6J5 input swing

lndm · 29th December 2006, 12:20 AM

What is the best way to have a 6J5 accept a 7Vrms input cleanly whilst retaining a good operating point. I want to avoid an unbypassed Rk as I want a low rp for low noise.

Geek · 29th December 2006, 01:43 AM

LED's? Mu-follower?

SY · 29th December 2006, 02:08 AM

Nope and nope. You can't exceed the bias voltage at peak in order to avoid grid current. The requirement is odd- lndm, care to elaborate?

lndm · 29th December 2006, 08:07 AM

Sure. I am designing a phono/pre and have a cascode on paper. With EQ it puts out 7Vrms below 1kHz with my MM cart giving occasional peaks of 70mV. I simply want the second stage to endure these peaks and I have had trouble with another amp that couldn't handle that level. The cascode seems to be happy with this level.

Miles Prower · 29th December 2006, 08:24 AM

Quote:

Originally posted by lndm
What is the best way to have a 6J5 accept a 7Vrms input cleanly whilst retaining a good operating point. I want to avoid an unbypassed Rk as I want a low rp for low noise.

If you don't want to use an unbypassed Rk, the only way to do what you want is to run at a very high Vpk. Since 7.0Vrms is a bit less than 10Vp, that's what you're looking at: Vgk= -10Vdc. From the plate characteristics, that'll be right around 250Vdc. Depending on how large the passive load is, the DC rail will go a lot higher than that (or use an active load).

Other than that, unbypassed Rk is the only other option.

SY · 29th December 2006, 11:28 AM

Do you have passive EQ between the stages?

lndm · 29th December 2006, 06:08 PM

Yes, the 318us which allows 20kHz to be up by 20dB over the input.

SY · 29th December 2006, 07:12 PM

Other way around- that knocks down the level at high frequencies. With passive EQ, it's very doubtful that you need 7V of overload. But let's go through the exercise: what's your cartridge output spec and the first stage gain?

lndm · 29th December 2006, 07:38 PM

Below 1kHz the gain is 43dB. I am using an Ortofon OMB. I'm not aware of any specs for it, I just loaded the cartridge, played a few records and watched the screen. Most program material seems to be within 5-10mV with regular peaks at 30mV, some up to 50mV with some recordings, and occasionally 70mV.

Wavebourn · 29th December 2006, 07:49 PM

If you don't want a local feedback put a global one on the same cathode, no other way except attenuating input signal, i.e. loosing precious signal power.

29th December 2006, 12:20 AM	#1
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	6J5 input swing What is the best way to have a 6J5 accept a 7Vrms input cleanly whilst retaining a good operating point. I want to avoid an unbypassed Rk as I want a low rp for low noise.

29th December 2006, 02:08 AM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Nope and nope. You can't exceed the bias voltage at peak in order to avoid grid current. The requirement is odd- lndm, care to elaborate? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

29th December 2006, 11:28 AM	#6
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Do you have passive EQ between the stages? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

29th December 2006, 07:12 PM	#8
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Other way around- that knocks down the level at high frequencies. With passive EQ, it's very doubtful that you need 7V of overload. But let's go through the exercise: what's your cartridge output spec and the first stage gain? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

29th December 2006, 07:49 PM	#10
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	If you don't want a local feedback put a global one on the same cathode, no other way except attenuating input signal, i.e. loosing precious signal power. __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

29th December 2006, 01:43 AM	#2
Geek diyAudio Member Join Date: Sep 2004	LED's? Mu-follower?

29th December 2006, 08:07 AM	#4
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Sure. I am designing a phono/pre and have a cascode on paper. With EQ it puts out 7Vrms below 1kHz with my MM cart giving occasional peaks of 70mV. I simply want the second stage to endure these peaks and I have had trouble with another amp that couldn't handle that level. The cascode seems to be happy with this level.

29th December 2006, 06:08 PM	#7
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Yes, the 318us which allows 20kHz to be up by 20dB over the input.

29th December 2006, 07:38 PM	#9
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Below 1kHz the gain is 43dB. I am using an Ortofon OMB. I'm not aware of any specs for it, I just loaded the cartridge, played a few records and watched the screen. Most program material seems to be within 5-10mV with regular peaks at 30mV, some up to 50mV with some recordings, and occasionally 70mV.

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

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
Q on voltage swing	JoshK	Tubes / Valves	4	13th December 2006 07:11 PM
Manger SWING	inertial	Planars & Exotics	27	20th November 2006 10:34 AM
how much above B+ will voltage swing in OPT?	AudioGeek	Tubes / Valves	2	15th April 2005 04:17 AM
Not enough voltage swing in P3A amp ??	Stormo	Solid State	1	30th June 2003 08:02 AM
How to swing (for those skilled in the art)	Circlotron	Everything Else	1	4th December 2002 12:51 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