors and outputs that make use of cheaper op amps rather than discrete devices. Hence the screech. Save up for a good DAC instead. You won't regret it.

I am well aware of the ill effects of op-amp output stages. The problem is that so many players--even multi-thousand dollar units--have op-amp output stages or op-amps elsewhere in the design. Indeed, a discrete output stage will always sound better. Though, this HDAM thing in the Marantz units is pretty good. Some say its an op-amp, others say it is not. I have yet to figure out what, exactly, it is. In any case, is sounds better than whatever "OPA" three or four digit number (i.e. 627, 2132, 2134, and on and on) is offered by Burr Brown and the like.

A discrete output stage requires real design skills, and an op-amp is an inexpensive shortcut. This trend shows not the slightest sign of being reversed.

I forgot to add that I am hesitant about adding yet another component to the signal chain, i.e. a DAC. While if I spend a bunch of money, I may get one with a discrete output stage, I may then perhaps introduce other issues or problems. At minimum, I have added a whole other component--with its own an input and out section--and another length of cable.

They're are both upper mid-fi players.. If I was looking for a great one box solution I'd look for a used Meridian G08.2 should be close to your price range. Just my opinion..

Ayre condones the use toroidal's, they have some of the best sounding gear around so I won't argue the point.

Regarding the G08.2, this is an interesting comment. Even the G06.2, at $3,500 MSRP, would be out of my reach.

With regard to the sound of my SA-15S2 (and its effects), I think I have determined the nature of the problem. My ears seemed somewhat "pluggy," and so I applied a few treatments of Murine, and my ears feel much better. Not a whole lot of wax was removed, but my ears seem back to normal now. I have listened briefly, as I have been busy, and have sensed no negative effect upon my ears. I will now return to evaluating the performance of the 15S2.

Indeed, Ayre gear would seem to be of the highest caliber. Charles Hansen despises op-amps.

Picking up on Nonoise's earlier comment, yes proper implementation of R-core transformers can result in excellent sound. My previous reference dac (Vimak DS-1800mk2) used 2 R-core transformers, whilst my current cdp/pre/dac (Ayon CD-5s) uses 3 x custom Kitamura Kiden r-cores (two for the analogue section & one for the digital). Similar custom R-cores were used in the legendary Reimyo CDP-777. C-cores can sound lovely as also as used by AMR, whilst the best trannies i've heard are the UI-core transformers used by Vitus!

Thanks for sharing good information.

Advantages of the Toroidal Transformer:

Nearly Ideal Magnetic Circuit
Lower Stray Magnetic Field
Less Volume and Weight
Less Audible Hum
Higher Efficiency

Other Transformers are;

Medical Isolation Transformer
E & I Transformer
SMPS Transformer