This is my third "from-scratch" build. Its a KF50 preamp + tweaks paired up with a KT66 PA biased for class A.
Hammond PT, Marstran JTM45 OT w/ 8K pri.
Preamp heaters are 12vdc.
V1 and V2 are 12AX7
PI is a 12AV7 - love the sound of it in this position.
The KT66 screen supply and preamp supplies are stabilized with mosfet / zener circuit from Merlin's book.
I added LP powerscaling but wouldn't bother with it again - the BadCat unleash is my new favorite dB reduction toy.
The cab is a modified cherry dovetailed drawer box.
The faceplates were purchased from Lindz on this forum. They are on a printed medium used for ski/snowboard caps - very durable. I think they look great. Lindsay was great to do business with and turned them around quickly.
It sounds like a KF50 mated with a JTM45. Nice bloom, solid bottom, cleans up nicely with rolled back guitar volume, very low noise floor. Really a joy to play.
I've previously built a 2W express and a RT66.
KF50-ish build
Moderators: pompeiisneaks, Colossal
KF50-ish build
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Steve
Re: KF50-ish build
The way you have everything laid out is rocking my world! Never seen that before. 
How about some gut shots?
How about some gut shots?-
Reeltarded
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Re: KF50-ish build
Nice rig!
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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Smokebreak
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Re: KF50-ish build
Double gutshots! That is really cool.
Re: KF50-ish build
Nice amp and I waiting for details about the split chassis on this. 
Re: KF50-ish build
Top guts:
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Steve
Re: KF50-ish build
PowerScaling
Stabilized screen and preamp supplies w/ current limiting.
PA - 390v plates, 275v screens, 250ohm shared cathode w/ 1000uF bypass, 8K primary
PREAMP
I didn't love the fast or gradual modes. I ended up using split load with the resistors flipped.
Tweaked coupling and bypass caps to taste.
Stabilized screen and preamp supplies w/ current limiting.
PA - 390v plates, 275v screens, 250ohm shared cathode w/ 1000uF bypass, 8K primary
PREAMP
I didn't love the fast or gradual modes. I ended up using split load with the resistors flipped.
Tweaked coupling and bypass caps to taste.
You do not have the required permissions to view the files attached to this post.
Steve
Re: KF50-ish build
Wow I wouldn't know where to begin with this circuit no wonder I like simple amps.
Very nice!
Very nice!
Re: KF50-ish build
Thank-you.
The audio part is pretty simple, the power supply is a little more involved, but not too bad. I've been at this one for a couple of years.
I wanted to get as close to the lofty goal of "clean to mean" as possible and be able to retain string definition in overdrive. I think the superstiff PS helped with the latter. I think the stabilized screen supply should prolong screen life as well.
The overdrive order is PA > PI > Pre.
The class A PA doesn't take much to overdrive, its very smooth, and has great percussive bass.
The audio part is pretty simple, the power supply is a little more involved, but not too bad. I've been at this one for a couple of years.
I wanted to get as close to the lofty goal of "clean to mean" as possible and be able to retain string definition in overdrive. I think the superstiff PS helped with the latter. I think the stabilized screen supply should prolong screen life as well.
The overdrive order is PA > PI > Pre.
The class A PA doesn't take much to overdrive, its very smooth, and has great percussive bass.
Steve
Re: KF50-ish build
Nice! Good to see someone else implement the voltage clamps on Vs and pre too.
What is it that you don't like about power scaling? I have found it to be very transparent in sound and feeling... for the most part as our ears react differently to different spls'. Also, I'm curious how or if you implemented a drive comp and what you scaled?
Not dissing Marstran, I'm surprised that the jtm45 OT can handle "Class A", I'm interested as to what current you are biased up to? True class A is a helluva lot of power dissipated as heat.
Nice build with the extras...
John
What is it that you don't like about power scaling? I have found it to be very transparent in sound and feeling... for the most part as our ears react differently to different spls'. Also, I'm curious how or if you implemented a drive comp and what you scaled?
Not dissing Marstran, I'm surprised that the jtm45 OT can handle "Class A", I'm interested as to what current you are biased up to? True class A is a helluva lot of power dissipated as heat.
Nice build with the extras...
John
Re: KF50-ish build
Sorry, I didn't mean to imply that powerscaling isn't a good solution - I prefer using the Unleash though. I think it is much more transparent and I really like being able to add effects after the PA.
I tried a few different implementations of drive comp / master volume and didn't care for its effect on the PI. The PI was the area I spent most of the tweak time on and it really adds a lot to the overall tone of the amp.
At design voltages, it idles at 52 mA / KT66. At max signal, 62mA. The design uses values from a KT66 datasheet for Class A1 PP operation rated at 30 watts clean power.
I tried a few different implementations of drive comp / master volume and didn't care for its effect on the PI. The PI was the area I spent most of the tweak time on and it really adds a lot to the overall tone of the amp.
At design voltages, it idles at 52 mA / KT66. At max signal, 62mA. The design uses values from a KT66 datasheet for Class A1 PP operation rated at 30 watts clean power.
Steve