OTL Amplifiers

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zingo
zingo Posts: 11,258
edited August 2008 in Electronics
I just stumbled onto this idea of of OTL or output transformer-less tube amplifier. Does anyone have any experience with them? The claim is that since there is not output transformer, the signal from the output tubes is being sent straight to the speaker and that will produce a better sound quality. However, this will also give the amp less power, and thus more tubes required for the same output. For example, the single-ended, 1.5wpc amp uses 8 output tubes and the 15wpc stereo amp used 16 total tubes; and they claim low heat...

Transcendent Sound makes OTL amplifiers that look pretty interesting.

My choice off of the site would be the balanced input "The Beast" monoblock that outputs 160w at 8 Ohms that uses 16 EL509 tubes!

newBEAST.gif
Jake
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  • Face
    Face Posts: 14,340
    edited August 2008
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    I've never heard one, but would love to. I'd imagine it would have better highs.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • Systems
    Systems Posts: 14,872
    edited August 2008
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    OTL' s need lots of tubes to overcome the impedance mismatch between the output and speaker,thats usually the job of the tranformer.OTL are to some the Holy Grail as it removes a possible degradating component(all that copper in the trans).Back in the 80's Futterman made some good ones but they were very expensive.
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    Have you ever heard one GV?
    Jake
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  • RuSsMaN
    RuSsMaN Posts: 17,985
    edited August 2008
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    I like transformers between my tubes and my speakers. I've seen an OTL amp blow a resistor and dump several tubes which resulted in some very expensive, very rare Spendor drivers needing to be replaced.

    In my experience, I'd take a good singled ended amp over a OTL for sound quality. Push pull triode is still the cats meow in my book.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • Systems
    Systems Posts: 14,872
    edited August 2008
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    zingo wrote: »
    Have you ever heard one GV?
    No I haven't they are a rare beast.
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  • Systems
    Systems Posts: 14,872
    edited August 2008
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    RuSsMaN wrote: »
    I've seen an OTL amp blow a resistor and dump several tubes which resulted in some very expensive, very rare Spendor drivers needing to be replaced.
    Ouch.
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  • mhardy6647
    mhardy6647 Posts: 35,522
    edited August 2008
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    Yup, having a transformer between the output tubes (and the high B+) and your speakers is a nice buffer. No doubt that transformers offer plenty of opportunity for signal degradation, but a properly designed output transformer is a high-performance device with plenty of audio bandwidth (albeit at a cost of size, weight, and $). Lower-power tube amps are probably more cost effective in terms of their output iron requirements! :-)

    That said, the concept of an OTL is attractive; I think Transcendent's little low-power single-ended OTL would be a fine toy to try with high-efficiency speakers. The high-power OTL amps are scary...

    BTW, Transcendent (i.e., Bruce Rozenblit) has a nice preamp kit, too...
    http://www.transcendentsound.com/
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    How could this be scary?!? :D

    DSC_0017-copy.gif
    Jake
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  • Systems
    Systems Posts: 14,872
    edited August 2008
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    zingo wrote: »
    How could this be scary?!? :D
    The cost of retubing for one.:eek:
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  • mhardy6647
    mhardy6647 Posts: 35,522
    edited August 2008
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    Naw, the B+ being applied to your speakers if there's a short.
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    Are you saying that a couple hundred volts DC to your speakers is a bad thing? :p
    Jake
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  • mhardy6647
    mhardy6647 Posts: 35,522
    edited August 2008
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    maybe...
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    Bruce Rozenblit of Transcendent Sound: "In the unlikely event of a short in an output tube, a fuse blows and the fault clears. There's no damage to the tubes, the amplifier circuitry, or your speakers. Most people don't know that an arced tube often isn't fatal."
    Jake
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  • Systems
    Systems Posts: 14,872
    edited August 2008
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    And if the fuse does'nt react quick enough.:eek:
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    GV#27 wrote: »
    And if the fuse does'nt react quick enough.:eek:

    ... I'm sure my ears would.

    page.aspx?ImgID=1491
    Jake
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  • Systems
    Systems Posts: 14,872
    edited August 2008
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    Or worse have it induce the notorious brown note.:D
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    recorder_m4.jpg
    Jake
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    But seriously,
    I read a review in Stereophile about Transcendent Sound's T8 monoblock and it was raving. If a "budget" amplifier can make a Stereophile reviewer happy, I've got to get my hands on one of their products.
    Jake
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  • mhardy6647
    mhardy6647 Posts: 35,522
    edited August 2008
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    I like Bruce's iconoclastic, somewhat contrarian approach, and if I were gonna taste an OTL amp, I'd go with a Transcendent kit. That little single-ended OTL amp is wicked cute and not stupid-expensive.

    I also think his Grounded Grid preamp kit is a nice value for the $. I think I may have mentioned that already :-)

    His book Beginner's Guide to Tube Audio Design is good, too (one of a couple he's published).
    http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=500-108


    500-108L.jpg
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  • gidrah
    gidrah Posts: 3,050
    edited August 2008
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    zingo wrote: »
    Most people don't know that an arced tube often isn't fatal."[/I]

    LOL - Most, often isn't fatal, ..........explosion, etc
    Make it Funky! :)
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  • zingo
    zingo Posts: 11,258
    edited August 2008
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    gidrah wrote: »
    LOL - Most, often isn't fatal, ..........explosion, etc

    broken-6n9p.jpg
    Jake
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