John Curl's Blowtorch preamplifier - Page 387

courage · 9th April 2008, 06:30 PM

Pavel,

Great effort and very instructive!

Thanks.

PMA · 9th April 2008, 06:35 PM

Franklin,

thanks. There is a lot to be done, still.

Pavel

john curl · 9th April 2008, 06:39 PM

PMA, what happens if you replace the 10ma current source with a short? This could be very important.

PMA · 9th April 2008, 06:49 PM

Quote:

Originally posted by john curl
PMA, what happens if you replace the 10ma current source with a short? This could be very important.

My deep admiration, John.

Pavel

john curl · 9th April 2008, 07:33 PM

PMA, it looks a little too amazing! How about changing the Idss to 15 ma, which is more reasonable? Also, a single 10 ohm resistor instead of the short would be interesting.

PMA · 9th April 2008, 07:36 PM

In case we replaced CCS by short, there was not much means to set Id, only JFET parameters (Vt etc.). I will try resistor, this will definitely set the current.

PMA · 9th April 2008, 07:42 PM

With 20 ohm, we are slightly above 20mA Id, but still excellent distortion!!

john curl · 9th April 2008, 07:49 PM

Interesting!

PMA · 9th April 2008, 07:51 PM

It depends on Isignal/Id ratio. Also, in case of complementary diff circuit, the 4 devices contribute by their currents, they can operate with smaller amplitude, in more linear part of transfer function. And distortion cancellation, it all leads to very good results, in real circuit depending on parameter and thermal matching of the devices.

john curl · 9th April 2008, 08:18 PM

Yes, but there should be an interaction between the top and bottom devices, as well. We need a way to control Ids better. Perhaps a small floating Voltage source rather than a resistor or short to get down to 10-15ma. The resistor will change the interaction, so it is problematic.

9th April 2008, 06:30 PM	#3861
courage diyAudio Member Join Date: Feb 2006 Location: Neverland	Pavel, Great effort and very instructive! Thanks. __________________ Franklin

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9th April 2008, 06:35 PM	#3862
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	Franklin, thanks. There is a lot to be done, still. Pavel

9th April 2008, 06:39 PM	#3863
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	PMA, what happens if you replace the 10ma current source with a short? This could be very important.

9th April 2008, 07:33 PM	#3865
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	PMA, it looks a little too amazing! How about changing the Idss to 15 ma, which is more reasonable? Also, a single 10 ohm resistor instead of the short would be interesting.

9th April 2008, 07:36 PM	#3866
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	In case we replaced CCS by short, there was not much means to set Id, only JFET parameters (Vt etc.). I will try resistor, this will definitely set the current.

9th April 2008, 07:49 PM	#3868
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Interesting!

9th April 2008, 07:51 PM	#3869
PMA diyAudio Member Join Date: Apr 2002 Location: Prague, Kitakyushu, Fukuoka	It depends on Isignal/Id ratio. Also, in case of complementary diff circuit, the 4 devices contribute by their currents, they can operate with smaller amplitude, in more linear part of transfer function. And distortion cancellation, it all leads to very good results, in real circuit depending on parameter and thermal matching of the devices.

9th April 2008, 08:18 PM	#3870
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	Yes, but there should be an interaction between the top and bottom devices, as well. We need a way to control Ids better. Perhaps a small floating Voltage source rather than a resistor or short to get down to 10-15ma. The resistor will change the interaction, so it is problematic.

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