Tube rating

CarlyBoy · 19th January 2008, 01:59 PM

Hello. I'm considering building Rozenblit's T8 OTL. Seems to have been a successful design and yet the 12AU7s are running very hot, one at 475V on the plate (manual says 330V max for this tube).

I'd like to ditch the 12AU7s in favor of a 6SN7GTA/B which at least has max rating of 450V. Whatchall think? Thanks..

Colt45 · 19th January 2008, 02:05 PM

schematic?

CarlyBoy · 19th January 2008, 02:47 PM

Sorry, imageshack not liking me this morning. Full schematic will not upload. Here's the signal portion:

Sherman · 19th January 2008, 02:50 PM

It appears there is only 100V across that tube. 475 at the plate, 375 at the cathode. Way under the 330V rating. Am I missing something?

CarlyBoy · 19th January 2008, 03:43 PM

Nope, you're missing nothing. Apparently I'm an idiot. I still might try *SN7s here, though. Not a big fan of the *AU7 as an audio device.

Cycline3 · 19th January 2008, 04:28 PM

Quote:

Originally posted by CarlyBoy
Nope, you're missing nothing. Apparently I'm an idiot. I still might try *SN7s here, though. Not a big fan of the *AU7 as an audio device.

I don't have a problem with you wanting to change out a tube type, but why do you have to add a myth/stereotype/nonsense at the end? There is nothing wrong with the 12AU7... and according to Crowhurst, "the tubes are nearly identical, except the 12au7 is a miniature tube type."

The 12au7 can be used in and has been used in many fine sounding amps, it's cheap and NOS readily available; as well as the current production JJ tube which is a great sounding/performing tube too.

So you could build it as it was designed, and then make your decision on the sound quality, or you could swap it out and get a very similar sound from a 6sn7; which should take minimal circuit tweaking because the tubes are so similar.

19th January 2008, 01:59 PM	#1
CarlyBoy diyAudio Member Join Date: Aug 2006	Tube rating Hello. I'm considering building Rozenblit's T8 OTL. Seems to have been a successful design and yet the 12AU7s are running very hot, one at 475V on the plate (manual says 330V max for this tube). I'd like to ditch the 12AU7s in favor of a 6SN7GTA/B which at least has max rating of 450V. Whatchall think? Thanks..

19th January 2008, 02:50 PM	#4
Sherman diyAudio Member Join Date: Feb 2004 Location: Chicago area	It appears there is only 100V across that tube. 475 at the plate, 375 at the cathode. Way under the 330V rating. Am I missing something? __________________ --Sherman

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
difference between power rating of tube and chip amps	winner	Chip Amps	1	21st March 2009 08:10 AM
power transformer rating and tube current - SimpleSE	cbutterworth	Tubes / Valves	17	12th June 2008 10:54 PM
max plate voltage rating in tube datasheet	jarthel	Tubes / Valves	11	25th October 2006 04:24 PM
Current rating and tube current draw	cbutterworth	Tubes / Valves	1	13th October 2006 04:42 AM
Transformer VA Rating vs. Current Rating	JhonDoe	Chip Amps	45	5th June 2004 01:11 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

19th January 2008, 02:05 PM	#2
Colt45 diyAudio Member Join Date: Feb 2002 Location: Canada	schematic?

19th January 2008, 02:47 PM	#3
CarlyBoy diyAudio Member Join Date: Aug 2006	Sorry, imageshack not liking me this morning. Full schematic will not upload. Here's the signal portion:

19th January 2008, 03:43 PM	#5
CarlyBoy diyAudio Member Join Date: Aug 2006	Nope, you're missing nothing. Apparently I'm an idiot. I still might try SN7s here, though. Not a big fan of the AU7 as an audio device.

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