12AV7s

marshman · April 10th, 2008, 09:52 PM

Well, I found a few of these, and research has led me to find that they have an 'amplification factor' of 41, which puts 'em about dead even with the 12AY7, BUUUT they have huge plate current and transconductance specs. I have virtually NO idea what that means, but when comparing them, they seem rated a lot more like the 'driver tubes', the 12AT7 and 12AU7. Might I then be allowed to assume that they'd be useful for similar things, like reverb drivers and maybe some sort of freak 1-watt SE craziness?

They look purrrty, though...

Billm · April 10th, 2008, 10:21 PM

That's correct. The 12AV7 is a driver tube, with specs that fall between the 12AT7 and the 12AU7. It never got used much because it was the "middle child." The 12AU7's plate impedance makes it more useful for good impedance match when driving small output transformers, as with a 1-watt guitar amp. You can do a neat little push-pull amp with it.

Here's an example:

http://www.diyguitarist.com/GuitarAmps/FireFly.htm

marshman · April 11th, 2008, 10:14 AM

Thanks, Billm, it looks cool. I'd been thinking about one of the SE types using the reverb tranny--would there be any real advantage (besides higher output--1 watt vs 2.2--wooooo!) to going PP?

Billm · April 11th, 2008, 11:39 AM

No real advantage. Just fun experimenting with different circuits.

Pepi · April 11th, 2008, 02:23 PM

I use 12AV7 tubes in my EPI VJ. It is perfect for it.

eugenedunn · April 11th, 2008, 06:22 PM

Wow, the 12AV7 has some interesting numbers. So it has some mighty current handling capabilities. And a very large conductance spec. So does that translate to low impedance for that tube compared to the 12AT7 and 12AU7?

marshman · April 11th, 2008, 07:22 PM

Pepi--I'm running a 12AU7 in there now, you can bet one of these is goin' in there first chance I get.

ED--I noticed that this tube has the most extreme ratings of all of those listed. Unfortunately, I still don't know what it means. Does it mean that one of these might be good for 2 watts compared to @ 1 watt for the AT7? Inquirin' minds wanna know!

Pepi · April 12th, 2008, 08:57 AM

Quote:

Originally Posted by marshman

Pepi--I'm running a 12AU7 in there now, you can bet one of these is goin' in there first chance I get.

ED--I noticed that this tube has the most extreme ratings of all of those listed. Unfortunately, I still don't know what it means. Does it mean that one of these might be good for 2 watts compared to @ 1 watt for the AT7? Inquirin' minds wanna know!

Since they are cheap buy a few. I've got a couple that are microphonic as heck. I have a feeling that it may be the nature of this design

eugenedunn · April 12th, 2008, 10:24 AM

Hey Marshman, 12AT7's are often the stock reverb driver tubes in many amps because of their current handling capabilities..... and 12AU7's also have that property.... I have found subbing a 12AU7 is a good fit because it tends to make the reverb more tunable over a wide range of travel. Before I switched, my Princeton was pretty much NO REVERB until about 3.... then it was ON and it was splashy from 4 on up. Now, with the 12AU7, it has a lot more usable lush reverb tone throughout the dial.... and you can still get splashy up at 10.... just not so over the top. I think it sounds more airy. And that's good to me.

So maybe the 12AV7 would be a good halfway choice to try. I never see them around though.... I need to keep an eye out.

EdMax · April 12th, 2008, 11:33 AM

I have no less than 50 NOS 12AV7's & 5965's from various manufactures and the majority are by no means suitable for pre-amp tubes especially in the V1 position.

These were intended for computer/switching use where microphonics was not an issue. I have noticed that there are at least 8 different internal plate configurations on these tubes. The only ones I have ever been able to put in an amp without them squealing like a pig were short plate Sylvania branded.

The 5965 version is even worse. Data Sheet
Miniature type used for on-off control applications involving long periods of operation under cutoff conditions.

Some data sheets do say suitable for AF and oscillator use, but good luck having that work in the real world applications like guitar amps.

You might find the odd one in the bunch that works, but just remember, if they were any good for audio apps, they would cost far more than $1.99 each on ebay.

Ed

eugenedunn · April 12th, 2008, 11:38 AM

So darn it Ed, what ARE ya doin' with all those 12AV7's and 5965's ?!

Thanks for the insight though.... really interesting. Do you have any other arcane uses for them?

marshman · April 12th, 2008, 05:07 PM

Well, that's good to know, and the perspective vis-a-vis their going rate on ebay is outstanding. I guess I'll do some experimenting when I get a chance, knowing not to expect too much.

And really, what else can you do with 'em?

Now there's a thead I'd like to see--"what else do our tubes do?"

EdMax · April 12th, 2008, 06:02 PM

I had gotten a huge hoard of tubes from an old TV shop I bought out. When I started sorting out all the audio tubes from the less desireable TV tubes I ended up with a big stash of the 12AV7's. I was pretty excited when I looked them up and the specs looked great.

I tried sticking one in my 5E3 and the squeal about knocked me over when I flipped the standby switch to play. (The volume control was dimed).

I played around with all the different brands, GE, RCA, Sylvania, and found 3 out of about 50 that only borderline worked.

I put one in a champ and it was equally as bad. In the PI position on the 5E3 it worked(sort of) but really weakened the amps output.
So I listed the entire batch on ebay twice! I swear it felt like I could not give them away. So, I ended up packing them away for someday in the future when I have more time to experiment with them.

Good luck trying them out, just do not spend any serious coin on them!!

Ed

Pepi · April 12th, 2008, 08:53 PM

Quote:

Originally Posted by EdMax

I had gotten a huge hoard of tubes from an old TV shop I bought out. When I started sorting out all the audio tubes from the less desireable TV tubes I ended up with a big stash of the 12AV7's. I was pretty excited when I looked them up and the specs looked great.

I tried sticking one in my 5E3 and the squeal about knocked me over when I flipped the standby switch to play. (The volume control was dimed).

I played around with all the different brands, GE, RCA, Sylvania, and found 3 out of about 50 that only borderline worked.

I put one in a champ and it was equally as bad. In the PI position on the 5E3 it worked(sort of) but really weakened the amps output.
So I listed the entire batch on ebay twice! I swear it felt like I could not give them away. So, I ended up packing them away for someday in the future when I have more time to experiment with them.

Good luck trying them out, just do not spend any serious coin on them!!

Ed

If they are used for computer switching why would a TV repairman have all of these

eugenedunn · April 12th, 2008, 09:39 PM

Maybe because back in the day, computers were driven by tubes. BIG INEFFICIENT, Heat mongering tube computers.

marshman · April 12th, 2008, 10:31 PM

I'd like to thank y'all for your continued discussion, it's interesting to hear. I scored a few (5 or 6) recently, but haven't felt the need to stick 'em in anything just yet. Maybe someday.

EdMax · April 13th, 2008, 07:59 AM

Quote:

Originally Posted by Pepi

If they are used for computer switching why would a TV repairman have all of these

They were commonly used back in the day of tube TV sets as an oscillator/ mixer tube in VHF circuits.

April 10th, 2008, 09:52 PM	#1 (permalink)
marshman Tele-Holic Join Date: Feb 2007 Location: SE PA Posts: 587	12AV7s Well, I found a few of these, and research has led me to find that they have an 'amplification factor' of 41, which puts 'em about dead even with the 12AY7, BUUUT they have huge plate current and transconductance specs. I have virtually NO idea what that means, but when comparing them, they seem rated a lot more like the 'driver tubes', the 12AT7 and 12AU7. Might I then be allowed to assume that they'd be useful for similar things, like reverb drivers and maybe some sort of freak 1-watt SE craziness? They look purrrty, though... __________________ 42

April 11th, 2008, 10:14 AM	#3 (permalink)
marshman Tele-Holic Join Date: Feb 2007 Location: SE PA Posts: 587	Thanks, Billm, it looks cool. I'd been thinking about one of the SE types using the reverb tranny--would there be any real advantage (besides higher output--1 watt vs 2.2--wooooo!) to going PP? __________________ 42

April 11th, 2008, 07:22 PM	#7 (permalink)
marshman Tele-Holic Join Date: Feb 2007 Location: SE PA Posts: 587	Pepi--I'm running a 12AU7 in there now, you can bet one of these is goin' in there first chance I get. ED--I noticed that this tube has the most extreme ratings of all of those listed. Unfortunately, I still don't know what it means. Does it mean that one of these might be good for 2 watts compared to @ 1 watt for the AT7? Inquirin' minds wanna know! __________________ 42

April 12th, 2008, 10:24 AM	#9 (permalink)
eugenedunn Tele-Holic Join Date: Dec 2006 Location: Sacramento, CA Age: 54 Posts: 612 33 Photos	Hey Marshman, 12AT7's are often the stock reverb driver tubes in many amps because of their current handling capabilities..... and 12AU7's also have that property.... I have found subbing a 12AU7 is a good fit because it tends to make the reverb more tunable over a wide range of travel. Before I switched, my Princeton was pretty much NO REVERB until about 3.... then it was ON and it was splashy from 4 on up. Now, with the 12AU7, it has a lot more usable lush reverb tone throughout the dial.... and you can still get splashy up at 10.... just not so over the top. I think it sounds more airy. And that's good to me. So maybe the 12AV7 would be a good halfway choice to try. I never see them around though.... I need to keep an eye out. __________________ Ono Boy says "good n' swampy....."

April 12th, 2008, 11:38 AM	#11 (permalink)
eugenedunn Tele-Holic Join Date: Dec 2006 Location: Sacramento, CA Age: 54 Posts: 612 33 Photos	So darn it Ed, what ARE ya doin' with all those 12AV7's and 5965's ?! Thanks for the insight though.... really interesting. Do you have any other arcane uses for them? __________________ Ono Boy says "good n' swampy....."

April 10th, 2008, 10:21 PM	#2 (permalink)
Billm Tele-Meister Join Date: Mar 2008 Location: New Jersey Age: 61 Posts: 252	That's correct. The 12AV7 is a driver tube, with specs that fall between the 12AT7 and the 12AU7. It never got used much because it was the "middle child." The 12AU7's plate impedance makes it more useful for good impedance match when driving small output transformers, as with a 1-watt guitar amp. You can do a neat little push-pull amp with it. Here's an example: http://www.diyguitarist.com/GuitarAmps/FireFly.htm

April 11th, 2008, 11:39 AM	#4 (permalink)
Billm Tele-Meister Join Date: Mar 2008 Location: New Jersey Age: 61 Posts: 252	No real advantage. Just fun experimenting with different circuits.

April 11th, 2008, 02:23 PM	#5 (permalink)
Pepi Tele-Meister Join Date: Aug 2004 Location: Indiana Age: 54 Posts: 204	I use 12AV7 tubes in my EPI VJ. It is perfect for it.

April 12th, 2008, 11:33 AM	#10 (permalink)
EdMax TDPRI Member Join Date: Mar 2008 Location: Geneva Age: 53 Posts: 27	I have no less than 50 NOS 12AV7's & 5965's from various manufactures and the majority are by no means suitable for pre-amp tubes especially in the V1 position. These were intended for computer/switching use where microphonics was not an issue. I have noticed that there are at least 8 different internal plate configurations on these tubes. The only ones I have ever been able to put in an amp without them squealing like a pig were short plate Sylvania branded. The 5965 version is even worse. Data Sheet Miniature type used for on-off control applications involving long periods of operation under cutoff conditions. Some data sheets do say suitable for AF and oscillator use, but good luck having that work in the real world applications like guitar amps. You might find the odd one in the bunch that works, but just remember, if they were any good for audio apps, they would cost far more than $1.99 each on ebay. Ed

April 12th, 2008, 05:07 PM	#12 (permalink)
marshman Tele-Holic Join Date: Feb 2007 Location: SE PA Posts: 587	Well, that's good to know, and the perspective vis-a-vis their going rate on ebay is outstanding. I guess I'll do some experimenting when I get a chance, knowing not to expect too much. And really, what else can you do with 'em? Now there's a thead I'd like to see--"what else do our tubes do?" __________________ 42

April 12th, 2008, 06:02 PM	#13 (permalink)
EdMax TDPRI Member Join Date: Mar 2008 Location: Geneva Age: 53 Posts: 27	I had gotten a huge hoard of tubes from an old TV shop I bought out. When I started sorting out all the audio tubes from the less desireable TV tubes I ended up with a big stash of the 12AV7's. I was pretty excited when I looked them up and the specs looked great. I tried sticking one in my 5E3 and the squeal about knocked me over when I flipped the standby switch to play. (The volume control was dimed). I played around with all the different brands, GE, RCA, Sylvania, and found 3 out of about 50 that only borderline worked. I put one in a champ and it was equally as bad. In the PI position on the 5E3 it worked(sort of) but really weakened the amps output. So I listed the entire batch on ebay twice! I swear it felt like I could not give them away. So, I ended up packing them away for someday in the future when I have more time to experiment with them. Good luck trying them out, just do not spend any serious coin on them!! Ed

April 12th, 2008, 09:39 PM	#15 (permalink)
eugenedunn Tele-Holic Join Date: Dec 2006 Location: Sacramento, CA Age: 54 Posts: 612 33 Photos	Maybe because back in the day, computers were driven by tubes. BIG INEFFICIENT, Heat mongering tube computers. __________________ Ono Boy says "good n' swampy....."

April 12th, 2008, 10:31 PM	#16 (permalink)
marshman Tele-Holic Join Date: Feb 2007 Location: SE PA Posts: 587	I'd like to thank y'all for your continued discussion, it's interesting to hear. I scored a few (5 or 6) recently, but haven't felt the need to stick 'em in anything just yet. Maybe someday. __________________ 42