Is there a "sweet spot" in tube amps?

[Kosthrash]

...or it's just an urban legend? I'm referring to high gain tones... What's your opinion on this?

 

[SamSam]

Yes there is. It's the spot which sounds best to you

 

[sleewell]

mine is sweet when its turned on.

 

[cmpxchg]

Yes there is. It's the spot which sounds best to you

this is it. maybe you want a ton of preamp gain, maybe you want power amp distortion. maybe you want lots of mids or you want them scooped. it all depends on your playing, your signal chain, your intent, and your taste.

 

[Kosthrash]

Yes there is. It's the spot which sounds best to you

So it is an urban legend, as it's totally subjective according to each one's personal taste (how we dial in our amp to our tone), not something specific for each tube amp, as it's being referring to, right?

 

[Drew]

...or it's just an urban legend? I'm referring to high gain tones... What's your opinion on this?

Broadly speaking I'll agree with @sleewell - they do sound different at different points, and nothing wrong with having a favorite.

For modern high gain tube amps, though, the old adage about they have to be cranked up to sound their best is a lot less true than it used to be - that was back in the day when power amp compression, and then actual distortion, was supposed to be a big part of their sound. Modern high gain designs use cascading gain stages in the preamp to generate essentilly all of their gain, and poweramp design is really about preserving headroom. I'm, like, WILDLY simplifying things here, but play an old non-master Marshall 1959 Super Lead and play a Dual Rectifier's clean channel, and start cranking them up, and you'll hear the difference in response pretty quickly.

 

[MoistTowelette]

Yes, when you turn mids to zero.

 

[4Eyes]

Yes and no, like with all the gear - with certain guitars and amps/preamps/amp sims you'll have your preferred settings for your playing style and music. Use your ears and have fun.

Speaking of tube amps specifically - most of the modern amps sound good at low volumes, the only "sweet" spot in regards of the cranking the volume is where you start to drive guitar spekaers enough to move air and sound good, which usually equals to loud TV - then it's up to you how much you want your ears to bleed.

 

[Celtic Frosted Flakes]

...or it's just an urban legend? I'm referring to high gain tones... What's your opinion on this?

The sweet spot in high gain tones is when you turn the gain down and volume up.

 

[thraxil]

The other thing you have to keep in mind is the Fletcher-Munson curve. Basically, you percieve the frequency spectrum differently at different volumes. If you dial in an amp in at bedroom volumes, change nothing in the EQ and then just turn it up to gig level (or vice versa), it's not going to sound the same, even if there's no additional EQ changes or power amp distortion introduced. So, it's not specific to tube amps, but you definitely can have a "sweet spot" insofar as an amp sounding better/worse at a particular volume. (and for recording, there will be similar a similar effect because microphones respond differently at different volumes, so that's part of the whole process of getting the positioning, distance, and volume all right).

 

[cwhitey2]

In my cl100 there is deff a sweet spot in the power section. Crank that baby to 1-2 o'clock the amp realllly starts to open up and comes to life.

 

[Estilo]

Legend is if you play a G note at the amp's sweet spot, they coverge to become the sweetest G spot.

 

[GreatGreen]

To answer that question, you need to understand specifically what turning up the Master volume does to the tone, independent of volume. To sum it up, the more you turn up the Master, the more the loudest frequencies of the signal get clipped off to being the same voulme, while the rest of the signal gets boosted closer to the clipped frequencies.

Below are a few diagrams of how poweramps typically distort. The basic EQ of a tube poweramp typically follows the impedance curve of the cab or reactive load to which it's connected, and the Master volume controls how that curve interacts with the headroom limits of the power section.

This is just a crappy drawing and obviously not the exact way it happens, as power tubes usually clip more gradually than the hard red line in the graph, but it kind of shows the basic idea:



The degree of poweramp saturation and darkening that will sound best, the "sweet spot," will depend on the amp itself.

If you're using a modern high gain amp and want a very clear, bright, articulate tone where all of the distortion comes from the preamp, then the Master volume's best sounding setting will be anywhere between the amp being just loud enough that all frequencies are represented, and just low enough that the poweramp doesn't clip away those articulate highs. Figure 1.

Then you have rigs that ride the line between vintage and modern, like boosted JCM 800's. They get a percentage of their distortion and clipping from their boosted preamps but not all of it. On its own, even boosted, those preamps are just a bit too clean and bright, so if you set the Master low enough that the poweramp doesn't clip, the rig still be a bit too bright and clean. Turning it up right until you get just a little bit of poweramp clipping, like in Figure 2, tends to sound best there.

Now let's take something like a vintage Marshall Plexi. That amp has an extremely clean, bright, and sibilant preamp. With that amp, you're going to want to turn the Volume up enough so the brightness is tamed by the poweramp and it starts to overdrive, which mostly comes from the phase inverter (really, most of the distortion you hear from a Plexi comes from overdriving the phase inverter, not really the power tubes themselves, but I'm trying to keep this relatively simple). This looks like Figure 3. Most Plexi guys tend to prefer those amps around 6-8, which is about where that kind of sound is in that amp. Not so loud that it's totally saturated but loud enough to round off the super high highs and get some good sounding and feeling compression and sag. Note that Plexi's amps don't actually have a true master volume control. Instead, the full signal of the preamp is always sent straight to the poweramp. It's like setting a modern amp's master volume on 10 and using the Gain knob as the volume control.

Any amp will do this but it's easiest to hear on older non Master volume Plexis, and if you plug into one and mic up its cab in another room and listen through monitors to account for volume, you can hit notes and chords on the guitar and turn the volume knob to listen in real time as the amp gets brighter and darker with that volume setting. At sufficient loudness, the Volume knob stops controlling the actual loudness of the amp and instead starts acting more like a combination Gain and High Cut control.

Again, this is by no means totally scientific but I think it conveys the general idea. An amp's "sweet spot" depends entirely on the amp itself and what you're trying to get out of it.

 

[loganflynn294]

Yes, but it’s a combination of the volume sweet spot for both the amp AND the speakers. Most modern high gain amps need some volume to sound best, as do the speakers. Amps AND speakers will sound different at low, medium, and high volumes, gotta find what’s best for each particular combo.

 

[GreatGreen]

Yes, but it’s a combination of the volume sweet spot for both the amp AND the speakers. Most modern high gain amps need some volume to sound best, as do the speakers. Amps AND speakers will sound different at low, medium, and high volumes, gotta find what’s best for each particular combo.

Most Modern amps really don't need any significant volume at all to sound their "best." All they need is just enough volume to drown out any treble or bass leaks (like you hear with all versions of 5150's, or a Mesa Recto in Modern mode, for example) if the amp has leaks at all. If the amp doesn't have any of those small frequency leaks though, the tone doesn't really change at all until you hit the headroom limits of the poweramp or speakers themselves.

If you put a modern amp with a great master volume through a reactive load and turn the reactive load's volume down as you turn the amp up, you can hear for yourself that the tone doesn't change until the poweramp starts to break up.

Speakers can start to compress at very high volumes as well but not nearly to the extent or effect that an amp will, and again we're talking very high volumes.

The vast majority of everything that happens below the *extremely* loud volumes required for guitar rigs to begin poweramp breakup and speaker compression are mostly a matter of how humans percieve different levels of loudness (fletcher-munson, etc). At that point, the sweet spot has nothing to do with the gear itself, but instead the ears of the listener.

 

[loganflynn294]

Most Modern amps really don't need any significant volume at all to sound their "best." All they need is just enough volume to drown out any treble or bass leaks (like you hear with all versions of 5150's, or a Mesa Recto in Modern mode, for example) if the amp has leaks at all. If the amp doesn't have any of those small frequency leaks though, the tone doesn't really change at all until you hit the headroom limits of the poweramp or speakers themselves.

If you put a modern amp with a great master volume through a reactive load and turn the reactive load's volume down as you turn the amp up, you can hear for yourself that the tone doesn't change until the poweramp starts to break up.

Speakers can start to compress at very high volumes as well but not nearly to the extent or effect that an amp will, and again we're talking very high volumes.

The vast majority of everything that happens below the *extremely* loud volumes required for guitar rigs to begin poweramp breakup and speaker compression are mostly a matter of how humans percieve different levels of loudness (fletcher-munson, etc). At that point, the sweet spot has nothing to do with the gear itself, but instead the ears of the listener.

I hear what you're saying, but I disagree. I'm not talking about classic amps and speakers that rely on high volume for poweramp or speaker breakup like a Plexi or Greenbacks, I'm talking just average high gain amp and speaker combos. I don't care how good the master volume is, a lot of amps will sound different at bedroom practice volume, medium volumes, full band volumes, and everything in between. I'm not talking fletcher-munson either, I'm talking about tone. Mic up an amp and speaker combo at different volumes and each one can sound vastly different when played back at the same playback volume. I do agree about playing a modern amp through a reactive load while turning the amp up and load down, you'll definitely hear an audible difference as the tubes distort. I'm mostly talking about the tone differences at volumes below that. As you turn up the volume and the voltage in the circuit goes up, the tone will change. I've spent a lot of time tracking at home and in the studio, always comparing tracks recorded at different volume levels. Some high gain amps sounded better at lower volumes than they did at higher volumes and vice versa. There's so many variables, always best to just try everything and see what ends up sounding best.

 

[GreatGreen]

There's so many variables, always best to just try everything and see what ends up sounding best.

This I definitely agree with. There are so many ingredients to any given rig that at the end of the day, the best thing you can do is just get in there and start turning knobs, listening for yourself, and going with whatever lights you up the most.

 

[FloridaRolf]

Disregarding volume, some amps like Marshalls do crazy things when going wild with their eq. Diming the bass/mid/(treble) and gain on a JCM can make it sound really sick, just like Tom from Celtic Frost does.

 

[TheBolivianSniper]

Disregarding volume, some amps like Marshalls do crazy things when going wild with their eq. Diming the bass/mid/(treble) and gain on a JCM can make it sound really sick, just like Tom from Celtic Frost does.

Cranking the presence on my Archon makes it come alive in a different way. I don't always like the sound, but it gets really bright as soon as that knob hits past 3/4s in a way that you wouldn't expect, kinda like taking a cover off of the sound. It's too much sometimes but super dramatic.

 

[cGoEcYk]

I tried to measure it on my Tremoverb. On the gain channel it starts around 118-122 dB measured from about a meter away.