general question about audio amplifiers

Hi.

Good places to ask this, after reading their FAQs, would be rec.audio.tech and rec.audio.opinion . This is undoubtedly covered in a FAQ.

Some people like the distortion of some tube based amplifiers. Some imagine they like it. The simple fact is that if such sound was all that desirable, it would be on CD's and such for the benefit of those with low distortion audio systems.

Tube based amps will limit more softly than simple implementations of transistor based amplifiers. But again, if that characteristic was so desirable, it would be effected by non-linear shaping circuits in solid-state gear. The fact that such gear has not been marketed (much, at all?) indicates that it is not an important technical feature.

In fact, most people to whom such gear would be marketed would still prefer vacuum tube amps, magnetic bracelets, and sea salt.

Only when the amp is underpowered for the signal it is being asked to pass.

You can take my FAQ reading suggestion as a not too bad flame, if you like.

So solid-state is now "the traditional electronic amplifier", and tubes are new? To some people, I guess.

This is notoriously subjective, like wine tasting. It would be interesting to have him do a blind listening comparison and see if he can tell the difference. Some tube amps *do* have a lot of distortion, and some people do like the resulting sound. Tube amps have bad damping factors, so speakers boom more, and some people like that, too.

John

Thanks for the suggestion.

Interesting reading.

Mike

But there is some rationality to sea salt.

John

Eddie's thing was to mod the Marshall he was using by using a Variac to up the tube voltages (or was it down them - can't remember now). Anyway, he claims he had to retube once a week!! He used very little in the way of effects, but one of his secrets was to use a phaser (and MXR I think) turned barely on for a little treble boost. You can actually hear the phasing if you listen closely though.

Tube amps softens the curve form, a soft clipping action, because they are not good components. But this is a fault which some people like better than a perfect reproduction in a modern transistor amp.

There is a whole industry based on making transistor amps sound like tube amps. And some people build real tube amps after old schematics. Guitarists are the main target group for this, but other audio enthusiasts also buy tube amps or effect boxes which reproduce a classic tube sound.

google: tube screamer effect box schematic

A good text about creating tube sound in different ways, simple do-it-yourself circuit schematics.

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classic

As an amateur guitarist of about 20 years (late starter ;-), I can attest to the _fact_ that there is a world of difference between solid state and tube. It's mostly a behavior thing IMO. Feedback in a solid state amp is a terribly atrocious noise. It tends to seek some magic frequency known only to the evil force driving it and having nothing to do with the notes currently being played. The victim has no semblance of control over the howling and screeching noise that is known as solid-state feedback.

OTOH, a good tube amp can "sustain" any chosen note for an indefinite amount of time. The practiced player can have an amazing amount of control over the effect. Just listen to an early Van Halen album for an example of what's possible with tubes.

Outside of this, I believe that most audio-phool hype is nothing more than another form of snake oil for the modern times. For reproduced audio, I have no qualms with solid state equipment. But a guitar should only be plugged in to a tube amp, period. ;-)

Me too. I have a Casio MG510, a famous guitar you have probably never heard of. A stratocaster type body with three analog pickups, one of them is a double humbucker pickup.

The guitars themselves were produced under contract for Casio by Fuji Gen Gakki, who also built the Roland and Ibanez MIDI guitars. It has a traditional analog output jack like all electric guitars, and a midi output like a midi keyboard.

I cut away a lot of wood from its body to make it lighter, and slimmer. Electric guitars weigh too much in my view, or I am simply not well trained and strong. It looks better after the slimming. I can use it as a keyboard and use a sequenser program in the computer to record in midi, or I use a Zoom 505 effectbox and record analog tracks.

Mechanically it is the best guitar I have ever played, very soft and easy action. It is probably taken from the same production line as high quality Ibanez guitars.

I think he uses more than just a tube amp. He uses effect boxes, like the tube screamer I wrote about in another message. You can build your own effects boxes if you know a little electronics. There are schematics for most older commercial effects on the web, geofex.com is a good starting point.

The latest word in the effects world is "guitar modeller". It is an effects unit which simulates different guitars, combo cabinets, amps, loudspeakers, etc.. So you can sound like you are playing a 1972 Fender with a Marshall amp.

An example:

them

Cool. I have exactly one guitar (the one I started on), an Ibanez Strat copy with a maple fingerboard. It still looks pretty good even after more than 20 years. I changed one of the single coils out to a Seymour Duncan hum bucker that fit in the pick gaurd without cutting (i.e. looks just like the stock single coil) Ah...way less hum. ;-) I've had several amps, but I finally found one that I like. It's a Mesa Boogie DC-3.

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slimmer.

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midi,

easy

I kinda gave up on the stomp boxes when I got a decent amp. Even my Zoom 505 just didn't sound right. It stole all my head room. I suspect that more modern stuff may be better now, however I don't play a whole lot anyway so straight in is fine for me.

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Yeah, the amp modeling stuff has been around for a little while, but I didn't know about guitar modeling. That's pretty impressive looking for the price, I'd like to hear one. I need to go check out what's available at Guitar City, I haven't been there in eons. Do you remember The Rockman?

I think I'll stick with my Boogie though, it really does kick butt. Worth every penny and then some. It's the freakin' loudest 35W I ever heard in my life. My cats agree. ;-)

Yes, if we are talking pocket sized units. I wanted one 10-15 years ago, when they came out on the market. but never actually got my hands on one. I built my own effects for several years instead.

The best homebuilt unit made the guitar sound like an organ, with infinite sustain in its maximum sustain position. I could also set it to swell, the tone starts quiet and builds up volume.

Years later I got a Zoom 9002 pocket multiprocessor, which I liked very much. It was trashed by lightning, so I went out and bought the Zoom 505, because it was the most common unit, I had read a lot about it, and I got a very good price.

On Wed, 9 Mar 2005 14:05:48 -0800 in sci.electronics.basics, "Larry Brasfield" wrote msg :

There are now available PC sound cards with a vacuum tube final stage. While I am nostalgic about vacuum tubes, having worked extensively early in my career with tube power supplies and pentode analog computers, I don't harbor any great desire to spend the kind of money necessary to get tube audio equipment. But, I do like sea salt. :-)

That might have been overstated a bit. But I think the point is correct that a large fragment of those who insist that tube amp distortion is preferable attribute tubes with magical properties than can never be replicated otherwise, no matter what thorough instrumentation might indicate. And among that fragment, you will find many with magnetic shoe inserts, copper bracelets, or a cupboard containing many items with sea salt in the ingredient list. The superstitious mind is rarely content with isolated obeisances.

Do you believe that, within the nearly linear output range of a tube amp, the output transformer is usually going to smooth out the content that a high fidelity amplifier would have passed? If that is the basis of your contention, then I must point out that transistor amplifiers can also act as low pass filters, either intentionally (treble control) or not. If your contention is not about frequency response, maybe your could explain your contradiction.

....

You are mistaken about my preferences. I cringe when I hear hard-limited sound and would prefer the softer limiting that tube amps can provide.

My "singling out" is directed not to those who may prefer a given type of distortion or limiting, but to those who believe only tube amps can deliver that performance. I have seen no studies of how tube amp preference correlates to superstition, so my above statement is based on a small sample and may well be unrepresentative.

Well, prepending 'not' to what I posted can certainly be reasonably interpreted as a contradiction.

For a linear time-invariant system, the transient response is perfectly predictable from the frequency response. So your distinction is somewhat puzzling in this context.

As for the properties you attribute to the transient response that are not visible in a magnitude versus frequency plot, my understanding is that humans are insensitive to the phase relationships among components of an audio signal.

Such fidelity would surpise me.

I agree with that. But I doubt anybody could hear the difference provided that there was no wild difference in the phase response of the two systems, such as delay in excess of a mS.

What triggers my skepticism is the suggestion that transformer transient response uniformly tends to smooth output waveforms. I expect that in the case of soft limiting, but I see little reason to predict that the uneven phase response of a transformer, together with the phase response of whatever is done to preceeding stages to get the magnitude response straightened out, will act to produce smoother outputs.

A relative-by-marriage used to be head chemist for a big salt mine in Louisiana. Every day he'd go to work, analyze some samples, and file a report: yep, it's still salt. He got bored, took up selling drugs, and now he's a successful and respected mobster, sort of the cajun Tony Soprano.

John

Oh, don't be bitter.

John

Get a bunch of skinny asparagus. Spray with Pam, sprinkle with coarse sea salt, grind a little pepper on top, and broil until the tips turn black. Yummy.

John

The identity of a good number of those nutricious micro things will depend on where the nearest sewage outflow is and what people in the nearest city eat.

If I was buying sea salt, I would want to know precisely where the water came from and what protection the evaporation ponds were given. All the more so now that avian borne diseases are becoming a threat.

Do you suppose sea salt vendors would do anything so artificial as sterilizing their product with unnatural heat?

I often use a triangle wave from a function generator as input signal to test and trim circuits to simulate tube distortion.

When I adjust a jfet or mosfet stage, or a tube screamer diode clipping circuit, I can see on the oscilloscope how the peaks of the triangle wave are rounded.

It sounds better if the positive peaks and the negative peaks are rounded differently. That gives a more interesting spectrum of overtones than if the soft clipping is symmetrical, which sounds more neutral.