Supertriode with PNP transistors

Hylle · 6th June 2010, 04:10 PM

Found on John Bronski´s site :
SuperTriodes & Inverted ES Speakers

Can a tube really drive the output transistor if a powerfull output is needed, like for a speaker!

Can some one explain to me how it works, what about termal run away in the trasistors? and idle current?
Is there a working amp on the internet somewhere i can learn from?

Regards Allan

janneman · 6th June 2010, 04:56 PM

Quote:

Originally Posted by Hylle

Found on John Bronski´s site :
SuperTriodes & Inverted ES Speakers

Can a tube really drive the output transistor if a powerfull output is needed, like for a speaker!

Can some one explain to me how it works, what about termal run away in the trasistors? and idle current?
Is there a working amp on the internet somewhere i can learn from?

Regards Allan

Seems to me that the only thing the tube does is drive the gainclone-type amp as a cathode follower or buffer. Since the gainclone has a high input Z, that's a no brainer. So, your question should really be directed at a gainclone amp, not at the tube.
The tube isn't really required but does impart a 'tubey' sound (tube-type distortion spectrum) to the output.

jd

Fenris · 7th June 2010, 12:33 AM

The tube actually looks like it's in the feedback loop, the gainclone is just a current booster. I've got a PCB for this design in the works, when I get it built, I'll report on the results.

Hylle · 7th June 2010, 06:57 AM

Sorry guys for not beeing precise enough. Please take a look at the middle of the page. subject "SuperTriode Meets the Aikido".

WT · 7th June 2010, 09:00 AM

Look like a good idea tube sound with current of gainclone. Do we need high voltage swing to drive the super triode with gainclone.

Fenris - Please report back when you are done.

Hylle · 7th June 2010, 11:22 AM

Please keep the gain clone of of this, I refer to the circuit in the middle of the page, with an akido tubeamp with NPN or a PNP output transistors added.
Can the tubes really drive the transistors. I guess the transistors will only have 25-50 time current gain.

TheGimp · 7th June 2010, 01:38 PM

I think MOS-FETs would have been a better choice due to the gain of Beta*Ib of the bipolar transistors (Yes 25-50 is probably a good range).

However, the combination of source follower on top and common emitter on bottom is going to give some additional non-linearity and the output impedance of the two is quite different.

kenpeter · 7th June 2010, 05:06 PM

mosfet has to worry gate blowout when the cathode is cold.
PNP at the plate by itself is already perfect, no need to fix.

Hylle · 8th June 2010, 07:04 AM

I guess peak currents in a speaker can be pretty high, do you think the tube can drive the Transistor good enough if the transistor HFE is around 25-50. I guess it will have to be a power tube to make it work?

6th June 2010, 04:10 PM	#1
Hylle diyAudio Member Join Date: Feb 2005 Location: Denmark	Supertriode with PNP transistors Found on John Bronski´s site : SuperTriodes & Inverted ES Speakers Can a tube really drive the output transistor if a powerfull output is needed, like for a speaker! Can some one explain to me how it works, what about termal run away in the trasistors? and idle current? Is there a working amp on the internet somewhere i can learn from? Regards Allan

7th June 2010, 12:33 AM	#3
Fenris diyAudio Member Join Date: Jun 2004 Location: The last frontier	The tube actually looks like it's in the feedback loop, the gainclone is just a current booster. I've got a PCB for this design in the works, when I get it built, I'll report on the results. __________________ Listen to the music through the stereo, not the stereo through the music.

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7th June 2010, 06:57 AM	#4
Hylle diyAudio Member Join Date: Feb 2005 Location: Denmark	Sorry guys for not beeing precise enough. Please take a look at the middle of the page. subject "SuperTriode Meets the Aikido".

7th June 2010, 09:00 AM	#5
WT diyAudio Member Join Date: Jun 2002 Location: Bangkok, Thailand	Look like a good idea tube sound with current of gainclone. Do we need high voltage swing to drive the super triode with gainclone. Fenris - Please report back when you are done.

7th June 2010, 11:22 AM	#6
Hylle diyAudio Member Join Date: Feb 2005 Location: Denmark	Please keep the gain clone of of this, I refer to the circuit in the middle of the page, with an akido tubeamp with NPN or a PNP output transistors added. Can the tubes really drive the transistors. I guess the transistors will only have 25-50 time current gain.

7th June 2010, 01:38 PM	#7
TheGimp diyAudio Member Join Date: Aug 2009 Location: Johnson City, TN	I think MOS-FETs would have been a better choice due to the gain of Beta*Ib of the bipolar transistors (Yes 25-50 is probably a good range). However, the combination of source follower on top and common emitter on bottom is going to give some additional non-linearity and the output impedance of the two is quite different.

7th June 2010, 05:06 PM	#8
kenpeter diyAudio Member Join Date: Nov 2007 Location: Dallas	mosfet has to worry gate blowout when the cathode is cold. PNP at the plate by itself is already perfect, no need to fix.

8th June 2010, 07:04 AM	#9
Hylle diyAudio Member Join Date: Feb 2005 Location: Denmark	I guess peak currents in a speaker can be pretty high, do you think the tube can drive the Transistor good enough if the transistor HFE is around 25-50. I guess it will have to be a power tube to make it work?

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