My update lin topology - Page 6

GEirin · 25th October 2009, 06:59 PM

Stevens says of the Phase Linear PL400
"I think the main reason for connecting C11 to the emitter of the driver is that this emitter voltage follows the AC signal on the collector of Q5 much better than the output does, so the voltage across R18 is kept more constant and the collector impedance of Q5 becomes higher and more linear. I think even harmonic distortion is lower because the half wave rectified (class B) non linearity of the voltage across emitter resistors R40, 43, 45 is not fed back."

Bigun · 26th October 2009, 11:56 PM

GErin,

My vote: I like the buffer + VAS, this was where TGM was headed. It allows some interesting options with Cdom and it simulates very nicely. I believe it has the possibility to retain the Bootstrap sound that is key.

I hope you will try the experiment and build this kind of VAS as I have little time these days and have been interested in trying it out for ages

GEirin · 27th October 2009, 01:09 AM

Hi Bigun.

Thanks for you reply. I have litle time also. I will try your recommendation.

Your vote is: CFP input + buffer - VAS + CFP driver + EF output?

Guillermo

Bigun · 27th October 2009, 01:27 AM

Quote:

Originally Posted by GEirin

Hi Bigun.

Thanks for you reply. I have litle time also. I will try your recommendation.

Your vote is: CFP input + buffer - VAS + CFP driver + EF output?

Guillermo

Yes !

Actually, I'm also quite interested in CFP for the power output, but I have mixed feelings on this and I'm still reading and learning about the use of CFP in the output. My thinking is that CFP is the ultimate configuration but it works better in Class A. By using it for the driver stage you operate it in Class A and get lots of benefits.

I partly blame my love of the CFP on Lumba, who encouraged me early on during my formative learning stages to look at them...

CBS240 · 27th October 2009, 01:48 AM

Hi

It might be prudent to have the same Vce (Pd) on Q4 as on Q3. This can easily be accomplished by adding a PNP transistor cascode to Q4's collector wrt GND. The collector of Q4 to its emitter, base to GND, collector to the diodes where Q4 collector is now.

GEirin · 27th October 2009, 02:09 AM

Hi CBS240
Which schema?

CBS240 · 02:17 AM

post #51

Q3 Vce is 75V, and Q4 Vce extends all the way to the negative rail. Assuming the current is ~equal, Pd would be twice that of Q3. Vbe is affected by temperature, so you would want it the same for both devices, no?

GEirin · 28th October 2009, 05:24 PM

Hi all
A new idea in the VAS, (single folded).
Is a crazy amplifier? FCP input + single folded VAS - buffer + EF output.
Any opinions?
Thanks

Lumba Ogir · 28th October 2009, 05:55 PM

GEirin,
very nice. I would remove the CC stage after the VAS and that 180pF cap. Consider active current sources.

Bigun · 28th October 2009, 06:49 PM

Common base doesn't like to be loaded at the output, a buffer is generally needed.

26th October 2009, 11:56 PM	#52
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	GErin, My vote: I like the buffer + VAS, this was where TGM was headed. It allows some interesting options with Cdom and it simulates very nicely. I believe it has the possibility to retain the Bootstrap sound that is key. I hope you will try the experiment and build this kind of VAS as I have little time these days and have been interested in trying it out for ages __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

27th October 2009, 01:48 AM	#55
CBS240 diyAudio Member Join Date: Aug 2005 Location: K-town	Hi It might be prudent to have the same Vce (Pd) on Q4 as on Q3. This can easily be accomplished by adding a PNP transistor cascode to Q4's collector wrt GND. The collector of Q4 to its emitter, base to GND, collector to the diodes where Q4 collector is now. __________________ All the trouble I've ever been in started out as fun......

27th October 2009, 02:13 AM	#57
CBS240 diyAudio Member Join Date: Aug 2005 Location: K-town	post #51 Q3 Vce is 75V, and Q4 Vce extends all the way to the negative rail. Assuming the current is ~equal, Pd would be twice that of Q3. Vbe is affected by temperature, so you would want it the same for both devices, no? __________________ All the trouble I've ever been in started out as fun...... Last edited by CBS240; 27th October 2009 at 02:17 AM.

28th October 2009, 06:49 PM	#60
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	Common base doesn't like to be loaded at the output, a buffer is generally needed. __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

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27th October 2009, 01:09 AM	#53
GEirin diyAudio Member Join Date: Jun 2004 Location: Mendoza	Hi Bigun. Thanks for you reply. I have litle time also. I will try your recommendation. Your vote is: CFP input + buffer - VAS + CFP driver + EF output? Guillermo

27th October 2009, 02:09 AM	#56
GEirin diyAudio Member Join Date: Jun 2004 Location: Mendoza	Hi CBS240 Which schema?

28th October 2009, 05:55 PM	#59
Lumba Ogir Banned Join Date: Apr 2005 Location: Stockholm	GEirin, very nice. I would remove the CC stage after the VAS and that 180pF cap. Consider active current sources.

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