It was some time I last updated my blog. I have been busy designing a new EL34 amplifier to replace my old 1989 design. Itís ready and under listening tests and I have to say itís 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. Itís 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 Iím 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. Iíll 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 ďtechnical pagesĒ. 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 itís an expert.
I will not tell who it is, Iím 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. Weíll see when itís 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 itís 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 itís still simple. Iím 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. Weíll 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.