Valves verus Transistors


Do I need valves to sound good? well er, Yes and No?

 

Very desireable Mullard EL34 power valves/tubes

Types power of transistors

 

Let me explain.

Valves or Tubes are old technology, invented in the early part of the last century. Transistors are now also old technology invented in the latter half of last century. Without getting all technical and boffin like they both have the same job to do, to amplify. They both turn a relatively small signal into a larger more powerfull signal with enough power to drive a loudspeaker or loudspeakers.

So they are both doing the same job but it's the way they do it that makes the difference. The valve needs a lot of voltage to work and along with this it adds un-wanted noise and distortion and changes the tone slightly. The transistor however uses much less voltage and tries to do it's job without adding anything.

Valves eventually burn themselves out and need replacement, pre amp valves are ok to just replace but power valves need to be biased by someone who knows what they are doing in order to run reliably in an amp. But transistors if effectively heatsinked and run within their power range can last a lifetime, heat by the way is a by product of both technologies. 

The art in designing a transistor amp to sound like a valve amp is just that, an art, and can be done if the engineer knows exactly what he is doing. A well designed transistor amp can sound just as good as a vintage, or new valve amp. This I was told by a famous amp designer and engineer.

I use a transistor amp to gig and rehearse with however, I love the sound of a valve amp cooking, just on the edge of sanity. The truth is we play different venues both large and small and some like it resonably loud and others like it whisper quiet.  We also play venues with the dreaded traffic light system (more about this later) so I need an amp that will sound good at all volume levels and will remain reliable.

I had a Marshall Plexi 1987 model 50 watt valve amp in the early seventies that sounded really good until one night it lost power just when I needed it. Ruined the rest of the gig for me, the other band members, and I guess the audience. I bought new power valves (exactly the ones on the top left of this page) put them in (I knew nothing about valve bias back then) and used the amp at rehearsal in a friends bedroom and It worked fine no problem, or so I thought. At the next gig the first half hour or so went well and then the dreaded power loss kicked in exactly the same as before. Another ruined gig... I took the ailing amp to the local music shop for repair where they confirmed they would find the fault and repair it no problem, ready for the next gig. On collection they said they had found no fault and the amp had a clean bill of health, they left it on test for 24 hours without a problem. I was at first sceptical but again assured that the amp was fine I handed over the money for the test and took the amp home.

You're way ahead of me now aren't you, yes, you guessed it half way through the first set the amp lost power again. I came to the conclusion that the amp only played up when it was under load and being stressed, that's why being soak tested for 24 hours showed no faults, it was amplifying nothing but white noise.

I needed an amp to gig with that was reliable so I traded it in for a brand new HH transistor amp with a glowing green facia plate (stupid boy), it took a while to get used to but solved the problem. I later found out that the fault with my old amp was diagnosed and repaired, I offered to buy the amp back but sadly it had been sold.

I have a few olld valve amps that I really enjoy using but valves are expensive, especially good quality NOS (new old stock) and new valves dont sound as good as their NOS equivelent, although the quality of new valves is improving all the time. Valve amps need a little more care and attention especially if you are playing them hard and will need to be serviced regularly to keep them in tip top reliable working condition. But if you can find a good valve supplier and carry spares then valve amps are no more of a problem than their tranny counterparts. However having said that I gig with a transistor amp for the added reliability.

Tip: Valve amps like proper impedence matching with speakers so if your cab is 16 ohms then set the amp to 16 ohms, and if changing a speaker in a valve combo make sure you buy the same impedence speaker as your old one, your output transformer will love you for it. Transistor amps are more flexible with speaker impedence matching with normally a minimum rating of 4 ohms on the amp. You could connect a 16 ohm speaker to a 4 ohm (min load) transistor amp with no problems at all, it just won't be as loud as a 4 ohm speaker would be, and the wasted 12 ohms would just be burnt off in heat as the power amp would have to work a little harder to reach the same volume.

Traffic lights,  because of certain laws in the UK the owner of public performance areas has a resposibility to the public to protect them from, well everything really. So in order to keep their Public Performance Licence the proprieter must follow certain guidelines and one of them limits noise pollution.

So basically traffic lights control volume by cutting off the electric supply if the volume exceeds a set limit. If the light stays green and there is no problem, if the light goes orange then you are getting a bit too loud, and if it goes red for more than a set amount of seconds (usually about 5) then your drummer has an un-planned drum solo for between 10 to 30 seconds until the power switches back on again.

On one gig we played recently with traffic lights, the Bingo caller was laughingly too loud and it kept switching the power off to his machine. They had to bypass the system by plugging into one of our long extention leads that was mysteriously plugged into a wall socket in the dressing room, of course that socket was not controlled by the traffic light system.    Shhhh...

Anyway I have been to many Rock concerts and played in loud bands for longer than I care to remember and it hasn't done my hearing any harm, well apart from the tinnitus that is, pardon...