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Post subject: Solid State Watts Vs Tube Watts
Posted: Tue Oct 02, 2012 10:00 pm
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My question is this......My MIII amp is 100 watts solid state soooo, is that equal to about 40 watts on a tube amp? If so, how does that effect a speaker rated at 50 watts going in a 100 watt solid state amp. Some people are doing this so I thought I would ask. Thanks in advance!


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Tue Oct 02, 2012 11:16 pm
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Hi - 100 watts solid state power = 100 watts tube power, 100 watts is 100 watts. The difference between Solid State and Tube is the percieved volume level because a Tube amp saturates and distorts better than a Solid State amp therefore giving the perception that it is louder! Thus a 40 watt tube amp sounds as loud as a 100 watt Solid State Amp.

Now this means that the Speaker must handle the wattage of the amp. So a 40 watt valve amp needs a 40watt+ speaker and a 100 watt Solid State amp still needs a 100watt+ speaker.

So don't under rate your solid state amp speaker because you will be asking for trouble when you crank it to it's full power.

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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Tue Oct 02, 2012 11:26 pm
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Thank You!!


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Wed Oct 03, 2012 12:58 am
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TOOOBE WHATS!!! :wink:

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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Wed Oct 03, 2012 3:08 am
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The short answer is that there is no meaningful quantitative comparison (in terms of perceived loudness, sound quality, etc) between wattage of valve/tube amps and solid-state (SS) amps. Even two SS amps with the same power could be very different in volume - depending on how that power is used, the efficiency of the speakers, etc.

Part of it is, as AaronK says, because a valve amp can be (and is usually intended to be) overdriven; that creates both more amplitude and harmonics, and thus "sound energy" than its on-paper wattage would suggest.

Related to this is the way manufacturers have to (by law) quote the peak power figures for amps. That peak is for a 'clean' signal (getting technical, I think the limit is 5% THD). As we all know, as soon as a SS amp starts distorting, it sounds bad. So an SS amp can only be used up to the power limit to which its rated.

However, a valve/tube amp starts to sound good once it is distorting - so really, the peak power figure quoted for a valve/tube amp isn't a peak at all, it's the point at which most people will be using the amp! The actual peak power handling capacity of the amp will be much higher than its rated power, which is just the limit of its clean amplification.

What would be far more useful would be for manufactureres to quote sound pressure levels for amps, that's a better measure of loudness. But this is fraught with issues too - do you measure it right in front of the amp, or off to one side, etc? Some amps, due to cabinet / speaker / grille design might sound louder off-axis and some might sound better dead-on-centre. So it wouldn't be totally meaningful. Also, different signals with the same peak amplitude can have very different volumes (as perceived by human ear) based on the shape of the waveform.

Ultimately, the only useful test is to play two amps side-by-side and listen to the volume difference for the type of instrument and playing they'll be amplifying.

But if you want a rough-and-ready guideline, I've seen reported in multiple places (although haven't verified myself) that a valve/tube amp of a certain rated power will be about as loud as a SS amp with four times the power (some say three times, some say five or six times). But that's very, very approximate and there will be as many examples that disprove that as support it.


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Wed Oct 03, 2012 3:59 am
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As stated above, solid state watts = tube watts.

However, stick your average solid state combo next to a similarly rated tube combo, and yes, the tube combo will more than likely stomp all over the SS one.

To be honest, I think a lot of the difference is usually on the speaker side of things rather than the harmonic side - most solid state amps are just fitted with much cheaper and less efficient speakers than their tube based brethren. You'd be amazed just how much extra volume (and indeed tone!) can come out of a decent speaker, or how much a cheap one can cripple an otherwise rather decent amp.

Same applies to cheaper tube amps, of course - lost count of the amount of actually rather good sounding amps I've played through which are nobbled from the start by a cheap speaker. I've heard 100w tube combos which were barely audible above a pub band, and I've heard 40w SS combos that would stun small mammals at 50 paces.

In fact, you'd be amazed how loud a 5w head can be through some very efficient speakers - certainly very giggable if you're not too worried about clean headroom. :shock:


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Sun Feb 03, 2013 9:22 am
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From my own personal experience regarding speakers and amps, I totally agree with you! All too often it is the speaker that is either the deal maker or deal breaker in an amp's sound, performance and volume. I am usually one to very quickly change out stock speakers for more efficient speakers soon after I purchase an amp that I like. I usually make that recommendation to friends as well. I've been a tube guy all my life and wouldn't give a SS the time of day until several years ago, after a speaker change-out in a Peavey Special 130. An EV12L turned that brittle sounding amp into a warm, sparkly stage monster! I haven't shunned a well made SS amp since. I have upgraded the speakers in almost every old Fender tuber I own as well (yes I kept the stock speakers) and with always satisfying results. Speakers DO make a difference. :D


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Sun Feb 03, 2013 11:28 am
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telecastoff wrote:
Speakers DO make a difference. :D


Indeed - I'm of the opinion these days that speakers are almost slightly more important than the amp itself. A decent well chosen speaker can sometimes make an average sounding amp sound superb, but equally, a bad speaker can make the most exotic boutique amp sound like a bee in a jar.

A lot of solid state amps aren't even given a chance with some of the speakers they ship with. Seen at least one 50w tranny amp with a speaker efficiency of 87db. :shock:


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Sun Feb 03, 2013 1:39 pm
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Like you guys said, my MIII is just about as loud as my Blues Deluxe. 100 SS watts = 40 tube watts. Roughly. Of course like you say, speaker efficiency makes a big difference as well.


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Mon Feb 04, 2013 7:20 am
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just to show how miningless amps and watts comparisons are, try this simple experiment on your Mustang:

-if you are in a small room
-put your master volume knob on 5
-select the basic twin 65 preset: very playable at that level huh?
-now just turn the knob and select basic Metal 2000: make sure your cat is not in front of your amp when you test it or you are going to need a new one (a cat that is)

Same amp, same power setting, just sound wave shape is different, which is what matters the most in the end. That's why putting a distortion pedal in front of any amp makes it sound louder.

Now mostly all tube amps start to distort with volume around 5 or so, which the mustang will not do cranking the master volume alone. A more fair comparison with the mustang will be to crank the master volume AND amp gain at the same time, then you will see how loud this thingy is.


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Sat Feb 09, 2013 3:10 pm
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To me the Watt question is irrelevant. My experiences are:

A good tube amp will almost always sound good, a Virtual Analog Solid State can sound almost as good.

A tube amp sounds and feels good to me, a VA SS amp can only sound good but will never feel good.

A current VA SS amp will sound today but probably sound artificial in some years time, even a 50 year old tube amp still sounds good today.

VA SS amps may be limited, they are very versatile especially for practice and demo usage (that's why I bought Mustang I)

If you need more volume than an amp can give: amp it up using a PA system.

My Marshall JCM 800 wakes up the whole neighbourhood when it sounds and feels "good", my new Mustang doesn't even wake up my little girl when I practice in the evening :-)

My conclusion: these are different amps, made for different purposes. For an amp to feel good it needs to be a tube amp at high volume... But then again this is my humble opinion!


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Post subject: Re: Solid State Watts Vs Tube Watts
Posted: Thu Feb 14, 2013 12:53 am
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I dunno. There's all this "perception" theory. But a saturated/distorted waveform isn't just perceived louder. It is louder. It's like the compression used on commercials. It packs all the signal up to red line. It IS louder, because there are now no dips, even the quietest moments are cranked up to max.

But the rated wattage issue isn't that. By law, an amp's wattage is specified at 5% total harmonic distortion. That's reasonably clean. A transistor amplifies very cleanly, because the gain curve has a nice straight s l o p e. Above the linear part of the curve, it sharply plateaus. The 5% distortion point is where the knee is, and right above that is the flat plateau. If you raise the signal above the linear portion, it hits that plateau, and no longer gives more gain. The signal waveform flattens, and that quickly gives 10, 20, 50, 100% distortion. Can't give more.

A tube has an S shaped gain curve. An amp is normally operated in the (limited) straight sloped portion. The wattage is rated at the 5% point. That 5% distortion point is where the gain curve is no longer linear, which is why it's starting to distort the signal, just as in the case of the transistor, but for the tube that's nowhere near the max. The gain curve flattens, but gradually, there is no immediate hard plateau. You can keep going 3, maybe 4 times hotter, before total distortion red line, where you run out of gain.

So it's not a matter of "perception". Or tubes having even harmonics. It's actual usable (though distorted) amplification. On a transistor amp that's right above the 5% THD level. On a tube amp it's much more.

Now the limitation of a speaker is in both the peak excursion of the cone, and the heat that it can dissipate. A more distorting waveform doesn't push the speaker cone as far. But a compressed signal gives it no rest. There's a margin in the rating of speakers, but I think using the nominal 5% THD wattage of a tube amp to match the speaker pushes it right up to that margin.


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