F5 meets Buzquito

[juma]

Originally Posted by VladimirK

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) ?

[VladimirK]

Originally Posted by juma

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.

[tinitus]

Originally Posted by juma

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 ?

[juma]

Originally Posted by tinitus

...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)

Originally Posted by tinitus

...
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)...

[tinitus]

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

[juma]

Originally Posted by tinitus

...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.

Originally Posted by tinitus

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

[zhoufang]

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.

[tinitus]

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

[gaborbela]

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

[gaborbela]

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