I am looking for a tube to use in a preamp. I need a single triode, or pentode that can be triode strapped, has a mu in the area of 15 to 25, and has an rp of 2K5 or lower. Octal or loctal is ideal, but 9 pin will work, and if possible, a 12V heater is preferred.
I have already used 6688's and 7788's, so I don't want to use them again. 5842's and 7737's are a little too expensive, 12j5's and their variants have too high of an rp. 6t4 is a 7 pin but otherwise promising. C3m looks almost ideal except for the price and lack of availability. Really, I am looking for 1/2 of a 5687 if it exists.
Any other suggestions?
I have already used 6688's and 7788's, so I don't want to use them again. 5842's and 7737's are a little too expensive, 12j5's and their variants have too high of an rp. 6t4 is a 7 pin but otherwise promising. C3m looks almost ideal except for the price and lack of availability. Really, I am looking for 1/2 of a 5687 if it exists.
Any other suggestions?
Borderline between big signal tubes and little power tubes...
Maybe triode-connected 6CL6, or 12EH5/12CA5? Cheap and worth a try...
I know there are also similar tubes in loktal bases, just don't know the numbers offhand. Try cruising through the "14xx" tubes in the Sylvania manual:
http://www.pmillett.com/sylvania_tube_manuals_online.htm
you might see something good.
Pete
Maybe triode-connected 6CL6, or 12EH5/12CA5? Cheap and worth a try...
I know there are also similar tubes in loktal bases, just don't know the numbers offhand. Try cruising through the "14xx" tubes in the Sylvania manual:
http://www.pmillett.com/sylvania_tube_manuals_online.htm
you might see something good.
Pete
sorenj07 said:a 5687 paralleled? rp of 1000 or so
JimW said:
I'm trying to avoid parallel sections, if for no other reasons because it feels like cheating, and I'm not sure I have the heater current.
KaDe said:
If I could only find some. neat tube.
pmillett said:
Thanks Pete. The only real issue is that there are already octal holes cut, and while I have some octal to 9 pin hole shrinkers, I have never seen either octal to 7 pin, or a 7 pin socket that is as large as a 9 pin. I'll look around though as it seems like a good option.
I'll look for a loctal too.
siang said:
mu seems a little high, but it seems like a useful tube for other things.
Keep in mind that for what you are asking, there will be trade off's.....such as a hefty bit a DC idle current for your requirements,,, None the less....to answer your request, take a 6V6 in TRIODE mode...Rp is about 2.4K and the mu is about 10....and it is an octal base....
Either tie the L and R stereo 6.3V heaters in series for 12.6V or use the 12V6 .....
Should get the job done....
Chris
Either tie the L and R stereo 6.3V heaters in series for 12.6V or use the 12V6 .....
Should get the job done....
Chris
I'm going to take some liberties with your request, and recommend the 5676. This is cheaply available and mu of 15 but different in all other respects. Miniature directly heated triode with four wires coming out the bottom. So various ways of attaching. I solder to a tag strip. Must be used vertical, and must have a good DC supply to each tube, though this is low current. Batteries are another possibility. It's not particularly microphonic.
What you will get is crystal clear sound - it's in my current favourite preamp, working parafeed. This tube came close to winning the European Triode Festival prize for phono stages in one design.
http://www.rintelen.ch/hifi/lil_sis.pdf
You could be very surprised!
What you will get is crystal clear sound - it's in my current favourite preamp, working parafeed. This tube came close to winning the European Triode Festival prize for phono stages in one design.
http://www.rintelen.ch/hifi/lil_sis.pdf
You could be very surprised!
Here's a picture of the existing pre which is using 12J5GT's. This should show why I would prefer single triodes. But, I think it just is lacking and that lacking seems to be due to the weakness of the tubes, and that the output transformers just have too low of a primary impedance.
I think that the best option is probably either 5687's or 8416's and leaving the outside spots empty. (My power transformer would need to be replaced for anything requiring more current I am afraid.) Not a huge deal, but not as pretty to look at either -- the glowing through the perforated front is pretty neat.
I think that the best option is probably either 5687's or 8416's and leaving the outside spots empty. (My power transformer would need to be replaced for anything requiring more current I am afraid.) Not a huge deal, but not as pretty to look at either -- the glowing through the perforated front is pretty neat.
Attachments
Just a thought - the 1626 would slot right into a 12J5GT socket - same heaters and pinout. That might float your boat. I've used this tube in a preamp, and its enduring quality is boogie factor - it really rocks. It's a Jimmy Smith/Ray Charles kind of tube. I substituted a 12J5GT for it and it was a bit of a yawn - certainly preferred the 1626. Pretty cheap tube as well, and low plate resistance, though gain will be less. Andy
D,
I'm using the 6T4. It works a treat; Rp=1.8K, S=6, Mu=11. Very linear, over the throw of a line tube, absolutely nonmicrophonic. Very clear, very quiet. It does have an eggstreemly restrictive Vh-k rating, so you got to deal with that.
You want some well-matched ones, let me know.
Aloha,
Poinz
I'm using the 6T4. It works a treat; Rp=1.8K, S=6, Mu=11. Very linear, over the throw of a line tube, absolutely nonmicrophonic. Very clear, very quiet. It does have an eggstreemly restrictive Vh-k rating, so you got to deal with that.
You want some well-matched ones, let me know.
Aloha,
Poinz
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