Been foolin' around with a Tiny Blues Express for some time now. It ended up as a combo w. one 8".
See http://ampgarage.com/forum/viewtopic.php?t=3029 for Timos original documentation.
Slightly changed the layout. Two more resistors mounted on the turret board.
Since I decided to use a toroidal PT w. lower Voltages (200 V AC), I had to change some values.
I used a 100V PA transformer as OT. Primary load is 8k. Secondary outputs for 4/8/16 Ohms. Hammond has some nice OT for low power PP. Spend the extra 15 bucks for those Hammonds.
Here are the differences:
- tonestack treble capacitor 47 pF Silver Mica
- mid pot is 100k log. Gives a nice boost, when maxed. OK, treble&bass will be less effective.
- second triode 500 pF across Ra (less sizzle/buzz)
- after second triode and the coupling capacitor (2n2) there's 100k to ground. Tweak here!
- third triode has Rk=4k7 (10k original)
- 470k gridstopper before cathodyne
- cathodyne w. 56k - 1k - 56k
- 47pF (was 100pF) across cathodyne output
- output triods have 4k7 opposed to 5k6 gridstoppers
- 500 Ohm instead of 470 Ohm as Rk for the PP triodes
Power supply without sag R (original 180 Ohm)
chain: 47uF (220k/5W to ground, discharge) - 10k - 22uF - 4k7 - 22uF - 5k6 - 22uF
Voltages are: 273 270 265 254 [V]
Somehow all my builds end up as fully crammed lil boxes. Dunno why...
![Smile :)](./images/smilies/icon_smile.gif)
Lots of parts from the parts boxes. objet trouvé.
The little beast is still way too loud for bedroom level. Even w. the 8". Like its sound most w. Cel. 65 W (yep, that RF D-type speaker). ECC99 will be accepted as "power" tube.
Its very touch sensitive for an amp of this size (~1,5 W). Clean will be with lower volume. When cranked, there's a lot(!) of gain for three gain stages. For some more tweakin, I'd work on the PI and the output tubes. Maybe some capacitors here&there. Or some Zobel around the OT (like in some TW w. EL84).
Thanks for krash/joshs and UR12/danas valuable input.
Enjoy
Martin