832A PP Amp LTP

alexg · 13th June 2007, 12:10 PM

I am building an 832A PP amp based on the attached schematic from ultranalog.com.

Unfortunately, I cannot source the transistor for the CCS, if I have to replace it with resistors, would I need a cathode resistor and then a tail resistor? How do I compute the values?

If I wanted to replace the driver/phase inverter tubes with a tube with octal base, any recommendation?

Would 6n1p work instead of the 5670?

Thanks.

analog_sa · 13th June 2007, 12:45 PM

Replacing with a resistor is not a good idea. You might need a negative supply voltage or at least raise the main supply.

Why don't you just use other npn transistors? I can't see supermatching being important here. Or just use another type of CCS - many options.

arnoldc · 13th June 2007, 02:43 PM

Alex, those transistors are available at our local Farnell (Order code 9605088 ) and RS Components (Order code 522-9868 )

If you should replace those with resistors, I'd suggest a negative supply.

Why not use the diyAudio CCS?

Svein_B · 13th June 2007, 03:12 PM

I think a negative supply is higly recommended for the CCS. As shown, there is very little voltage for the CCS to work with.

A small 6-12V transformer salvaged from an old fasioned power supply should work fine. Then you will be free to use the DIYAudio CCS, or any other CCS of your choice.

SveinB.

Tony · 13th June 2007, 07:12 PM

alexg,

2sc945, & 2sc1815 are common, there are lots of to92 npn trannies that are available, they are abundant as they are cheap in RAON.

13th June 2007, 07:12 PM	#5
Tony diyAudio Member Join Date: May 2003 Location: Palatiw, Pasig City	alexg, 2sc945, & 2sc1815 are common, there are lots of to92 npn trannies that are available, they are abundant as they are cheap in RAON. __________________ http://www.electronicslab.ph/forum/i...?topic=32688.0

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13th June 2007, 12:45 PM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Replacing with a resistor is not a good idea. You might need a negative supply voltage or at least raise the main supply. Why don't you just use other npn transistors? I can't see supermatching being important here. Or just use another type of CCS - many options.

13th June 2007, 02:43 PM	#3
arnoldc diyAudio Member Join Date: Apr 2003 Location: Makati	Alex, those transistors are available at our local Farnell (Order code 9605088 ) and RS Components (Order code 522-9868 ) If you should replace those with resistors, I'd suggest a negative supply. Why not use the diyAudio CCS?

13th June 2007, 03:12 PM	#4
Svein_B diyAudio Member Join Date: Oct 2005	I think a negative supply is higly recommended for the CCS. As shown, there is very little voltage for the CCS to work with. A small 6-12V transformer salvaged from an old fasioned power supply should work fine. Then you will be free to use the DIYAudio CCS, or any other CCS of your choice. SveinB.

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