hi there..
I'm on progress building this amp with choke load and a bit confuse about resistor between bias trimpot wiper to gate stopper resistor. which the exact value? 10K or 47K?
with 10k or 47k I think coupling capacitor (10uF) is too much overkill
10k with 10uF 1.5Hz
47k with 10uF 0.3Hz
please enlighten me....
I had same thought with you, but just do it
what i have used : 47K with 2.2uFPart one and deux have 47K
i use 4x cree schotky diodes for cathode bias in my tube amp to get 4V , why not try them for the 2SK82 no need of bypass cap or input cap
Can you link to any webstore for my reference for which item?
and schematic please
diodes bias
http://www.mouser.fr/ProductDetail/Cree-Inc/C3D08060A/?qs=sGAEpiMZZMtQ8nqTKtFS%2fCwtife2N73IBkBxIS6S7m8%3d
just as sample , there are many others . just put them in series like you do with led to get the desire voltage ( for this one it"s 1,8v each)
http://www.mouser.fr/ProductDetail/Cree-Inc/C3D08060A/?qs=sGAEpiMZZMtQ8nqTKtFS%2fCwtife2N73IBkBxIS6S7m8%3d
just as sample , there are many others . just put them in series like you do with led to get the desire voltage ( for this one it"s 1,8v each)
say hello to my newly born SIT amp with inductor
hello folks..
after digging few years in forum, consulting and collecting parts.. yesterday is the day!
power supply from dual secondary18V 300VA power transformer. rectified and CLCC kendeil K02 47000uF air core 2.2mH 47000uF and sikorel 10000uF
hand wound choke 160mH to 2SK82. output cap are sikorel 10000uF bypassed with 20uF and 470nF
still using what i have in my messy drawer
i'm running bias supply from dedicated petit toroidal transformer which always on. Bias supply using capacitance multiplier to 7912 and set to 1.8A
mosfet temperature almost 60 celcius and heatsink almost 45 celcius after 45 minutes
room temperature 37 celcius.. very hot lately in my city.. this amp not for regular peoples which living in equator area
hello folks..
after digging few years in forum, consulting and collecting parts.. yesterday is the day!
power supply from dual secondary18V 300VA power transformer. rectified and CLCC kendeil K02 47000uF air core 2.2mH 47000uF and sikorel 10000uF
hand wound choke 160mH to 2SK82. output cap are sikorel 10000uF bypassed with 20uF and 470nF
still using what i have in my messy drawer
i'm running bias supply from dedicated petit toroidal transformer which always on. Bias supply using capacitance multiplier to 7912 and set to 1.8A
mosfet temperature almost 60 celcius and heatsink almost 45 celcius after 45 minutes
room temperature 37 celcius.. very hot lately in my city.. this amp not for regular peoples which living in equator area
yes, I put thin layer of thermal grease between 2sk82 to silpad and L bracket to heatsink.
and also i did polishing the surface of aluminum to make sure it flat..
room temperature 37 celcius.. very hot lately in my city.. this amp not for regular peoples which living in equator area
Oh my.... 37 Celsius
I like the way you have built it.
It's all very neat and tidy, you have taken your time
Do you have picture of the bottom? How did you mount the four squares L brackets?
Oh my.... 37 Celsius
I like the way you have built it.
It's all very neat and tidy, you have taken your time
Do you have picture of the bottom? How did you mount the four squares L brackets?
hello Walter,
first I put L brackets on horizontal to be a part of the deck
then another 4 vertical L brackets bolted on those horizontal L bracket.
rear L bracket drilled also for RCA input, speakers binding posts, power switch, IEC input and two heatsinks.
a lot of metalworks
this is the pic of lower deck sans power transformer during construction
on the rear there is horizontal L bracket that i mention.
green board with white coffin resistor is soft start module
Very nice. How's the sound?
You can always direct a little fan towards the sink if things get too hot.
Mi MR.
the sound is fabulous. but I will do little tweak step by step.
this morning I replace the c in (20uF) to vintage siderealkaps 5uF
they sound better and the bass is still there.
maybe because my DAC (ES9018 with digital volume controller) using Lundahl transformer out with 600z ?
later I will change input resistor (47K) to 10K
will try later -when i have muscle to drag this beast
- with high efficiency speakers in my room..
Hello albertli. Your idea of making lamp with 2sk180 is very good. I have done some versions. The first was with thf51 and 65Vdc 4A of quiescent current. The second one with 2sk180D and 84Vdc 2A; next one with thf51 and the same that second one. And the last with 193V and thf51.
All except the last one were done with resistor (10 ohm 600W and 22 ohm 300W) as drain load.
For me, the first is the better, but heat dissipation was enormous (240W) and the gigant heatsink (50cm x 30 cm and 8 cm) impossible of touch. I got almost 18W rms. Sound, for me very very good. The second better (actual amp) is thf51 with 84Vdc and 2A. With this I get 8Wrms. Enough for me (I am using 100db speakers in open baffle).
The third version, with 2sk180D selected, had worse highs than thf51. Sorry, this was my impression. When I used a scope, I saw that all measurements all worse than thf51, square wave, frequency response and output impedance (more o less 4 ohm). I do not know why nobody want to try this wonderful vfet. I am using low output impedance pre and highs are wonderful.
The last one, 193V version will be a gift for a friend, and sound, for me, is a little dark compare with resistor version. The advantage is heat dissipation a lot lower.
One thing more. For getting channels sound equal,you need select very well vfets. If you can, try use a economic curve tracer, as there is in ebay, because variability is a lot bigger than 2sk82.
If you can get 2sk180, try get D version. They are very very similar each other (at least I own).
Well, good luck in your project.
All except the last one were done with resistor (10 ohm 600W and 22 ohm 300W) as drain load.
For me, the first is the better, but heat dissipation was enormous (240W) and the gigant heatsink (50cm x 30 cm and 8 cm) impossible of touch. I got almost 18W rms. Sound, for me very very good. The second better (actual amp) is thf51 with 84Vdc and 2A. With this I get 8Wrms. Enough for me (I am using 100db speakers in open baffle).
The third version, with 2sk180D selected, had worse highs than thf51. Sorry, this was my impression. When I used a scope, I saw that all measurements all worse than thf51, square wave, frequency response and output impedance (more o less 4 ohm). I do not know why nobody want to try this wonderful vfet. I am using low output impedance pre and highs are wonderful.
The last one, 193V version will be a gift for a friend, and sound, for me, is a little dark compare with resistor version. The advantage is heat dissipation a lot lower.
One thing more. For getting channels sound equal,you need select very well vfets. If you can, try use a economic curve tracer, as there is in ebay, because variability is a lot bigger than 2sk82.
If you can get 2sk180, try get D version. They are very very similar each other (at least I own).
Well, good luck in your project.
Attachments
nope . if that's powder (ferrite) , it'll saturate at smidge of DC current