I have decided to proceed with the UFO transformers for the Zen Triode Amplifiers.
As of today, they are now an option in the shopping cart for the model SE84CKC and SE84CKCS. We have after almost 20 years, stopped production on the original transformers, so once our inventory runs out - these amplifiers will only be available with the UFO transformers and the price of the amps will increase by around $200. Once the original inventory is depleted and UFO's become standard, there will no longer be an option for different transformers in the shopping cart.
What is a UFO transformer?
UFO stands for
Ultra Fidelity Output which is simply a wider bandwidth and better sounding transformer with even flatter frequency response. They are the same physical size as the originals except that the winding now completely fills the core window. You can see the two in the picture below. Top one with the blue bobbin is the original, bottom one is the UFO.
These transformers feature a lamination that is half as thick as the original so there are twice as many to create a core that is more efficient with less saturation. In addition, the copper windings feature considerably more paper interleaving and more precision in how their made. These two things are what make possible 3 times the bandwidth of the original Zen Triode transformers. Also improved were the lead wires. We doubled the thickness of the wire, changed from copper to silver, and use a Teflon insulator and now run the leads from the bottom rather than the top of the bobbin.
We will be offering the UFO mod to existing Zen Triode Amps built back to 001 in 1996. Cost of the upgrade will be $300 parts and labor and take between a week and ten days on average.
UFO transformers are hand made in the USA with USA wire, USA steel and USA labor.
Operationally the 2 watt UFO transformer used in the Zen Triode Model SE84CKC and SE84CKCS will replace the two prior models. In the past, the stock transformer was a 9800 ohm primary against a 6 ohm secondary. This makes the amp capable of driving speaker loads below 1 ohm, which very few if any other SET amps can do. An optional transformer was offered with a 3300 ohm primary against a 6 ohm secondary to better accommodate speakers above 8 ohms. You could have your amp built with one or the other.
The new UFO transformers achieve both ratios by having a 6600 ohm primary against a dual 4 and 8 ohm secondary.. the trick being to hook 8 ohm speakers to the 4 ohm tap and 4 ohm speakers to the 8 ohm tap and let the reflected impedance change the primary impedance to nearly match original specs.
The beauty of this is that we now have a switch to go between the two secondaries so now you no longer need to worry or care what impedance your speakers are, you simply move the switch to the better sounding setting. The advantage of this is that both settings will usually sound good, the difference will be power. For many who don't need every drop of power the amp can muster, this switch will be like having two different sounding amps. In fact, when used with the front located bias switch that adjusts the voicing of the input tube, you can effectively say you have a choice of four different amplifiers at your fingertips.
ZEN TIP:
High Impedance primaries in output transformers can have better transparency in the top end when compared to a lower primary impedance. What I doubt many people realize is that creating a primary with a higher impedance than optimal for a given tube and then creating a secondary tap that is lower than optimal for a given speaker makes the reflected impedance adjust the primary to the ideal value for the tube and the gains in top end transparency are not lost. ;) UFO transformer design for the SE34I.4 is almost complete... We will increasing the size of the transformer over the original for this amp as well as making some other changes to the circuit.
Steve
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DECWARE UFO MOD (Read 116363 times)
