The Phantom was specifically designed to preserve the tone of the amplifier at all volumes. It doesn’t get “fizzy”, “boomy”, “tinny”, “mushy”, “compressed”, or any of those other adjectives used to describe bad tone. At lower volumes, it sounds basically like the amp at higher volumes.  Of course, as volume is lowered, you don't get that impact that you get at higher volumes because the speaker is just not moving as much air. There is no way to get around those physics.  But the Phantom doesn't add any negative artifacts to the tone at low volumes.
 
 

Yes, you can… but I’m not so certain that you should! The Phantom has been over-engineered to handle a “dimed” 100 watt amp, which actually puts out significantly more than 100 watts. But running an amp at full volume, particularly if it’s producing a lot of distortion, isn’t necessarily a good idea.
 
Playing at high power levels naturally requires the output tubes and the output transformer to work harder and creates more heat in the amplifier electronics. Not all amplifiers are created equal. Some amps have been engineered with components that can withstand that kind of beating, and some amps have components that could potentially fail running at “full blast” for any length of time. One of the dangers in “diming” an amplifier into the Phantom, or any attenuator, is this: without the bone crushing wall of sound that you would normally experience from a “dimed” 100 watt amp, it’s easy to become complacent and forget how hard your amp is really working, which could lead you to routinely run your amp on the edge of it’s design limits, or beyond!
 
At the very least, you will have to replace your power tubes more often. Worst case: repeatedly generating excessive heat in your output transformer could cause eventual failure of the winding insulation, leading to transformer failure. Of course, that’s just my opinion… some guitarists have been running their amps wide-open for years and would beg to differ! I can’t recommend “diming” an amp into the Phantom, so proceed at your own risk.
 
 

This question is probably asked more than any other, and deserves a thorough answer. It dovetails nicely onto the previous question. 
 
The simple answer is NO, if you properly use the Phantom, it won’t harm your amplifier. It has been designed to withstand more power than it’s rated for, it has a selectable impedance of 4, 8, or 16 ohms so that it can be used in any amp / speaker configuration and it has a reactive load that is modeled after the characteristic impedance curve of a speaker. Connecting a Phantom to your amp is no more harmful than connecting a speaker.
 
But the Phantom, like any other power attenuator, has the potential to be misused, and that’s where you can get into trouble. If you follow some basic rules, you won’t have any issues.
 

• You shouldn’t “dime” your amp into the Phantom for extended periods for the reasons previously mentioned. If you can find your amp’s “sweet spot” without having to turn it all the way up, your amp and attenuator will be much happier.
   

• Don’t exceed the power rating of the Phantom. It’s designed for amplifiers rated at a maximum of 100 watts RMS. That doesn't mean that it's incapable of handling more power, it has been engineered to handle a 100 watt amplifier at full volume, which can put out substantially more than 100 watts.  But don't use it with an amp that's "rated" at more than 100 watts RMS. It will, of course, work with any amp rated below 100 watts RMS.
   

• Set the Phantom impedance to match your amplifier and speaker(s). If your speaker is 8 ohms, set your amplifier impedance and the Phantom’s impedance to 8 ohms. Impedance mismatching has the potential to cause problems with your output transformer, output tubes, and other components of the output circuit. It can also be a detriment to your tone by lowering your amps' headroom and changing your amps' frequency response.
   

• Always use approved 2-conductor speaker cable, preferably 16 gauge or larger, for all speaker-level connections. That would include connections from the amplifier speaker output to the Phantom In jack, and connections from the Phantom SPR A Out and/or SPKR B Out jacks to speakers. Never use shielded guitar cord for speaker connections.

If you follow these basic common-sense rules, you should have no problems. The simple truth is this: the Phantom VRA will put no more stress on your amplifier's output transformer than playing straight into a speaker at the same volume settings. Properly matching the Phantom VRA to the amplifier's output is THE KEY. 
 
 

Yes. The Attenuation controls on the front panel must be configured for the Load setting. Turn the Attenuate [dB] control counter-clockwise to the Var position. This selects the Variable Control. Now turn the Variable Control all the way down (counter-clockwise) to the Load position. At that point, you can disconnect the speaker and the Phantom will provide a reactive load of the proper impedance to the amplifier. 
 
You can continue to use the adjustable Line Level output for recording, re-amplifying, etc.
 
In all other attenuation settings, a speaker MUST BE CONNECTED to the Phantom to insure a proper load on your amplifier. 
 
 

I use a 4 ohm head with a 8 ohm speaker cabinet.  How should I use the Phantom with this setup?
 

I don’t recommend mismatching the speaker impedance to the amplifier, but some amplifiers can tolerate a small impedance mismatch with no harm to the amplifier. Don’t mismatch by more than a 2:1 ratio. For instance, 4 ohms to 8 ohms is a 1:2 impedance increase. 16 ohms to 8 ohms is 2:1 impedance decrease. 16 ohms to 4 ohms is a 4:1 ratio impedance change and is too much of a mismatch to be safe.

When using a mismatched speaker with your amp, always set the Phantom’s impedance selector to match the amplifier, not the speaker. Using the above example, the 4 ohm amplifier head would connect to the Phantom IN jack, the Phantom impedance selector would be set for 4 ohms, and the 8 ohm speaker cabinet would connect to one of the Phantom’s speaker OUT jacks.
 
 

Can I use the “line level” output as a headphone jack for practicing silently?
 

No. The output level, impedance, and frequency response of the "line level" output jack is not compatible with headphones.
 
 

Can the “line level” output be used for recording, re-amplifying, FOH mix, etc.?
 

Yes. When recording from the line level output, the speaker is being bypassed and removed from the recording signal chain. But the speaker in a guitar amp has a profound effect on the frequency response of your amplifier. The output transformer of a tube guitar amp has a wide, flat frequency response (typically about 60 Hz to 15,000 Hz) but the guitar amp’s speaker has a narrower frequency response (typically about 75Hz to 5,000 Hz) with a pretty steep frequency roll-off above 4,000 hertz. 

Since the line level output of the Phantom has the wide frequency response of the output transformer, and it is not filtered (or “cabinet voiced”), the signal must be processed through an equalizer or “speaker emulator” in order to roll-off the high frequencies the way a guitar amplifier speaker would. 

Re-amplifying the line level output typically does not require any such processing. Usually, the last device in a re-amplified signal chain is a speaker, so there is no need to use signal processing tricks to emulate the speaker.

When the line level output is used in a “wet / dry” setup, as detailed in previous pages, this is essentially the same as re-amplifying. The difference is that a “wet” or “effected” signal is being re-amplified.

You can send the line level output signal to your FOH (front-of-house) mix as a replacement (or supplement) for an amplifier’s speaker microphone. But the signal should be processed through a multi-band equalizer or “speaker emulator” in order to roll off the high frequencies as described previously.
 
 

I use the Phantom with my 100 watt Marshall amp for practicing late at night.  When I have the amp cranked and the Phantom is at low "bedroom" volume, it gets very hot.  Is this normal?
 

Yes, it's normal.  The Phantom is designed to dissipate 100 watts of continuous power.  A cranked 100 watt Marshall amplifier can produce significantly more than 100 watts of average power when it is driven into distortion, even if it's not turned all the way up.  When you are producing so much power and the Phantom is at "bedroom" volume, only a very small fraction of that power is being delivered to your speakers (often less than 1 percent), the rest is being dissipated by the Phantom and the heat sinks may become very hot to the touch.  If you are going to use the Phantom in this extreme manner, it is recommended that you take occasional breaks to allow the Phantom to cool down.
 
When the Phantom is used in band practice, recording, or performance situations, it's not normally operating under such extreme conditions and will not generate as much heat.