12AX7, 12AT7, 12AY7 - Guitar Preamp Tube Shootout (Milkman Hi-Fi 5W Mini Amplifier Head)

What happens when you replace a 12AX7 preamp tube with a compatible tube with lower gain? It's not as simple as lowering the volume - by changing the relationship between the input signal from your guitar and the amplifier's preamp and power amp sections, the extent of clipping at each tube, compression and tone are all impacted.
Using a simple tweed Princeton or Champ style tube amp from Milkman Sound, let's see what happens!
Timestamps:
2:30 - 12AX7
4:05 - 12AT7
6:17 - 12AY7
8:32 - 12AY7 Full volume
9:54 - 12AX7 Full volume

[@gcensing6351]

I built myself an amp that is basically a Fender blackface preamp with a vox power amp. Originally I had all 12AX7s in the preamp, and it sounded very harsh and unpleasant. First I changed the PI to a 12AT7, which was a great improvement but not quite. Later I changed both the preamp tubes (first and second stage) out to 12AY7s, and there is no way back! The amp has more headroom, and the distortion is so much more relaxed and detailed, but still big and chunky. 12AY7 for the win!

[@NoStringsAttached777]

If you think about it you can't get more headroom from a change to a lower gain preamp tube. What you do get is the ability to turn the volume knob around further before clipping takes place. Put another way a bigger sweep of the pot occurs before distortion is heard which is not more clean headroom.Reduced maximum volume is also a consequence of reducing the input into the power amp.Tube rolling is still a great pastime which I do so often my amps have no backs on them..

[@chilidogcowboy]

Thank you. Most helpful! I put a 12AT7 in a boogie V Twin and it helped smooth things out for me this week vs the 12AX7s it had in it.

[@bluesbondsman]

12AY7 for the win ! Usable tone and crunch all the way across the volume range. I'm using a vintage 5751 in my 5F1 right now, however I'm going to try a 12AY7 today !

[@marklondon2008]

I put a 12AY7 in my Blackstar 5 head and it's a game changer - really opened the amp up

[@jrockofages5413]

Thanks! I will do the same. Maybe a difference maker

[@JasonFerguson1283]

At full volume the AY7 maintains discernable dynamics within the full power tube volume

[@adjustablebias]

Timestamps: 2:30 - 12AX7 4:05 - 12AT7 6:17 - 12AY7 8:32 - 12AY7 Full volume 9:54 - 12AX7 Full volume

[@cta.k.a.barrychan2460]

Hey you still around/alive? You plan on putting out some more stuff later down the road? If so would love to see!

[@kaschbowman]

Thanks for this! I am ordering a 5F1 kit and they send it with AX7's and this convinced me to order w/ out tubes and to order a 12AY7. To my ear that's my favored sound. THANKS!

[@adjustablebias]

Awesome - let us know how it goes!

[@billyhenley6968]

This is awesome man! This helped me determine that I want the AT7 to tame my gain channel on my Blackstar HT. Thanks

[@adjustablebias]

That's great! Let us know how it went - I think that there may be some solid state clipping circuitry in some of the Blackstar HTs - curious if changing the tube made a difference there.

[@cirjames2540]

Great video, this is a topic I have been struggling with for a while with my Fender Pro jr. The 12Ay7 sounds fantastic especially when it does finally break up. THX

[@russellesimonetta3835]

I liked the at7!

[@JasonFerguson1283]

I don't know if it's because I always played Fender amps with 12AX7 I prefer them but definitely low volume 12AX7 sound better to my ear. However at full volume the 12AT7 sound way better. Great video!!

[@joetoe9207]

Thank you for this!!! I’m trying to understand the properties of these tubes. - very helpful. I’m either of the AT or AY. Thanks again!

[@ChayBode]

Looking into this, and the 12AXT is blackboard scratchy, unlike the warm 12AY7, which can express the tone/notes without bleeding the ears, informative video, Thanks :)

[@michaelmcwilliams4705]

Your distortion is coming from the power tubes when using the 12AY7 as you need to crank it to get the same volume as opposed to using a higher gain12AX7 preamp tube.

[@spider5001]

Wow the range on that 12ay7 is nice!

[@crunch_amp9282]

12at7 sounds really good

[@smokepeddler]

12AY7 definitely sounds the best.

[@adjustablebias]

Agreed!

[@hadleymanmusic]

You think its smoother and less harsh? And possibly brighter? Cause im hatin the harsh ax7's im stuck with harsh clip and noise and im about to order some "Y"'s or " W"'s. I need some hifi preamp tubes thats more positive harmonic and not so harsh clip a singing type smoothe

[@adjustablebias]

@@hadleymanmusic I'm not sure I'd describe them as less harsh - they are definitely less gain-ey, and will stay quieter and cleaner further through the dial. It should also be easier and cheaper to find nice NOS options, which may allow you to find ones that break up more to your liking. It'll of course depend on your amplifier and what position you put it in.

[@davidlalremruata]

I really like the 12AT7

[@sam-ww1wk]

Great video man. So, what I'm gathering is the higher gain preamp tubes just fall apart sooner. Volume more a factor of watts, power tubes, circuit, etc. Excatly what I wanted to know because I have an amp that farts out a little soon. Seems like high gain tubes are like hot pickups; not for everyone and every application.

[@cheersdonsanders]

Hey..thanks for this experiment. I'd put an AY7 in my deluxe tweed and it tamed just the right amount of sag, but not having a db meter, I had been curious if the there was any db drop.

[@oficinadomarcheto]

12ax7 more fuzz and confused dirty

[@randyheath8566]

Great Information 👍

[@PhatLvis]

Can't quite tell what amp sounds like with camera audio obscuring it and also producing a slap-back.

[@adjustablebias]

No camera audio or vocal mics in the playing sections (you can hear my lazy editing whenever I didn't wait long enough to start playing after talking or talking before I stop playing)! A bit of room mics in mid-side mixed in to give a sense of what it actually sounds like in the room - close mic on the cab is never going to represent that well at all. This video is from a long time ago, and the room itself was pretty bare, so fair enough that there may be some slapback just from the room itself.

[@jcool0122]

I wonder how any of the less common 12A tubes would stack up. Like the U, the V and the Z

[@giulioluzzardi7632]

12AY7 sounds really nice and clear.

[@garymattischannel6207]

In that Amp The 12AT7 sounds the best.

[@rhythmcake]

Wow! Glad I happened upon this excellent and informative video sir! Much appreciated. Love those tones you got. Whats that mike?

[@rasalrew]

Sontronics Delta (either 1 or 2)

[@rennpart]

your videos are very informative and very helpful. I feel like you could be a double for Fred Armisen from Portlandia.

[@southernpride2003]

Anyone know what the best preamp tubes would be for the best Luther Perkins tone

[@joeromito299]

On a fender deluxe with 3 preamp tubes So if I’m going to replace just 1 ax7 with an at7 or ay7 which position should I switch out, input middle or closest to speaker preamp tube?

[@adjustablebias]

Assuming you have a deluxe reverb, you want the second from the far right (V2), which is the first tube your guitar hits if you're using the vibrato channel (or V1, the farthest away from the power tubes if you're using the normal channel, aka the one without reverb). With most other amps, you most likely want to change V1.

[@johndenby6192]

CV6091 is the King of them all

[@TheChadPad]

What mic you using in front of the cab? Sounds great

[@adjustablebias]

Thanks! It's a Sontronics Delta 2 ribbon mic - they sound pretty great, just dead on the middle of the cone - super easy. I think I may have also had a Rode condenser room mic mixed in at a pretty low volume. If you're in the US, don't try to buy one locally - they're way cheaper in Europe, and shipping is still pretty fast from places like Andertons or Thomann. When I got mine, it was way cheaper than like a Royer 121.

[@gettin_while_growin7]

Are they all the same brand of tubes?Are some long plate tubes and sum short plate? From brand to brand they have different gain factors also. Just a thought.

[@adjustablebias]

They are not - just what I had laying around. I'm sure there'd be some variation from brand and construction differences, but might be hard to even figure out how to control from that across all types.

[@sloppy_hand]

12at7 sounds the best

[@BigFuzzyLHG]

Same volume and more headroom?

[@craigjacob3704]

I have 3 preamp tubes in my amp. Which ones and what would be best? They are all 12ax7 now.

[@adjustablebias]

It depends on your amp, but you want the first gain stage for whatever channel you're on. Usually that's V1, on reissue fenders it's v2 for the reverb channel. (#'ing starts on the far right if you're looking at the back of the amp for both amps - there should also be a tube chart). When in doubt, it's easy enough to turn off the amp and then swap them out at a time and try each one!

[@craigjacob3704]

@@adjustablebias ok I'll have to expirament with it I guess. I have one of those new Monoprice stage right 30watt tube heads

[@bobking7347]

thats worth every bit of the 700 bucks

[@Booze4Blues]

Try the 5751 🤘🏻

[@michelangelocanonico]

Hi, thanks for the video. This test is a good idea, but as it is, it not very useful. I would record the guitar using a loop to do a more accurate analysis because the difference among tubes is not only about sound level. Please mention what recording setup are you using, mic and card interface.

[@adjustablebias]

Thanks - my thought about gear is that if you can't tell the difference with normal playing, why bother? It's not important enough to worry about if the difference is so small that variances like picking intensity, recording interface etc (other than possibly picking intensity, none of these varied throughout the test) are enough to be unable to tell a difference. You're going to be playing guitar through the thing (hopefully), not looping the same sound. If the difference isn't obvious when doing that, why bother? IMO, the difference was very noticeable, both in the room & on the video, just in terms of the amount of breakup as well as whether the preamp section was completely caving in, even at lower volume settings.

[@BellTunnel]

I think I prefer the 12AX7. What does it come with?

[@adjustablebias]

Ships with a Ruby Tubes 12ax7!

[@BellTunnel]

@@adjustablebias Thanks. Sounds great!

[@davidlalremruata]

The AY has a very Heavy Metal way of breaking up, huh?

[@generalawareness101]

A year later.

[@davidlalremruata]

why do I feel the need to hear those tubes with a humbucker on your Telecaster? Keith Richards? Probably, yeah.

[@psyren7587]

The 12AY7 sounded MUCH better at full volume. That 12AX7 just flubbed out completely....

[@marcadamo6224]

12at7

[@alvagoldbook2]

This is not a well thought out experiment. While there’s plenty of 9 pin tubes with the same pin out, it doesn’t mean that they’re interchangeable. The circuitry on this amp is specifically for a 12ax7. In order to change it for other bottles you’d have to completely rebias the preamp tubes. For example, at 300v, a center biased 12ax7 would typically have a 100k plate resistor and a 2k7 cathode resistor. But because a 12at7 is capable of only two thirds the voltage gain of the 12ax7, but 10 times the current gain, then a more suitable plate resistor is around 18k. To make a car analogy, this is like comparing the handling of a monster truck and a Camry if both vehicles had the same sized wheels.

[@adjustablebias]

Well, I guess it depends - do you want to know what your Camry is going to do if you change the wheels, or do you want to buy a monster truck? Most of us probably aren't going to buy a monster truck, just like most of us are fine swapping out a tube and seeing what the new sound is but not swapping out resistors. Regardless of the analogy, guitar amps are not hifi amplifiers and are definitely at all about operating your equipment within designed efficient limits in order to get a pristine signal - they're all about pushing things well past those and enjoying all those nice harmonics, compression and distortion. If someone likes the way a 12at7 sounds in an amp designed for a 12ax7 more power to them (and a lot of the tweed models were designed for 12ay7s, but folks swapped in 12ax7s for the added gain). Playing around with reasonable replacement options and determining if you like the sonic character those changes impart is both easy and worthwhile!

[@alvagoldbook2]

@@adjustablebias Well tube rolling is fine, but my only point is that people really don't know what a 12at7 sounds like if they just use it in a 12ax7 circuit. In fact, most of the old Fender circuits were biased for 12ax7s and they'd put things like 12ay7s in there. You didn't see Fender actually bias a 12at7 correctly in a phase inverter circuit until the late 70's. The degree of this error cannot be overstated. While preamp tubes are quite forgiving, they weren't designed to be run like power tubes where you push their limits. Pre-amp tubes are ideally center or warm biased. But biasing a 12at7 with a 12ax7 circuit makes it very cold, and if it wasn't for tubes being so forgiving, it wouldn't even conduct at all. I will post a load line to show you what I mean.

[@alvagoldbook2]

@@adjustablebias How the 12ax7 is biased in this amp (or a very close approximation). ibb.co/LNV5SxJ How a 12AT7 is biased in this amp. ibb.co/1dHZ13T How a 12AY7 is biased in this amp. ibb.co/BKCF1hg How a 12AU7 is biased in this amp. ibb.co/qC5RTGy

[@jrockofages5413]

@@alvagoldbook2 so it isn't a good/safe idea? I was considering this for Blackstar HT5

[@alvagoldbook2]

@@jrockofages5413 Is it safe? Yeh, probably. People have been doing it for years. But check to make sure your power transformer isn't running too hot and only do it one 1 tube socket. Power transformers can be pretty forgiving, and preamps don't draw much current, but a single tube going from pulling 1mA to 10mA is significant enough that you just want to make sure your power transformer is doing ok. It most likely can handle it fine, because most amps are built to handle more than their design calls for. Is it a good idea? No, not really. I mean, try it, you might like it. But don't think that this is how a 12at7 or a 12ay7 really sounds.

[@andrewcain116]

SAY IT AINT SOOOOOO

[@yaniv-nos-tubes]

modern tubes are as good as chinese pickups random gain and noise levels bad quality control even robotube can't save the tone

[@adjustablebias]

Yeah... You can go through 3+ new 12ax7s without finding one without serious issues (although tone-wise they can be ok). Yet another reason to try out alternate 12a*7s - you can get the desirable NOS options for about the same price as a new 12ax7!

[@BladeDoomer86]

108db is very, very bad for your ears people. Just saying.. Don't do this at home.