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Post subject: 1 watt Valve vs. 1 watt Transistor
Posted: Sat Jul 23, 2011 5:37 pm
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Hi to all,

There has been a lot of discussion over the years about whether 1 watt of valve power is the same as 1 watt of transistor power and for those uneducated, looking at buying an amp, they will quite often get caught out by purchasing something that is under-powered for their needs.

I don't profess to know the truth about this, so I am throwing this out to the wider audience to discuss. Maybe the boys and girls from Fender (if you read this) could shed some light on the truth or maybe if there are any qualified techs that read this that can clear this up.

Currently I am using a Bugera 333xl 120watt valve amp, that I bought about 18 months ago, because the Fender Hotrod (40watt) was just not able to keep a clean sound for long as it ran out of headroom to quickly. The Bugera sounded good when I bought it, but has sounded like crap for about the last 6 to 8 months. Might need new valves, but if they need to be replaced that often, it is just a pain, not to mention the on-going costs. Hence the reason I have now ordered a Mustang IV combo (150watt). But will this 150 watts of transistor power equat to the same power as the 120watts of Bugera valve power.

In reality, sound levels are based on db's not watts, so I guess if you put say a 100watt Fender valve combo amp next to say the Mustang 3 100watt and put a DB meter say 4 or 5 metres in front of both and then behind both amps, you would maybe get a clearer picture of the truth from these db readings. I don't know. It would be interesting to know if anyone has 2 amps like this, that they could do the analysis and maybe post the results.

Anyway, I haven't got the answer, hence the post, but after playing for nearly 40 years, it would be good to get the perspective from the people who build and work with this kind of equipment. All I know, is that I have owned a lot of valve and transistor amps over the years and the valve amps (to my ears) do sound louder at comparable wattage ratings. I do understand that many manufacturers over rate the RMS on their products and there really doesn't seem to be any uniformity in these ratings, but here is a chance for those technical people to help educate the less knowledgable like myself in this area.

Thanks
8beggars


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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Sat Jul 23, 2011 7:54 pm
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Tube amps should be louder for the same wattage rating as solid state amps when compared to each other,i would go to G.C. or some other music store that has the bugera 333xl and the mustang IV and then you can compare these amps for yourself and decide wich one sounds louder on the clean amp tone.


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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Sat Jul 23, 2011 8:36 pm
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Watts are very confusing and so not representative. 1w tube RMS = 1w SS RMS, this is true, but a 100w SS head <> 100w tube head.

You can have a 5 watts tube head and run it in a 4x12 and it will be ear shattering.

50w to 100w <> twice the power.

As for SS amps, the real wattage you should be looking at is the RMS. This is the "perceived number of watts. For example, a Carvin 2x12 cab is 2x50watts BUT the RMS wattage you are going to perceive is more around 150watts...SO if you plug in a 100W head in that, don't stand too close and wear earplugs if you run the master at 8+ :)

100w tube <> 100w SS, for the SS the speakers make the difference not the amp. The amp wattage will determine how many watts RMS they can "drive", hence keep articulation and dynamics, it is not the number of watts you hear.

Tube amps amplification are more complex in that regard and the whole chain will affect the final RMS, this is why a 60w tube amp will be more than enough to cover just about any venue you would be playing hat is not a stadium. :) 60w tube full blast is going to redo your hair do :)


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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Sun Jul 24, 2011 11:05 am
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"Tube Watts are equal to 2 Joules/second, but Solid state Watts are only equal to the 1 Joule/second". I think that's a quote from Dr. D. but I could be wrong about that. :wink:

I'm thinking the real reason why the tubes sound louder is about what's happening after you reach the rated power of the amp. The solid state starts to clip and distort the sound in a hard way and that lets you know you've reached its limit. The tubes start to compress the sound and distort in a softer way that lets you know that you can push things some more.

I'm also thinking that the tubes are likely to have more actual distortion at the rated power limit than the solid state but the difference doesn't realy bother most people. Most people like the extra distortion that the tubes are giving them at rated power.


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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Sun Jul 24, 2011 4:11 pm
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There is a lot of myth & confusion on this subject, but only one correct answer: They are identical - 1w tube has exactly the same scientific measurable volume as 1w SS. HOWEVER, this statement is made with certain 'qualifications': -

1. If you have 2 identically rated and constructed 50w amps with identical speakers, the real measurable volume will be identical - but tube amps generate more of the mid range harmonic frequencies that our ears like compared to a SS/DSP amp. So our ears perceive it to be louder. This has been proven with scientific measurement of output volumes.

2. The 'rating' techniques of an amp's output in RMS watts by manufacturers can be, shall we say, somewhat 'imaginative' and labeled for 'commerciality'. This can be misleading & confusing.

In reality, manufacturers tend to 'overstate' the wattage of modeling amps for commercial reasons - e.g. the latest generation of Vox Valvetronix amps are referred to as 'VT+' - the '+' signifies that (for example) the power output of its 1x10" VT40+ can go up to 60w when cranked. Yet the older AD60VTX (also 60w) is significantly louder!

3. Speakers - The RMS rating on speakers has nothing to do with volume - it indicates power handling capacity only. Its the sensitivity rating that indicates volume - higher sensitivity means more volume. Take a 100w Marshall combo & an identical 50w combo each with a 1x12" 100w 97db speakers - the 100w amp will be about 3dB louder. Put in x 101dB speakers in the 50w amp - and it will actually be louder than the 100w combo with the 97dB speaker.

Now, generally speaking: modeling amps are made on a tight budget with budget speakers (eg Vox use 'Vox own' speakers & there are no specs for these readily available) - valve amps tend to be more expensive and usually come with better quality speakers perhaps with a higher sensitivity - for example, Celestion Vintage 30's is a popular choice and these are 100dB sensitivity. So even if you are comparing a valve and SS amp both independently rated in the same way at 100w, most often the modeling amp won't have as good or as high a sensitivity rated speaker.

Next, cabinet design & whether its open back vs closed back cabinets. Generally, valve amps tend to be open backed whereas a lot of modeling combo's are closed back or semi-open. The perceived volume of a closed back amp varies much more depending on where you're standing, whereas open-backed will spread sound better, adding to the perception of more volume. The material of the cab is another factor impacting on tone & volume eg baltic birch ply vs cheaper block board - modeling amps tend to have cheaper, simpler cab structures to keep manufacturing costs down.

Last, consider speaker size - 2x12" will push out more air & volume than a 1x12" or 1x10" speaker. So even if the power-rating of the amps are truly identical a 30w 1x10" combo can't match the volume output of a 30w 2x12" combo.

Rich :wink:

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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Sun Jul 24, 2011 5:11 pm
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I think rootcat pretty much nailed it.

A watt is a watt whether the energy comes from tube, solid state, or an internal combustion engine.

But wattage is only one of several factors that contribute to perceived loudness as rootcat mentioned.

Regards,

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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Mon Jul 25, 2011 5:34 am
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....or even rockcat! :lol:

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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Tue Jul 26, 2011 5:35 am
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Quote:
1. If you have 2 identically rated and constructed 50w amps with identical speakers, the real measurable volume will be identical - but tube amps generate more of the mid range harmonic frequencies that our ears like compared to a SS/DSP amp. So our ears perceive it to be louder. This has been proven with scientific measurement of output volumes.



Modern solid state modeling amps can give a lot of control over mid range harmonics, they're not limited in ways that they were in the past. Still, tubes amps at the same rated wattage sound louder. And they sound louder while the amps are still at a clean point. That is, where for the most part, the harmonics are coming from the guitar and not artifacts of the amp.


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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Wed Jul 27, 2011 10:22 pm
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Rockcat wrote:
....or even rockcat! :lol:


Sorry about that. Guess I should cntrl+ in the browser. :?

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Post subject: Re: 1 watt Valve vs. 1 watt Transistor
Posted: Wed Jul 27, 2011 10:39 pm
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johnjaypl wrote:
Quote:
1. If you have 2 identically rated and constructed 50w amps with identical speakers, the real measurable volume will be identical - but tube amps generate more of the mid range harmonic frequencies that our ears like compared to a SS/DSP amp. So our ears perceive it to be louder. This has been proven with scientific measurement of output volumes.



Modern solid state modeling amps can give a lot of control over mid range harmonics, they're not limited in ways that they were in the past. Still, tubes amps at the same rated wattage sound louder. And they sound louder while the amps are still at a clean point. That is, where for the most part, the harmonics are coming from the guitar and not artifacts of the amp.


Various frequency responses can be designed into any amp.

Tube amps have a high output impedance and are much more responsive to the frequency response characteristics of the load (the load is most often a speaker). Solid state amps can be designed to have high output impedance to mimic this tube amp characteristic. I think this is done in Marshall's valvestate amps.

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