Back to the original schematic I am all out of 10k resistors so I was thinking I could just use this self biasing device. Actually this is an interesting device first it's rather cheap at $6 for a 190W part the ciss is rather low at 650pf and it takes a - voltage to turn it off. In the 4 devices I tested with the gate grounded I dropped about 8v across a 8 ohm source resistor and this didn't go up much as I raised the source to drain voltage. https://www.mouser.com/datasheet/2/827/DS_UJ3N065080K3S-1530401.pdf
here's ZM
can' have a gain , being source follower
Not voltage gain, but current gain and power gain aren't to be ignored!
is there gonna be a PCB available for this one?
I don't know what's funnier, seing you here or the question in itself...
cause why not?
need a decent desktop amp to power my Woden Lance's. Been using a TDA7297. Going to use IRFP240 or 250.Attachments
In trying to learn a bit more about source followers, playing with the sim and kicad, I added a pot to set the bias. Is the aim to set the S-GND at 1/2 rail? Doing so makes the disspiation more or less equal on the fet and power resistor. Is that ideal? May be time to figure out how to use a O'scope.
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If you are doing sims, you can vary parameters and check the results for differences. In LTSpice, FFTs can be done for distortion analysis, and AC analysis will give frequency response.
I started playing around with LTSpice this year and it has been very educational. Circuits can be tried without parts, power supplies, or oscilloscopes, etc. The only limiting factor is the accuracy of some of the more exotic components such as SITs.
In your example, you can run it in LTSpice, vary the bias and also vary R4 to see the effects on harmonic distortion. Vary V+ too to see what happens.
Another point - an USB sound card and a program such as REW or ARTA are probably more useful than an oscilloscope for evaluating amplifiers after they are built.
I started playing around with LTSpice this year and it has been very educational. Circuits can be tried without parts, power supplies, or oscilloscopes, etc. The only limiting factor is the accuracy of some of the more exotic components such as SITs.
In your example, you can run it in LTSpice, vary the bias and also vary R4 to see the effects on harmonic distortion. Vary V+ too to see what happens.
Another point - an USB sound card and a program such as REW or ARTA are probably more useful than an oscilloscope for evaluating amplifiers after they are built.
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Hi Michael,
As chance would have it, I just picked up a pair of 193S cheap on ebay. Did you ever try them out in this schematic, or the one from post #101?
Best
Nigel
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I remember that circuit. I just couldn't tame the LU1014D in that one. It required really careful selection, and even with that it was pretty wobbly. A cascode of some sort might be the ticket.
Or, some other more agreeable depletion part, perhaps with some voltage feedback to make it more triodey.
Or, some other more agreeable depletion part, perhaps with some voltage feedback to make it more triodey.
LU1014D is very stable in cascode with usual IRFP240. I have driven it as high as 6A but 2A to 3A it’s perfectly happy as a nice source follower.
LuFo Amp - 39w SE Class A from 28v Rail
You could replace the choke load with a resistive load and it sound work fine, albeit lower max power.
Yes, I've been reading the LuFo thread - looks very cool indeed. At 39W it's way bigger than a 1W amp, though. Having said that, just using one IRFP240 would allow for more current than the 193S can handle before saturating, I think, so maybe I can figure something out.
And yes, I suppose I could switch to a resistive load, but part of the fun here is try these big chokes out. Of course I dare say there are other things I might try with them.
Best
Nigel
And yes, I suppose I could switch to a resistive load, but part of the fun here is try these big chokes out. Of course I dare say there are other things I might try with them.
Best
Nigel
To the extent I have thought this through at all (which isn't very much, at this point) I was thinking of running at about 0.5A, because the 193S is rated at 1A, so I was guesstimating that about 0.5A would be about as much as it could handle without saturating.
I know what you mean about the LU1014D and headphones. I built Patrick's DAO amp a few years ago, which sounds just great. In fact, it's because of that and my recent F3 build (which I am also v. happy with) that I am keen to play more with the Lovoltech jfets.
Best
Nigel
I know what you mean about the LU1014D and headphones. I built Patrick's DAO amp a few years ago, which sounds just great. In fact, it's because of that and my recent F3 build (which I am also v. happy with) that I am keen to play more with the Lovoltech jfets.
Best
Nigel
