If you changed to tubes with a lower resistance without biasing the amp you would quickly burn through those tubes and potentially damage the amp and yourself in the process. This is because the amp is still pushing out current at a higher level than the valves are able to take.
Tubes, like analog recordings, have a more full-bodied sound than transistor gear. There's a "roundness" to tube sound that solid-state gear never equals. Tubes are less forgiving about mismatches, so to get the best out of a tube amp it must be used with just the right speaker.
Crackling, squeals and feedback, excessive noise and muddiness or low output are all evidence of tube problems. Power tubes. The two main symptoms of a power tube problem are a blown fuse or a tube that begins to glow cherry red. Either are typically indicative of a power tube failure.
Power valves should be replaced every 18 months to 2 years and all valves should be changed at the same time. The amplifier should then be re-biased. Preamp valves should be replaced every 4 years and can be replaced individually. The amplifier won't require biasing after this.
In many cases, tube amps do not require the amount of maintenance that they have a reputation for. As long as you properly take care of your gear, owning a tube amp is simple and very well worth it for the tone.
Yes good amp makes HUGE difference. Long answer: tube amps will most definitely improve your sound versus a solid state amp like your 15G. Now there are some great sounding solid state amps out there but those are rare and nothing beats the full sound of a tube amp.
The power amp doesn't make a lot of difference in the tone, but it can make a big difference in the sound.
Bowers: There are some solid-state circuits that do an impressive job for tone, but the reason guitarists gravitate to tube amps is the harmonics. The secondary harmonics of a tube are additive to the harmony of the note, where the secondary harmonics of a solid-state amplifier are dissident to the tone.
The Valvestate technique was to put a single 12AX7 valve into the pre-amp section of the amplifier while retaining the solid-state technology in the rest of the amp. This in effect created a hybrid, valve-state amplifier that delivered traditional Marshall tone in a more robust format.
Hybrid Guitar Amps. Hybrid amps are made by several manufacturers with the intent on giving you the best of both worlds. the basic idea is a great tube sound, while providing the signal processing and reliability of a digital amp. Line 6 uses an all solid state preamp and a Bogner designed tube power amp.
The name originates from its shiny, Plexiglas panel, commonly used on Marshall amps between 1965-1969. The 68 specification amps were a hit with Jimi Hendrix, Cream and The Who, creating huge amounts of exposure and marking the 'Plexi sound' as the sound of rock.
The 'Plexi' nickname refers to the control faceplates Marshall used on their earliest amplifiers, which were made from clear plastic with black lettering screen-printed onto the back face and over-sprayed with gold paint.
At its heart, and in terms of its aesthetics and power, the JMP 2203 — which eventually became the JCM 800 — is very much in the same spirit as a 100 watt Marshall Plexi with four EL34s in its power section. But the biggest difference is the JMP 2203's master volume and “Pre-Amp” volume controls.
In 1972 EL34 tubes were getting harder to come by, so the American distributor started replacing them with 6550 tubes. In 1973 Marshall switched to printed circuit boards (no more point-to-point hand wiring), marking the end of an era but not the end of classic Marshall tone.
