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Old 26th January 2012, 04:54 AM   #1821
mikelm is offline mikelm  England
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I suspect that Jfets can be brought to life if the circuit architecture around them allows for their inherent characteristics and I also suspect that in the the right system the B1 would sound just fine.

However, for me it's o/p impedance of 1000R would be enough to explain why some amps may sound a bit tame when partnered with it - I would prefer 10 - 50R

I believe it's down to the designer to design the "life" into a circuit.

Also, some systems / speakers already abound with "life" & excitement while others need all the help they can get.

I don't believe Jfets have some mystical lifeless quality that forever dooms any circuit / system they are used in to sound boring but, like any other component, they do need to be implemented well in a circuit and that circuit to be partnered well in a system.

mike

Last edited by mikelm; 26th January 2012 at 05:10 AM.
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Old 26th January 2012, 06:47 AM   #1822
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Originally Posted by Jay View Post
As for input stage, I prefer bipolar to the standard JFET (K170). Standard JFET do not have "live" to my ears (=boring).
And what is your feeling about Mosfets ?
About JFETs, may-be the problem do not come from them, but the way they are used ? They love to be polarized with a lot of quiescent current (chosen for that) and kept hot.
Often, too, and because the high Z of the gate, the gate resistance to ground is sometimes set at a hight value, so the input impedance..
But more current flow in signal wires better it is and charging more the previous preamp can change a lot the way it sound ?
They are supposed to be more linear than bipolars (more like a tube), is this "liveness" just less distortion or some small signal losses ? Or their different noise factor's curve ?
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Old 26th January 2012, 11:51 AM   #1823
Salas is offline Salas  Greece
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Originally Posted by Ruwe View Post

However, I don't believe that Pass F5, for example, being with J-FET input and very similar to SSA would sound the same.
I had F5 in my system for a brief, and as far as I can remember it was a much different sound to SSA with laterals.
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Old 26th January 2012, 09:00 PM   #1824
tinitus is offline tinitus  Europe
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homemodder have a new thread

Sidetrack Simple Symmetric Amplifier


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Old 28th January 2012, 12:17 PM   #1825
PauloPT is online now PauloPT  Portugal
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Default Group buy?

Sorry for the intromission. I was wondering if it will be a group buy for pcbs of this amp?

Thanks
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Old 28th January 2012, 05:53 PM   #1826
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PauloPT, see post #1708 and see Lazy Cat reply. I think he wants to show the finished product first before offering the group buy. I think most of us here on this thread is looking forward to build this project and wants to hear how it sounds. It might be an amp to be considered " The Very Best Amplifier I Have Ever Hear!!!"
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Old 28th January 2012, 06:02 PM   #1827
shaan is offline shaan  India
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Originally Posted by fredlock View Post
It might be an amp to be considered " The Very Best Amplifier I Have Ever Hear!!!"
It is.

Even my awfully inefficient speakers came alive when I played SSA through them. Beforehand, only my JLH could do this, but it had a volume limit for clean listening. SSA, on the other hand, sounded more and more cleaner and ALIVE as I turned the knob clockwise. I am building it again!
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Old 28th January 2012, 09:05 PM   #1828
a.wayne is offline a.wayne  United States
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It is.

Even my awfully inefficient speakers came alive when I played SSA through them. Beforehand, only my JLH could do this, but it had a volume limit for clean listening. SSA, on the other hand, sounded more and more cleaner and ALIVE as I turned the knob clockwise. I am building it again!
Which version did you build ..... ?
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Old 29th January 2012, 05:46 PM   #1829
shaan is offline shaan  India
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a.wayne,

I built the Lateral output version with BD139/140 VAS, +-24V Supply.

Lynk-> Simple Symetrical Amplifier
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Last edited by shaan; 29th January 2012 at 05:57 PM. Reason: lynk
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Old 31st January 2012, 07:59 PM   #1830
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Hi. New to the thread I'm finding quite a bit to take in. It's fun to see all of the great ideas and try to follow the evolution and forks of the circuit. Great work guys! Knowing that even small things can be significant, it's easy to miss the thinking behind some of the details but I'm trying. Looking at the circuit in post 916 (with both PNP and NPN current boosters for each FET): Both types of transistors seem to be doing the same thing. Was the combination of both PNP and NPN boosters used to make the upper and lower output halves more inherently matched? I can see that the .22 Ohm resistors improve the behavior of the added bipolars. I was pondering whether it might be worthwhile to have the .22 Ohm resistors towards the supplies also include the FETs in the local feedback provided (to help linearize and match FET behavior) by moving the 1K cascode load resistors to the other side of the .22's (then going directly to the power supplies)? Then any drop across those .22 resistors would slightly reduce the FET drive. I've probably missed something, but figured I'd put the idea out there before I forgot about it.
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