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Output Transformerless vs Transformer Coupled Output Tube Amps

Discussion in 'Sound Science' started by ptom, Jan 17, 2014.
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  1. skhan007
    Yeah, it's a good topic and I'm assuming that all the information here is still relevant. I'm just trying to understand why some people are not fans of O TL amplifiers. I am relatively new to this topic and I'm trying to learn as much as possible.
  2. watchnerd
    You really have to narrow it down to the type.
    There are huge differences between the pros and cons between a SE-OTL, Circlotron-OTL, Futterman, etc.
    Secondly, they tend to have highish output impedances compared to SS equivalents, which limits the types of transducers they can drive well.
    Thirdly, can need copious amounts of NFB to get the output Z down to acceptable levels and some have hatred of NFB.
    Lastly, some feel they don't really sound any better than an amp with a good output transformer. 
  3. SP Wild
    Yeah, I think once we get beyond cheap and nasty output transformers, OTLs lose their advantage. Then again, OTLs seem to have a sound of its own different to OTs and people may well prefer the sound of an OTL.

    I'd be quite content with a HD650 and speedball crack, and never bother with other headphones.
  4. cupofwrathcom
    The preferred quality of tube sound probably comes from their higher output impedance and therefore lower damping factor. Full range drivers in particular benefit the most from this because of the lack of a crossover and also the drivers themselves are often heavily overdamped with monster magnets, light cones and an overall low qts. Compression drivers would also benefit, but typical box speakers not as much.

    This is a good piece on building a full range speaker designed to take advantage of tube amps. http://www.diyaudio.com/forums/diyaudio-com-articles/158899-arpeggio-loudspeaker.html

    The flabbier bass and frequency response variations from the output impedance are part of the tube sound, just not a positiive ones. There are a number of articles online saying that the harmonic distortions of tube amps really don't sound that good. Some might like them, but transformers themselves create odd order harmonics. In other words there is a lot of variation. The concensus is that all amps sound better without distortion.

    As to whether to go OTL or transformer would depend on a lot of variables and how its integrated.
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