Amp for low impedance ...???

Hello,
sorry for my poor englisch language, but I've some questions:

I can get some amounts of 2N 3773 realy cheap (Price about 0,30 $), but only the NPN not the PNP (2n6609) :(

-is the 2N3773 suitible for Audio (bass Amp only) or is it useless?
the PDF file looks good so far
here's a link with spec's: http://www.onsemi.com/pub/Collateral/2N3773-D.PDF
(150W @100V, [email protected] 8A min, Ic= 16/30 A(peak) 150 W 140V)
-because there are no cheap PNP 2N6609 (complementary of 3773) i've thougt "re"designing a Quasicomplementary Amp
I found a schematic but i want modify it to 2n3773 but lower supply Voltage (+-65 Volts) for lower output impedance (i want achive 2 ohms or so)
-I know Quasi Complementary Designs are from the 70ies but ist the sound realy so bad?
is it suitible for Bass in Bi Amped system?

original Transistor was MJ15024 & much higher Supply but I want to drive low impedance Speakers
so 2x6 of the 2N's I Think are good for driving 1,5... 2 Ohm's @ +-65 Volt ???

any comments? try it oder not???
thank you,
Stefan

edit:schematic simplified to the basics...
 

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djk

R.I.P
2001-02-04 4:23 am
USA
How fast are these 2N3773s? The Motorola (ON) are 4Mhz. I got some $0.30 Solitron 2N3773s, they aren't fast enough for an audio amplifier. In any event I would use a tripple output stage, (pre-driver, driver, and then the outputs) otherwise you won't have enough current gain.
 
For 2N3773 Ft = 0.3Mhz so the amp can work only for subbass aplication. If you have good devices made by Motorola or ON Semiconductors ( Toshiba branded are counterfit ) , you will can make a good and very cheap amp.
I used this parts year ago , and I have good impresions .
( Only for general audio , like PA or something like this ).

For pre-drivers I strongly recomend 2SC5200/2SA1943 . If you will use something smaller the fail will be posible.

Please tell us about your progres about this project.

Regards !
 
I saw many negative opinions about " low impendance " subject in this forum.

If the power devices are very cheap, what is the problem to use 60 pieces for a single power amp and leave any curent protection away ?

(Only 7w - 8w disipation for tranzistor).

In this case will cost 36 $ for 120 pieces 2N3773 . I saw too many bad schematics with a single pair of power tranzistors selled with 100$ or more.

For somebody how like to make audio amps ( DIY ) it is somethig fun and interestig to built this kind of experiments.

Regards !
 
thank You for so much reply!

Yes I see, the Driver must be very strong because of the small hfe
the base current becomes high of the output stage the driver should deliver it ...

You mentioned the 2SC5200/2SA1943 - I think there is a risk of getting counterfeit transistors (toshiba I think is a very good "chance" to get counterfeit)
what would be alternatives - if there are some one?
BD139/140 ist tooo small i think :(
 
Bass amp: It should be for my subwoofer 15...100 Hz active crossover @100 Hz

hm Mosfet Amp: I'm afraid i get an oscilating Amp ???
the 2n3773 are cheap available cheap Mosfet's i've no idea :(

driver's: hm Ive to visit local electronic shop tomorrow if there are good driver Transistors available

thank you for the Idea with "multiple" dirvers
 
Since you are going to use it for bass only (<100Hz), you can slow down the MOSFET's _very_ much before you get too slow fet's.

I made a subwoofer with a 500 W /4 ohms amp (+- 75 V). Total current consumption was (if I remember right) only 4 mA at full power! The bandwith was < 2 kHz. The sub works between 20-100 Hz. Pictures at my homepage.