Thought on OTL tube amps

The ZERO will not kill dynamics. The ZERO is a problem solver, used when someone wants to drive a speaker that is lower impedance, perhaps too low for the OTL to do on its own. All you have to do if you don't want to use the ZEROs is get a speaker of higher impedance (8 ohms minimum usually works with our stuff) or get a bigger OTL.

The ZEROs usually get used with our smaller OTLs, an example being our M-60s used with Magnaplanar 3.7s or the like. The result of using the ZEROs is that the output power of the amp is doubled (from 40 watts to 80 watts), the distortion is reduced and the tubes run cooler as the power they are making is dissipated in the load rather than in the output section. MA-1 amplifiers drive the Magnaplanars just fine without the ZEROs.

The ZERO would not be possible if the amp did not already have a lower output impedance and did not make any DC voltage at its output. The result is that the ZERO then has actually greater bandwidth than the amps- going from 2Hz to 2MHz. So it does not limit bandwidth of the amp. The resulting combination is impressive- a tube power amp with full power from 2Hz to about 100KHz or so, which can drive 2 ohms or more. You can't do that with a regular tube amp!

The output can not be equal to input always,How do you categorize amplifier with an output transformer?OTL?Are we going in circle?or we might just go back to SE or PP.The mean reason why  these amp were design is that they will work without OPT.

Al,That's their selling point plus the exotic wooden case, which has nothing to do with sound or else  zero will not be in bizznes,I already ask him,the autotransformer maker  about if it kills dymanics and  he said decide it yourself.Auto transformer works two ways either step up which makes the sound louder or step down which make the sound lower.

How do you categorize amplifier with an output transformer?OTL?Are we going in circle?or we might just go back to SE or PP.The mean reason why these amp were design is that they will work without OPT.

Again, what we found after getting into the business is that some people wanted to use our amps with really low impedance speakers. The combination was non-functional. Like many tube amps, OTLs don't like low impedance loads. So what to do? If the customer really wants to use the OTL with that kind of speaker then you make it possible by using a set of ZEROs.

In some cases its just the woofer section that might have the low impedance. In such cases you can install the ZEROs so the amp is driving the mids and highs directly while using the ZEROs to deal with the lower impedance of the woofer array.

The ZERO is intended as a problem solver plain and simple.

Paralleling a choke/inductor/coil in the amps 4 ohms output will  be  less than 4 ohms and same thing to a voice coil of 4 ohms will  be  less than 4 ohms due to ohms law,then sound will be louder due to less resistance and more current.The only way to increase the impedance of the speaker is to put a coil/inductor   in series with the voice coil,which of course it kills dynamics.