My old emails seem to be a treasure trove of advice! Here’s one I wrote to someone who is looking for the Holy Grail of rock and blues guitar:  a tone that is clean when you play with moderate force but starts to break up the harder you play. A number of people have made (and spent) small fortunes on this quest. Here’s my two cents, based on the assumption that you don’t have a small fortune to spend.

There are four different ways to get distortion.

• You can introduce the distortion before you get to the amp input (with a fuzz box, amp simulator, or anything that adds an extra gain stage and level control in the circuit).
• You can introduce the distortion by overloading the preamp circuit (the little tubes). This is how early master volume circuits like the Mesa/Boogie worked. They simply took a two channel Fender amp and ran the output of one preamp stage into the input of the next stage.
• You can overwork the power tubes (this is what you do when you turn a one-tube amp like a Champ up all the way).
• Or you can overwork the speaker.

For completeness, I must also add that if you are recording or miking the amp, you can also introduce distortion in that process (the guitars on “Revolution” were recorded direct into the board and the channel outputs were cascaded; it was a tube board which is a lot more forgiving). There are also lots of excellent sounding amp simulation plugins. I use them myself a lot in the studio. But this won’t help you for live applications unless you want to bring your laptop to the gig and patch it into your rig. There are people who do this, but they usually have road crews and large budgets. I don’t recommend it; there are too many things that can go wrong.

Each of these types of distortion has a characteristic sound, with pluses and minuses. A distortion pedal allows you to dial in a good clean sound on the amp and modify it for solos, but often the solo sound isn’t as convincing as the clean sound. Preamp distortion often sounds overly compressed (think Larry Carlton seventies session stuff, a great sound but not a lot of dynamic range). Power tube distortion often sounds the best, but it generally involves running the amp up at least 3/4 of the way, depending on the circuit, and with a big amp that gets LOUD. And speaker distortion risks frying the speakers. Also, with power amp and speaker distortion, the bass strings can get floppy.

Probably some combination of the various types of distortion will give you what you want. To control distortion from the guitar’s volume knob effectively, at least one gain stage, and probably two, have to be distorting when the guitar is up all the way.

First, get the speaker up off the floor so that it’s out of the equation. Put it on a chair or small table so it decouples from the floor. (The floor can add bass and be very deceptive when trying to figure out how the amp works.) Start with your guitar’s tone control up al the way and your volume pot at around seven. If there are two inputs, plug into both of them in turn and start with the louder one if there is a difference. If there’s a bright switch, turn it on. Pick a bit lighter than normal. Then set the amp with modest settings on your tone controls (all on 5) and gradually turn up the amp until it distorts noticeably on your lowest note.

Do you like how it sounds? If so, now experiment with your guitar volume and see where it cleans up to the extent you want it to. Now use the amp tone controls to EQ your clean tone to where you want it, and you’re done. (They have much less effect at higher volumes.) Turn it back up to your solo volume. If the lowest note is woofy, roll off some bass, then check your clean setting again. Go back and forth until you find a medium you like.

If you don’t like the sound, analyze the problem. If you are basically happy with the tone you’re getting but it’s too loud, you need to cut the efficiency of the power tubes.

The first thing I would try is running the amp with a mismatched impedance, if you have that option. For example, if you have an 8 ohm speaker, use the 4 ohm speaker output. This will make the amp operate less efficiently and will also change how it responds to the speaker. You’ll have to turn it up louder to get the same amount of volume so the power tubes will have to work harder. (Larry Carlton used to do this back in the day.) You will wear out the tubes a bit faster, but as long as the differential is within a factor of 2 it’s not a big deal. However, the speaker resistance should always be equal to or greater than the amp’s output impedance. A 4 ohm amp into an 8 ohm speaker is fine. (I do this all the time with my 1962 Bassman.) An 8 ohm amp into a 4 ohm speaker is not a good idea for the speaker. A 4 ohm amp into a 16 amp speaker will work, but maybe not for long depending on how overbuilt it is. Old Fenders can take a surprising amount of electrical abuse both at the input and the output stages, but I can’t promise the same for newer ones, or any other model for that matter.

The next option is to pull two of the power tubes. Yes, you can do this! On a Fender style four tube amp, pull out the two middle ones. (Use gloves and be careful, they get hot.) This cuts your power by half and also induces an impedance mismatch, so it’s a more radical effect than just an impedance mismatch. If you don’t like how it sounds put them back in. I would call a tech first though to make sure that this will work with your particular amp. There are a LOT of circuit designs out there these days, not like 30 years ago.

To overload the preamp section in a non-master volume control amp, you will need to introduce a gain stage in front of it. This can either be a distortion/fuzz box or simply any preamp that you can patch into the circuit. (People used to use Revox tape recorders back in the day, among other things. The preamp circuit sounded great for guitar.) Tube preamps are particularly good, but anything that boosts your signal can work.

You can turn most distortion boxes into more or less clean boosts by turning the volume all the way up and the gain almost all the way down. Turn down your amp volume and, with your guitar volume on about 8, turn the gain/distortion/preamp up until the amp distorts. Now bring your amp volume up. It will be a lot louder! Hopefully you will like what this does to the sound. If it’s much too loud try either the impedance mismatch or removing the tubes to tame it.

If the sound is close, start playing with the amp eq to tailor it a bit. Remember in most tube amps the tone controls are passive, meaning that they are “flat” (no guitar amp is flat) when turned up all the way. So when you turn up the treble, you are actually letting the treble the amp is generating actually pass through to the output stage, for example.

Another thing you can try with a passive EQ is to turn all the tone controls down all the way. With a Fender style circuit you will get either no volume or very little. Then turn up the amp to, say 8. Now, GRADUALLY turn the EQ up a number at a time until you start getting the volume you want, balancing the tone as you do. I don’t like how this sounds but some people swear by it.

What you are trying to do with all this fiddling is get to a place where the power amp and preamp are both working pretty hard, to the point of overload. At that point, a number or two on your guitar’s volume control will make a lot of difference in the amount of distortion you hear. Note also that most guitar volume controls are tapered so that most of the volume increase happens between 7 and 10. If you tweak your amp so it’s clean at 4 or 5, a small adjustment will get you into distorto world. But it will also give you a big volume boost more often than not.

With master volume amps (any amp with two volume controls on the same channel), with your guitar at around 7 or 8 set the first volume control up to the point of distortion with the master down to maybe 3 or 4. Then turn up the master volume to the volume you want. Now when you turn your guitar down it should clean up nicely.

Here are a couple of further thoughts. First of all, not all distortion boxes are created equal! My old yellow Boss one lets lots of articulation through. My Tube Screamers, less so. But I like their midrange peak because I play clean Fenders a lot and they work well for the two or three solos I take a night in that setting. I wouldn’t use one as my main distortion sound for a rock gig. I just got a Carl Martin one that does an amazing, just about amp-proof Marshall simulation into the most characterless amps you can imagine, and it has a clean boost too.

What I do on rock and blues gigs is to either bring my weird 100 watt Marshall combo (which defaults to distortion even at low volumes) or, for smaller rooms, I bring a couple of small amps that break up well and patch them together with my stereo chorus or echo. I have an Ampeg Gemini I which sounds absolutely amazing and works just as you describe without any additional gear needed, but isn’t loud enough to get over a strong drummer, as well as an Epiphone Valve Jr. that does a great AC 30 imitation at a quarter of the volume.

With two small amps you can also run stereo effects if you like that sort of thing. The disadvantages are that they aren’t necessarily any lighter and it’s really hard to carry two amps on a train. You might want to look into the Fender Blues Jr. amps, which are quite loud for their size and very portable, especially if you are being miked up.

Any old Silvertone amp will break up nicely. They used to be very affordable before that horrible Jack White drove up the price by getting popular. Look around for off-brand old tube amps of any description, not just guitar amps. Look for old PA heads too. Some of them are super cheap and built with very similar circuits to guitar amps.

If you ever come into some money, look into the Dr. Z amps. They do what you describe very well, aren’t unbearably expensive for a boutique amp, and hold up on the road. The new Vox AC-15 with Celestions sounds great too, though I don’t think it will travel as well without a good road case.