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With the assistance of Kevin Carter at K&K Audio I have built a linestage using the 12P17L indirectly heated pentode connected in triode. Since starting this project Kevin has an updated circuit board that combines several individual boards that I used into one. The 12P17L is cousin to the 4P1L which is a directly heated pentode. Chassis is comprised of .125" aluminum plate, perforated steel with 1/4" holes and 7/8" mesquite from a tree that once resided in my front yard. Components are mounted on a mid-plate with cut-outs beneath the circuit boards to allow access to both sides. Control knobs are ebony and the feet are cocobolo. Picture of the inside of the chassis shows the wiring completed with the exception of four wires that were soldered in the day after the picture was taken
After three weeks I think the unit is burned in. Soundstage is deep and wide with individual players assuming places within the room. Clarity allows you to follow the different lines of each musician within the space easily. Detailed without sounding analytical.
Contact Kevin at K&K Audio on details of pricing and the new circuit boards to build this very sweet linestage.
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Wonderful workmanship!
I've turned wooden knobs, always with the same poor result. Can't drill and emplace a threaded insert close enough to the end to grab a standard shaft without a blowout.
Do you simply tap the hole and run the set screw directly in the wood?
I usually use either cocobolo or ebony for control knobs. Both are hard and dense enough to drill and tap for set screws. Run the tap in some and then out several times as you cut the threads to relieve any stress on the wood.
It's a decent valve . Built an amp with de-canned 12P17L . Ran them with 7N7 driver and used cathode feedback on the output stage . Not as good sounding as 4P1L but then again I wouldn't be able to fit a 4P1L amp in a beer keg ;)
Al
Very nice implementation.
I'm currently laying out his 4P1L version - a little more complicated on the input side as I am wiring for 3xXLR and 3xSE inputs utilizing relays, using Kevin recommended LL1544A inputs and all his current boards.
I'm concerned if I have enough real estate with a 16Wx12D chassis. What is the size of your chassis plate?
I like your chassis - well done. The mid-plate that the components are mounted on is 14.25" X 17.375". The extra boards and transformers needed for the 4P1L filaments does take up some extra space. Are you are going to use a remote volume control? I thought about implemeting a remote but changed my mind.
The 12P17L filaments are running at AC now but will be changed to DC soon. Other than that I'm very pleased on how the linestage construction went and how well it mates with the 6C33C PSE monoblocs that I finished building in January.
Most of the chassis credit goes to FPE (Front Panel Express) ..... I am using a 10K Goldpoint which I had on hand looking for a project. I wanted to use the Bent Audio remote stepper add-on, but not sure if John is currently supporting it to DIY. Have emailed him to verify.
The chassis is 5" tall, hoping I can do some creative stacking ...
The linestage will drive a Marchand active crossover biamped system, upper ranges using either Kevin's scratch build "ST-70" board (pic), or my pair of 300B monoblocks, sand amps on subwoofers.
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