Question about tubes?

[gagelle]

I've been looking around at different tube amps and was wondering how much power I would need. Is a 15 watt tube amp with KLF-30s enough power for a small room? I'm currently using a Sansui amp rated about 70 watts and can barely turn the volume a small amount without blasting me out of the room. I guess Klipsch speakers are perfect for tubes because they're so efficient.

I still have to wait awhile because I've been spending too much on audio. I'm really curious now. I may drive to the Bay area to listen to a good tube setup at a high end shop. People have told me that once I experience Klipsch on tubes, I won't be able to go back.

[tube fanatic]

Is a 15 watt tube amp with KLF-30s enough power for a small room?

More than enough!

[captmobley]

I power my Klipschorns with Welborne Moondogs 2A3 tubes putting out a mighty 3.5 watts and can't turn it up over 3(out of ten). Tube watts are different than solid state watts.

Horns love tubes!

[tube fanatic]

I power my Klipschorns with Welborne Moondogs 2A3 tubes putting out a mighty 3.5 watts and can't turn it up over 3(out of ten). Tube watts are different than solid state watts.
Horns love tubes!

Just to clarify an imortant point, there is no difference between the power generated by a tube amp and solid state amp. The distortion characteristics are different, and the behavior of the amp when it clips (i.e. driven beyond its maximum output voltage or current) is different. But, watts are still watts.

[artto]

For me, it depends.

It depends on the kind of music you listen to, and how loud you listen to it. And on the kind of tube amplifier.

The KLF-30 are fairly efficient, so as other have mentioned, you may not have any problems. I can only speak for myself.

Just as a point of reference, my room is rather generous in size (aprox 20x30) and I'm using Khorns. The power amps I have available are Crown D-60, D150A, PSA2, McIntosh MC7205, Luxman MB3045 and Wright 2A3.

While I love many aspects of the 3.5 watt Wrights, with certain music it just doesn't cut it. In other words don't expect a good experience with the Wright 2A3 driving Khorns playing Aerosmith at concert levels in the above room. On the other hand, the 50 watt Luxman sound more powerful (and much better) than the 275 watt/ch Crown PSA2.

I generally use the Crown D-60 or McIntosh MC7205 for everyday use now as the tube amps do require more maintenance and change in sound character over time as the tubes deteriorate. Tube amps can be a pain-in-the-@ss.

On the other hand, as I've said before, the "technical term" for a transitor is "gate". A vacuum tube is called an electron "valve". Which do you think is more capable of naturally reproducing MUSIC, a device that operates like a "gate", or as a "valve"? Valves do it naturally, transistors have to be kinived into accomplishing the same thing.

Since you're the one who has to listen to it the only way to know for sure is to try it in your setup.

[gagelle]

Thanks Artto and everyone else. Artto, your explanation is direct and to the point. (And you have some wonderful equipment.) The primary reason for my enquiry is that there seem to be many more tube units with low power ratings. But I've learned that the quality of the sound is much more important than RMS power ratings. If you have a rich, full sound, you don't have to turn the volume up to compensate for missing sound quality. And then there's the issue of power rating reliability. Sansui underated the power output of all their old units. My Sansui 881 tested almost 10 watts higher than the official published ratings.

As far as transistors go, its invention is probably the single most significant technological breakthrough we've ever had--I mean the miniaturation led to the idea of putting microscopic transistors on a silicon chip. But for music, I see the point about tubes. Sometimes the old things are the best.

[gagelle]

Here's an explanation by Bob Carver: "It's easy to believe that a watt is a watt is a watt - but wait - it
turns out that a tube amp watt sounds much more powerful than the same
audio watt delivered from a transistor amp. How can that be? How can a
tube-amp watt sound more powerful than a transistor-amp watt? The answer
is because it IS more powerful! The output voltage of a tube amp
follows the impedance curve of our loudspeakers, thereby rising
substantially higher than it would if the load were a resistor. Solid
state amps don't, and cannot, do that. The increase is HALF AGAIN to
TWICE the effective power."

[russ69]

I've got tube amps in 15, 25, and 55 wpc. Don't get me wrong but the 15 watt amp has some limitations, the 25 watt amps are pretty strong and the 55 watt amps are powerful. A little power never hurts, it adds weight even if you are not playing loud. Having said that, I'd rather use my 15 watt tube amps than a new 100wpc SS receiver. I don't know whats wrong with the new stuff but they just don't have any balls.

[SWL]

Here's an explanation by Bob Carver: "It's easy to believe that a watt is a watt is a watt - but wait - it
turns out that a tube amp watt sounds much more powerful than the same
audio watt delivered from a transistor amp

I was very surprised the first time I put an HH Scott 222c (20 watts) into my KLF-30's. The power, headroom and overall sound quality was very impressive for only 20 watts. It was limited however, 80-85db was pretty much max.....but these days I can live with that 90 percent of the time. []

For two-channel listening...tubes rule. [Y]

[tube fanatic]

Here's an explanation by Bob Carver: "It's easy to believe that a watt is a watt is a watt - but wait - it
turns out that a tube amp watt sounds much more powerful than the same
audio watt delivered from a transistor amp. How can that be? How can a
tube-amp watt sound more powerful than a transistor-amp watt? The answer
is because it IS more powerful! The output voltage of a tube amp
follows the impedance curve of our loudspeakers, thereby rising
substantially higher than it would if the load were a resistor. Solid
state amps don't, and cannot, do that. The increase is HALF AGAIN to
TWICE the effective power."

Can you cite the reference for the above?

[JJkizak]

Curious, but I don't buy that explanation, period.

JJK

[gagelle]

Hi SWL

The main obstacle for me is money. I've been following some tube units on Ebay and am in disbelief at how high these things are being bid up.

[gagelle]

It's on this Ebay page:

http://tinyurl.com/3j5n5l5

[

Open in new window

]

It's at the question and answer part at the bottom. Obviously, lacks objectivity when ones trying to sell something. I don't know the guy in any way. Looks like a nice unit but I would never bid on something that will obviously go very high just on the seller's reputation.

[JL Sargent]

JJK, you're just not over giving that Scott away. []

[gagelle]

Fair enough. I don't know enough about the subject to judge the veracity of his explanation.

[JJkizak]

Voltage, current, impedance, resistance, capacitance, and Inductance are all physical laws and constants that exist in our Milky Way Galaxy, and cannot be violated by a human.

JJK

[Ski Bum]

While not for everybody, I find SET amps to be oddly addictive little suckers. Clear as a mountain stream presentation. Incredibly seductive. You really should hear one sometime, particularly if your room is small and you can legitimately get away with low power. SET + Klipsch = []

[Don Richard]

Bipolar transistors are current control devices - a current into the base controls collector current. Tubes are transconductance devices - a voltage into the control grid controls the plate current. FETs are also transconductance devices. Current control devices and transconductance devices require different types of circuitry to make an amplifier.

Most vacuum tube amplifiers are current source amplifiers, while most solid state amplifiers are voltage source amplifiers. Current source amplifiers will follow the impedance curve of a loudspeaker as Bob Carver said whereas voltage source amplifiers don't. This can cause a change in sound, the degree of which depends on the loudspeaker. Current source amplifiers can deliver nearly equal power into a low or high impedance load, whereas voltage source amplifiers can deliver more power into lower impedance loads.

Another difference between SS and tube amplifiers is the way they distort. Tube equipment generally distorts more gradually, rising as a gentle curve past rated power whereas the distortion curve of most SS amplifiers takes off almost straight vertically past rated power, like a F-15 on full afterburners. Because of that you can squeeze more than rated power from a tube amplifier before audible distortion becomes apparent.

[JJkizak]

How much more voltage on an SS amp versus how much more current on a tube amp equals the same SPL output? My old Fisher tube amp would put out roughly about 25 volts at 2.5 amps wide open resistive load. Then for the same power would the SS amp be putting out 50 volts at 1.3 amps?

JJK

[Don Richard]

From Wikipedia:

Most sources of electrical energy (mains electricity, a battery, ...) are best modeled as voltage sources. Such sources provide constant voltage, which means that as long as the amount of current drawn from the source is within the source's capabilities, its output voltage stays constant. An ideal voltage source provides no energy when it is loaded by an open circuit (i.e. an infinite impedance), but approaches infinite power and current when the load resistance approaches zero (a short circuit). Such a theoretical device would have a zero ohm output impedance in series with the source. A real-world voltage source has a very low, but non-zero output impedance: often much less than 1 ohm.

Conversely, a current source provides a constant current, as long as the load connected to the source terminals has sufficiently low impedance. An ideal current source would provide no energy to a short circuit and approach infinite energy and voltage as the load resistance approaches infinity (an open circuit). An ideal current source has an infinite output impedance in parallel with the source. A real-world current source has a very high, but finite output impedance. In the case of transistor current sources, impedances of a few megohms (at DC) are typical.

An ideal current source cannot be connected to an ideal open circuit because this would create the paradox of running a constant, non-zero current (from the current source) through an element with a defined zero current (the open circuit). Also, a current source should not be connected to another current source if their currents differ but this arrangement is frequently used (e.g., in amplifying stages with dynamic load, CMOS circuits, etc.)

Similarly, an ideal voltage source cannot be connected to an ideal short circuit (R=0), since this would result a similar paradox of finite non zero voltage across an element with defined zero voltage (the short circuit). Also, a voltage source should not be connected to another voltage source if their voltages differ but again this arrangement is frequently used (e.g., in common base and differential amplifying stages).

Contrary, current and voltage sources can be connected to each other without any problems and this technique is widely used in circuitry (e.g., in cascode circuits, differential amplifier stages with common emitter current source, etc.)

Because no ideal sources of either variety exist (all real-world examples have finite and non-zero source impedance), any current source can be considered as a voltage source with the same source impedance and vice versa. These concepts are dealt with by Norton's and Thévenin's theorems.

In English this means that a current source amplifier outputs a current controlled by the input voltage with the output voltage being whatever it takes to force that current into the load. A voltage source amplifier outputs a voltage equal to the input voltage times the amplifier's gain, with the current determined by the load impedance according to Ohm's Law, I = E/Z. The voltages and curents presented by each type of amplifier would depend on the load's impedance at any specific frequency.