The whole idea is to make a mini tube amp that's everyone can built for their office/bedroom.
Highlights:
-Open schematics
-Low component count
-Very affordable
-Extremely easy to build
-Sounds great
-Solid, Sexy & Sleek
-Wife friendly
Topology: SET Ultra Linear
Signal Tube: 6J8P <-very affordable
Power Tube: KT88 <-decent price
Power: 2 x 6.5W
Feature:
-2 pairs selectable stereo input
-Balanced XLR & Phono Headphone output (Wires Tap from the speaker output)
-4ohm/8ohm
-Bluetooth PCM5102/ES9023 in future*.
Built:
-strictly no "audiophiles parts" in the built
Things that are still under optimizing:
-slight of 50hz/100hz humming when the ear is put 2cm next to the speaker drivers, not ideal for headphone users. Still figuring a way to remove to hum without rectifying the 6.3Vac. Planning to lift the heater voltage referencing to a common that is far above the cathode voltage.
-Very limited bandwidth to 15khz@-3dB although one can hear sparkling and vivid highs from this amp.
-PCB Layout needed to optimized for easier installation and better layout.
-Chassis need a handle
The whole amp is functioning and the sound is surprisingly really very nice, spacious, great soundstage, sparkling high, fluidy mid, and i believe it can sound better than many of the commercial solid-state power amp out there easily. (I know everybody claim the things that born out from their hands are the best. 🤣 ) But its really good, the schematics is in this post and you might want to try it out.
I'm still figuring and compiling any possible way to further improve the performance and outlook, any suggestion is much appreciated.
A bit progress here:
CNC cut on a ready made waterproof aluminium enclosure
laser cut bottom faceplate with gold anodizing and black rubber feets.
And older model with high gloss black powder coat.
Bottom PCB, with chokes, connectors and SMD components on it.
Top PCB, with Tube mounting on it.
PS: I don't wish that there is anyone taking this out for commercial purposes.
Attachments
Uploaded a video about the measurement with QA400. Full of 2nd Harmonics fun.
Such a lovely looking amplifier! I love the finish. The tubes are a little close together for my liking, but I'll be following this project 😀.
The amp looks very nice and compact, I like it. Is it possible to switch the position for the driver tube and power tube?
Sometimes the driver tube just few inches away from the power transformer will make the different for hum, but may need to add heat a shield plate.
Sometimes the driver tube just few inches away from the power transformer will make the different for hum, but may need to add heat a shield plate.
Thank You!! Hope you will like my progress on improving it over time.
Thank You!! The power tube is sitting on the most corner side, and the power trans is in the middle.
I have measured with the QA400 and the current -60dB of 50hz is not affected from the distance Power tube <-> power transformer by putting the power transformer further away. I'm still figuring how to address this and minimize to 50Hz down to -80dB or even -90dB.
Just added a pair of sandblasted black anodized aluminum handle for this miniKT88, and it does looks even lovelier now! I'm so glad that this aluminium water proof box comes with 4 holes at the corner to fit this in. 😊
Hands just got itchy and get myself a pair of NOS 6SJ7 to swap away the cheap 6J8P. And my ears told me that the result is very positive 😱!
Very cool, I hope you disclose a supplier for that nice enclosure! a work of art for sure. People do so much more listening at their computers these days unlike the 1970's 80's and 90's such a design makes sense.
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For low noise heater application use a valve built for the job...
one-electron.com/Archives/RCA/RCA-LB/LB-861%20RCA%20Labs%201952%20Heater-Cathode%20Leakage%20Hun%20Reduction%20by%20Means%20of%20a%20Shielded%20Heater.pdf
btw your amp is a looker!
one-electron.com/Archives/RCA/RCA-LB/LB-861%20RCA%20Labs%201952%20Heater-Cathode%20Leakage%20Hun%20Reduction%20by%20Means%20of%20a%20Shielded%20Heater.pdf
btw your amp is a looker!
Sure! Here you go for the enclosure box : https://www.aliexpress.com/item/4001313401318.html
it was made from a very standard dimension junction box. 😊
For -60dB @ 50hz, yes there is a very low hum on the headphone out if listen properly. Its already quieter than many commercial valves amp that I have heard, but I am still thinking a way to make it even quieter!😀
Thank you for sharing this! Let me go through with it and see if I can make this amp shines even better!