After having used old tube scopes for over 20 years, I finally bit the bullet and bought something from this century, heck, this millenium. Now I can finaly do some decent measurements again. I found a Rigol DS1054Z at a good price that had a sale to include all the extra software options (might never use any but it's freeeeeeee). It's a four channel 50MHz scope than can be hacked to 100MHz; gotta love software options.
Put the eTracer to good use and found a good operating point to aim for in the output stage. See the info here on the project page.
After playing with the eTracer for a while, I realized I had not done the most relevant tube yet. Shame!! Here it is: Click here
So many exciting ideas to try out as an alternative to the 5842 driver in my 1626 amps. Besides all the high-gm little triodes I have, the pentode fettish has peaked my curiosity. Sometime last decade I bought some pentodes already, which makes me think I wanted to try some even back then but never got around to it. So a good opertunity to make good on that. Some candidates will include Mullard E180F, WE 404A/5847, Siemens D3a, Amperex 6688, Philips E810F and the russian 6E5P, 6E6P-DR(U), 6J9P, 6J11P, 6J49P-DRU.
Ordered the output transformers for the 26 Usagi preamp. I'll be trying out my first set of Lundahl transformers in the form of the LL2763A which has 4+4:1+1+1+1 taps for 8:1, 4:1 or 2:1 ratios. I was thinking of a 2:1 primarily, but couldn't really make up my mind. Now I can have it both ways :) The rated 7mA and 280H is perfect for the 26.
Along with the 26 stepdown I also scored some Amplimo 18V/4A transformers that were on sale for €12 each. These will go into the filament supplies for the Usagi and Yojimbo amps.
5am, can't sleep... let's draw up the concept of the Usagi-Yojimbo.
Yojimbo turned out to be a no-R no-C amp in the concept (in the signal part at least). Initially I wanted a 2:1 stepdown, if any, in the 26 preamp as it seemed like such a waste. I remember I had a set of Tribute amorphous 1:4 step-up transformers, so I could actually get back the gain of the 26 preamp which now sports a 4:1 stepdown in the output. Best of both worlds?
The supply PCBs arrived yesterday and I started soldering the parts on. Two of these will go towards the Prologue 2.0 build for the 12V and 6V heaters, the other two are for future use. I have some toroid transformers laying around that will be used for these supplies. The PCBs are $3.50 each on ebay, better than any breadboard I would cook up.