I read an article today about how there are more cats on the web than there are dogs and I thought (angrily!) that that was a situation which needed addressing pronto. Hence the spotlight on Sam "Samwich" Oler Epstein, our dog.
Sam is a pretty handsome guy:
He loves everybody, but what he really loves is his lacrosse ball:

Being somewhat obsessive myself, I can really relate to the way Sam will chase this lacrosse ball over and over and over again. We had Sam up in the country, with twin 6-year-old boys last weekend and it was quite the battle of wills. A draw.

-j

OK, I just played my first record with this new phono preamp, but I didn't get it working the way I showed it below. The absolute voltage reference of the gas reg and the (slightly) mismatched sections of the 6N1P didn't allow enough leeway for the DC voltages to settle correctly. So I punted.


As you can see, I had to put cathode bypass electrolytics back for the 6SL7. I sure hope they break in :)

I'm not listening too closely, the air conditioner is making some noise (that's actually a GOOD thing, trust me) but so far I am not really impressed. I've got David & Igor Oistrakh on DG playing, a nifty record, and it sounds OK.

I'll keep it playing for a while and see what we get. Maybe I'll put in some film bypasses on those cathode caps, but that never seems to do much.

Any suggestions?

-j

I finished (or so I thought) a new phono stage today, but I tried to test it and it isn't working right.

In addition, two seperate room air conditioners, the coolant system in my car, and a wireless card for my laptop all malfunctioned.

I decided I'd wait until tomorrow to debug the phono stage. If I try it today I'm pretty sure what'll happen: I'll land somewhere on the spectrum between breaking it and electrocuting myself.

-j

Well, I decided not to build an Aikido phono yet. I got a different idea as a result of a conversation with Chris Boettcher, who is very happy with an Artemis Labs PH-1 phono preamp he is using.

I took a look at the Artemis Labs schematic which is available here.

The designer, John Atwood, has done a couple of things differently than I have ever done in a phono preamp and I decided to try a couple of his ideas. Specifically, I'm going to build a phono with 6N1P as the input tube, biased with a battery in series with the grid. This will be direct-coupled to an "all-in-one" RIAA network and the second stage will be a conventionally plate-loaded 6SL7 to get a bit of gain (6SL7 mu = 70.)

I've gotten this circuit partly wired up already and I should have something to listen to this week - provided I can find all the necessary parts values in my stash.

-j

According to the contributor "01A" over at Audio Asylum, this is the formula for the Zout of the Aikido circuit:

Zo=(rp/mu+1)+Rk||(rp(mu+1)Rk)

I calculated the Zout of my variant to be approximately 583 ohms, using these values:

rp=6050
Rk=325
Mu=20

This calculation will be useful in trying to design a phono preamp around this circuit, which is why I was curious.

I think I may try to do an Aikido phono, maybe using a 6N1P as the first tube.

-j

I've recently gotten back into doing a little bit with DIY audio after about a year off. I've been busy with my new career, as a HS math teacher, and simultaneously going to grad school for my Master's degree. Meanwhile there's been a backlog (just like a blog, only different) of projects building up.

Here's my To Do list:

• SE 7591 UL amp using basement parts
• rebuilding the Free Lunch amp into a clean chassis
• trying to better my 6C45π phono preamp somehow
• improving the Small Saul one-tube 13FM7 amps a bit

Let's see what I get done in the next few weeks while summer lasts!

-j

I'm starting this blog with a report on a new line stage I built according to John Broskie's "Aikido" design. I chose to use 6SN7 tubes; their gain works out to be just right in my system.

I've been listening for a day now, and the sound is excellent, and I hope it will just get better when I replace the awful coupling caps with some good ones (I used whatever parts I had on hand to build this at first.) I used this schematic:



It was very simple to build and the parts were all available at Radio Shack other than the tube sockets.

-j