Directly Heated Triode preamps, anyone own one?

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invalid
invalid Posts: 1,277
in 2 Channel Audio
Just wanted to get someone's take on the sound quality of these kind of preamps, I've never been able to get my ears on one.
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  • mhardy6647
    mhardy6647 Posts: 33,043
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    Hmm... not many DHT small signal tubes, although in the modern era there are some pretty weird tube choices being used in preamps :| Most of the classic small signal tubes (e.g., the 27, 56, and 76, progenitors to the 6J5 and thus the 6SN7) all have indirectly heated cathodes.

    http://vinylsavor.blogspot.com/2015/06/tube-of-month-27.html
    http://vinylsavor.blogspot.com/2015/08/tube-of-month-56.html
    http://vinylsavor.blogspot.com/2015/09/tube-of-month-76.html

    I've been playing with a "Berman" style (documented in Joe Roberts' legendary Sound Practices magazine) preamp built by my friend Alan -- no DHTs in it, though; it uses 76s (which are microphonic as all getout) and 6J5s (IIRC).

    50171657062_f27ae687a6_b.jpgDSC_0121 (2) by Mark Hardy, on Flickr

    One interesting exception to the "not too many DHT small signal tubes" was a bevy of odd (by modern standard) little tubes made for old-time portable battery radios. Many of them had directly heated 1.5 V (DC) filaments -- not so many of them were triodes, rhough -- but some were (e.g., the "1B5", see data from RCA RC-18, below:

    7iwygquhee4o.png

    The two diodes were for the "radio" circuit and can be essentially ignored if one wanted to use a tube like this as an AF amplifer. :)
    By and large, they're not "hifi" tubes, though.

    The direct heated 3S4 is (was) used as the active element in Doc Bottlehead's adorable little "Quickie" preamp. The 3S4 is a "power pentode" (albeit a kind of wussy one), though. ;)

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  • mhardy6647
    mhardy6647 Posts: 33,043
    edited October 2020
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    Do you have any specific preamps in mind -- and, if so, what DHTs are they using (and in what roles in the circuit)? One is most curious. :)

    Oh, the Berman-esque preamp above does use a 5R4(WGY) "potato masher" for HV rectification... that's direct heated, but of course not a triode :p

    No electrolytics at all in that bad boy, either :)


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  • invalid
    invalid Posts: 1,277
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    Bottlehead also has a 300b tube preamp kit. Coincidence has a 101D preamp called the statement that has gotten good user reviews as well as professional reviews. The 101D tube is kinda cool looking, I believe it's called a tennis ball style tube.
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  • mhardy6647
    mhardy6647 Posts: 33,043
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    The 101D is, yes, a real,and very early, DHT :)
    Not sure how easy to find those tubes as NOS in 2020 AD, though? :neutral:

    I do know of that Bottlehead preamp, now that you mention it... but I cannot see the real wisdom in using a 300B power triode (and a pretty serious, and expensive one, at that) in a preamp. I'm funny that way. OK, I am funny lotsa ways, but particularly when it comes to using 300Bs in preamps ;)

    I was pretty favorably impressed with a little "Quickie" that someone brought over here once. The 3S4s also tend to be microphonic, but overall it sounded good (especially for the price).



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  • invalid
    invalid Posts: 1,277
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    You can get current production 300b tubes for $150 a matched pair, about what I paid for my nos 6sl7 tubes.
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  • invalid
    invalid Posts: 1,277
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    I guess nobody has one of these preamps.
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  • txcoastal1
    txcoastal1 Posts: 13,132
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    I own the Melody Valve HiFi Pure Black 101 Preamplifier with the 101D Triode Tubes
    2-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
    Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
    Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
    Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC

    erat interfectorem cesar et **** dictatorem dicere a
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  • invalid
    invalid Posts: 1,277
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    txcoastal1 wrote: »
    I own the Melody Valve HiFi Pure Black 101 Preamplifier with the 101D Triode Tubes

    Those look cool, and I believe it is point to point wired if I'm not mistaken. I'm wondering how different it sounds than an octal tube preamp?
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  • invalid
    invalid Posts: 1,277
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    txcoastal1 wrote: »
    I own the Melody Valve HiFi Pure Black 101 Preamplifier with the 101D Triode Tubes

    Do you have any problem finding the 101D tubes, and are they expensive?
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  • GlennDog
    GlennDog Posts: 3,085
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    This puppy's FS and can be used as a pre . . . Lampi is VG Kit. Deep pockets may apply lol

    Uses DHT 45, 203 and 300B

    https://www.usaudiomart.com/details/649809974-lampizator-big-7-se-mk2/
    AC Regenerator PS Audio PerfectWave Power Plant 10
    Source Lumin U1 Mini into Lampi Baltic 4
    Pre Cary SLP-05
    Power Rogue M180 Dark monos
    Mains Salk HT2-TL
    Rythmik F12
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