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Mike
27-10-2008, 17:50
While doing a bit of trolling for DIY designs for a PreAmp I stumbled upon this site:

http://www.shine7.com/audio/12ax7_pre.htm

Now that's what I call high quality work! :)

I found the name of the site a bit spooky though. :stalks:

Mike
27-10-2008, 23:49
Oh!... I did mention that this is DIY stuff didn't I ? :)

alb
28-10-2008, 07:59
Nice site Mike.

I like the way he justifies his circuits with some calculations.

The blue board and gold pins look nice but take up a lot of space.
An awful waste of wire in my opinion.

Most of those components could hang off the tube sockets, and with some hot melt glue and anti-gravity devices, would probably stay put.

Filterlab
28-10-2008, 08:53
Very nice indeed, excellent internal finish, how high end should be built.

Marco
28-10-2008, 09:13
Nice stuff indeed - I like his design principles :)

Spooky name indeed, Mikey! I've always meant to ask and forgot what your username is/means - where did you get "Shian7" from?

Marco.

Mike
31-10-2008, 16:05
I wonder where he gets those cases from? :scratch:

I like!... :)

alb
31-10-2008, 16:26
I wonder where he gets those cases from?

If he lives in Hong Kong, then he is probably spoilt for choice when buying anything HIFI. It must be an off the shelf item because it has more pre drilled holes than he needed. Also the central ally divider looks a bit homemade.

Mike
31-10-2008, 17:28
An awful waste of wire in my opinion.

I know what you mean Al, not the shortest signal path in the world is it! :eyebrows:

Marco
04-11-2008, 17:43
Me about a 'year' ago ;):


I've always meant to ask and forgot what your username is/means - where did you get "Shian7" from?


Ahem! :eyebrows:

Marco.

Mike
04-11-2008, 21:47
I saw....

But I'm ignoring you. It's a secret! :ner:

Marco
04-11-2008, 21:50
S'ok, I'll torture it out of you at the Toyster's party :eyebrows:

Marco.

johnrtd
15-11-2008, 10:08
No one having a comment on that cathode follower? At higher output it will distort (the same with emitter followers of course).
IMHO the bandwidth is rather small and he didn't measure distortion at (very) low and high frequencies.

John

i_should_coco
15-11-2008, 19:34
No one having a comment on that cathode follower? At higher output it will distort (the same with emitter followers of course).
IMHO the bandwidth is rather small and he didn't measure distortion at (very) low and high frequencies.

John

Well, IMO a 12AX7 makes a crap cathode follower. A high-Gm Pentode is much better, I feel.

johnrtd
16-11-2008, 08:45
We use a cathode follower with the intention of having a low impedance at the output. This works fine but, having a resistor in series between cathode and ground, the current will vary with the signal. So the tube is "swaying" along its curves when a signal is fed through. Those curves are not really linear and distortion will be the result.
A good thing then is to use a constant current source instead of that resistor. That current source could be a tube or a transistor. When using a tube the Lofton-White follower comes into the picture. The latter has an output impedance <500 Ohm.
Another way to achieve a low output impedance is using a kind of SRPP or Mu-follower. That gives an output impedance of around 1 - 1,5 kOhm and very low distortion. If the interlinks are shorter then, say, 5 meters the signal will stay linear up to around 500 kHz.

John