current production pentode, I_a ~ 8mA

Rundmaus · 7th February 2011, 07:21 PM

Hi there,

does anyone know about a current production signal pentode capable of delivering 8mA in a CCS without getting red?

Currently I am thinking about using EF184, but as all other tubes of the planned amplifier (EL34, ECC88, 5AR4, EZ81) are still produced, I would like to have also a current production pentode for the CCS...

Any ideas?

Greetings,
Andreas

SemperFi · 7th February 2011, 08:15 PM

Have u concidered a 6550 yet? Or maybe a 813?

Rundmaus · 08:23 PM

Both tubes are rated for higher dissipation than my output tubes! Not quite what one wants to use for a CCS in the driver stage. I think its hardly possible to turn them "off" enough to give just 8mA...

I hoped for something like a EF86, just with a current capability of 8-10mA in continuous operation...

leadbelly · 09:07 PM

You haven't quite said what you want to do with them yet, so I'll just assume you want to use a pentode CCS for an LTP?

Trying to remember the table from Morgan Jones, I think it goes something like 6AU6 up to 5 mA, EF184 up to 10 mA, EF86 up to 15 or 20mA?

Rundmaus · 7th February 2011, 09:09 PM

Hi leadbelly,

the Morgan Jones table you mentioned lies here in front of me^^ Unfortunately no current production tubes in that table...

EF184 is good for the task up to 15mA, but also not current production...

EF86 would be good and is still produced, but will deliver hardly 4mA, definitely not 8.

leadbelly · 7th February 2011, 09:25 PM

Maybe use the pentode section of a 6BM8?

Although I have to be my normally blunt self and ask why are you so fixated on new production? I doubt you will run out of NOS supply on these in your DIY lifetime! New production is only necessary for commercial amps, and if you were in a position to be designing a commercial amp you would probably have known better than to just say "CCS" without describing the intended use and think that people would have known what you were talking about

Rundmaus · 7th February 2011, 09:29 PM

Not really fixated on new production, just thought it would be nice as all other tubes in the amp are still manufactured...

No, I am not building or designing amps commercially, but I thought that in the "tubes" forum of DIYaudio most readers can extract enough information from pentode, CCS=constant current source/sink and 8mA. What more simple information is there to describe a current source that the intended current?

SY · 7th February 2011, 09:30 PM

EL84.

Rundmaus · 7th February 2011, 09:34 PM

Hi SY,

Quote:

Originally Posted by SY

EL84.

Thought about that, yes. Operating point is on the lower edge of the curve sheet then, but might work. First amplifier testing will be with the FET current sink proposed by the designer anyway. Enough time then to take an old EL84 (have lots of them around from tube radios), set it up as CCS and see what happens...

Greetings,
Andreas

richwalters · 8th February 2011, 02:08 PM

Prefer the NOS EF184. It's screened, cheap & plentiful. No reason for going to new.
The EL84, the greedy heater current for a few mA CCS operation... is it justifyable ?

richy

7th February 2011, 07:21 PM	#1
Rundmaus diyAudio Member Join Date: Aug 2005	current production pentode, I_a ~ 8mA Hi there, does anyone know about a current production signal pentode capable of delivering 8mA in a CCS without getting red? Currently I am thinking about using EF184, but as all other tubes of the planned amplifier (EL34, ECC88, 5AR4, EZ81) are still produced, I would like to have also a current production pentode for the CCS... Any ideas? Greetings, Andreas

7th February 2011, 08:21 PM	#3
Rundmaus diyAudio Member Join Date: Aug 2005	Both tubes are rated for higher dissipation than my output tubes! Not quite what one wants to use for a CCS in the driver stage. I think its hardly possible to turn them "off" enough to give just 8mA... I hoped for something like a EF86, just with a current capability of 8-10mA in continuous operation... Last edited by Rundmaus; 7th February 2011 at 08:23 PM. Reason: clarification, added last sentence.

7th February 2011, 09:01 PM	#4
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	You haven't quite said what you want to do with them yet, so I'll just assume you want to use a pentode CCS for an LTP? Trying to remember the table from Morgan Jones, I think it goes something like 6AU6 up to 5 mA, EF184 up to 10 mA, EF86 up to 15 or 20mA? __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari Last edited by leadbelly; 7th February 2011 at 09:07 PM.

7th February 2011, 09:25 PM	#6
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	Maybe use the pentode section of a 6BM8? Although I have to be my normally blunt self and ask why are you so fixated on new production? I doubt you will run out of NOS supply on these in your DIY lifetime! New production is only necessary for commercial amps, and if you were in a position to be designing a commercial amp you would probably have known better than to just say "CCS" without describing the intended use and think that people would have known what you were talking about __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

7th February 2011, 09:30 PM	#8
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	EL84. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

7th February 2011, 08:15 PM	#2
SemperFi diyAudio Member Join Date: Jan 2002 Location: nowhere	Have u concidered a 6550 yet? Or maybe a 813?

7th February 2011, 09:09 PM	#5
Rundmaus diyAudio Member Join Date: Aug 2005	Hi leadbelly, the Morgan Jones table you mentioned lies here in front of me^^ Unfortunately no current production tubes in that table... EF184 is good for the task up to 15mA, but also not current production... EF86 would be good and is still produced, but will deliver hardly 4mA, definitely not 8.

7th February 2011, 09:29 PM	#7
Rundmaus diyAudio Member Join Date: Aug 2005	Not really fixated on new production, just thought it would be nice as all other tubes in the amp are still manufactured... No, I am not building or designing amps commercially, but I thought that in the "tubes" forum of DIYaudio most readers can extract enough information from pentode, CCS=constant current source/sink and 8mA. What more simple information is there to describe a current source that the intended current?

8th February 2011, 02:08 PM	#10
richwalters diyAudio Member Join Date: Sep 2003 Location: Alps:Tube amp designs over 150W, SMPS guru.	Prefer the NOS EF184. It's screened, cheap & plentiful. No reason for going to new. The EL84, the greedy heater current for a few mA CCS operation... is it justifyable ? richy

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
Best current production 2a3	feket663	Tubes / Valves	6	9th May 2010 02:34 PM
best current production el34	katopis	Tubes / Valves	7	7th June 2008 02:49 PM
Current production EL34	Klimon	Tubes / Valves	1	12th January 2007 07:54 PM
Signal pentode in current production	Gold_xyz	Tubes / Valves	2	12th November 2006 12:05 PM
Current production rectifiers	Tim Wyatt	Tubes / Valves	6	10th September 2004 03:27 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