ThermalTrak transistor application.

Jeb-D. · 6th May 2009, 04:21 AM

Balancing current in PP amplifiers. What do you think?

revintage · 6th May 2009, 06:00 AM

Great use of a Thermaltrak!

Same, same but different

:

http://www.diyaudio.com/forums/showt...05#post1613405

For a "normal" PP I would substitute the cathode resistor(above the diode) with a CCS as to make both tubes having CCSs at their cathodes.

Also Audiodesignguide has something alike at his site.

Arnulf · 6th May 2009, 08:42 AM

This assumes ideal (matched) output tubes that don't 'age' differently through use ?

revintage · 6th May 2009, 08:52 AM

Quote:

This assumes ideal (matched) output tubes that don't 'age' differently through use ?

No, the rightmost tube(slave) will get the same current as the left(master). This due to the currentmirror configuration.

JoshK · 6th May 2009, 01:57 PM

Does this keep them in strict class A?

janneman · 6th May 2009, 02:04 PM

Nice app!

But the transistor current is not automatically the same as the diode current. They will track, but you need something more to make sure they are the same.

Jan Didden

revintage · 6th May 2009, 03:04 PM

Hey Jan,
As you see in my SEPTOR schematic there are resistors below the transistors. This way you can finetune tracking.

kenpeter · 6th May 2009, 04:30 PM

I am fairly sure the thermaltrak diode is NOT the same as the
bipolar's emitter. And I'm not sure why it was done that way.

Jeb-D. · 6th May 2009, 04:54 PM

Quote:

Does this keep them in strict class A?

No, it just balances current between the two. Could be used for class A or AB.

Quote:

For a "normal" PP I would substitute the cathode resistor(above the diode) with a CCS as to make both tubes having CCSs at their cathodes.

Good idea. I just used a resistor so that it could be used for class AB also. Thanks for the link to the Septor schematic. Have you had good results with the current mirror? I'd think it provides good DC balance regardless of signal amplitude. Opposed to using trimmer methods, which will only balance DC at idle.

Quote:

But the transistor current is not automatically the same as the diode current. They will track, but you need something more to make sure they are the same.

A resistor will be added to the diodes cathode and the BJT's emitter.

Jeb-D. · 6th May 2009, 04:58 PM

Quote:

I am fairly sure the thermaltrak diode is NOT the same as the bipolar's emitter. And I'm not sure why it was done that way.

You may be right. I ordered the parts to give it a go. I'll provide some data when done.

6th May 2009, 04:21 AM	#1
Jeb-D. diyAudio Member Join Date: Nov 2005 Location: SoCal	ThermalTrak transistor application. Balancing current in PP amplifiers. What do you think?

6th May 2009, 06:00 AM	#2
revintage diyAudio Member Join Date: May 2007 Location: Eskilstuna, Sweden	Great use of a Thermaltrak! Same, same but different : http://www.diyaudio.com/forums/showt...05#post1613405 For a "normal" PP I would substitute the cathode resistor(above the diode) with a CCS as to make both tubes having CCSs at their cathodes. Also Audiodesignguide has something alike at his site. __________________ Brgds Lars

6th May 2009, 02:04 PM	#6
janneman diyAudio Member Join Date: May 2002 Location: Where Germany, The Netherlands and Belgium meet Blog Entries: 6	Nice app! But the transistor current is not automatically the same as the diode current. They will track, but you need something more to make sure they are the same. Jan Didden __________________ /Another new issue: Linear Audio Volume 3!

6th May 2009, 03:04 PM	#7
revintage diyAudio Member Join Date: May 2007 Location: Eskilstuna, Sweden	Hey Jan, As you see in my SEPTOR schematic there are resistors below the transistors. This way you can finetune tracking. __________________ Brgds Lars

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6th May 2009, 08:42 AM	#3
Arnulf diyAudio Member Join Date: Feb 2009	This assumes ideal (matched) output tubes that don't 'age' differently through use ?

6th May 2009, 01:57 PM	#5
JoshK diyAudio Member Join Date: May 2004 Location: Toronto, ON	Does this keep them in strict class A?

6th May 2009, 04:30 PM	#8
kenpeter diyAudio Member Join Date: Nov 2007 Location: Dallas	I am fairly sure the thermaltrak diode is NOT the same as the bipolar's emitter. And I'm not sure why it was done that way.

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