Input stage tube

Steen Bentzen · 6th October 2005, 01:05 PM

Witch double triode to prefere for the input stage in a power amp. I need a amplification factor of approx. 55 and have good sound?
The input stage are balanced with a CCS in the catode.
Is 12AT7 a possible choice?

SY · 6th October 2005, 01:27 PM

A 12AT7 will work well in that application. My measurements show that as a differential amp, it can have quite low distortion at moderate voltage swings. In a CCDA, expect a gain of something like 30. A single stage gain of 55 can only be gotten with a VERY high mu triode, a cascode, or pentodes.

ErikdeBest · 6th October 2005, 03:39 PM

Im Valve Amplifiers Morgan Jones refer to a (big and heavy) regulated PS using cascaded 12AT7's in a differential amplifier. Probably the same concept can be used here, gain would be more than enough - but you need two tubes (instead of one in a simple CCDA).

Erik

PS. I am a newbie - but the other people know that and can correct what I say!

6th October 2005, 01:05 PM	#1
Steen Bentzen diyAudio Member Join Date: Jul 2005 Location: Hilleroed, Denmark	Input stage tube Witch double triode to prefere for the input stage in a power amp. I need a amplification factor of approx. 55 and have good sound? The input stage are balanced with a CCS in the catode. Is 12AT7 a possible choice?

6th October 2005, 01:27 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	A 12AT7 will work well in that application. My measurements show that as a differential amp, it can have quite low distortion at moderate voltage swings. In a CCDA, expect a gain of something like 30. A single stage gain of 55 can only be gotten with a VERY high mu triode, a cascode, or pentodes. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

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
Adding a third input to a differential input stage?	maudio	Solid State	15	11th October 2006 02:16 AM
need diy tube preamp (line-stage) recommendation and general tube advice	Musiclover4	Tubes / Valves	15	24th November 2005 01:19 AM
current bias j-fet input 2sk170 ,2sj74 at input stage	YUTK	Solid State	11	2nd June 2005 03:34 AM
NPN vs PNP input stage	zapo	Solid State	37	3rd May 2004 04:16 PM

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 October 2005, 03:39 PM	#3
ErikdeBest diyAudio Member Join Date: Mar 2003 Location: Itoculo	Im Valve Amplifiers Morgan Jones refer to a (big and heavy) regulated PS using cascaded 12AT7's in a differential amplifier. Probably the same concept can be used here, gain would be more than enough - but you need two tubes (instead of one in a simple CCDA). Erik PS. I am a newbie - but the other people know that and can correct what I say!

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