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Old 13th July 2004, 11:48 PM   #1
lgreen is offline lgreen  United States
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Default Tube Input on Aleph/Zen/X?

Anyone build one of these? What do you think?

http://digilander.libero.it/essentialaudio/index.htm

Any interest in a tube input stage to the pass amps, like this (from above site)?


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Old 14th July 2004, 12:50 AM   #2
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First off using the irf9540 as an output device at 35v and 3 amps
what is this 105 watts well the device is rated at 150 W. I seem
to recall ((the one and only)) saying something in the Pass A40
article something like (( It has been my experience that designes
with a 2x saftey margin usualy blow up)) I may not have quoted that verbatum.

The spice must flow

Woody
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Old 14th July 2004, 02:23 AM   #3
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Two comments.
1) Why on earth would you want to goof up the sound with a current mirror? You only need about 20 dB gain out of the differential to equal the original MOSFET front end. That's well within the reach of any reasonable tube choice.
2) I don't think direct coupling the front end to the output is such a good idea. Use a coupling cap and bias the output independently from the differential. Amongst other things, the output is going to come up instantly on turn-on, whereas the tube will take twenty seconds plus or minus a bit. You're not going to want to let the output flop around like that while waiting for the tube to warm up. Not a pretty picture.
That said, there's certainly no reason not to use a tube front end.
With a little more work you could even have a tube output stage...
Jump on it.

Grey
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Old 14th July 2004, 09:51 AM   #4
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KK made a Zen hybrid, http://web.vip.hr/pcb-design.vip/zen-hyb.html

I'm building a pair but haven't got the time to finish them
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Old 17th July 2004, 06:35 PM   #5
Tyimo is online now Tyimo  Hungary
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Hi Iqreen!
Do not build the circuit from Generoso!!! It is not working! I have made some investigations and everybody who met with this circuit had problems and a lot of out blowed Fets...!
I tryed too :-((
The original circuit (a preamp) created by Ernő Borbély, thats is working and great.
Greets
Tyimo
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