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Thought on OTL tube amps

Just curious....how do these sound/perform compared to tube amps with transformers? Why do you prefer one or the other? Any particular brands of OTL amps you would recommend listening to? You can see my system on my tag here...listen mostly to rock and roll with a smattering of jazz and a bit of classical once in a while. The next stop on my amplifier adventure is an OTL model, and I have no intention of trading it for either SET I currently have, as I'm very happy with both. One of the ways I enjoy experimenting with different "sound" is by switching up the amps. Just trying to solicit some opinions, of which I know there are many strong ones here at A-Gon. Thanks in advance!
afc
atmasphere's avatar
atmasphere
7,068 posts
 
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.
xonex77
42 posts
 
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.
atmasphere's avatar
atmasphere
7,068 posts
 
It not exactly clear what you are talking about, but if I read this right you are incorrect about increasing the impedance of a speaker. One way to do it is to put drivers in series rather than parallel; of course that is a design issue.

There are a good number of 16 ohm speakers made these days, on account of the fact that 16 ohms works extremely well with tubes. The speakers we use at our shop are 16 ohms. They have two woofers which are in series.
almarg's avatar
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almarg
8,673 posts
 
Ralph (Atmasphere), I think that when Xonex77 refers to "increasing the impedance of a speaker" in the second sentence of his latest post, he is referring to increasing the load impedance seen by the amplifier, for a given speaker. But more significantly, in the first sentence of that post he appears to be envisioning that a Zero, when inserted between an amp and a speaker, would act as an inductor (rather than acting as an autoformer), with much of its inductance placed in parallel with the speaker's impedance. Resulting in a lower overall impedance, as seen by the amp, than if no Zero were present. Which as you'll certainly agree is not correct.

Best regards,
-- Al
 
xonex77
42 posts
 
Most OTL design  require high high impedance speakers,flaws in the design that these amps should work without these impedance matching,but not all OTL have these inherent disadvantage,I have an OTL using KT120 or VV52/300B output tubes  that welcomes 4 or 8 ohms  and a   full-range speakers.But if I insert  the ZERO, it  kills every thing.  
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