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Author Topic: Tubes Versus Transistors in Electric Guitar Amplifiers  (Read 10652 times)

skey

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Tubes Versus Transistors in Electric Guitar Amplifiers
« on: March 30, 2006, 12:04:00 AM »
I ran across this study
http://milbert.com/articles/TvsT/tvtiega.html

The amp in the study was a standard old BJT.

If you've ever been on the edge of thinking SS wasn't good enough you'll appreciate that 25 years later, SS has only got better. 

I would love to see a new study done.

Crystallas

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #1 on: March 30, 2006, 02:23:30 AM »
Good read.  Dont get me wrong about this site. I sure hope people dont think SS vs Tube makes sence as a general debate. Both have their place, and both have advanced aswell. Becoming a fanboy of either will only limit you.

teemuk

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #2 on: March 30, 2006, 05:59:16 AM »
I think reading the Russell O. Hamm's article is worthwhile too. Both articles are quite old which leaves lot to argument about, still i think that the authors have nailed the main issues quite right. Now, today's transistor amplifiers are indeed more developed but (unfortunately) a huge part of that development has been happening on audio reproduction area: Numerous ways to lower the distortion in transistor amplifiers have been developed and as a side effect the clipping's "knee" has become harder and circuits more complicated. Opamps are a good example of this - actually many of todays power amplifiers are mainly like high power opamps. It could be different.

What's concerning is that Biggest guitar amp manufacturers still tend to make their designs based on the principles of audio reproduction when they should concentrate on the character of guitar signal instead: To avoid clipping, increase sustain and "psychoacustical power" the solid state guitar power amplifiers really should have a built-in limiter circuit. It really should be mandatory and how many of them have one: I can come up with only few and there are thousands of amplifier models out there? Bass amplifier designers seem to have noted this shortcome but they are lightyears ahead in some other issues anyway: They exploit crossovers and biamping while guitar amps still rely on principles developed on 50's or even earlier. I hate the modern attitude that selling an amplifier actually means selling a complicated preamplifier hooked to a mediocre power amp and cheap speaker system. This is cheap for manufacturers and makes a lot of profit so why change it - the pro consumers are not the main source of their income.

It's quite strange that the article mentions the power response issue to a frequency dependant resistance (impedance) since it really isn't that big deal and mixed-mode-feedback amplifier design has been around for few decades. Rod Elliott has made a nice article about it, which is definitely more worthy reading than articles about transistors vs. tubes:
http://sound.westhost.com/project56.htm
Other way around the poor impedance matching would be to use an output transformer's or chokes but it is quite expensive and people are used to design based on "modern" transistor guidelines.

Teemu K

skey

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #3 on: March 30, 2006, 11:41:56 AM »
What's most interesting to me, is that 25 years ago musicians really couldn't tell the difference between the type of amps.  I would like to see modern tests, but I bet they reveal the same.  What I would really like to see is a combination of tests of whole tube, verses various preamps with a transparent SS amp behind them.


teemuk

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #4 on: March 30, 2006, 12:08:49 PM »
I think it's quite impossible to find such thing as a "transparent SS amplifier" - it's actually impossible to find a transparent amplifier whether it's SS or not. I mean, it's possible to have something very close to one with either highly sensitive speakers, low listening levels or hundreds of watts of power but an average musician probably has neither one of these in a real-life situation. When you have to play with a drummer and use your amplifier as a monitor it will surely distort in some way. This is where the major difference between tube and transistor amplifier's really starts to matter.

joecool85

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #5 on: March 30, 2006, 12:43:14 PM »
As far as transparency goes, the lm3886 is pretty close.  Little to no coloring of the sound at all.  Actually, any good poweramp is like that, the non transparency is coming from the preamp.
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teemuk

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #6 on: March 30, 2006, 01:06:27 PM »
The maximum 68 watts RMS of LM3886 is not my idea of transparency unless you happen to have a very efficient speaker system. Even my 2 x 75W amplifier starts to distort notably when i turn it to a point where it can compete with a drummer. Besides that LM3886 is equipped with protection circuitry (SPiKe) that isn't very ear-pleasing when it happens to kick on. I have heard several comments on LM3886's trasparency and i do not doubt them but the truth is that those comments have come from people who use their amps at "normal" listening levels. Granted that with a good and efficient speaker cabinet 60 watts might be adequate for stage use, but transparent? No way.

skey

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #7 on: March 30, 2006, 01:30:27 PM »
... Besides that LM3886 is equipped with protection circuitry (SPiKe) that isn't very ear-pleasing when it happens to kick on. I have heard several comments on LM3886's trasparency and i do not doubt them but the truth is that those comments have come from people who use their amps at "normal" listening levels. Granted that with a good and efficient speaker cabinet 60 watts might be adequate for stage use, but transparent? No way.

For guitars, These are the kind of things I would like to see blind tested.  Does the protection circuitry cause distortion people distinguish and find negative?  Based on that, what are the components of the distortion they don't like, and can it be counteracted with a simple filter?   ???

When I was saying transparent SS amp I guess I was thinking of a couple of hundred watts.  With limiting to prevent it's own clipping.  Which means it'd compress which isn't transparent, but this purpose close enough.  It could also be a transparent tube amp.  What I was interested in was down stream components - amp and speaker, being transparent and reproducing the signal processing/preamp and giving people a sound they can't distinguish from another combination colored amp.

When I think about it, I guess it can because I can play back a recording of a good sounding guitar through a transparent amp, and it sounds like a good sounding guitar.  I just need to get that signal to the transparent amp in the shape that it's what I want out.  I think this is possible.   

Some people could still probably tell the difference, but a blind test may prove otherwise.  :)

joecool85

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #8 on: March 30, 2006, 01:42:12 PM »
I didn't mean at full volume.  You could get plenty of clean volume out of a bridged parallel lm4780 setup with 200w.

**edit**
And as far as the SPIKe protection kicking it, its never happened to me, and I have played mine at painfully high levels.  It seems to be that you just need a massive heatsink, and a large transformer and you'll be fine.  Ask RDV about that.
« Last Edit: March 30, 2006, 01:43:29 PM by joecool85 »
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teemuk

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #9 on: March 30, 2006, 02:42:06 PM »
The effect of SPiKe protection on sine wave can be seen at LM3886 datasheet page 9. It quickly decreases the gain after the sine peak leaving sort of "spikes" to the signal. Ever heard how a CD rip sounds when the CD is corrupted? I guess it might be quite close of describing the sound. I think some of these spikes are already filtered out by the guitar speaker itself but really the protection should never even go on - after all, it is a protection. You got that right about massive heatsinks. ;) Top quality SS amplifiers need lot of heatsinking iron, especially if they're put on a 35 degree celcius warm stage with a stage light blasting on them.

I believe we have run into a collision of terms in this thread: I mean, how do define concepts like "transparent amplifier" or "painfully high levels"? The later actually tells nothing about a tone of an amplifier: The level can be painfully high with huge distortion or painfully high with no distortion at all. Maybe we should try to be more accurate in choosing the terms we use in order to leave less room for speculation.

If the power amp is indeed "transparent", which i guess in this case means that it never distorts in a way that can be perceived as "distortion", i think it shouldn't be all that difficult to mimick, for example, a high gain tube amplifier or a speaker system's frequency response. Hardly anyone, even the "all-tube" - fanatics deny this. The common argument coming from almost anyone, myself included, is that the modelling sounds good only at "bedroom" levels. This only implies that the power amplifier is not up to it's job.

To get back to the original topic, i'd like to see a new study about solid state and tube amplifier differences too. The question is how should the study be made: Wouldn't the result be biased if the circuits aren't "identical"? Testing a triode gain stage against, say, common emitter and common source gain stages is pretty straigtforward but how about against an opamp, which is a complicated IC? And how about if we're talking about a complete amplifier system?

joecool85

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #10 on: March 30, 2006, 02:57:18 PM »
I think that regardless of how scientific it is or not, it would be interesting to compare some top end SS equiptment with some top end tube equiptment.  Have the same guitarist play on both sets of equiptment, and have "tube lovers" and "SS lovers" listen and see if they can tell the difference.  Have the amp and guitarist behind a wall with the speaker cab in the "audience."  It would be interesting at least.
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RDV

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #11 on: March 30, 2006, 03:17:47 PM »
I've only used my LM3886 based amp in a medium volume duo situation, in other words, with no drums. I'm not sold on using chipamps in a high-volume(competing with live drums) as yet. I may try it soon, but I'm bringing the Marshall too.

I am sold on chipamps making great stereo amps for household use though.

RDV

teemuk

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #12 on: March 30, 2006, 03:39:31 PM »
Nice idea. My guess is that the audience could tell a difference between amps but could not tell whether they are tube or solid state. The whole debate is actually quite funny considering the fact that at least 60% of a typical audience is not educated in electronics at any way and could not tell a difference between a SS and tube amplifier - even if they saw one.  :) I go to many shows and see both SS and tube amps used by the musicians regularly: Some of them use budget line Crates and some of them top quality tube amplifiers - without hassle. The way to ruin a performance has more to do with horrible balance between instruments and the singer than with the used equipment.

Everytime i find myself jumping too much on the "wonderful tone of tube amplifiers" bandwagon i take a look at this picture and return to ground level... (I believe that's a Crate GX-65)  :)
http://www.trollech.com/gallery/gigs/firstgig7.jpg

RDV

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Re: Tubes Versus Transistors in Electric Guitar Amplifiers
« Reply #13 on: March 30, 2006, 04:18:20 PM »
That's a great picture, I can just hear it.

My chipamp guitar is a good sounding amp, but I don't know if tube-like quite describes it though it is quite warm IMO. I built a Thomas/Vox SS brilliant channel w/midrange boost preamp for the front end and it sounds like nothing else you'll hear. It really sticks out of a mix without being annoying. I would post some sound samples to give you an idea but my website is down for a while. It takes to pedals really well, even a TS type pedal which almost never sounds good with SS amps works well with it. It'd be too unique to market though as it doesn't sound like everybody else.

RDV