Tube type acoustic guitar amp??
 

In a related thread someone asked opinions concerning an amp for an 814 and a Vox AGA150 amp was mentioned and was said to be a tube amp. I did a little research and found it does indead have a 12AU7 vacuum tube in the preamp. I have never heard of such an amp but I am really curious.

Does this amp make a difference in the sound of an acoustic guitar that is really superior?? I currently play a Taylor through a Loudbox 100 and have been perfectly happy. I know vacuum tubes make a tremendous differnce in regular guitar amps but what about in an acoustic situation??

I live in a small town and the closest large music store is several miles away so it is difficult to just run out and try one.

Is this AGA150 worth trading my Loudbox for??

Tube amps have never been the best choice for acoustic guitars. The idea with an acoustic amp is to reproduce the sound of the guitar as faithfully as possible.
For electric guitars, the tube amp becomes almost an instrument onto itself as it can color the sound significantly. Which is why some electric players have more than one tube amp just to achieve different sounds.

As an electric lead guitarist in bar bands for many decades I'm all about tube amps. My favorite amps even have tube rectifiers, and my Mesa Blue Angel uses a combination of 4;EL84's AND 2;6V6's along with 5;12AX7 preamp tubes.

I would NOT want a tube in an acoustic guitar amp. Tubes are still used in (electric) guitar amps because they distort, even if slightly, the signal.

Acoustic guitar amps were INVENTED, and are voiced, to give us a nice clean acoustic sound.

This is, of course, my opinion. (but I'm right.....)

I've played through two of these and loved the sound - really warm and full

The previous posters have valid points in that, tubes do, in fact, color tone, but this can be a desirable characteristic, even for acoustic guitar. Tubes create "compression" which is almost universally desirable for elec., but still being investigated for acoustic. Basically, the more juice you send thru a tube, the more compression it creates. That's why Vox put a 12ax7 in the pre section of the 150, because it was successful in creating compression in their line of ADxxVT amps for electric. An additional reason is arguably for marketing reasons. I have the AD50VT. There are a couple of tube amps designed for acoustic, which, coupled with their ability to accept the Taylor TRS signal, yield fantastic tone. As I've said before, "the guitar is what you play, the amp is what you HEAR". If you want truly transparent tone, look at some of the great PA's out there. Amps tend toward colored tone anyway, and usually come with effects, like chorus, reverb, feedback suppression (yes, that colors tone too) I love the clean warm tone of my Rivera amp, which work really well for vocals too (makes me sound better than I am) and much prefer it to the colder, thinner tone of my solid state acoustic amp. Is the Vox worth trading the Loudbox for? Probably not, because in that price range, the Loudbox is alot of amp. But one day, you might consider ADDING the Vox to your collection.;)

The problem with tubes:

1. They begin to deteriorate from the moment you first turn them on.
2. Tube amps typically have much higher distortion levels before the onset of clipping.
3. They cost more.

Most people favoring tube amps, in applications other than for electric guitars, do so for romantic reasons.

I tend to agree. It depends a lot on the amp. I've played a Humphrey amp
http://site.humphreyamps.com/
And it sounded fabulous! with my CA OX Raw/K&K PWM... Even without the Baggs para DI (which is an "essential" on a solid state amp)...

My biggest concerns with tube is weight, cost, and reliability... not necessarily in that order ;)

I was the one that posted about the Vox 150 on the aforementioned thread. I would agree that most often one would want to have a clean "uncolored" sound for an acoustic. That's the reason I bought the Loudbox 100 a few years ago. It was the cleanest, uncolored sound I could find in a small format amp.

However the Vox provided a really good alternative with one clean acoustic channel and one acoustic tube channel (xlr inputs and phantom power on both channels)

I had a Traynor tube amp for a while before I bought my Loudbox and I used to play my nylon string guitars through it........nice '40's sound. I think the Vox tube sound is better than the Traynor as it didn't distort as much when turned up (at least as I recall).

I don't think anyone here is advocating using a tube amp in place of a clean acoustic amp. But the Vox was pretty neat by adding that tube channel; made my ears smile.

Gary

Some of the finest Audiophile amps in the world employ tube circuitry .. They are amazingly accurate at reproducing the recording space and the ambiance of the room that acoustic instruments were recorded in.. Acoustic instruments sound very real with these types of amplifiers .And there is no reason that a great tube amp could be designed and voiced to work as an acoustic amplifier ..You would need a high powered amp to reduce clipping/distortion The added warmth/depth that tubes deliver would probably tame those brittle highs that many pickup systems exhibit .... The drawbacks would be....Weight (HUGE TRANSFORMERS).. Tube life.. maintenance.. expensive to build ...

tube amps
 

I have the K&K progression tube preamp. It uses two tubes. I really like what it does to the K&K PWM sound. It is a bit noisy but it really smooths out the sound. It is no longer my gigging set up but it sounds sweet. With certain types of pickups I feel tubes make a big posutive differnce not only in tone but feel.

Exactly.

The "correct" tube amp for the acoustic guitarist has to be designed thusly from the get-go, not just a tube power or preamp section as if this were some solution to add "warmth" or blah blah. Tube amps for acoustic (or clean Sound Reinforcement applications) can sound stellar. But the path to those ends costs you in weight, bulk, and continued maintenance, not to mention dollars. All of which are part-and-parcel to us electric guys who adore our amps because they are essential for our tone. But until makers see a market for it in the acoustic world, it won't happen ...especially since SS does such a fine job of it right now.

Edward

No it's not worth trading your loudbox in for. Check out Rivera amps though, they have an acoustic/electric amp that kills

The Sedona 55 is the acoustic/electric amp (very expensive)
I really like my Sedona Lite (not as expensive or as heavy as the Sedona 55) for that very reason. It's their dedicated acoustic amp.

Herb is right though: Tube amps are more expensive, tubes are more expensive, and they in fact, do begin to wear out from the minute you install them. "Most people favoring tube amps, in applications other than for electric guitars, do so for romantic reasons."

Taylor uses the Sedona 55 as the reference amp in their shop, and they are a bunch of romantic SOB's, just like me.:D In fact, I've never heard a more romantic tone from any acoustic amp, but careful, they are expensive, and I've already replaced a pair of tubes once. 500 hrs = $70.

Best $70 I've ever spent!

Tube amp designed for acoustic guitar
 

I know this thread's a couple of months old, and that I might be inviting all kinds of criticism and nay-saying, but regardless, I can't resist throwing in my 2c-worth.

I'm the designer & builder of the Humphrey Amp mentioned above. It took over a year of full-time 7-day weeks to finalize the design & testing (I might be slow, but I'm big :)
First, I'll point out some obvious negatives, which really isn't good marketing practice - but I'm not marketing here, just explaining why I do what I do, so I guess it's ok.
1* Cost - yup, tube amps are more expensive than solid-state in general, and as mine are hand-built starting from raw lumber, and hand-wired, they are even more expensive - but they're certainly not targeted at the general market.
A typical solid-state amp can be made with a bill-of-materials total cost that is less than the cost of a pair of quality EL84's

Don't get me wrong - there's some fine s.s. amps out there and the fact that they CAN be made at low-cost and in high volume gives a lot of folks access to good gear.

2* Weight - yup, a Humphrey Amp weighs about 37lbs, depending on the wood used. We do need some hefty transformers. Actually more hefty than those used in electric guitar tube amps (don't want to saturate the xformer in an acoustic amp).
Also - we use a very heavy hi-fi class 10" speaker and brick of a horn-tweeter (all for good reasons)

3* Reliability. Depends what you're doing with it really. Tubes do wear out over time, but it depends largely on the voltage supply and how long they're played. My Marshall amp drives the EL84's with more than 420V (they're spec'ed for 300V) and after 5 years I'm thinking it's time for new tubes. I just use it for personal playing though - not gigging every night.
A Humphrey Amp using high quality JJ EL84's, running at much lower voltages, would run for many years before the sound degraded - unless you ride it hard & put it up wet every night of the week, of course.

There's actually fewer components & connections in a well-designed tube amp, so the reliability is inherently 'better' from the get-go.
It depends on a lot of factors though, and I'm not saying S.S. is inherently unreliable.
If I were to play the most important gig of my life & could choose only one amp, it would certainly be a (good) tube amp.

Okay - the positive stuff :)
1* I think it was Rollie that pointed out that some of the finest hi-fi amps in the world use vacuum tubes, so I'll not repeat what he said already. He's right, but I'd say that MOST of them use tubes. There's reasons for that.

We use a similar design methodology in our acoustic amp - it's all about the signal quality. In an electric guitar tube amp, everything about the design contributes to shaping, coloring and distorting the sound in ways that are pleasing to our ears. Understanding those things means that we can avoid the stuff that would be considered nasty for acoustic guitars, while still benefiting from the acoustic qualities that only tubes can deliver.

As Edward said . . . " . . The "correct" tube amp for the acoustic guitarist has to be designed thusly from the get-go, . . . "
Well said.

Add some secret sauce in the cabinet/speaker design and you have an amp that will cause you to pick up and play your guitar for longer, and more frequently (that's what my customers tell me).

Because it's not cheap to make, we figured it needed to bring as much to the table in aesthetic appeal as it does in sound quality, giving it some 'collectability' value, like one of the fine guitars it would be married to.
Like I said - I know it's not everyone's ideal, so don't knock us for going out on a limb with what we believe is solid product that meets an unmet need (yes, it's a niche market, but we're happy to serve it).

The interest is growing rapidly, I'm happy to say, and we're totally pumped at the reaction we get from folks that try/buy them.
There's a really nice video of Al Petteway doing a demo if you'd like to check it out. http://www.youtube.com/watch?v=k4Wm0nl1tWk

Hopefully, this late night rambling will be received in the spirit in which it was given. I'm just offering a perspective & an explanation for why there's yet another piece of cool gear available for ACOUSTIC guitar enthusiasts. Maybe some of what I said is helpful in some way - I hope so. I don't intend to engage in arguments or respond to slams - but I'd sure welcome any good questions or fair comments.
Thanks!
Gerry Humphrey

It was a wise man who once said "tube amps are for people who enjoy listening to the sound of their amps malfunctioning." ;)