Tube Amp Question

[9f9c7z]

Never had a tube amp, don’t know anything about them, so perhaps a silly question…

Amps are available in all kinds output wattage, 100w being pretty common, and more watts is not unusual. I think my surround system has somewhere around 225w per spkr, the sub has 400w available. But when I see tube amps online, they are always have much lower output, 12w, 20w, seen a couple that were around 60w or 75w. Why is the output watts from a tube amp so much lower than other types of amps?

 

[MDS]

Mainly because they use Class A amplifiers. A class A amp that could produce 100 wpc or more would be way too expensive for mere mortals.

 

[sts9fan]

Not all tube amps are class A

 

[mattpower3000]

More Watts = Better sounds
This statement is normally wrong, tube amps prove this, they are just more musical, the best thing to do is hear one. You will appreciate they are about rythum and tambe rather than sheer guts. If that makes any sense.


Seriously go take a listen, pure 2-channel hi-fi is much different to AV, loudness is calculated from amp power and speaker sensitivity. with 3db of sensititity equalling double the amp power. So 125W amp with 90db speakers would give the same loudness (grunt) as a 250W amp with 87db speakers.

Mattpower

 

[9f9c7z]

Thanks for all of the input. I was looking at the Decware tube amps. Something about 3w per channel for a stereo amp, 6w for a mono amp just sounds a little marginal when there is 225w/channel with the amp I have. My spkrs have sensitivity of 91db. Depending on the amp, Decware recommends a minimum spkr sensitivity of 88, 89, or 90db, with 96db being ideal, so I guess my spkrs would be just marginally ok to use. There’s a 25w amp but it’s about twice the price per watt as the others.


Matt – I presumer your example, 125w w/90db spkrs = 250w w/87db spkrs, is if listening at full volume. I’m told do most of my listening at about 3watts max, so maybe a 6w amp is ok?!?

 

[WmAx]

Thanks for all of the input. I was looking at the Decware tube amps. Something about 3w per channel for a stereo amp, 6w for a mono amp just sounds a little marginal when there is 225w/channel with the amp I have. My spkrs have sensitivity of 91db. Depending on the amp, Decware recommends a minimum spkr sensitivity of 88, 89, or 90db, with 96db being ideal, so I guess my spkrs would be just marginally ok to use. There’s a 25w amp but it’s about twice the price per watt as the others.


Matt – I presumer your example, 125w w/90db spkrs = 250w w/87db spkrs, is if listening at full volume. I’m told do most of my listening at about 3watts max, so maybe a 6w amp is ok?!?

3 watts? 96db sensitivity is more like a minimum requirement if you want undistorted moderate amplitude dynamics. BTW, that Decware amp probably does sound DIFFERENT as compared to your current amp. Your current amp probably has a flat frequency response, whereas that Decware probably has a non-flat response. Do yourself a favor: Do your equalizing with an equalizer, not a hardwired tone control built into an amplifier. Additionally, with 3 watts power, you will be often overdriving the signal[causing distortion on even moderate dynamics unless you have extremely sensitive speakers], thus causing probably significant levels of distortion. The 3 watts figure is an average -- but you are not accounting for any dynamics. If you listen to only highly compressed modern top 40 major releases, you'll probalby be fine, however. But dynamic recordings? I have one recording that has 30+ dB dynamics relative to the main signal levels. BTW, you can do FAR BETTER in coloring your sound by using a professional mastering equalizer and a tube saturation preamp to do these things, where you can control/custumize the specific amount of coloration(s) that you desire, or bypass[an option you don't have if you use the colored from the get-go amplifier for example] the coloration(s) alltogether if you desire.

-Chris

 

[9f9c7z]

WmAx – thanks for the info. I thought it would be fun to try a tube amp to see what the diff was but at 3watts it seemed a little underpowered. I'm not willing to throw out some big bucks for a higher watt amp just to play around. And yes, I have some dynamic source material that I would want to listen to. I’m not interested in accruing a bunch of electronics (eqs, tube preamp, etc) so I think I will pass on the tube amp…for now. Or maybe I'll build my own some day.

 

[WmAx]

WmAx – thanks for the info. I thought it would be fun to try a tube amp to see what the diff was but at 3watts it seemed a little underpowered. I'm not willing to throw out some big bucks for a higher watt amp just to play around. And yes, I have some dynamic source material that I would want to listen to. I’m not interested in accruing a bunch of electronics (eqs, tube preamp, etc) so I think I will pass on the tube amp…for now. Or maybe I'll build my own some day.

I don't remember the price of the 3 watt tube amp in question, but FYI, due to the extreme competition in professional/home recording today, you can aquire an excellent quality, dead-silent noise floor DSP equalizer[Behringer DEQ2496 or DCX2496] and a good tube preamp with adjustable tube saturation/coloration adjustment[Behringer T1953] for around $400-$500 total for both units. If you just get the preamp, that's about $130, so that is a very affordable way to experiment. It is not a preamp with source selections, btw, it is a device that you would put between the output of your normal preamp and the amp input -- as a sound processor. It allows for you to specifically dial-in the amount of tube coloration that you desire. It is a recording/mastering tool. You can also change the type/brand of tubes[which are not expensive] in it to get different distortion signatures. For a little bit more, you could get a DSP sound processor that can replicate the distortion of various tubes[user selectable], and has a dead silent noise floor, such as the Behringer DSP9024. About $200.

-Chris

 

[mtrycrafts]

WmAx – thanks for the info. I thought it would be fun to try a tube amp to see what the diff was but at 3watts it seemed a little underpowered. I'm not willing to throw out some big bucks for a higher watt amp just to play around. And yes, I have some dynamic source material that I would want to listen to. I’m not interested in accruing a bunch of electronics (eqs, tube preamp, etc) so I think I will pass on the tube amp…for now. Or maybe I'll build my own some day.

Whats the THD rating on that amp, if you want to call it an amp
Both at 1 and 3 watts. I bet it is pretty high.

Don't forget, the spl level drops drastically, 6 dB at 2 meters and another 6 dB at 4 meters, so, that is a 12 dB loss. 3dB is about a 4 dB gain, so you are in the hole by 8 dBs less than that sensitivity rating. Good luck.

 

[tbewick]

Hi WinAx,

You fail to mention that using filters will distort/affect the sound at frequencies you're not interested in. This can be seen in the impulse response of the filter.

Tube amps are used because the type of distortion they produce is pleasant sounding, especially in the treble and mid-range.

In regards to amplifier specifications, I've heard Mission, a respected speaker company, criticise the specifications typically produced by amplifier manufacturers, since the measurements they take are done in conditions which never would occur in the real world.

 

[Dinkar Rai]

You must check out the Cayin tube amps before you decide on any purchase. i have been using the A88T for four months and fall more in love with it every day. i have paired it with Dynaudio and now that the speakers are broken in, the sound is just amazing. the clarity of the vocals is very pyre and musical. the dynas are 87db so not very sensitive but nevertheless the sound is some of the best i have heard. i highly recomend to anyone who is interested in buying a tube amp.

 

[WmAx]

Hi WinAx,

You fail to mention that using filters will distort/affect the sound at frequencies you're not interested in. This can be seen in the impulse response of the filter.

Any modification of frequency response affects the impulse response. It does not matter if it's done via an equalizer, or due to the inherant frequency response difference of the amplifier, or due to a frequency response anomoly of a speaker. However, you would only affect frequencies distant from the ones being filtered, if you were to use a rather sharp filter. And at high frequencies, for example, you rapidly lose ability to detect even rather large time based distortions.

Tube amps are used because the type of distortion they produce is pleasant sounding, especially in the treble and mid-range.

Well, in most cases as confirmed by 3rd party measurements[Stereophile is good for something!], tube amps do not typically produce harmonic distortion that is within known human thresholds of audibility. Distortion would not tend to approach audible levels unless a very low powered amp was coupled with a speaker of moderate or low sensitivity, which when used, clipped on loud/dynamic part of the music program, or if one of the extremely poor SET tube amps, that have THD in the 3-5% range in normal use, was used. The main artifiact from a tube amp that is typically audible is a frequency response difference, usually due to the use of an output coupling transformer that has a high output impedance. You can replicate the sound of the frequency response difference of such a tube amplifier by using a sufficiently precision equalizer on a solid state amplifier.

I suggested a special preamp that allows the user to adjust the tube saturation in order to vary the tube harmonic distortion in order to see if he actually would like such an effect.

-Chris

 

[Pyrrho]

Never had a tube amp, don’t know anything about them, so perhaps a silly question…

Amps are available in all kinds output wattage, 100w being pretty common, and more watts is not unusual. I think my surround system has somewhere around 225w per spkr, the sub has 400w available. But when I see tube amps online, they are always have much lower output, 12w, 20w, seen a couple that were around 60w or 75w. Why is the output watts from a tube amp so much lower than other types of amps?

There are several reasons why tube amplifiers tend to produce less power. First of all, tube amplifiers are less efficient than transistor amplifiers. Thus, to be able to use it in an ordinary home, it cannot be as powerful as the most powerful transistor amplifiers, because it would draw too much power from the wall. (This, of course, does not explain why someone would want a mere 12-watt tube amplifier.) Second, tube amplifiers cost more to make than transistor amplifiers, and it costs more to make a powerful amplifier than a less powerful one. Thus, a high-powered tube amplifier would be very expensive. (Please remember, cost to make and retail price can have little in common, as expensive interconnects demonstrate vividly.) Third, the main reason to buy a tube amplifier these days is to get the extra distortion that tube amplifiers add to the sound. (The extra distortion adds "warmth" to the signal. Tube amplifiers also often have a less flat frequency response, and if the treble is slightly diminished, this, too, adds “warmth” to the sound.) If you have a very low powered tube amplifier, you are more likely to be able to get even more distortion in actual use, as you are more likely to drive it into clipping (and tube amplifiers tend to have different distortion in clipping than transistor amplifiers). Thus, a low powered tube amplifier may be regarded as "better" by tube lovers.

The real question is this: Why on earth would you want a tube amplifier? Do you want distortion added to your sound? Do you want your system to be unable to accurately reproduce the signal it is given, making everything seem "smoother" and "warmer" than it really is? I used to have a tube system, and it made Jimi Hendrix sound like Mozart (an exaggeration, but I hope you get the point). The trouble is, Hendrix is not supposed to sound like Mozart.

 

[soccercoach61]

The real question is this: Why on earth would you want a tube amplifier? Do you want distortion added to your sound? Do you want your system to be unable to accurately reproduce the signal it is given, making everything seem "smoother" and "warmer" than it really is? I used to have a tube system, and it made Jimi Hendrix sound like Mozart (an exaggeration, but I hope you get the point). The trouble is, Hendrix is not supposed to sound like Mozart.

I have a Harman Kardon Citation II tube amp (KT88 output tubes) and a H/K Citation I tube preamp... and a collection of Hendrix vinyl that is played over a Dual 1249 turntable with a Shure V15 cartridge, and I think Jimi sounds just like Jimi is supposed to sound.

 

[jaxvon]

It is possible to build a tube amp with low distortion. Gordon Gow (and engineer from McIntosh) built a tube amp with 50w output and distortion <1% back in 1949. Kinda makes a lot of the designs today seem silly, doesn't it?

 

[soccercoach61]

It is possible to build a tube amp with low distortion. Gordon Gow (and engineer from McIntosh) built a tube amp with 50w output and distortion <1% back in 1949. Kinda makes a lot of the designs today seem silly, doesn't it?

My dad built the Citation I and II from kits when I was a mere baby. We have the original manuals and Photofacts with the schematics and parts lists. It is amazing how these things are built, and the kind of sound you get out of them. It will drive almost anything. Plus, it will keep the room warm on cold winter nights!

 

[jaxvon]

Agreed. I'm a big fan of vintage. Few manufacturers make amps and receivers like they used to. I have an old Yamaha receiver from the 70s (CR-1020) and it's 70wpc will beat the pants of any 100wpc receiver you can find today. The power supply section on this thing is HUGE and the amp section will really live up to the claims, and at low distortion. The same goes for great old stuff like Harman Citations. A friend of mine has the 17 and 19 (matching preamp and amp). Another great Solid State combo that's all beef, no frill.

 

[9f9c7z]

My dad built the Citation I and II from kits when I was a mere baby. We have the original manuals and Photofacts with the schematics and parts lists. It is amazing how these things are built, and the kind of sound you get out of them. It will drive almost anything. Plus, it will keep the room warm on cold winter nights!

Soccer Coach - you have a private msg.