Old MOSFET schema. Opinions?

[Vesa]

Hi!

Yes, I'm very new here (my first post). Hope I fit in

What do you think about this amp. Desingn is quite old (but gold?). I was build one of these years ago, but then sold it after usin a few month. Now missing that thing.

Basic schema includes only one pair of FET's. I build it using 2 pair of them. More can be added. With two pairs of FET's and +/- 55V rails, amp produced 100W@8ohm and 200W@4ohm. With 500mA bias, amp working class A up to 1W.

What else can I tell.. Output devices are SK1058 and SJ162, if I remember right.

I was planning to make these kind of power amp again. I'm still confused, wich amp I choose. There's Leach, Krell-cone, Aleph's. I heard about Aleph first time in here. interesting "machine"

But can you experts tell me something this amp, that shema I post? Maybe build it again.. or not.

[johnnyx]

We cann't say anything without a schematic, we don't know what you're referring to.

[Vesa]

For some reason, my schema does'n show. Let's try again..

[Vesa]

I have also (naturally) pictures about that amp. Ihope, my files end up on board. As new member, I could not see my message immediately on the board.

[djk]

Your schema is a straight forward rip of a Hafler DH200/220/500

If you look at the Krell KSA50/100 schema you will notice they are the same except for the heavier drivers and BJT outputs.

The same cound be said for the:

Accuphase P300
Leach (a favorite of mine)
GAS Son of Ampzilla

[tschrama]

Looks fine to me too.. but a bit off topic... R6 R17... What's the function of these resistors...?


Happy building in 2005 ..
Thijs

[AndrewT]

Hi,
The doubling up of the zobel circuit seems a bit unusual R34/35 and C15/16.
What are the advantages?
regards Andrew T.

[Tube_Dude]

Originally posted by tschrama
... R6 R17... What's the function of these resistors...?

R16 and R17 equalize the voltage gain of T2,T6 with gain of T1,T5 by both "seeing" the some collector load resistor.

That way , the Miller capacity , will be similar in all the four transistors and the differentials will be more balanced in the high frequencies.

Cheers and a Happy New Year

[Vesa]

These aforementioned schemas looks quite similar (topology) to me. Thaks. Maybe that's one reason, why I'm askin, after analyzing Krell's schematics and other similar. But I am not expert of amp circuit

I'd like to build Krell, Aleph or other "beast", but huge class A blocks.. They cost a fortune I think I need at least 50-60W, maybe 100W@8ohm (or more )

Do I hear differense between class A or B, Don't know.

R6, R17. I can't tell functions of these, sorry.


Happy new year to all !!

[Duo]

Well, this is almost a copy of the schematic in my hafler dh200 except for the CCS on each differential amplifier and a couple of other things including the outputs.

I find it's a pretty nice amp.

If you go to build it, I hope you have a chart of all the various resistor and part values