1/2 of 12AX7 in single envelope?

jmillerdoc · 23rd February 2010, 02:03 AM

I was wondering if there is such a tube.....a single triode/envelope identical to the 12AX7? Conversely, a 12AX7 that is not a twin triode but a single triode.

Thanks,
Jeff

Bob_345 · 23rd February 2010, 02:15 AM

a 6av6 will supposedly work. but it is not pin compatible as it is a 7 pin tube. but they do have similar characteristics

Eli Duttman · 23rd February 2010, 02:17 AM

Your wish is my command.

The 6AV6 triode/twin diode is what you need. Ground the diode plates and you're in business.

Bob_345 · 23rd February 2010, 03:41 AM

hmmm i just looked over the datasheets between the 6av6 and a 6at6 because they look very similar. after looking them over they are almost the same!!! same pin-outs too. its is also a triode/double diode. the main difference is the plate impedance. the 6av6 has 86k impedance and the 6at6 has 58k but other than that, they are preety mutch the same. and the 6at6 is verry cheap. highest i have seen them for is $3. you should check it out

jmillerdoc · 23rd February 2010, 04:31 AM

This is an interesting tube. The reason I was wanting something like this is b/c I am building a hybrid guitar amp head with a LM3886 based chip amp. I have a schematic for this thing I am building and it calls for two inputs, each one using either triode of the first 12AX7. I am electing not to use a two input arrangement so I didn't want to "waste" a good 12AX7 section (sillly, I know). The twin diodes are interesting too. Maybe they could be used somehow in a feedback loop since their output should fall some when the triode conducts. That may have some interesting uses, I'll have to give it some thought. Since these things are so cheap too I might just have to build the entire preamp (3 of these total) with these tubes.

Eli, do you have any experience in using this as a form of a 12AX7 in a HiFi circuit? How do they sound? Are there any preferred types out there I should look to purchase?

While were on this subject of single small triodes.....is there an equivalent one like this for the 6922 and the 5687?

Thanks again for the Help.

Jeff

kenpeter · 23rd February 2010, 05:25 AM

6J6 is cheap, and has a Mu similar to 6922.
Ok, so its two triodes, but only one cathode...
Strap grid to grid and plate to plate...

db! · 23rd February 2010, 05:39 AM

I personally like the russian 6S3P-EV triode, they're cheap and widely available. It has a lower Mu compared to the 12AX7 but the plate dissipation is much higher (3W compared to 1.2W).

You could also use the WE417A/5842 triode but they are much more expensive and harder to find.

nafunga · 23rd February 2010, 07:45 AM

The 6SQ7 (Octal) is very close? I've used them for the same purpose.

MarkER · 23rd February 2010, 12:02 PM

6SF5 is very close to half a 12AX7. It is used as the driver in the FiX amp. Metal shell and economically priced.

barretter · 23rd February 2010, 12:24 PM

There's also the seven-pin EC91, which has a mu of 100 but higher transconductance and lower anode impedance.

23rd February 2010, 02:03 AM	#1
jmillerdoc diyAudio Member Join Date: Mar 2009 Location: Lawton, OK, USA	1/2 of 12AX7 in single envelope? I was wondering if there is such a tube.....a single triode/envelope identical to the 12AX7? Conversely, a 12AX7 that is not a twin triode but a single triode. Thanks, Jeff

23rd February 2010, 02:17 AM	#3
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Your wish is my command. The 6AV6 triode/twin diode is what you need. Ground the diode plates and you're in business. __________________ Eli D.

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23rd February 2010, 02:15 AM	#2
Bob_345 diyAudio Member Join Date: Jan 2010 Location: Saratoga,CA	a 6av6 will supposedly work. but it is not pin compatible as it is a 7 pin tube. but they do have similar characteristics

23rd February 2010, 03:41 AM	#4
Bob_345 diyAudio Member Join Date: Jan 2010 Location: Saratoga,CA	hmmm i just looked over the datasheets between the 6av6 and a 6at6 because they look very similar. after looking them over they are almost the same!!! same pin-outs too. its is also a triode/double diode. the main difference is the plate impedance. the 6av6 has 86k impedance and the 6at6 has 58k but other than that, they are preety mutch the same. and the 6at6 is verry cheap. highest i have seen them for is $3. you should check it out

23rd February 2010, 04:31 AM	#5
jmillerdoc diyAudio Member Join Date: Mar 2009 Location: Lawton, OK, USA	This is an interesting tube. The reason I was wanting something like this is b/c I am building a hybrid guitar amp head with a LM3886 based chip amp. I have a schematic for this thing I am building and it calls for two inputs, each one using either triode of the first 12AX7. I am electing not to use a two input arrangement so I didn't want to "waste" a good 12AX7 section (sillly, I know). The twin diodes are interesting too. Maybe they could be used somehow in a feedback loop since their output should fall some when the triode conducts. That may have some interesting uses, I'll have to give it some thought. Since these things are so cheap too I might just have to build the entire preamp (3 of these total) with these tubes. Eli, do you have any experience in using this as a form of a 12AX7 in a HiFi circuit? How do they sound? Are there any preferred types out there I should look to purchase? While were on this subject of single small triodes.....is there an equivalent one like this for the 6922 and the 5687? Thanks again for the Help. Jeff

23rd February 2010, 05:25 AM	#6
kenpeter diyAudio Member Join Date: Nov 2007 Location: Dallas	6J6 is cheap, and has a Mu similar to 6922. Ok, so its two triodes, but only one cathode... Strap grid to grid and plate to plate...

23rd February 2010, 05:39 AM	#7
db! diyAudio Member Join Date: Nov 2009 Location: Ontario	I personally like the russian 6S3P-EV triode, they're cheap and widely available. It has a lower Mu compared to the 12AX7 but the plate dissipation is much higher (3W compared to 1.2W). You could also use the WE417A/5842 triode but they are much more expensive and harder to find.

23rd February 2010, 07:45 AM	#8
nafunga diyAudio Member Join Date: Jul 2005 Location: Whitstable , Kent. UK	The 6SQ7 (Octal) is very close? I've used them for the same purpose.

23rd February 2010, 12:02 PM	#9
MarkER diyAudio Member Join Date: Aug 2005	6SF5 is very close to half a 12AX7. It is used as the driver in the FiX amp. Metal shell and economically priced.

23rd February 2010, 12:24 PM	#10
barretter diyAudio Member Join Date: Apr 2003 Location: West Yorkshire, UK.	There's also the seven-pin EC91, which has a mu of 100 but higher transconductance and lower anode impedance.

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