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Old 26th February 2010, 01:51 PM   #21
juma is offline juma  Germany
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Quote:
Originally Posted by VladimirK View Post
In my 50W Zen9 I use matched triplets of 2SK1058, total current 3,9A (1,3A and 40W per transistor), do not feel any problem.
In which position you use them as paralleled triplets without source resistors (Q2, Q3, Q4) ?
How tight are they matched (Vgs diff. 0.01V, 0.001V or less) ?
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Old 1st March 2010, 06:11 AM   #22
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Quote:
Originally Posted by juma View Post
In which position you use them as paralleled triplets without source resistors (Q2, Q3, Q4) ?
How tight are they matched (Vgs diff. 0.01V, 0.001V or less) ?
They are used in Q2, Q3 positions, matched to 0,05V, but I am sure 0,1V or even higher will cause no risk of thermal runaway (although that will be negative for a sound). Only violation of SOA can be a problem for laterals.
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Old 23rd April 2010, 01:35 AM   #23
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Originally Posted by juma View Post
I tried using Hitachi/Renesas lateral MOSFETs in F5 but they lack transconductance and can not provide sufficient gain as drain followers without harming the sound.
Hey Juma

Is this in general, or because you have tried to get higher gain ?

I mean, Profet with same input Jfet and the laterals is supposed to be ok, or ?
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Old 23rd April 2010, 01:49 PM   #24
juma is offline juma  Germany
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Originally Posted by tinitus View Post
...Is this in general, or because you have tried to get higher gain ?...
I didn't try to get more gain from laterals when building F5 with them. The point is that gm of laterals is low - you don't get enough Amperes for Volts invested (in this type of amp - F5)

Quote:
Originally Posted by tinitus View Post
...
I mean, Profet with same input Jfet and the laterals is supposed to be ok, or ?
If you by "OK" mean that it works, you are right, it is OK. But how it works, i.e. how it sounds? is where it's not OK (IMHO)...

Last edited by juma; 23rd April 2010 at 01:55 PM.
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Old 23rd April 2010, 02:02 PM   #25
tinitus is offline tinitus  Europe
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Ah, OK

Those drivers k2013 / j313 seems not so easy to find, or am I looking in the wrong places ?

You have chosen not to cascode the input jfets
Maybe you like to say something about that ?

Btw, slightly OT, but I suppose you know Elliot(ESP) did a design(AB) with these Hitachi laterals, project 101
But at some point he put it on hold because he found Hitachi devices hard to get, and most were fakes
Tho this may have changed with the Renesas

But yours is more interesting to me as I have not only Renesas but also the Jfets, and its outsprung from F5
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Old 23rd April 2010, 05:21 PM   #26
juma is offline juma  Germany
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Originally Posted by tinitus View Post
...Those drivers k2013 / j313 seems not so easy to find, or am I looking in the wrong places ?
I don't know - j313s were a gift from a friend (thanks estman) and k2013s were bought for me by a friend on a bussines trip to Tokyo.

Quote:
Originally Posted by tinitus View Post
You have chosen not to cascode the input jfets
Maybe you like to say something about that ?
No need for cascoding here, although I understand that it's a popular fetish these days
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Old 4th May 2010, 06:42 AM   #27
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The few k2013 / j313 I can find on the net are all $$$ price, as costly as TO-247/264 power device from Toshiba.
I'm checking to see how much it actually cost from Toshiba distributor.
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Old 12th July 2010, 02:17 AM   #28
tinitus is offline tinitus  Europe
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Hey, I was looking at Lundahl trafos
theres a special grid choke
it can be coupled with 1:2 gain

would it be possible...

or maybe interstage trafo
theres also a few with 1:2 gain
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Old 17th August 2010, 04:23 PM   #29
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Hello Juma

Do you still using these amplifier?
I want to know because probably I will give try. I have some orig Japanese Hitachi laterals .
I like these amp , has better feedback than Zenquito .
I have one question , what type of capacitors U use parallel with the feedback resistors and what is the value ?
Please let me know .
Thank you
Cheers
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Old 19th August 2010, 08:15 PM   #30
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Hello Juma

Please be so kind answer my question .I'm serious about your amp , I wanted to give a try to the Zenquito but I like these one better .
I think the current feedback much better than what Zenquito amp uses . And the fet driver also I think better than hat old BJT what the Zenquito use for driver .
I already made the PC boards and I ordered the Dale resisters .
I promise I do not bother you just please let me know the missing capacitor values .
I think foil capacitors U use but can be polyprop ,PIO etc .Also the value is important to .
Thanks
Greetings gabor
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