Ive breadboarded a simple Inverted Futterman OTL based on the Ciuffoli 'cheap and cheerful' design.
I noticed in the original design the neg/lower valve was apparently autobias, so Ive done the same with the top tube too....(100 ohm decoupled by 2200uF both tubes)
Its supply is only around 100V plus/minus for the O/P stage and I'm using 6C33 biassed at 175mA. so there'll be much lower power than the original.
--I dont need huge power, at a guess, Its making around 10-15W, not checked yet...
Its been run for a few days on all sorts of music and different sources. Ive made a few changes to the original design like the coupling-caps to the O/P pair are now 0.22 instead of 22uF and the grid-resistors are now 180K instead of 68K. (originals caused pumping/blocking)
A few more simple alterations, and I must say it sounds really quite good.
Any thoughts...?
I noticed in the original design the neg/lower valve was apparently autobias, so Ive done the same with the top tube too....(100 ohm decoupled by 2200uF both tubes)
Its supply is only around 100V plus/minus for the O/P stage and I'm using 6C33 biassed at 175mA. so there'll be much lower power than the original.
--I dont need huge power, at a guess, Its making around 10-15W, not checked yet...
Its been run for a few days on all sorts of music and different sources. Ive made a few changes to the original design like the coupling-caps to the O/P pair are now 0.22 instead of 22uF and the grid-resistors are now 180K instead of 68K. (originals caused pumping/blocking)
A few more simple alterations, and I must say it sounds really quite good.
Any thoughts...?