Bipolar Power Amp With Single Ended Input Stage Inpired by Mooly

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Tekko

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Joined 2004
Then how can a maximum of 20mA VAS current drive the drivers and the output transistors to full saturation when the IPS is a LTP ?

The VAS transistors dont even get warm, but LTspice suggest they should be dissipating around 3 watts with the current resistor values.
 
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Tekko

Banned
Joined 2004
I did a quick test, i hooked a MJE15030 to a MJL4281, givig the base of the MJE15030 direct 42V rail voltage results in a 2mA base current with a two ohm load on the MJL4281 which is actually less than what LTspice shows.

This was withj my DMM set to the 20mA scale and wired in series between the base of the driver transistor and a pot, so i think Lazy Cat's comment about the IPS fits better than VAS beeing unable to provice the current to drive the drivers.
 
Mooly

Mooly

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Tekko said:
Using a trible deep EF actually did cure the distortion issue, my DMM must be broken.

A video of "Mooly the SE IPS amp" rockin out: Mooly the SE IPS Amplifier - YouTube
Click to expand...

It's good to see a working amp. And another big advantage of the single ended input, it's very stable even in a lash up with less than perfect grounding and layout. Try doing that with an LTP and you might run into trouble.

Seriously though folks, don't you think a spin off thread might be a good idea if you want to work on and develop a bjt version ?
 
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Tekko

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Joined 2004
Don't bother.

I'm deciding to pull the plug on this project, had too many stability issues and i dont feel willing to put any more time on it... for now.

Implementing the DC servo just ended up in spiking toward the negative rail with any kinda signal input.

I also ended up frying my 2x30VAC ~200VA test psu transformer.
 
Lazy Cat

Lazy Cat

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Tekko said:
I'm deciding to pull the plug on this project, had too many stability issues and i dont feel willing to put any more time on it... for now.

Implementing the DC servo just ended up in spiking toward the negative rail with any kinda signal input.

I also ended up frying my 2x30VAC ~200VA test psu transformer.
Click to expand...

Adding one more driver and quadrupole output stage would definitely solve the problem. :D
 
homemodder

homemodder

Disabled Account
Joined 2006
Tekko I think youre trying to build it too fast and making mistakes, its very difficult going wrong with this design. It does distort more than blameless but its not such a huge difference. If you a a Jfet available I can supply you a schematic of my own design that is sold comercially and is very well regarded, people think there is a mega complicated amp in there. :D:D:D
Its as complicated as Moolys amp, except for use of triple outputstage, nothing more needed for very good sound.
 
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