Balance in CCS Long Tailed Pairs - Page 11

Yvesm · 6th November 2010, 09:03 AM

OMG ! I missed this wonderfull thread and I've just read it back from the start with complete agreement with SY.

Now, what about using pentodes to obtain more gain (more drive) without any additional stage ?
The offender is that "shitty" screen current wich does not participate to the output voltage while it passes trhu the CCS and may unbalance the whole thing . . . at least until you read the Franck Blöhbaum 'Best Pentode" paper in Linear Audio.

Then you can use pentode LTP PI without adding some form of (un)balance adjustment . . . Problem solved

Yves.

Sch3mat1c · 7th November 2010, 10:51 PM

Tektronix used pentode LTPs all the time. As long as you stay out of saturation, screen current is pretty much linear with plate current, so it balances out and nothing happens.

And when you hit saturation, cathode current essentially remains constant, which might actually be an advantage for clipping recovery -- the extra current being sunk from the screen. Even so, an LTP can easily be made so it "never" saturates.

Tim

Wavebourn · 7th November 2010, 11:13 PM

Here you go, again:

http://wavebourn.com/forum/download.php?id=460&f=7

Concertina + LTP driving GU-50 output with parallel feedback:

http://wavebourn.com/forum/download.php?id=462&f=7

7th November 2010, 10:51 PM	#102
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Tektronix used pentode LTPs all the time. As long as you stay out of saturation, screen current is pretty much linear with plate current, so it balances out and nothing happens. And when you hit saturation, cathode current essentially remains constant, which might actually be an advantage for clipping recovery -- the extra current being sunk from the screen. Even so, an LTP can easily be made so it "never" saturates. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

7th November 2010, 11:13 PM	#103
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	Here you go, again: http://wavebourn.com/forum/download.php?id=460&f=7 Concertina + LTP driving GU-50 output with parallel feedback: http://wavebourn.com/forum/download.php?id=462&f=7 __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Long tailed pair schematic questions	martyh	Tubes / Valves	17	28th January 2009 10:27 PM
LTPZen, Zen with long tailed pair input stage	Allen Newby	Pass Labs	18	28th January 2007 03:19 PM
DC coupled long tailed pairs	sajti	Tubes / Valves	10	23rd February 2005 07:16 PM
CCS Conceptual Qs, Using Gary Pimm CCS as Example	DrDeville	Tubes / Valves	20	12th May 2004 02:41 PM
Long Tailed Pair Modification	lubbie	Solid State	31	11th May 2004 07:11 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read

6th November 2010, 09:03 AM	#101
Yvesm diyAudio Member Join Date: Jul 2004 Location: Ardeche	OMG ! I missed this wonderfull thread and I've just read it back from the start with complete agreement with SY. Now, what about using pentodes to obtain more gain (more drive) without any additional stage ? The offender is that "shitty" screen current wich does not participate to the output voltage while it passes trhu the CCS and may unbalance the whole thing . . . at least until you read the Franck Blöhbaum 'Best Pentode" paper in Linear Audio. Then you can use pentode LTP PI without adding some form of (un)balance adjustment . . . Problem solved Yves.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)