The Blog |
It was
some time I last updated my blog. I have been busy
designing a new EL34 amplifier to replace my old 1989 design. It’s ready and under listening tests and I have to say it’s
a success. I did the design using Microsim PSPICE
evaluation package, rev 6.3 I found somewhere. Everything could be simulated
with a reasonably high accuracy including the phase compensation network.
What is difficult to do in SPICE is simulation of max power and clipping due
to limitations in the tube models. I have
had a lot of inspiration from people on the Swedish forum hififorum.nu
during the design. Thanks, Hans et al. A project
page is coming up during the day. My SE
amplifier is on hold for the moment but I did have an email exchange with
Brian Sowter about the transformers and it is
possible to wind an 8.5k/8 iron with 20W @ 25Hz and 90mA using standard
parts. Today I
bought me a new turntable. I thought it was a shame to just let the old vinyl
sit there not played. It’s a Pro-ject 1 Xpression and came with an Audio Technica
AT-95 installed. A cartridge which has been in production for over 25 years.
Not too expensive and in my opinion lot of value for the money. This
called for some update of my RIAA amplifier. I have updated the tube audio
page with the new version. Right now
I’m investigating what tools are available for SPICE simulation of tube
circuits. I have seen OrCad and their Pspice but the evaluation package seems to be rather
limited. There are other ways it seems. Winspice
using Berkeley SPICE 3f4 is free and unlimited but has no schematic capture.
However, googling around can be fruitful. I found a
user script for EAGLE which creates a SPICE 3f4 compatible netlist from a schematic. I’ll see what I can come up
with. I also
asked Sowter if it was possible to make a P sized
transformer with 8.5 kohm primary at 90mA, it was
possible but had to be limited to 20W at 25Hz instead of 20. I have not
placed an order yet. Sometimes
I just want to rant. Today I browsed a homepage of a guy selling tube
amplifiers either fully assembled or in kit form. I read through the site and
the so called “technical pages”. The guy knows nothing. His amplifiers are
rips of other designs, anyone can do this. What scares me is that this guy
with his limited knowledge is selling tube amps to people who in their
ignorance think it’s an expert. I will
not tell who it is, I’m not that mean. Charlatan. So I
asked Sowter if it was possible to wind a
transformer with 6.5 kohm primary at 90 mA and 20W at 20 Hz. It is possible heh,
on a size P iron. 6.5 kg. Not exactly the smallest iron around. Fiddling
around with the curves somemore made me think. It
looks like 8 to 8.5 kohm would be better at 900V
90mA bias. The
embryo of an SE amplifier is slowly coming up. It will use tubes I have in my
stock, the 813. I think this tube triode connected is superior to 211 and
maybe 845. We’ll see when it’s ready, maybe it will
have the sound of 211 without grid current just like 845? With an S of 3-4 mA/V and a mu of around 8.5
it’s easier to drive than any of the 211 or 845. So I
finally got my butt off to do something about my web. Well, here it is. I
like simplicity so even if I decided to use frames it’s still simple. I’m not
into trying to win a beauty contest. There are a lot left to do in order to
shape this dinosaur up. I had
ideas with php and a database connected to this, perhaps
even a forum like phpBB. We’ll see in the future if
my lazy butt will move once more. Having a blog
seems to be the latest fashion so I created this. I have a
parallel web coming up which will be my Dr. Hyde pages where I ponder and rant
about online games. Enough
now. |