Tonefiend Forum

This is a very old debate - WHY do amplifiers made from tubes sound different than amplifiers made from transistors?

Here's an engineering perspective:
Part 1:
https://electronicdesign.com/article/analog-and-mixed-signal/-house-of-fire-firebottles-and-groove-tubes-versus-devices-that-find-their-origins-in-sand-part-1-

Part 2:
https://electronicdesign.com/article/analog-and-mixed-signal/Tubes-Versus-Solid-State-Audio-Amps-The-Last-Word-Or-House-Of-Fire-Part-2-

Hi Bear,

I agree with the statement that if you actually make Solid State behave with characteristics similar to tubes, they would sound similar. Actually, that's what modeling amps do, but they do it digitally rather than through direct circuit implementation.

For me, tubes sound "Bigger". I have a 15watt tube amp, and a 65watt solid-state. The tube amp just seems to get louder and sound bigger - it's all perception, but that's how it feels.

-Jeff

I just got a tube amp, and I've been loving it. It's such an improvement over my SS amp, even though the SS has had five decades of technological improvement.

Here's a fun fact, though. My SS cost $100. It was made in the simplest and cheapest way possible. I think more than one person has compared their new, shiny, expensive tube amp to their bottom-of-the-line SS amp, and been wowed. There are some great transistorized amplifiers out there, but they cost a little bit more.

Far as I know, the Tech21 Sansamp and related products do (to various levels) actually use semiconductors, but in an amp structure/layout similar to a tube amp. One of the things SS amp designers were somewhat keen to get rid of was the output transformer, which if nothing else is heavy.

I don't really trust any listening results that are not done using double-blind.

The Pearce guitar amps built in the 80's/90's were great sounding guitar amps and they had a good rep among many guitarists The were fairly expensive compared to most amps on the market and never got very wide distribution or usage. I serviced a number of them over the years but never had a chance to play one in a band situation just testing in my shop. That is where the rubber hits the road and I have never been satisfied with anything but tubes playing in a band because the real difference is what happens when you run out of amp headroom. Tubes compress the signal and creates pleasing sounding distortion, transistors (and ICs ) tend to be very harsh when the run out of headroom. The main way to avoid this to use a really big pwr amp (200-400 watts or more) I played a system we built back in the early 80's with a Carver PM 1.5T pwr amp and a seperate preamp powering a pair of 18" 3 way spkrs in a thiel designed enclosure. It sounded great in a band situation as long as I didn't overdo the volume and drown out the drummer :-). The thing is with 750 watts per channel it never clipped the amp much (and Carver designed the PM1.5T to clip a little more nicely than many amps) so it sounded very smooth and sweet. The system pretty much filled up a van so it was impractical unless you had a semi and roadies. That setup would have made a lot of doom metal players very happy, it worked great for low tuned guitars as well as basses.

As far as bigger sounding tube amps have always been described that way. A Dynaco ST-70 at 35 watts per channel beat SS amps that were 10 or more times as powerful in listening tests run by many different folk. There are many reasons that this may occur but AFAIK nobody has really ever managed to scientifically define the difference. I believe it is technology and human psycho-acoustics combined that are responsible. I have over the years heard some great sounding SS stuff but that is in hifi where clipping occurs much less than guitar amps. The other thing that we need to consider is the program source and a guitar signal is much different than a stereo mix. A guitar's signal is much more demanding of the pwr amp. A final consideration is the circuits themselves, a tube amp has a far lower parts count than a SS amp and IMHO this complication causes a lot of unintended side effects when the amp is operated outside it's design specs.