KT120 SE UL mono block Tube Amplifier: Parts & Layout

This video goes over the parts used and also the layout of the components in the chassis.

This series is a DIY project building a pair of single ended, ultralinear KT120 mono block style vacuum tube audio amplifiers. The goal is a pair of high power single ended amps, using only high quality parts, with as few things in the signal path as possible.

It looks like KT120 tubes are available again, partsconnexion in Canada has pairs for like $140!

This project is using output transformers from Thermionic Labs, custom made to use with KT120 output tubes, which you can buy here:

They also should have power transformers and chokes for this project available.

You can send me links and messaged at:

Here is my Patreon, as well as the donation page at my site, if you feel so inclined to help fund some of the future projects for the channel!

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[cobar]

The layout is first class. A credit to you, Stephe

[nevillegoddard]

Good quality components make a good amp! Those Vishay resistors are physically larger & longer, which gives them a higher voltage rating as well.

Should be good! It will be interesting to hear how a pair of these sound from you! I think you said you were pleased with the first one, so hopefully you'll be twice as pleased with a stereo pair of them huh?

Great idea to coil up & hide spare transformer taps inside the 'bells'!

[extraclaic]

Wonderful video! Thank you for the clear explanation and rationale of the well designed layout.

[adamphillips]

Thank you for the BOM!!! I decided to go with the angel eye power switches. I didn't see which bridge rectifier, resistor and lil cap you used. I threw a NTE5332 600V 1A in my shopping cart but it ships separately at 3X the part cost. I'm hoping to find one that DK has in stock so it can ship with the rest of my order. Obviously, if not using an LED-illuminated switch, no extra parts are needed. Thanks again for all you do!

[rickg]

Hi Stephe.. I used a 3M Heavy Duty double-sided mounting tape for the DC Link decouplimg caps before, they hold up well.. It’s the Red colored mounting tape that could hold a heavy load..

[stiffwin]

Another excellent tutorial Stephe! What values do you recommend for the X/Y safety caps?

[petegaslondon]

Dang it Skunkie/Stephie you raise a valid point - if I'm sensing cathode current I'll need something precision - I tend toward Carbon Composition as theyre best for squishing RF oscillations, but then I cant use 'em to sense current due to their crazy tolerance .. maybe I'll compromise and use an oversized 1% Carbon Film - thanks for reminding me :)

Personally I cant bring myself to make a SE much bigger than 5 watts, or headphones - all that iron, heat and horsepower - so, a question - to you or everybody out there..

..Has the TRANSFORMER (not tube) 'crossover distortion' that SE is supposed to prevent ( no current / flux reversals ) ever actually been MEASURED? if so how high is it? For, say a quality (amorphous, even) transformer ? Can anybody tell me?
Yours, a PP fan :)

[johnstuchlik]

I learned a lot.vishay resistor over sizing, filter led, good camera work.and you stay on one spot long enough for me to pause.forgive this question but I'm looking on a cell phone.are you running the input tube grid to ground resistor and cathode resistor ground point directly to chassis common ground point or in other words no ground of input tube tag strip to chassis only a wire from tag strip to common ground?next question I see you are using a Polycap after the rect.is this the best location if you use only one? I ask as I have some that the voltage is bit low and the cap value a bit high to follow the rect but I think would work ok after the choke or pi resistor.what about parallel caps?not talking about small film bypass but say 2uf poly parallel w 8uf electrolytic for filter caps not coupling.your layout video definitely bridge gap from working only from a schematic.how to remove scratches from aluminum? learned the hard way about protective film.

[OpossumPiper]

Where are you getting those RCA jacks from? I am trying hunting some down, but I couldn't find the ones with the solder body that you used on the 834 amp and this build. My googling skills are failing me :/