I'm not sure if this belongs here...
As usual, I am late to the party...
Finally, I had the time to build a SIT amp, a single ended 2SK82 but with Rload (15Ohm) instead of bulb. No Rsource. One channel for now. I am making a box with left overs, as you can see on the picture. It can go upside down (w/r to the picture) or upright for a strong chimney effect..
I decided on an inexpensive SMPS from Connex further regulated with PowerReg from Teddy Pardo, for various reasons, including cost, weight, efficiency, nice security traits, added auxiliary supply (+/- 12VDC, for bias control--> variable TeddyReg), and because it was lying there...
No noises, pops or hum whatsoever; just nice Music. The Regs do a delayed, gradual startup (fortunately the (-)bias Reg seems a little faster) and the final Voltages I chose are: V(+)= 26.7V; VDS= 12V; Vbias= (-)4.1V. so around only 1 amp at iddle, I guess.
Fortunately it rides well my Audio Nirvana super10 on downsized 2:3 Autograph corner speakers.
Anyway, I perhaps will try to increase bias current to the recommended around 2amps. What to do? Reduce Rload or increase V supply? Add CCS or a big choke? No, better not a big choke.
The VFets are something special as per preliminary listening.
As usual, I am late to the party...
Finally, I had the time to build a SIT amp, a single ended 2SK82 but with Rload (15Ohm) instead of bulb. No Rsource. One channel for now. I am making a box with left overs, as you can see on the picture. It can go upside down (w/r to the picture) or upright for a strong chimney effect..
I decided on an inexpensive SMPS from Connex further regulated with PowerReg from Teddy Pardo, for various reasons, including cost, weight, efficiency, nice security traits, added auxiliary supply (+/- 12VDC, for bias control--> variable TeddyReg), and because it was lying there...
No noises, pops or hum whatsoever; just nice Music. The Regs do a delayed, gradual startup (fortunately the (-)bias Reg seems a little faster) and the final Voltages I chose are: V(+)= 26.7V; VDS= 12V; Vbias= (-)4.1V. so around only 1 amp at iddle, I guess.
Fortunately it rides well my Audio Nirvana super10 on downsized 2:3 Autograph corner speakers.
Anyway, I perhaps will try to increase bias current to the recommended around 2amps. What to do? Reduce Rload or increase V supply? Add CCS or a big choke? No, better not a big choke.
The VFets are something special as per preliminary listening.
Attachments
Never too late to join the party
I'd increase the supply voltage next.
Thank you Michael.
I can't afford to loose gain, so increasing VDD seams the right way. More heat though. What would be reasonable VDD and VDS for the SK82?
Actually I may be making my own DIY non-inductive, non capacitive resistors, honeycomb style.
surrounded by clay, perhaps, and bolted to the heat-sinks. Cheers,
M.
Thank you, Master.
Actually, I don't really know if those can be found around here...
Anyway, I have to get a proper single rail SMPS. Meanwhile, I am studying some tutorials to really know what I'm doing
I will use my secret weapons: parallel Russian military surplus polyestyrene caps for bypass and coupling.
Cheers,
M.
Hi Max,
I've often wondered if stove top heating elements
(something like this:
GE 8 in. Heating Element for Non-GE Electric Ranges-PM30X208DS - The Home Depot)
can be used.
I've often wondered if stove top heating elements
(something like this:
GE 8 in. Heating Element for Non-GE Electric Ranges-PM30X208DS - The Home Depot)
can be used.
Of course the answer depends on what the constraints (what we're not allowed to change) are, and there are many acceptable load lines to pursue, but looking at figure 10 in the original article, let's guess we want 13-14V across the SIT, with Iq in the area of 2.3-2.6A. Your resistor is 15 Ohms, so supply range will be 47-53V and your SIT will be dissipating between 30 and 37 watts.
Experiment, YMMV
Of course the answer depends on what the constraints (what we're not allowed to change) are, and there are many acceptable load lines to pursue, but looking at figure 10 in the original article, let's guess we want 13-14V across the SIT, with Iq in the area of 2.3-2.6A. Your resistor is 15 Ohms, so supply range will be 47-53V and your SIT will be dissipating between 30 and 37 watts.
Experiment, YMMV
Thank you very much. That's what I thought and for that I will need another SMPS and to parallel Rload resistors to cope with heat...in that scenario, if I increase total Rload I could have more gain, sacrificing distortion figures a little, right? I will take another look at the article.
Best wishes.
M.
Thank you, Master.
Actually, I don't really know if those can be found around here...
Anyway, I have to get a proper single rail SMPS. Meanwhile, I am studying some tutorials to really know what I'm doing
I will use my secret weapons: parallel Russian military surplus polyestyrene caps for bypass and coupling.
Cheers,
M.
300w halogen "torchiere" style lamps were really popular once and bulbs can still be found - they just don't look like traditional light bulbs with a socket.
https://www.lightbulbs.com/product/westinghouse-04775/
$3
Final build. Reduced the buzz/hum I had by rotating one of the chokes and re-configuring my star earth setup. Inductors on the powersupply rails instead of the 1W resistors also seemed to clear up general noise and made the sound a bit quieter overall. Very happy with this.....
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Thank you!
They look nice. I will search for them, with multimeter in hand.
Yesterday I added the second channel successfully
Even with a chip volume control it sounds great. Bass instruments get great articulation and harmonic content.
Cheers,
M.
Here's my lightweigth amp.
I recorded a couple of videos. See my signature. Unfortunately, mic's camera is not good.
They demonstrate that SMPS plus power regulator based single ended amp is feasible.
I don't know if anybody has gone this way previously, sorry...these Pass fora threads are hard to follow, to say the least. A pity.
Cheers,
M.
I recorded a couple of videos. See my signature. Unfortunately, mic's camera is not good.
They demonstrate that SMPS plus power regulator based single ended amp is feasible.
I don't know if anybody has gone this way previously, sorry...these Pass fora threads are hard to follow, to say the least. A pity.
Cheers,
M.
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Greedy Boyz are used to that pity
He, he.
I may take some shots from scope to sustain my miserliness
Perhaps son´s iPhone records better than old camera...
(I begin to speak like ZM
)Hello,
I've been having trouble locating any reasonably priced SITs except for the 2SJ28 - KF33 grade and while I have build a few amplifiers in kit form I'm interested in trying my hands at a scratch build.
What does it mean when people mention reversing the polarity if one plans to use the 2SJ28?
