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Tubes are Still Better Than Transistors for Audio Amplifiers

Millions of guitar player can’t be wrong.  Well over 80% of guitar amplifiers new and existing still use vacuum tubes.  Based on my experience, that could really be over 90%.  Nevertheless, most guitar players won’t even consider using anything else.  As a guitar player myself, I have to agree.  In a side by side comparison, the tube amp always seems to sound a bit “sweeter” than the transistor amp.  It is subtle and certainly subjective but definitely noticeable.  Or maybe you just have to be a musician to hear it.  Nevertheless, even high end audiophiles still prefer tubes for their surround sound systems.  Why is that?  I started asking around and here’s what I found.  Nothing scientific, of course, but just some general opinions about this.

I live in a very music-active city, Austin, Texas.  It is known as the “Live Music Capital of the World”  since there seems to be live musicians or bands in every bar, club and restaurant in town.  There are also 16 recording studios here and the city sponsors two huge music events every year, Austin City Limits and South by Southwest.  There are unemployed or part time guitar players everywhere.  And more than a few places around where you can rent tube amps or get them repaired.  Not too many places are like that although I suspect Nashville is in this category. 

Recently, a friend, Jon Dotson, came into town to find some new 6L6GBs for his portable amp.  Jon is a classical guitarist and PhD grad from the University of Texas.  He teaches at UT in Brownsville.  I asked, “why tube amps?”  He said as most others I talked to that they just sound better.  They seem to have a “warmer” sound than some solid state amps.  Whatever that means.  I suspect his ear is tuned to classical acoustic guitar with an amp that does not hurt but perhaps enhances that sound.

Another friend Garrett Thacker, a doorman/bouncer at the famed Continental Club in Austin has listened to hundreds, maybe thousands, of bands and guitars.  His comment was that solid state amps were “irritating” after a while.  He preferred the “softer”  and “richer” sound of tube amps even when turned up to a volume of 10.

And so it goes.  Some say that it is the combination of the guitar plus the unique distortion when the volume is turned up to 10 that produces the sound everyone likes.  Others believe it is the tube amp characteristics blended with the speaker and its unique distortion that makes it sound good.  How much does the guitar pickup have to do with it?  I also have to wonder if the unique tube sound “standard” was set years ago by early country and rock bands is still trying to be emulated by the younger musicians today.

The only vacuum tube amplifier I ever designed was a class C power amp for my ham transmitter.  That is totally unlike a linear audio amp.  Class C distorts the signal like crazy but a tuned circuit takes out the harmonics and makes it useable.  It is more efficient that way.  In an audio amp you need linearity and low noise.  But from what I can gather at the higher volume levels tubes do distort from overload or poor power supply regulation from the tube rectifiers.  It is just that subtle distortion that people like.  It is not a harsh clipping but a more “rounded” distortion that just sounds better to calibrated ears.

Anyway, guitar amp manufacturers still use tube power amps but the preamps and mixers are sometimes solid state.  Most are class AB push pull using 6LGB, EL34, EL84, 6BQ5 and even the 6V6.  Don’t forget the big output transformer used to match the amp to the speakers.  This is a critical component as it determines frequency response.  There are still some tube preamps as well usually 12AX7 or 12AU7.  Another feature today is DSP where the guitar sound can be filtered or otherwise tailored to be what you want it to be.  Can you make a DSP that makes a solid state power amp sound like a tube amp?  It could be done no doubt but not easy.

You can actually still buy vacuum tubes.  You can get them online and in some local stores who cater to guitar players.  All tubes are made in Eastern European countries today.  And they are expensive.  A matched pair of 6L6GBs or EL84s will cost you $100 or so.  Guitar amp makers like Gibson, Marshall, Vox, Fender and a dozen or so others (not kidding) will keep on making tube amps as long as tubes are available.  Like incandescent bulbs they may eventually go away so stock up now.

Have you ever had a listening experience with a vacuum tube audio amplifier?  Let me hear your story.

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