Probably completely wrong but random thoughts:
1) If the Vgs is fixed, could the Vfet draw much more current, even if
you short the outputs?
2) Wouldn't the current still be limited by the resistor/bulb, even if it increases?
1) If the Vgs is fixed, could the Vfet draw much more current, even if
you short the outputs?
2) Wouldn't the current still be limited by the resistor/bulb, even if it increases?
Right, so no nuclear meltdown after all. 🙂
So, next puzzler: Describe the function of the zener in the picture soundhappy posted in #2634?
So, next puzzler: Describe the function of the zener in the picture soundhappy posted in #2634?
Another try (more a guess actually 🙂) ...
The Zener limits the leakage current of the SIT to the leakage current of the Zener, so the bias voltage won't be impacted too much when a leaky SIT is in place.
The Zener limits the leakage current of the SIT to the leakage current of the Zener, so the bias voltage won't be impacted too much when a leaky SIT is in place.
Mr.Pass say the zener diode 9V1 is vfet protection if some one use tube preamp without output cap 😀
While we're on the topic of failure modes and whatnot, I will mention that I've never lost a L'Amp having built dozens of copies and despite many stupid hookup mistakes on my part. This is not to say that you shouldn't try to protect your precious devices from things that go bump in the night, but temper your paranoia with joix de vivre. 🙂
That's interesting and reassuring at the same time. I thought for sure a short would have killed the vfet.
Thanks,
Vince
Thanks,
Vince
Perhaps Uncle Mike can comment on this. With a CCS, the current is limited
by design so things should be ok.
With inductor loading, I suspect there's not enough resistance for current limiting so one would
want to ensure the bias voltage to be up before and stays up after the main rail.
Would this be correct?
by design so things should be ok.
With inductor loading, I suspect there's not enough resistance for current limiting so one would
want to ensure the bias voltage to be up before and stays up after the main rail.
Would this be correct?
Strictly speaking, Yes. But this isn't too difficult to achieve practically. I refer you to these two posts where I took some pictures of the turn-on and turn-off events in the Part Deux amp. Just pay attention to your time constants in your supplies. 🙂
http://www.diyaudio.com/forums/pass-labs/201655-lamp-simple-sit-amp-189.html#post3665664
http://www.diyaudio.com/forums/pass-labs/201655-lamp-simple-sit-amp-189.html#post3665670
http://www.diyaudio.com/forums/pass-labs/201655-lamp-simple-sit-amp-189.html#post3665664
http://www.diyaudio.com/forums/pass-labs/201655-lamp-simple-sit-amp-189.html#post3665670
Michael,
I would like to know is there a monster gap in sound between the L'amp and SIT-1?
I know you heard them both! 🙂
Please. Thank you.
Vince
I would like to know is there a monster gap in sound between the L'amp and SIT-1?
I know you heard them both! 🙂
Please. Thank you.
Vince
Well, I've never spent time with a real official First Watt SIT-1 amp. Hopefully, someday. I'd love to spend more time with the Beasts (of thousands of JFETs) too, but talk about unobtanium 🙂
I have spent time with the devices themselves, and I think a patient (read: willing to experiment and tune) DIYer can approximate the sound of a SIT-1 to a very satisfying degree with the Sony or Tokin parts.
I have spent time with the devices themselves, and I think a patient (read: willing to experiment and tune) DIYer can approximate the sound of a SIT-1 to a very satisfying degree with the Sony or Tokin parts.
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I have the L'amps without the lamps, so I guess I'm doing alright. It's just that curiosity that keeps creeping in- 'what am I missing?'
Thank you
Vince
Thank you
Vince