Is this a joke?!!!

xeclipse · 07:51 AM

This:

DevilsDance · 22nd October 2010, 07:37 AM

For sure!

alexcp · 22nd October 2010, 09:27 AM

This is a simple three-stage, class B amp. It probably works, but "amazingly well" is a very subjective statement.

xeclipse · 22nd October 2010, 09:52 AM

I have almost everything in my 'shack' to build this,but i don't think i will!

jaycee · 22nd October 2010, 10:53 AM

Well you won't get 100-150W out of it. 45V rails is pushing it. Maybe 25-35V. TIP41 makes a lousy VAS. Diodes for biasing mean it'll run largely in class B - and the instructions dont say anything about mounting them on the heatsink with the output transistors, so it'll likely blow up due to thermal runaway under load.

With just a few more parts you can build a stable, reliable amp that doesnt sound too bad.

richie00boy · 22nd October 2010, 12:06 PM

Not this again, must be the fifth time round by now...

DF96 · 22nd October 2010, 12:16 PM

A poor circuit, drawn in a peculiar way which hides its operation. It would suffer from crossover distortion (from the crude diode bias), output DC offset (from the mismatched bias resistances for the input pair) and a big thump on switch-on (due to large input capacitor). Bass response stops at 20Hz due to the 100uF capacitor in the feedback loop, but as this is an electrolytic it is subject to low tolerance so a stereo pair could have LF points a long way apart. HF response is not defined at all, so there may be a risk of instability.

It looks like a first attempt by someone who has just come across the standard 'op-amp' topology, but has yet to really understand it.

Some little man in a Chinese workshop is probably tooling up to make these, as we speak. Put it in a fancy polished box and morons would buy it off ebay!

xeclipse · 22nd October 2010, 09:55 PM

Quote:

Originally Posted by DF96

Some little man in a Chinese workshop is probably tooling up to make these, as we speak. Put it in a fancy polished box and morons would buy it off ebay!

... and probably a sticker:'1000 WATTS'!

gaetan8888 · 10:52 PM

Hello

It's a bad joke, we see often this bad circuit on the Net.

There is no Zobel network at the output.

This circuit even don't have a cdom capacitor between the base and collector of the VAS transistor !

This circuit would oscillate, sound bad, overheat and die... requiem in pace.

Nobody should build this circuit.

If any would need an easy to build amp, try the Dx amp, it still simple to build and are way much better.

Bye

Gaetan

22nd October 2010, 09:52 AM	#4
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	I have almost everything in my 'shack' to build this,but i don't think i will! __________________ if there are no sparks,it probably doesn't work!

22nd October 2010, 12:06 PM	#6
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Not this again, must be the fifth time round by now... __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

22nd October 2010, 10:40 PM	#9
gaetan8888 diyAudio Member Join Date: Apr 2007	Hello It's a bad joke, we see often this bad circuit on the Net. There is no Zobel network at the output. This circuit even don't have a cdom capacitor between the base and collector of the VAS transistor ! This circuit would oscillate, sound bad, overheat and die... requiem in pace. Nobody should build this circuit. If any would need an easy to build amp, try the Dx amp, it still simple to build and are way much better. Bye Gaetan Last edited by gaetan8888; 22nd October 2010 at 10:52 PM.

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22nd October 2010, 07:37 AM	#2
DevilsDance diyAudio Member Join Date: Jul 2010 Location: somewhere in Ukraine	For sure!

22nd October 2010, 09:27 AM	#3
alexcp diyAudio Member Join Date: Jun 2009 Location: Florida Blog Entries: 28	This is a simple three-stage, class B amp. It probably works, but "amazingly well" is a very subjective statement.

22nd October 2010, 10:53 AM	#5
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Well you won't get 100-150W out of it. 45V rails is pushing it. Maybe 25-35V. TIP41 makes a lousy VAS. Diodes for biasing mean it'll run largely in class B - and the instructions dont say anything about mounting them on the heatsink with the output transistors, so it'll likely blow up due to thermal runaway under load. With just a few more parts you can build a stable, reliable amp that doesnt sound too bad.

22nd October 2010, 12:16 PM	#7
DF96 diyAudio Member Join Date: May 2007	A poor circuit, drawn in a peculiar way which hides its operation. It would suffer from crossover distortion (from the crude diode bias), output DC offset (from the mismatched bias resistances for the input pair) and a big thump on switch-on (due to large input capacitor). Bass response stops at 20Hz due to the 100uF capacitor in the feedback loop, but as this is an electrolytic it is subject to low tolerance so a stereo pair could have LF points a long way apart. HF response is not defined at all, so there may be a risk of instability. It looks like a first attempt by someone who has just come across the standard 'op-amp' topology, but has yet to really understand it. Some little man in a Chinese workshop is probably tooling up to make these, as we speak. Put it in a fancy polished box and morons would buy it off ebay!

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