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Old 3rd January 2002, 02:01 AM   #141
hifi is offline hifi  Sweden
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it would be nice if you could mail me that layout (for the pearl phono)

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Old 19th February 2002, 08:56 PM   #142
EngelholmAudio is offline EngelholmAudio
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Hi there,

Could you, Petter mail me?


Nice if us scandinavians keep toghether! ;-D
best regards Engelholm Audio
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Old 15th April 2002, 05:18 PM   #143
Musher is offline Musher
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Hello... This thread seems to have died out or something.

Did Petter ever get his X100 to work?

I have soon big populations of Fairchild IRFP240 and IRFP9240 here (the industry standard versions), and hopefully can then start obtaining the "lesser" parts and building an X circuit of my dreams.

What I am most afraid of is that as my room's temperature (or the amplifier's internal temperature) rises some degrees, the current sources go into a mismatch and smoke comes out from everywhere.

I think we can be quite sure that NP doesn't use "triplets" in his commercial amplifiers, or I'd be at least amazed if he did. By looking at the pictures in the Pass Labs' products section I have seen only one trimpot in a single X amplifier channel. I wonder would it be any more criminal than this thread to see if I can find a real X amplifier and see what's inside. But if there really aren't any stability problems with Petter's "triplets", I might as well be happy with them. And I don't seriously think any owner of a real X amp would appreciate me opening the case of his treasure.

BTW. Do I lose anything if I use IRF610 as the input pair and forget about JFETs?

-Kimmo Sundqvist
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Old 16th April 2002, 09:20 AM   #144
Petter is offline Petter
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I believe the most people use doublets, i.e a fixed resistor with say a 5K paralell pot. This means that if you turn the pot towards zero, you will get zero ohms.

The triplet approach basically gives you more useful turns (less sensitivity) on the turns but is by no means necessary. You can obtain a similar effect by using fixed resistor with series low value pot (say if target is 200-250 ohms, a 200 ohm unit with a 50 ohm series pot will give you maximum usage of all turns). The "Problem" with that approach is that you get all the current through the trimpot. Probably not all that much of a problem, but still ...

I thus believe triplets will give you the best result -- low power consumption in the trimpot + fairly linear use of all turns. This again leads to better stability.

A note on JFET's: If I found a better photo of the JFET pass units, I could probably see a little more. However, through the fuzz there seems to be 4 JFETS's parallelled per side (much like a double Pearl input stage) connected as a long tailed pair?

Sorry to all those who have made this thread exciting -- I have not yet had the time to complete the unit

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Old 16th April 2002, 12:37 PM   #145
Holger Barske is offline Holger Barske  Germany
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Perhaps this pic may help a little. It is the x-amp module from an X150. I hope Nelson doesn't mind if I post it here...


[image removed until further notice]
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Old 16th April 2002, 04:03 PM   #146
dlharmon is offline dlharmon  United States
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Default Circuit Simulation

Try searching for switchercad it's was created by a semiconductor company. It has IRFP240 and IRFP9240's (I think) - I am running linux now so I can't check. It is totally free and works well for me. The interface is different than Circuit Maker which I too tried, but it can be learned in about an hour. I think it even has tubes.

If anyone knows about a good simulator for linux I would like to know about it.

Darrell Harmon
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Old 16th April 2002, 04:16 PM   #147
HarryHaller is offline HarryHaller  United States
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Angry Nelson

He is going to have a fit........

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Old 16th April 2002, 04:37 PM   #148
jam is offline jam  United States
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You might want to remove the picture until you get permission from Mr.Pass, to post it.

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Old 16th April 2002, 04:44 PM   #149
HarryHaller is offline HarryHaller  United States
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Exclamation Absolutley

Mr. Pass has been much too generous to to treat this way. I feel fairly certain that he would not want this up there. Not just hobbyist read this forum.

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Old 16th April 2002, 04:54 PM   #150
tschrama is offline tschrama  Netherlands
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Dear HBarske,

I feel that maybe you have crossed a thin line there. Although your efforts are much apreciated I would feel more comfortable if the photo would be removed.

T. Schrama
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