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Old 14th January 2005, 02:24 PM   #11
jaycee is offline jaycee  United Kingdom
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If you want something different, I have also seen a TL431 used as a vbe device, with a string of diode-connected transistors for thermal tracking. Look at the Stochino amplifier for an example

BTW you can get at least one TL431 for free from a dead PC PSU. I have a stack of them.
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Old 14th January 2005, 02:31 PM   #12
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Default do you have schemes for this





jaycee:

hi do you have schemes for this.


hienrich
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Old 14th January 2005, 02:43 PM   #13
jaycee is offline jaycee  United Kingdom
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Here it is:

http://www.soton.ac.uk/~apm3/diyaudi...no_circuit.jpg

I just tried this TL431 in my triple darlington amp SPICE sim (similar to the Leach Amp) and found it to be a bit tricky to control. Maybe a simple Darlington VBE would be best.
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Old 14th January 2005, 02:59 PM   #14
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Talking thanks I got it....



thanks Jaycee,





I got it I on to it now.






hienrich

offline........
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Old 14th January 2005, 03:14 PM   #15
Jennice is offline Jennice  Denmark
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Heinrich,

When I sent my first reply, I didn't have time up open your schematic.
Therefore I didn't know that you were already using a capacitor. I am using a 100uF in mine, and it works well for me.
I don't see a need for the film too, as the frequencies are low. They're more relevant for HF problems, I think.

Who says your transistor needs to be on the PCB, and you need to redesign your PCB???
I have mine connected to the PCB with wires. Who cares - it's just a DC source with floating potential, so you won't have to worry about inductances in the wires and HF problems with the Vbe multiplier / thermal monitor.

Jennice
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Old 14th January 2005, 03:17 PM   #16
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Jennice, your assumptions are not correct according to Leach. See his website.
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Old 14th January 2005, 03:31 PM   #17
Jennice is offline Jennice  Denmark
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Which part of my assumptions?
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Old 14th January 2005, 03:52 PM   #18
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Quote:
Originally posted by Jennice
Who says your transistor needs to be on the PCB, and you need to redesign your PCB???
I have mine connected to the PCB with wires. Who cares - it's just a DC source with floating potential, so you won't have to worry about inductances in the wires and HF problems with the Vbe multiplier / thermal monitor.
That bit. It's not just a DC source with floating potential because it's in the path of the VAS which is subject to AC and is sensitive to capacitance.
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Old 14th January 2005, 04:04 PM   #19
Jennice is offline Jennice  Denmark
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And who tells you thet one cannot have a DC source in an AC path? It just gives an offset.

I know the Vbe isn't an idea DC source with zero output impedance, but that's why the capacitor is placed on the PCB.

Jennice
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Old 14th January 2005, 04:16 PM   #20
Cortez is offline Cortez  Hungary
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