Steve... another arcane tube question

Discussion in 'Audio Hardware' started by Drew, Feb 4, 2002.

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  1. Drew

    Drew Senior Member Thread Starter

    Location:
    Grand Junction, CO
    Do you have a preference for either solid state or vacuum tube AC to DC rectification in tube amps? I see this debated endlessly in other forums and was hoping if you could provide some insight.
     
  2. pigmode

    pigmode Active Member

    Location:
    HNL
    While you wait for Steve's response...

    I got this off the description of the WAVAC MD-300B:

    Filaments of vacuum tubes are supplied by well-filtered DC current. In order to get clean plate current, MD-300B employs special Silicon-diode rectifiers which minimize noise.
     
  3. Sckott

    Sckott Hand Tighten Only.

    Location:
    South Plymouth, Ma
    Yeah, there are ways to get around using tube rectifiers, but I'd rather use the 5AR4's on my Dynaco, for instance. They work FOR the music rather than against it (I've tried the SDS Cap replacement for the can cap in my Dynaco, and it's wonderful...BUT) Recifiers can be cheap, but I'm a tube sentimentalist, and I've never had a problem with reciting using toobes.

    Steve uses a lot of vintage amps that weren't exactly meant for SS recting. It can be done, but it's all about creating the perfect fit for the music, and using the circuit intended is simplicity, good sir, and that's what the idea's all about.

    Ever heard "Ella And Louis Again" (MFSL or Verve) on a vintage tube amp, restored to factory? Aint nothin like it. And unless I'm challanged for spare parts, it's where I'll go to get it right ;)
     
  4. Steve Hoffman

    Steve Hoffman Your host Your Host

    Well, I say this (lights cigar and puffs).

    It all depends on the design., eh? If it's a 40 year old amp, I never mess with it. I mean, my old McIntosh MC-30's use 5U4's for AC to DC, but the MC-240 uses SS. They BOTH use 6L6GC's as power tubes, but sound nothing like each other, sonically. So be it.

    Now of course, my WAVAC MD-300B single ended amp is not tube rectified. It sounds wonderful.

    All of my VAC tube amplifiers: Triode 140 monoblocks, Triode 70/70, EL-34 Avatar and Standard 240 monoblocks are solid state rectified, because that's how Kevin Hayes designed them. So, if you are asking me if the VAC stuff would sound BETTER using tube rectification, I would have to answer, no, just different.

    I've always found that the bass gets wooley and wobbly with tube rectification. I've lived with that with my vintage gear because I ALSO feel it adds a certain tubey magic to the music that SS rectification doesn't. Is it a coloration? Sure, but it's one I like.

    But if a modern tube amp designer wants his creation to be more accurate in the bass, but still have that great tube sound, solid state rectification it is!

    Just my opinion of course.

    Oh, and I don't really smoke.

    :)
     
  5. Drew

    Drew Senior Member Thread Starter

    Location:
    Grand Junction, CO
    Steve & Sckott:

    Cool Beans! I appreciate everybody's input. And its pretty much the reaction I thought I'd get. If I owned some vintage gear, I probably wouldn't modify it. At least not in a way that couldn't be undone. But with the stuff that I'm experimenting with, its a lot easier and cheaper to do solid state rectification. Searching the archives in audioasylum its difficult to build a concensus.



    Pigmode:

    One thing I think that should be mentioned is that some (a lot actually) of purist's over in audioasylum also say that that filaments on SET amps should always be AC powered (just DC on the plate). They claim DC on the filaments reduces hum but robs the music of life and vitality.
     
  6. pigmode

    pigmode Active Member

    Location:
    HNL

    I wonder about that. The WAVAC MD-300B is clearly an excellent piece of equipment. Some of these hardcore aficionados are really amazing. I read recently of a single driver fan who was bothered by the sound of the crossover kicking in normal speakers. Luckily, my needs are a bit simpler.

    I want to try SET next year so I've been researching and following some of the discussions over at Asylum. I may have to go 300B because of the speaker options, but the prices...yikes!
     
  7. Jim Ricketts

    Jim Ricketts Active Member

    Location:
    Freedom, USA
    PM,
    Keep in mind some great SET amps do not use a 300B output tube. You mentioned Wavac - their very top models (and "entry level" models) use transmitting triodes.
     
  8. pigmode

    pigmode Active Member

    Location:
    HNL
    Re: AC/DC

    Drew, I found this at a diy site for a 300B amp:

    "Directly heated tubes with dull emitters, such as the 300B, which have a barium oxide-coated filament, when subjected to DC can produce an uneven coating of metallic barium - whereas AC heaters will produce an even coating. This uneven coating can lessen emissivity and shorten the life of the tube."
     
  9. Drew

    Drew Senior Member Thread Starter

    Location:
    Grand Junction, CO
    I saw somewhere (I think it was over in the Bottlehead forum on audioasylum) that someone actually created a circuit to increase the frequency for alternating current fron 60 hz to over 30 kHz, obviously a frequence we can't hear. Thats dedication!

    Or, assuming that DC on the filament doesn't to detrimental things to the sound, it would seem to me that if you change the polarity of your DC on that filament between every album, it would keep that coating of barium relatively even on the filament. Truly a hack for someone who wants their amp to look like Frankenstein's monster.

    I have to stick my head down between the speakers to hear the hum with speakers that are 97 db sensitive. I never hear it when the music is playing.

    You have to remember that with a flea powered SET amp that more sensitive speakers will not only make the music louder but it would make that hum louder as well. I live in an apartment and if I turned my 3.5 watt amp up 1/8th of the way, I worry that I'm p*ssing off the neighbors. Yes... its that loud.
     
  10. pigmode

    pigmode Active Member

    Location:
    HNL
    Aren't you using a Foreplay? What is the issue I've seen mentioned with its so-called hair trigger vol. control? It doesn't seem like an optimal arrangement.


    How do you like the Pi?
     
  11. Drew

    Drew Senior Member Thread Starter

    Location:
    Grand Junction, CO
    I bought the stepper attenuator mod for my foreplay, but haven't installed it yet. With a more sensitive speakers the volume control would be even more hair trigger than what it is, but its really not THAT bad, I don't think.



    I don't know what to think of the Pi Studio Two's yet. Probably because I've been listening to music on lo-fi equipment for so long. I seem to have plenty of detail. I have tons of separation between the instruments. Treble seems fine and bass seems fine (for not running a sub) but sometimes it seems like the lower midrange/upper bass is missing. Doesn't really make sense, but I spent 2 years putting 105mm projectiles downrange in the field artillery in the U.S. Army, so I'm not confident about my hearing either.

    Guess thats why I'm not a remastering engineer. ;)
     
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