best use for 12AU7's?

appar111 · June 5th, 2007, 07:12 PM

What position do 12AU7's perform best in guitar amps? Phase inverter?

dibber124 · June 5th, 2007, 08:08 PM

I am an amp tech and for me 12AU7's are great Hi-Fi/Vintage/High-End audio tubes and not really guitar amp tubes. Gain is just too low.One use is to tame some of these channel switching overdrive screamer amps. Just my opinion, would like to see more takes on this one.

leewhit · June 5th, 2007, 10:53 PM

For jazz, these may be great but, anything else maybe not. I like a 12AY7. Anything cleaner than that is too clean for my tastes.

soma5 · June 5th, 2007, 11:21 PM

I have to agree about their use in a guitar amp. I think they are fun to play with and if you only have big amps and have to play a quiet gig they are nice to pop in for that. I use mine for my Steel Guitar Black Box, which is a 12AU7-based buffer that really isn't just for steel guitar but makes your signal chain sound better if you use FX pedals.

For less gain than a 12AX7 I like 12AT7, 12AY7 and 5751 tubes better.

-soma5

Tim Swartz · June 5th, 2007, 11:24 PM

They belong in Hammond organs.

stantheman · June 6th, 2007, 11:41 AM

I used to run them in my Reissue Bassman to take away the "brittleness" and they did a really good job of it. The ultimate cure for Fender's Reissues that sound "brittle" without "going to surgery" is to put it "back to stock" and then play through it for a month with a PAF equipped Les Paul with everything on "12" with exception of "bass" which we left on "5".
The 12AU7's that I was using were labled "Westinghouse".

appar111 · June 6th, 2007, 11:45 AM

I picked up a pair of NOS RCA 12AU7's (5963's) for a Real Tube pedal that it looks like I won't be purchasing, so I'm trying to find an inventive use for them now that I won't be getting the Real Tube.

I had heard they worked very well in the Real Tube to take out the buzziness of that pedal, so I got a pair of 5963's online.

If anyone needs a pair of NOS RCA 5963's, send me a PM!

The Radium King · June 6th, 2007, 12:23 PM

from what i've heard, the au7 is a driver tube. ie, it can carry more current/power than an ax7. so is the at7. ax7 and ay7 tubes can't handle the same amount of current as the au7 and at7. so, the au7 can be used in the reverb driver position, where you want the current but not as much voltage gain (ie, to tame an overly 'wet' reverb sound). in a pi slot you want gain and power, so the au7 doesn't perform well here as an at7 replacement, as you don't get the voltages to drive the power tubes. i've also heard that au7s make great cathode follower buffers in marshall/bassman setups, as they overdrive nice when slammed with a signal.

appar111 · June 6th, 2007, 01:06 PM

Quote:

Originally Posted by The Radium King

from what i've heard, the au7 is a driver tube. ie, it can carry more current/power than an ax7. so is the at7. ax7 and ay7 tubes can't handle the same amount of current as the au7 and at7. so, the au7 can be used in the reverb driver position, where you want the current but not as much voltage gain (ie, to tame an overly 'wet' reverb sound). in a pi slot you want gain and power, so the au7 doesn't perform well here as an at7 replacement, as you don't get the voltages to drive the power tubes. i've also heard that au7s make great cathode follower buffers in marshall/bassman setups, as they overdrive nice when slammed with a signal.

I have a Bassman RI, so I'd put it in the middle preamp tube position (i.e between V1 and the phase inverter position)?

The Radium King · June 6th, 2007, 02:06 PM

you could. the problem is that these are 'dual triode' tubes, so a 12ax7 has two separate gain stages, as does a 12au7. the bassman ri uses one tube to provide one triode as a gain stage and one triode as the cathode follower. if you replaced the 12ax7 in that position with a 12au7 you would get the 12au7 cathode follower, but also a 12au7 gain stage, which doesn't have the amplification of the original triode and you wouldn't be driving the cathode follower very hard. that's why, if you look around, you'll find old tubes that are dual triode with 1/2 as a 12ax7 and 1/2 as a 12au7, where the 12au7 is used as a buffer for the 12ax7 gain stage. not common in current guitar amps, however.

appar111 · June 6th, 2007, 02:50 PM

Quote:

Originally Posted by The Radium King

you could. the problem is that these are 'dual triode' tubes, so a 12ax7 has two separate gain stages, as does a 12au7. the bassman ri uses one tube to provide one triode as a gain stage and one triode as the cathode follower. if you replaced the 12ax7 in that position with a 12au7 you would get the 12au7 cathode follower, but also a 12au7 gain stage, which doesn't have the amplification of the original triode and you wouldn't be driving the cathode follower very hard. that's why, if you look around, you'll find old tubes that are dual triode with 1/2 as a 12ax7 and 1/2 as a 12au7, where the 12au7 is used as a buffer for the 12ax7 gain stage. not common in current guitar amps, however.

so if I understand right, the tube position I'm looking at putting the 12AU7 into pulls double duty, and while half of those duties would be served fine by the 12AU7, the other half wouldn't be, because the AU7 doesn't have enough gain. Is that about right?

But I thought you said in your previous post that the 12AU7 works great as a cathode buffer in marshall/bassman style amps? The Bassman RI is a pretty good bassman style amp, right?

The Radium King · June 6th, 2007, 03:20 PM

got me tripping over my own sentences. marshalls and bassmans use a cathode follower (a specific configuration of a tube triode) before the tone stack. this allows the tone stack to be designed with less resistance (typically, a smaller slope resistor) and the previous gain stage to be tuned for maximum gain; this results in less loss in the circuit and more signal to work with downstream. most say that this is what makes for the distinct 'marshall' tone. cathode followers do not provide any gain, just a buffer, so any triode can work, and some prefer the sound of a 12au7 triode to a 12ax7 triode as a cathode follower. however, while a cathode follower before a tone stack is definitive of a marshall 'style' circuit, the straight swap of a 12au7 dual triode tube into a marshall or bassman may not work given how they use the other triode in the tube. clear as mud?

appar111 · June 6th, 2007, 06:15 PM

Quote:

Originally Posted by The Radium King

got me tripping over my own sentences. marshalls and bassmans use a cathode follower (a specific configuration of a tube triode) before the tone stack. this allows the tone stack to be designed with less resistance (typically, a smaller slope resistor) and the previous gain stage to be tuned for maximum gain; this results in less loss in the circuit and more signal to work with downstream. most say that this is what makes for the distinct 'marshall' tone. cathode followers do not provide any gain, just a buffer, so any triode can work, and some prefer the sound of a 12au7 triode to a 12ax7 triode as a cathode follower. however, while a cathode follower before a tone stack is definitive of a marshall 'style' circuit, the straight swap of a 12au7 dual triode tube into a marshall or bassman may not work given how they use the other triode in the tube. clear as mud?

Yep, clear as mud

, because in your first post you say:

"i've also heard that au7s make great cathode follower buffers in marshall/bassman setups, as they overdrive nice when slammed with a signal"

And I have a bassman, so I think-- great, I can use the au7 in my bassman. I just need to figure out which position is the cathode follower so I can swap it out. Then your next post says that the au7 wouldn't be so good a choice in the Bassman.

I guess the question I need answered (in layman's terms) is: which preamp tube position in my '59 Bassman RI is the cathode follower buffer?

Basically, what you're saying is that the 12AU7 isn't the best choice as a cathode follower in marshalls or bassmans because it doesn't utilize the other half of the dual triode, right? If that's the case, then why did you say in your first post that "i've heard that au7s make great cathode follower buffers in marshall/bassman setups"?

The Radium King · June 6th, 2007, 11:07 PM

sorry, didn't mean to confuse. i was referring to that style of circuit (again, cathode follower into tone stack). many folks build their own 18 watt marshall clones (which is a copy of a bassman) and can reconfigure the circuit such that they use a 12au7 cathode follower (amoungst many other variations). i've heard that au7s make great cathode follower buffers in marshall/bassman setups. feel free to put a 12au7 in any of the noval sockets in your amp. nothing will break, burn up or stain the carpet. that's the most definitive way to find out if you like the sound, and a lot quicker than typing on the internet.

celeste · June 7th, 2007, 05:27 AM

If you want inventive uses for a 'u7, it is hard to beat these ax84 . look at the clean and blues preamps

marshman · June 9th, 2007, 07:56 AM

I bought a Epi Vjr a while back, one of the very early ones. Hummed like a mofo, so after trying to ignore it, I hopped it up a la ZPs recommendations at 18watt.com. BUT, I ended up with waaay more gain than I really wanted out of it, and I didn't feel like sorting out which mod was the cause, so I started doing the 12A?7 dance, and ended up with a 12AU7 in there, and now it sounds exactly like I want it to.

But only with my tele. Still sounds off with the strat, so the strat stays plugged into the Rivera.

June 5th, 2007, 07:12 PM	#1 (permalink)
appar111 Tele-Afflicted Join Date: Mar 2006 Location: Ohio Age: 33 Posts: 1,277	best use for 12AU7's? What position do 12AU7's perform best in guitar amps? Phase inverter?

June 5th, 2007, 08:08 PM	#2 (permalink)
dibber124 Tele-Afflicted Join Date: Dec 2006 Location: Long Island, New York Age: 54 Posts: 1,192	I am an amp tech and for me 12AU7's are great Hi-Fi/Vintage/High-End audio tubes and not really guitar amp tubes. Gain is just too low.One use is to tame some of these channel switching overdrive screamer amps. Just my opinion, would like to see more takes on this one. __________________ "I feel that it is healthier to look out at the world through a window than through a mirror. Otherwise, all you see is yourself and whatever is behind you." - Bill Withers

June 5th, 2007, 10:53 PM	#3 (permalink)
leewhit Tele-Meister Join Date: Dec 2003 Location: baltimore,md. Posts: 106	For jazz, these may be great but, anything else maybe not. I like a 12AY7. Anything cleaner than that is too clean for my tastes. __________________ leewhit

June 5th, 2007, 11:24 PM	#5 (permalink)
Tim Swartz Tele-Afflicted Join Date: Mar 2003 Location: Michigan - Tweenst the Great Lakes Posts: 1,827	They belong in Hammond organs. __________________

June 6th, 2007, 11:41 AM	#6 (permalink)
stantheman Friend of Leo's Join Date: Jun 2003 Location: White Mountains Posts: 4,936	I used to run them in my Reissue Bassman to take away the "brittleness" and they did a really good job of it. The ultimate cure for Fender's Reissues that sound "brittle" without "going to surgery" is to put it "back to stock" and then play through it for a month with a PAF equipped Les Paul with everything on "12" with exception of "bass" which we left on "5". The 12AU7's that I was using were labled "Westinghouse". __________________ Somebody Loan Me A Dime

June 5th, 2007, 11:21 PM	#4 (permalink)
soma5 Tele-Meister Join Date: Apr 2007 Location: Austin, Texas Posts: 118	I have to agree about their use in a guitar amp. I think they are fun to play with and if you only have big amps and have to play a quiet gig they are nice to pop in for that. I use mine for my Steel Guitar Black Box, which is a 12AU7-based buffer that really isn't just for steel guitar but makes your signal chain sound better if you use FX pedals. For less gain than a 12AX7 I like 12AT7, 12AY7 and 5751 tubes better. -soma5

June 6th, 2007, 11:45 AM	#7 (permalink)
appar111 Tele-Afflicted Join Date: Mar 2006 Location: Ohio Age: 33 Posts: 1,277	I picked up a pair of NOS RCA 12AU7's (5963's) for a Real Tube pedal that it looks like I won't be purchasing, so I'm trying to find an inventive use for them now that I won't be getting the Real Tube. I had heard they worked very well in the Real Tube to take out the buzziness of that pedal, so I got a pair of 5963's online. If anyone needs a pair of NOS RCA 5963's, send me a PM!

June 6th, 2007, 12:23 PM	#8 (permalink)
The Radium King Tele-Meister Join Date: Aug 2006 Location: Canada Posts: 106	from what i've heard, the au7 is a driver tube. ie, it can carry more current/power than an ax7. so is the at7. ax7 and ay7 tubes can't handle the same amount of current as the au7 and at7. so, the au7 can be used in the reverb driver position, where you want the current but not as much voltage gain (ie, to tame an overly 'wet' reverb sound). in a pi slot you want gain and power, so the au7 doesn't perform well here as an at7 replacement, as you don't get the voltages to drive the power tubes. i've also heard that au7s make great cathode follower buffers in marshall/bassman setups, as they overdrive nice when slammed with a signal.

June 6th, 2007, 02:06 PM	#10 (permalink)
The Radium King Tele-Meister Join Date: Aug 2006 Location: Canada Posts: 106	you could. the problem is that these are 'dual triode' tubes, so a 12ax7 has two separate gain stages, as does a 12au7. the bassman ri uses one tube to provide one triode as a gain stage and one triode as the cathode follower. if you replaced the 12ax7 in that position with a 12au7 you would get the 12au7 cathode follower, but also a 12au7 gain stage, which doesn't have the amplification of the original triode and you wouldn't be driving the cathode follower very hard. that's why, if you look around, you'll find old tubes that are dual triode with 1/2 as a 12ax7 and 1/2 as a 12au7, where the 12au7 is used as a buffer for the 12ax7 gain stage. not common in current guitar amps, however.

June 6th, 2007, 03:20 PM	#12 (permalink)
The Radium King Tele-Meister Join Date: Aug 2006 Location: Canada Posts: 106	got me tripping over my own sentences. marshalls and bassmans use a cathode follower (a specific configuration of a tube triode) before the tone stack. this allows the tone stack to be designed with less resistance (typically, a smaller slope resistor) and the previous gain stage to be tuned for maximum gain; this results in less loss in the circuit and more signal to work with downstream. most say that this is what makes for the distinct 'marshall' tone. cathode followers do not provide any gain, just a buffer, so any triode can work, and some prefer the sound of a 12au7 triode to a 12ax7 triode as a cathode follower. however, while a cathode follower before a tone stack is definitive of a marshall 'style' circuit, the straight swap of a 12au7 dual triode tube into a marshall or bassman may not work given how they use the other triode in the tube. clear as mud?

June 6th, 2007, 11:07 PM	#14 (permalink)
The Radium King Tele-Meister Join Date: Aug 2006 Location: Canada Posts: 106	sorry, didn't mean to confuse. i was referring to that style of circuit (again, cathode follower into tone stack). many folks build their own 18 watt marshall clones (which is a copy of a bassman) and can reconfigure the circuit such that they use a 12au7 cathode follower (amoungst many other variations). i've heard that au7s make great cathode follower buffers in marshall/bassman setups. feel free to put a 12au7 in any of the noval sockets in your amp. nothing will break, burn up or stain the carpet. that's the most definitive way to find out if you like the sound, and a lot quicker than typing on the internet.

June 7th, 2007, 05:27 AM	#15 (permalink)
celeste Tele-Meister Join Date: Jun 2006 Location: Maryland Age: 47 Posts: 217 12 Photos	If you want inventive uses for a 'u7, it is hard to beat these ax84 . look at the clean and blues preamps

June 9th, 2007, 07:56 AM	#16 (permalink)
marshman Tele-Holic Join Date: Feb 2007 Location: SE PA Posts: 729	I bought a Epi Vjr a while back, one of the very early ones. Hummed like a mofo, so after trying to ignore it, I hopped it up a la ZPs recommendations at 18watt.com. BUT, I ended up with waaay more gain than I really wanted out of it, and I didn't feel like sorting out which mod was the cause, so I started doing the 12A?7 dance, and ended up with a 12AU7 in there, and now it sounds exactly like I want it to. But only with my tele. Still sounds off with the strat, so the strat stays plugged into the Rivera.