Help with F5 with Gamut style MOSFET's

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#121
I am thinking about making a (buffered) Zen with the PM50502C.
Crss is 400pF according to the datasheet I found.
Should not be too bad?
http://kaitodenshi.sub.jp/datasheet/pm50502c.pdf

I have a pair of 2-way 4ohm DIY speakers with no real passive crossovers yet, so why not go 4-ch Zen with active Xover 🙂
They have 8+8 8ohm drivers each so my options of wiring them are 4 or 16ohms.
16 would be interesting too, but not that great for the "usual" amplifiers maybe.

And for the record I have had success with the SOT-227 IXYS mosfets in my Aleph monster, but in an unbuffered Zen the sound was not that superb 🙂
I can check types if someone is interested.
 
#126
Zen Mod said:
low Rout drive is must

and, again, ZM being too much of Chicken to even think of using them Pucks without constant monitoring .......... :clown:

meaning - active biasing circuit .....
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" low Rout drive is must "

Absolutely - IMO its all about having a low Zout so that current can get from the power supply to the load (speakers ).

Source resistors are used in Nelson Pass' XA25 design.

.
 
#127
Zen Mod said:
well, as I said - I'm too much of chicken , to rely on passive biasing arrangement, when dealing with parts having xconductance in range of medium car detonation
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I agree that transconductance of double lateral mosfet is an Order of magnitude lower than of the one of the high transconductance mosfet discussed here….as I said it was only for inspiration purpose…. surely a source resistor would be needed in this case. For lateral there is no real need for source resistor. In my case it is only very small value for mainly measurements purpose…. Lowest Zout is not my main objective in a practical system…
Fab
 
#128
I didn't mention source resistors at all, and name of the game for XA25-like amp is exclusion of source resistors at output

XA-25-like, meaning using big pucks in whatever arrangement without source resistors

in short (again) - big pucks , Square Law

not being interested in construction with pucks having source resistors, I don't even know what value of same could tame their behavior (thermal slide of Iq) nor I care to even calculate

in any case, don't take this as rant, enjoy in whatever you did, if it works
 
#129
You misunderstand me Zen Mod. I am not using these pucks but lateral mosfet with no source or very small value resistors thus square law too. Sorry if I have disturbed or hijacked this thread since I did not realize it was specific to XA-25 like amp (I tought more F5) …I just wanted to show the thread starter a possible driver arrangement. I will now get back to the Solid state forum…😉

Fab
 
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#131
Ok just had a good night sleep…. I should be relaxed 😉

Sorry if I have not consulted all posts/threads on this subject, but to be clear for my own knowledge, the goal here is to get class A envelope down to 2 ohms load for a same given output bias current that would be used for 8 ohms load (not considering square law use), and at the same time also provide more than 5 times damping factor than the original F5 (reference XA-25 specifications).
Fab
 
#132
fab said:
Sorry if I have disturbed or hijacked this thread since I did not realize it was specific to XA-25 like amp (I thought more F5) …I just wanted to show the thread starter a possible driver arrangement.

Fab
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Fab,

Actually, your input is well appreciated. I looked at some of your designs before commenting.
The USSR - 3 amp looks quite interesting - but the issue is getting a hold of 2sk2013 and 2sj313's - of which I have none.
I was hoping Exicon makes an equivalent , but it doesn't look like they do.
http://www.exicon.info/cross-ref.phpRegardless, I'll be sending a PM.


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