Amp basics
How to get a good guitar tone at low volume
Updated 7 min read8 sources
Turn the amp's power down rather than its Master almost off: on a BOSS Katana, set Power Control to 0.5 W and play with Master higher, or plug headphones into the phones jack, which mutes the speaker on the Katana MkII, the Katana Gen 3 and the Fender Mustang LT25. Then set the EQ at the volume you play at, with a little more bass and treble than you would use loud, because the ear hears less of both when it is quiet.
Halving an amp's power lowers its level by only about 3 dB, so a 100 W amp switched to 50 W is barely quieter; it takes a tenfold cut to lower it by 10 dB. Never make a tube amp quiet by unplugging the speaker: Marshall's handbook says not to switch an amp on without the loudspeaker connected. Use its master volume, power scaling or an attenuator instead.
Why does an amp sound thin at low volume?
It is mostly your ears. Hearing is less sensitive to the extremes of the range at low levels: Wikipedia's article on loudness compensation says the lowest and highest frequencies can drop below what you can hear when it is quiet, and that boosting them gives a flatter response that seems louder.[1] The equal-loudness contours, standardized as ISO 226:2003,[2] map the same effect.
So a tone set loud sounds thin and dull at home, and a tone set at home, with its extra bass and treble, turns boomy and harsh when the volume comes up. Set the EQ at the volume you will play at, with bass and treble a step higher at home than you would use loud.
Tube amps lose something else when they are quiet: the distortion of the output stage. Wikipedia's article on power attenuators says players drive the output stage for its distortion, and that the volume this takes is unsuitable for many places.[3] At bedroom level, all of the drive has to come from the preamp or a pedal.
- What the ear loses at low volume: bass and treble
- The fix at home: bass and treble a step higher
- Flat
- BassHeard less when it is quiet
- Middle
- TrebleHeard less when it is quiet
Set the EQ at the volume you will play at.
Is a 50 W amp half as loud as a 100 W amp?
No. Loudness follows decibels, not watts, and Wikipedia's decibel article gives the two figures that matter: halving or doubling the power changes the level by about 3 dB, and a factor of ten changes it by 10 dB.[4] So switching a 100 W amp to 50 W takes off only about 3 dB. Going from 100 W to 0.5 W, as a Katana-100 MkII's Power Control does, is a 200-fold cut, about 23 dB.
That is why a low power setting does more than the watts suggest at the bottom end and less at the top, and why a 5 W tube amp is still loud: 5 W is only about 13 dB below 100 W. These are the most each setting can put out; how loud you actually play still depends on Master.
| From 100 W to | Power left | Level change |
|---|---|---|
| 50 W | 50% | about 3 dB |
| 25 W | 25% | about 6 dB |
| 10 W | 10% | 10 dB |
| 5 W | 5% | about 13 dB |
| 1 W | 1% | 20 dB |
| 0.5 W | 0.5% | about 23 dB |
Boss Katana: Power Control first, then Master
BOSS built the Katana for this. Its Power Control switch sets the output of the power amp to suit where you are playing: STANDBY, 0.5 W, 25 W and 50 W on a Katana-50 MkII, STANDBY, 0.5 W, 50 W and 100 W on a Katana-100 MkII,[5] and STANDBY, 0.5 W, HALF and MAX on a Gen 3.[6] STANDBY mutes the amp without changing the volume or any other setting.[5]
At home, set Power Control to 0.5 W and bring Master up to a comfortable level, rather than leaving full power on with Master barely open. Then raise Bass and Treble a step if the sound is thin, for the reason above.
Silent practice with headphones
On the Katana MkII, plugging into the PHONES/REC OUT jack mutes the speaker, and on the Gen 3 the STEREO PHONES jack does the same; BOSS says this is convenient for practicing at night. On a MkII, set the headphone level with Volume along with Master;[5] on a Gen 3, with Master.[6]
Fender's manual for the Mustang LT25 says the same of its 1/8-inch headphone output: it disables the speaker.[7] Its auxiliary input lets you play along with a phone or other player, whose volume you set on that device.[7]
Tube amps: master volume, power scaling and attenuators
A master volume lets the preamp distort while the Master keeps the level down, so you get the preamp's distortion at a low volume but not the output stage's. To get the output stage working quietly, there are two other routes.
An attenuator sits between the amp and the speaker and diverts part of the power, which Wikipedia says lowers the volume without changing the overdriven sound.[3] Whether reactive attenuators keep the tone better than purely resistive ones is still debated.[3] Power scaling works differently: it lowers the supply voltage to the power tubes, and Wikipedia notes that this tends to add distortion, so it is not strictly an attenuator.[3]
For an amp designed for full-power use, Wikipedia says an attenuator neither increases nor reduces the chance of damage.[3] Running with no load is another matter. Marshall's JTM 30 handbook says not to switch the amp on without the loudspeaker connected, and to make sure any extension cabinet is the correct impedance.[8] Never unplug a tube amp's speaker to play quietly.
Is it bad to play a tube amp at low volume?
No. Marshall's handbook, for one, warns about running an amp without a speaker and into the wrong impedance, not about playing quietly.[8] What you give up at low volume is the output stage's distortion and some of the ear's sense of bass and treble, not the amp's health.
For the sound itself, the routine is the same on any amp: the lowest power setting it has, Master up to a comfortable level, and the EQ set at that level, with bass and treble a step higher than you would use loud. When you want a particular song's settings for the amp you own, Tonelify works them out for that amp; at home, start from them and add that step of bass and treble.
Common questions
What is the best Katana Power Control setting for home?
0.5 W. BOSS's Power Control sets the output of the power amp, and at 0.5 W you can bring Master up to a normal position at a quiet level. For no sound from the speaker at all, plug headphones into the phones jack, which mutes it on the MkII and the Gen 3.
Why does my amp sound bad at low volume?
The ear hears less bass and treble at low levels, so a tone set loud sounds thin when it is quiet. On a tube amp, the output stage is also not distorting. Set the EQ at the volume you play at, with bass and treble a step higher.
Is a 50 W amp half as loud as a 100 W amp?
No. Halving the power lowers the level by about 3 dB, a small change. It takes a tenfold cut, 100 W to 10 W, to lower it by 10 dB.
Can I run a tube amp without a speaker to play silently?
No. Marshall's handbook says not to switch the amp on without the loudspeaker connected. To play a tube amp quietly, use its master volume, power scaling or an attenuator.
Is an attenuator bad for a tube amp?
For an amp designed to run at full power, Wikipedia's article says an attenuator neither increases nor reduces the chance of damage. Whether reactive attenuators keep the tone better than resistive ones is still debated.
Do headphones turn off the speaker on a practice amp?
On the Katana MkII, the Katana Gen 3 and the Fender Mustang LT25, yes: their manuals say plugging headphones in mutes the speaker. On a MkII, set the headphone level with Volume and Master; on a Gen 3, with Master.
Sources
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