Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on June 29, 2012, 06:12:12 pm
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Hi guy's,I've had the solder iron glowing over the last couple of days and need some help with the PI.Looking at the BTO as a possible next build (because i NEED another AMP :laugh:) so i thought that the BTO would fit into the CASH BOX and was also to try some different types of builds. The James TS was the first that caught my eye and being a BASS type amp this TS can be tweaked easily into more of a lead TS (I felt in the other builds there was not much control over the bass and treble) hopefully this type TS will do that :icon_biggrin:
The BTO has a 6SN7 split PI and not having much to do with a split PI in any of my builds i thought this was a great time to try it but the 6SN7 is a different tube and it is hard to find Tube Data sheets that i can compare APPLES TO APPLES and i don't even know what i am supposed to be comparing :BangHead:
ANYWAY, I drew a schem with the PI as it is in the Garnet LIL ROCK (which looks to be a great little build :think1:) and i just need an OK that this circuit can be used with the ECL84s triodes.Thanks
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It should work.
The 6SN7 is probably the octal predecessor to the 12AU7, while the triode half of the ECL84 is a higher gain tube at a mu of 65. Regardless, the plan should work. The lowish 47k load resistors may actually work in your favor as it seems from your other threads the B+ is relatively low in your cash box amp.
I'd move your 120pF treble roll-off cap to before the coupling caps, and connect it directly from the plate to the cathode of the PI ECL84 section. It will work this way as expected; I recently added a Vox-style cut control to a split-load inverter by connecting the relevant parts from the split-load plate to cathode.
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The data sheets I found for the ECL84s referenced 15 volts on the heaters
are you sure ?
ECL84 means 6.3v heater
may be you've seen
PCL84 means 15v heater
K