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Old 31st May 2012, 12:04 AM   #501
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Old 31st May 2012, 03:23 AM   #502
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Originally Posted by EUVL View Post
You are misquoting me I am afraid.

My proposed alternative (in post #42) is not based on reducing the source resistor (only).
The key to my proposal is using MOSFETs with much higher Yfs (e.g. 2SK3497).
That, combined with a reduction in Rsource will give the same current gain as a 2SK1530 plus a diode.

See :
F5 Turbo is posted

And I do not consider 0R33 for Rsource to be low. The F5X uses 0R22 since day one.
Nor have I ever experienced any bias stability at steady state.
Yes, the bias is a bit lower when cold. But once it has warmed up, it stays there.
Assuming of course your heat sinks are properly sized.

And I am still not a believer of the diode.


Patrick
I was indeed "under-quoting" you.

My enthusiasm for the Turbo has declined to agnostic after more LTspice simulations. I do not trust the device models. Until I actually perform live tests I will defer judgement on the Turbo.

I do agree with you (EUVL) about the balanced F5 at 16V with low source resistors. I am built one as reported in: Balanced F5 in a Small Footprint. It uses .25 ohm source resistors and achieves very low THD up to 50 watts at bias currents as low as 1 amp.
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Old 31st May 2012, 03:44 AM   #503
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I am going to the pub

Last edited by Melon Head; 31st May 2012 at 03:47 AM.
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Old 31st May 2012, 03:53 AM   #504
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Just wondering whether you guys will believe in real world measurements.
We can quickly end all of this, if I do the measurements.
I generally prefer to use my ears though.
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Old 31st May 2012, 07:35 AM   #505
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Old 31st May 2012, 09:12 AM   #506
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Quote:
Originally Posted by lhquam View Post
I was indeed "under-quoting" you.

My enthusiasm for the Turbo has declined to agnostic after more LTspice simulations. I do not trust the device models. Until I actually perform live tests I will defer judgement on the Turbo.

I do agree with you (EUVL) about the balanced F5 at 16V with low source resistors. I am built one as reported in: Balanced F5 in a Small Footprint. It uses .25 ohm source resistors and achieves very low THD up to 50 watts at bias currents as low as 1 amp.
Funny thing is, you don thave to hav eon eor the other. Melon head has shown the improvement it makes. If you like Rs that is low, like .22R, then run the bias @ 2A an dstill use the diodes. You get the distortion improvement from higher bias, you are using a lower Rs, and the diode is still there for a little extra grunt.
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Old 31st May 2012, 09:40 AM   #507
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Yeah no worries.
You can have any source resistance you want (with or without the diodes).
The higher the source resistance the greater the bias will jump when the diode completely turns on.
The lower the source resistor the lower the bias will jump when the diode completely turns on.
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Old 31st May 2012, 10:49 AM   #508
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Old 31st May 2012, 11:08 AM   #509
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Old 31st May 2012, 11:15 AM   #510
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