[sdiy] Tube amplifier question

[jhaible at debitel.net]

> I think EL84 are a fine choice. They will give plenty of power for a home
> unit. Another output tube that you could consider is 2A3 direct heated
> triode. They are quite good and can be found fairly inexpensively. They are
> quite a bit bigger though and may take a 5U rack space to contain them.

These have already caught my attention - they seem to be quite popular with 
audiophiles. Bulbs to display, too (which I don't need).
So - what difference in sound would I expect from these, compared to, say,
EL84's that would be connected as triodes? And for that matter, *should* I 
go for triodes instead of pentodes in ultralinear configuration?

> Your headphone amp sounds OK to me. One place that has lots of different
> headphone info is headwize http://www.headwize.com/.

Thanks, I'll take a look!

JH.



> 
> Good luck,
> Thomas
> ----- Original Message ----- 
> From: <jhaible at debitel.net>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, August 04, 2004 5:26 AM
> Subject: [sdiy] Tube amplifier question
> 
> 
> > I've aquired a taste for building tubes stuff right now. (;->)
> >
> > I want to build a small amp that will replace the Studio monitor amp
> > and the HiFi amp in the basement. Right now I run both thru a cheap
> > Sony HiFi amp.
> >
> > I think of something like this:
> >
> > Small power amps with 2x EL84 push pull for the speakers (I never hear
> > music very loud over speakers, so that should be plenty)
> >
> > Separate Headphone amp with EF86 (connected as triode) and 12BH7 as
> > cathode follower with no overall negative feedback loop.
> >
> > Phono preamp (yes, for my old records) with 12AX7 and passive equalisation
> >
> > This all should fit into a 19" enclosure, 2 or 3U high. No need to display
> the
> > tubes outside (;->)
> >
> >
> > Now I have the following questions:
> >
> > (1) Is the 2x EL84 pp a good choice for a "transparent" HiFi amplifier?
> >     Is there an alternative that is only slightly more expensive (no
> vintage
> >     tubes in the 100 dollar price range), but which would give much
> >     improovement?
> >
> > (2) Is an ultralinear transformer the way to go? I have seen some "famous"
> >     amps like the Quad II use cathode feedback instead of the ultralinear
> >     configuration (other tubes, too, of course ...). What's the general
> >     pro and con of ultralinear vs. cathode feedback, or should I even use
> >     both ? (I see that the winding is easier in ultralinear, and these
> >     transformers are very common, so I'd need a good reason to do it
> >     otherwise.)
> >
> > (3) Is the headphones amp with EF86 and 12BH7 a good idea? Should I use
> >     an output transformer, or bring the output impedance down with a WCF
> >     and don't use a transformer? (My Sennheiser HD450 phones are 300 Ohm
> >     types, and I can get down to ca. 100 ... 150 Ohm with the 12BH7 in
> >     WCF configuration. Not much damping then, and I worry about the
> transients
> >     thru th ephones during power-on.
> >
> > Any ideas, hints, recommendations?
> >
> > Thanks in advance,
> >
> > JH.
> >
> >
> >
> > -------------------------------------------------
> > debitel.net Webmail
> >
> 
> 
> 
> 




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