In my last post I described the new Duelund CAST Copper & Silver Autotransformers designed by Frederik Carøe to replace the stock Tannoy autotransformer.

Tannoy autotransformer on left, Duelund CAST Silver Autotransformer on right.

The same model of Tannoy autotransformer is used in all Tannoy loudspeaker crossovers where an autotransformer is used, and like all of the parts choices in the stock Tannoy crossovers, they were chosen to a price point that would provide good performance without breaking the production pricing bank.

After completing the Duelund-WRSE external crossover project, I couldn't help but think the stock Tannoy autotransformer had become the weak link in the circuit, and a number of other members of the Tannoy tribe had come to the same conclusion. The Duelund CAST Autotransformers were the direct result of a number of Tannoy Westminster Royal SE enthusiasts petitioning Frederik for silver autotransformers, and for me they turned out to be the perfect complement to the cutting-edge quality of the Duelund CAST resistors, inductors, and capacitors used in the Duelund-WRSE Project external crossovers.

As you can see, Frederik listened to his customer petitions for silver autotransformers, and designed a premium Duelund CAST autotransformer from scratch to replace the stock Tannoy autotransformer, and he has decided to offer it in both copper and silver versions, just like he does with all of the Duelund CAST components.

I was excited by the prospect that the Duelund CAST autotransformer made possible an all Duelund CAST circuit in my Duelund-WRSE external crossovers, with every component from input to output being at the Duelund CAST level of quality, which was a really nice development.

As I shared earlier, the Duelund CAST autotransformers are completely hand-crafted in what is an even more involved process than for the Duelund inductors & resistors. Each autotransformer is wound around a core using copper or silver wire and paper, with each tap (blue, green, yellow, orange, and red) measured against the ground (black) to establish exact inductance and resistance values.

Frederik described the autotransformer's cores as a “material with very low magnetic losses, namely low hysteresis and eddy current losses, laminations lower than 50um thick, and a substantial air gap.” In other words, Frederik understandably doesn't want to divulge all the details. Once the construction of an autotransformer is complete, it is installed into a CAST enclosure: A ring of vacuum impregnated paper has been readied with a base of CAST material. The autotransformer is heated and then placed in the ring & base assembly, and CAST material is poured on top of it in five stages. Air bubbles in the CAST material are forced out by applying a very precisely controlled flame to the surface. Following this step the autotransformer is measured and checked (as it has been at every step along the way), and if everything is ok, then it is shipped it to the customer. Frederik says the total production time is typically six to eight weeks from the time you place your order.

Frederik says the Duelund CAST Autotransformers are very labor intensive and expensive to produce, as that is reflected in the price of €3200 euros ($4422.72 USD) for a pair of CAST Copper Autotransformers, and €4500 euros ($6219.45 USD) for a pair of CAST Silver Autotransformers. Frederik has tried to keep the cost of these custom autotransformers down by offering them direct so there would not be additional distributor and dealer markup, but that only helps so much, because they are an expensive custom item to produce.

Yes, they are expensive enough to make your teeth hurt (though not nearly as expensive as the CAST Silver capacitors that I wrote about earlier which are $7500 Euros each (that’s $10,289.48 USD each), and you probably wouldn't be surprised to hear that I've received several emails complaining about their high cost. I wish they were cheaper too, because that means more people would be able to enjoy their considerable charms, but they are not.

I thought about their high cost for quite a while because of the emails I got complaining about it. Is their high cost fair and reasonable? I decided to try to answer that question for myself by comparing them to other similar products. Autotransformers are transformers with multiple taps (five taps in this case, see the WRSE HF crossover digram below), and there just aren't a lot of them for audio use out there on the market, so I finally decided the closest comparison was step-up transformers (SUT) for moving coil phono cartridges, even though MC SUTs aren't as complex in their design as an autotransformer.

The basic Auditorium 23 Standard SUT I have retails for about $995 USD. The Auditorium 23 Hommage T1 & Hommage T2 SUTs both cost $4995 USD. Bob's Devices CineMag 1131 SUT sells for $1195. The Audio Note AN-S8 Silver SUT sells for $10,500 USD. The Kondo KSL SFz Silver SUT is $14,000 USD. So a pair of Duelund CAST copper autotransformers for $4423 USD, or Duelund CAST silver autotransformers for $6219 USD fits midway within the range of pricing for SUTs.

So after giving it some thought, my conclusion is that for a custom, hand-wound, hand-made, ultra-quality pair of Duelund CAST autotransformers with their 5 taps, their pricing is within the range of the market. You might not like the high price, but it is comparable to what other similar products cost.

Ok, now that I've addressed the grousing I've heard about the pricing of the Duelund CAST autotransformers, let me get to the actual purpose of this post: I've installed the Duelund CAST Silver autotransformers into the external Duelund crossovers of my Westminster Royal SEs.

Duelund CAST Silver autotransformer awaiting installation.

Here's the Duelund CAST Silver autotransformer waiting to be installed into my left Duelund external crossover.

View from the other side.

Here's the Duelund CAST Silver installed in the left Duelund external crossover of my Westminster Royal SE.

Duelund CAST Silver Autotransformer

Another view.

Duelund CAST Silver Autotransformer

Here's the Duelund CAST Silver autotransformer installed in the right channel crossover.

Duelund CAST Silver autotransformer installed in the right channel crossover.

Do the Duelund CAST Silver autotransformers sound as beautiful as they look? I've got bad news for you brothers - they do.

Top view of Duelund CAST Silver autotransformer.

The magnitude of change in performance isn't as huge and dramatic as I experienced when going from the Duelund CAST Copper 6.8 uF capacitors to the Duelund CAST Silver 6.8 uF capacitors in the C1 positions of the crossovers, but the overall sonic contribution was much the same.

Much as I said for the Duelund CAST silver capacitors, here's what I didn't hear: any traces of grain, grit, brightness, harshness, etching, or other nasties. It was readily apparent that the Tannoy Dual Concentric high-frequency drivers loved the silver autotransformers just like they did the silver capacitors. The overall voicing of the Duelund CAST Silver autotransformers were smooth, rich, natural, detailed, transparent, and incredibly musical.

I'll offer more detailed impressions in due time.

Thanks for stopping by!