I’m often asked, “What can I do to improve my tone without having to spend too much”. The following is a list of improvements that can be made with relatively low cost. This is assuming that you’re already set with your guitar (strings, pickups, controls, etc.):

• Make sure your equipment is in good working order. This includes cables, batteries, power cords, power sources and anything else you use so your rig is able to perform like it’s supposed to. This may sound obvious but there’s nothing like a bad guitar cable or weak battery in an effects pedal to disconnect your signal or suck the life out of your tone. With everything in good working order, you have a basis from which to start from.
• Have some idea of what sound you’re after. Do you want to sound more like Clapton, Page, SRV? Having at least a general idea will get you closer to finding YOUR tone. With big time players, their gear set up is usually listed in one of the guitar mags. You can see if you already have some of the same gear or if there’s something commonly used by many players (ex. McKinley Blonde).
• Evaluate your current set up. 400-watt Marshall stack for coffee house gigs? 5-watt amp with 8” speaker to fill in for Pete Townsend? Consider your current rig and see if it meets your needs. If not, think about what you want to change. If you can’t be heard, you may need more wattage, more speaker(s) or both. If you’re making everyone deaf, you may want to downsize. 
• Speaker placement For more low end, place your speaker cabinet closer to or against a wall. For less, move it away. This is similar to microphone placement for different sounds but applied to speakers.
• When was the last time you replaced your output tubes? Re-biased? Here you can greatly warm up the sound of your amp and increase its output for low cost. Tubes are like lightbulbs in that the harder they are pushed and the more often used, the quicker they will wear out. With regular use, they’ll last about a year before they’ll start to negatively affect your sound. With your bias, this will drift over time and a periodic re-bias is recommended or when changing tubes to get their best tone. With a new set of output tubes and a re-bias, new life will be breathed into your amp. It’s also a good idea to change your phase inverter / driver preamp tube at the same time as it is the link between your preamp and output stages. If you’re strapped for cash, just get the re-bias.
• Pre-Amp tubes Here’s another low cost improvement. These take the signal from your guitar and amplify it through the preamp. A weak signal will produce weak results. Recognize that stock tubes are usually lowest cost and therefore give, at best, average performance. They’re not necessarily bad, but their performance can be greatly improved upon. A quality signal will give your amp more to work with. Different types of preamp tubes deliver different levels of amplification (ex. low gain, high gain, etc). The first preamp tube in your amp will make the most difference and can be changed to suit different styles of music (i.e. one for blues, a different one for alt rock, a third for molten lava metal). This is a quick and easy change with big results.
• Speakers Do you want more of a “Fender” sound or more “Marshall”? The speaker is the next big improvement you can make with your sound. For more of a vintage sound with clear highs and deep, big lows, Jensen’s do an excellent job. For speakers suited for high gain with warm, solid mids and excellent break up, Celestion’s are awesome. You’ll want the total speaker wattage to be at least twice that of the amp as the output peaks beyond the amp’s rated value.
• Speaker cabinets Open back vs. closed back? Keep the speaker cabinet in mind as it can make a big difference. You want heavy, dense wood and a solidly constructed cabinet. Open backed cabs will fill a room better while closed back will have more low end but the sound will come out more like a beam.
• Effects pedals BOSS can be considered as the biggest name in pedals and while they do put out good products, their performance can be improved upon. This holds true for almost any stock pedal. When manufacturing a product in mass, a balance is reached between performance and cost. If these big companies used better quality components to yield superior tone, the costs would go up, they would have to charge a higher price and their sales volume would go down. When the circuit of a pedal has undergone a quality modification, the results are amazing. It’s like a blanket has been lifted off your sound. Your playing is featured, not the effect. Your sound is more organic and less processed sounding. The nuances of your playing come through with clarity and the depth of the effect is touch sensitive. It’s a real pleasure to use a quality modified effects pedal. It really does improve your playing through superior tone. It is for these reasons that I developed and offer effects pedal modifications by Steve McKinley Electronics. www.stevemckinleyelectronics.com 
• Variable AutoTransformer (see the Variac - Why You Should Have One tab)
• Attenuators Power attenuators are devices used to reduce the amount of power going from the amplifier to the speaker. As opposed to a volume control on an amp, attenuators are almost always external, outboard devices. People use power attenuators because they like the way an amp sounds when turned up loud, but don't need all that volume. I’ve heard very satisfying results with attenuators so realize what’s going on to get you that “golden” tube amp tone without going deaf in the process. From my experience, THD Hotplates and Weber Attenuators seemed to get the most consistently positive results, with the Power Soaks coming in next.

There are more improvements available beyond these but they get into circuit modification and output transformer replacement, which go beyond what can be briefly described here.

The key is to try each of the above individually and listen to how it affects your tone to the point where you have found YOUR signature sound.

The pursuit can sometimes be time consuming, require patience and at some cost but the results are most satisfying.

Now go forth and find YOUR tone!

Steve