[sdiy] Tube amplifier question

[jhaible at debitel.net]

Hi Motohiko Takeda,

interesting stuff - thanks for sharing this!

I see with the 100V mains supply you're facing more problems
to get a high secondary voltage than we have in Europe (using
standard power transformers at least).

What really caught my attention is the way the heater current
is created in this circuit:
http://www.asahi-net.or.jp/~cn3h-kkc/claft/12au7srp.htm

Using a capacitor as an almost no-loss almost-ideal current
source is a brilliant idea! But I would be frightened and worried
about safety issues, with the mains voltage so close to the
cathode of the tubes. (?)

JH.



> Hi rene, Jürgen and all,
> 
> I had learned tube for this 6 month and build some headphone amps by tubes.
> 6DJ8 is not easy to get here in Japan, But 6922 can be used instead of
> 6DJ8. it has not only good  sound but also easy price. I like it.
> http://www.aleph.co.jp/~takeda/radio/tube/img/6922-schem2.gif
> is one of my experiments. You may change the power voltage for FET 5V to
> 15V or so.
> Tubes are not so expensive, IMO. Output Transformer (We need 2 of then for
> 1 amp )and Power transformer are so expensive, and the Quality of amp
> depends on the quality of OPT's.
> http://www.aleph.co.jp/~takeda/radio/tube/plan1b.html
> is my Japanese Page.
> My broken Japanese are hated by this service.
> http://babelfish.altavista.com/
> but it may help you.
> I write so many Japanese local things in this page and I think that
> it not good information for the world, but I introduce so many awesome tube
> design by Japanese amateur hobbits in this page. please check them.
> 
> I also try HeadWize's project named 'Output Transformers Tube Headphone
> Amplifier' It works, but not so good. I think that it result depends on
> impdance
> of headphone . Mine is 64 ohm. More high one may get good result I think.
> It's page is here
> http://www.aleph.co.jp/~takeda/radio/tube/muFolower.html
> 
> Mr. kikuchi designed another SRPP one.
> http://www.asahi-net.or.jp/~cn3h-kkc/claft/12au7srp.htm
> I also build it
> http://www.aleph.co.jp/~takeda/radio/tube/12AU7-muFollow/12au7-mufollow.html
> we use small transformer for Transistor as matching transformer and it get
> so good result. I recommend this methods for headphone amp.
> 
> Simple Single ended by 12A6 and 12SL7GT with hi-quarity OPT is also my
> recommendation. Now I write page about this now.
> 
> cheers!
> Motohiko Takeda
> Tokyo Japan
> 
> 
> 
> 
> 




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