John Curl's Blowtorch preamplifier part II - Page 2771

john curl · 17th September 2012, 07:28 PM

It is just better to pay the price. You can't get quality for nothing, at least in my world view.

mullardel34 · 17th September 2012, 07:50 PM

John,

Agreed; I've already placed my order for the genuine Toshiba parts. I was trying to identify some points where those who don't want to incur the additional expense could go...

mullardel34 · 17th September 2012, 07:52 PM

John,

Is there anything in the topology presented in the schematic that would disqualify this PC board from successfully implementing a useful JC-80? Does the eBay-sourced JC-80 PC board face any showstopper issues?

Thanks in advance!

RNMarsh · 17th September 2012, 10:37 PM

take two jFETs of same type -- tie the drains together. tie the sources together. A dual gate jFET?
I saw this done somewhere, i think.

fas42 · 17th September 2012, 10:46 PM

Quote:

Originally Posted by john curl

It is just better to pay the price. You can't get quality for nothing, at least in my world view.

In fact there are two ways: money, or much personal effort; and money effectively merely passes the baton to someone else to hopefully apply similarly focused, appropriate effort ...

Frank

wayne · 17th September 2012, 11:03 PM

The Toshibas have a slight sonic advantage over the IR parts especially in the midrange clarity. I wish it wasn't so but it is. If you want the best for audio use the Toshibas.

john curl · 17th September 2012, 11:09 PM

I don't know WHY they switched to those Toshibas, but I think it is not a risk that I would do to change them, just to save a few dollars. There must have been SOME REASON that they chose these parts over the IR's.

john curl · 17th September 2012, 11:11 PM

34, so far, so good!

EUVL · 17th September 2012, 11:48 PM

> Since the independent JFET's don't share a common substrate, there's no inherent thermal balance, but .....

This one is really an old story. Doesn't time fly ....... :

The next best thing to 2SK389 / 2SJ109 ?
Toshiba Dual JFET Heatsink

Patrick

kamis · 18th September 2012, 06:31 AM

Quote:

Originally Posted by john curl

I don't know WHY they switched to those Toshibas, but I think it is not a risk that I would do to change them, just to save a few dollars. There must have been SOME REASON that they chose these parts over the IR's.

What about Hitachi K216/J79 in the same position, similar to Vendetta second stage? Lower capacitance compared to IR Mosfets?

17th September 2012, 07:50 PM	#27702
mullardel34 diyAudio Member Join Date: Mar 2005 Location: Midwestern US	John, Agreed; I've already placed my order for the genuine Toshiba parts. I was trying to identify some points where those who don't want to incur the additional expense could go... __________________ Mullard EL34

17th September 2012, 07:52 PM	#27703
mullardel34 diyAudio Member Join Date: Mar 2005 Location: Midwestern US	JC-80 Build Sub-Thread John, Is there anything in the topology presented in the schematic that would disqualify this PC board from successfully implementing a useful JC-80? Does the eBay-sourced JC-80 PC board face any showstopper issues? Thanks in advance! __________________ Mullard EL34

17th September 2012, 11:48 PM	#27709
EUVL diyAudio Member Join Date: Oct 2003	> Since the independent JFET's don't share a common substrate, there's no inherent thermal balance, but ..... This one is really an old story. Doesn't time fly ....... : The next best thing to 2SK389 / 2SJ109 ? Toshiba Dual JFET Heatsink Patrick __________________ xen-audio.com

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17th September 2012, 07:28 PM	#27701
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	It is just better to pay the price. You can't get quality for nothing, at least in my world view.

17th September 2012, 10:37 PM	#27704
RNMarsh diyAudio Member Join Date: May 2012 Location: 2457 Cascade Trail; Cool, CA. 95614	take two jFETs of same type -- tie the drains together. tie the sources together. A dual gate jFET? I saw this done somewhere, i think.

17th September 2012, 11:03 PM	#27706
wayne In the hills diyAudio Member Join Date: Jan 2002 Location: Northern California	The Toshibas have a slight sonic advantage over the IR parts especially in the midrange clarity. I wish it wasn't so but it is. If you want the best for audio use the Toshibas.

17th September 2012, 11:09 PM	#27707
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	I don't know WHY they switched to those Toshibas, but I think it is not a risk that I would do to change them, just to save a few dollars. There must have been SOME REASON that they chose these parts over the IR's.

17th September 2012, 11:11 PM	#27708
john curl diyAudio Member Join Date: Jul 2003 Location: berkeley ca	34, so far, so good!