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Re: Interesting theoretical question

4/20/2003 1:20 AM
R.G.	Re: Interesting theoretical question [QUOTE]If we can still tell, would solid state power amps work for some other way to make that same analog signal going into them? I'm not sure I understand this one. Can you rephrase it?[/QUOTE] See my reply to KB above. I'm wondering where in the signal path the magic tone lives. I know I can make it with, say a Strat and a 59 Bassman. I can capture it with a good mike in a recording studio. But is the full Bassman necessary? Can some of that be editted out and still have the essence of tube, whatever that is? My proposition is that running just the right signal through a high accuracy solid state amp and speakers can make a recognizable tube sound, so SS does not poison the tube tone. R.G.

4/20/2003 1:20 AM

R.G.

Re: Interesting theoretical question

[QUOTE]If we can still tell, would solid state power amps work for some other way to make that same analog signal going into them?

I'm not sure I understand this one. Can you rephrase it?[/QUOTE]

See my reply to KB above. I'm wondering where in the signal path the magic tone lives.

I know I can make it with, say a Strat and a 59 Bassman. I can capture it with a good mike in a recording studio. But is the full Bassman necessary? Can some of that be editted out and still have the essence of tube, whatever that is?

My proposition is that running just the right signal through a high accuracy solid state amp and speakers can make a recognizable tube sound, so SS does not poison the tube tone.

R.G.

4/20/2003 1:56 AM
bosephus	no, i doubt this is possible w normal SS devices. have to remember, that we run the signal thru a suspended wire, that is under tension, inside a vacuum, being drawn to an electrically charged plate at high voltage. something occurs in this transfer of energy and audio signal that imparts that wonderous magic that we know as tube guitar (or stereo) tone. SS devices arent made of the same materials, have a different construction, and are run in a much different environment, electrically, than tubes. but, this isnt to say a solid stae device cant be warm, or have good tone. far from it. remember, that the amp is only part of the tonal equation. i have heard many a guitar player make a beautiful tone machine sound like dawg, and cruddy Ross SS amps sound quite nice. bospehus

4/20/2003 1:56 AM

bosephus

no, i doubt this is possible w normal SS devices. have to remember, that we run the signal thru a suspended wire, that is under tension, inside a vacuum, being drawn to an electrically charged plate at high voltage. something occurs in this transfer of energy and audio signal that imparts that wonderous magic that we know as tube guitar (or stereo) tone. SS devices arent made of the same materials, have a different construction, and are run in a much different environment, electrically, than tubes.
but, this isnt to say a solid stae device cant be warm, or have good tone. far from it. remember, that the amp is only part of the tonal equation. i have heard many a guitar player make a beautiful tone machine sound like dawg, and cruddy Ross SS amps sound quite nice.

bospehus

4/20/2003 1:26 PM
R.G.	I'm well aware of how tubes and SS devices work, and the differences. I'm just observing that a recording of a tube amp still carries that difference. So how much of the tube amp do we have to have to make the tube tone? For instance, output transformers are not made of suspended wires under tension in a vacuum. Can we leave those out? Is the transformer part of the wonderous magic? Or can we sub in a clot of smaller parts and leave the high power stuff to some more accurate and lighter SS power amp? If not, why not? R.G.

4/20/2003 1:26 PM

R.G.

I'm well aware of how tubes and SS devices work, and the differences.

I'm just observing that a recording of a tube amp still carries that difference. So how much of the tube amp do we have to have to make the tube tone?

For instance, output transformers are not made of suspended wires under tension in a vacuum. Can we leave those out? Is the transformer part of the wonderous magic? Or can we sub in a clot of smaller parts and leave the high power stuff to some more accurate and lighter SS power amp?

If not, why not?

R.G.

4/19/2003 3:13 PM
Lee M.	What constitutes "tone?" Is it just frequency response? When the amp is operating in the linear region, I would say yes. However, we all know that tube amps sound most pleasing when operated outside the linear region, when they are overloaded, clipping, etc. Is it possible that somewhere in the recording chain, even if the frequency response is not altered, the amount or ratio of even to odd-order harmonics is changed? If so, I believe that's where the problem lies. In theory at least, a linear power amp (be it tube or s.s.) should only amplify the signal, not alter its frequency response. I think today's modeling amps do a pretty decent job of emulating the originals, at least as far as I can tell by the sound samples I hear on my little computer speakers. I'll bet most listeners couldn't tell the difference in a band setting where they are also hearing bass, drums, maybe another guitar and keyboards. The subtleties of tone tend to disappear with additional instruments. That's why I always find the discussions of amp tone so amusing. Most listeners don't care about individual instrument tone unless they are musicians and even then, most of them won't pay attention unless it's their own instrument. People buy records and go to clubs to listen to music, not tones. If the music is good and the band is having fun, the audience will like it. They are much more likely to be put off by a bad mix than lousy tones.

4/19/2003 3:13 PM

Lee M.

What constitutes "tone?" Is it just frequency response? When the amp is operating in the linear region, I would say yes. However, we all know that tube amps sound most pleasing when operated outside the linear region, when they are overloaded, clipping, etc. Is it possible that somewhere in the recording chain, even if the frequency response is not altered, the amount or ratio of even to odd-order harmonics is changed? If so, I believe that's where the problem lies. In theory at least, a linear power amp (be it tube or s.s.) should only amplify the signal, not alter its frequency response.

I think today's modeling amps do a pretty decent job of emulating the originals, at least as far as I can tell by the sound samples I hear on my little computer speakers. I'll bet most listeners couldn't tell the difference in a band setting where they are also hearing bass, drums, maybe another guitar and keyboards. The subtleties of tone tend to disappear with additional instruments.

That's why I always find the discussions of amp tone so amusing. Most listeners don't care about individual instrument tone unless they are musicians and even then, most of them won't pay attention unless it's their own instrument. People buy records and go to clubs to listen to music, not tones. If the music is good and the band is having fun, the audience will like it. They are much more likely to be put off by a bad mix than lousy tones.

4/19/2003 4:16 PM
LFOscalator	Live, one can immediately tell the difference between tube and SS, primarily because there is only one variable, that being the guitar amplifier. Playback, on the other hand is more complicated because recording and playback introduce additional variables that can either warm or sterilize the sound. For example, here's a short list of factors that can contribute to or detract from the listener's ability to detect the tube sound of a recorded tube amplifier: 1. Was the amp recorded using analog or digital? Analog sounds warmer and has a more 'tubelike' quality. 2. Was the mic preamp tube or SS? A tube preamp will tend to 'tubify' the recorded sound. 3. Was a minimalist SS approach used for the mixing board? In other words, was the sound passed through a minimal number of SS stages before it hit the recording device? Less SS devices in the recording path will often yield a warmer sound. 4. What was the musical quality of the mixing board used. Certain brands of mixing boards are more 'musical' sounding than others. 5. Were SS stages in the recording path made with conventional SS or were FET's used. FETs often warm the sound. 6. Was live reverberation included in the recording or was reverberation digitally and artificially produced. Live reverberation will warm the sound. 7. Likewise were digital effects such as chorus or delay used on the guitar, or were analog effects used. Analog effects will sound warmer. 8. Was a SS distortion/fuzz box used in guitar amp signal chain. If so, the guitar amp's sound will have heavy duty SS qualities to it. 9. What type of mic was used to mic the amp? What type of mic was used to mic room reverberation? Condensor mics sound warmer for recording reverberation. Dynamic mics tend to sound warmer for recording guitar amplifiers. 10. What micing technique was used to mic the speaker? What portion of the speaker was miced, the center or the cone? The cone tends to sound warmer. 11. If recorded digitally, what is the quality of the ADC's used for recording. Better analog-to-digital converters sound warmer. 12. If recorded digitally, was dithering used to convert between sample rate and sample depths. Dithering can make the recording sound warmer by introducing randomized noise. Also, some dither programs are better than others in terms of warming the sound. 13. Is playback via analog means such as vinyl or via digital media such as CD? Analog tends to sound warmer. 14. For digital playback, what is the quality of the DAC in the CD player. Better DACs sound more musical and tend to remove some of the digital quality in the sound. 15. Is playback through a tube or an SS amplifier? Also, is the playback preamp tube or SS? 16. If playback is through an SS amp, what is the quality of the amp. High end SS amps sound very different from consumer quality amps at the low end. High end amps remove graininess often asociated with SS devices and may warm the sound. This list could go on and on, but you get the idea. The recorded amp will undergo considerable transformation to the extent that it may be difficult to tell the difference absolutely between a SS and a tube amp upon playback. I have yet to ever hear any recorded instrument that sounds exactly like it does live in real air. Some recordings are close, but yet never quite reproduce the real thing. It's a fact of life. So, the answer to your question is a very noncommital MAYBE. LFO

4/19/2003 4:16 PM

LFOscalator

Live, one can immediately tell the difference between tube and SS, primarily because there is only one variable, that being the guitar amplifier.

Playback, on the other hand is more complicated because recording and playback introduce additional variables that can either warm or sterilize the sound. For example, here's a short list of factors that can contribute to or detract from the listener's ability to detect the tube sound of a recorded tube amplifier:

1. Was the amp recorded using analog or digital? Analog sounds warmer and has a more 'tubelike' quality.

2. Was the mic preamp tube or SS? A tube preamp will tend to 'tubify' the recorded sound.

3. Was a minimalist SS approach used for the mixing board? In other words, was the sound passed through a minimal number of SS stages before it hit the recording device? Less SS devices in the recording path will often yield a warmer sound.

4. What was the musical quality of the mixing board used. Certain brands of mixing boards are more 'musical' sounding than others.

5. Were SS stages in the recording path made with conventional SS or were FET's used. FETs often warm the sound.

6. Was live reverberation included in the recording or was reverberation digitally and artificially produced. Live reverberation will warm the sound.

7. Likewise were digital effects such as chorus or delay used on the guitar, or were analog effects used. Analog effects will sound warmer.

8. Was a SS distortion/fuzz box used in guitar amp signal chain. If so, the guitar amp's sound will have heavy duty SS qualities to it.

9. What type of mic was used to mic the amp? What type of mic was used to mic room reverberation? Condensor mics sound warmer for recording reverberation. Dynamic mics tend to sound warmer for recording guitar amplifiers.

10. What micing technique was used to mic the speaker? What portion of the speaker was miced, the center or the cone? The cone tends to sound warmer.

11. If recorded digitally, what is the quality of the ADC's used for recording. Better analog-to-digital converters sound warmer.

12. If recorded digitally, was dithering used to convert between sample rate and sample depths. Dithering can make the recording sound warmer by introducing randomized noise. Also, some dither programs are better than others in terms of warming the sound.

13. Is playback via analog means such as vinyl or via digital media such as CD? Analog tends to sound warmer.

14. For digital playback, what is the quality of the DAC in the CD player. Better DACs sound more musical and tend to remove some of the digital quality in the sound.

15. Is playback through a tube or an SS amplifier? Also, is the playback preamp tube or SS?

16. If playback is through an SS amp, what is the quality of the amp. High end SS amps sound very different from consumer quality amps at the low end. High end amps remove graininess often asociated with SS devices and may warm the sound.

This list could go on and on, but you get the idea. The recorded amp will undergo considerable transformation to the extent that it may be difficult to tell the difference absolutely between a SS and a tube amp upon playback.

I have yet to ever hear any recorded instrument that sounds exactly like it does live in real air. Some recordings are close, but yet never quite reproduce the real thing. It's a fact of life.

So, the answer to your question is a very noncommital MAYBE.

LFO

4/19/2003 8:13 PM
Shea	If the main differences between tube guitar amps and ss amps are soft-edged clipping, frequency response (such as a mid hump and a high-end rolloff), and second-order harmonics, then there is no reason why those differences shouldn't show up in a recording no matter what the recording process is. Think about it: if the sound coming out of a tube amp is down 3dB at 10k, a solid-state recording rig isn't going to boost the signal coming out of a tube amp back up 3dB at 10k unless it does the same thing to solid state amps, in which case the two amps will still sound different at 10k. If an 800hz note comes out of the tube amp colored with audible 1600hz harmonic, then a solid-state recording device isn't going to surgically remove the 1600hz. From what I've read on Ampage, Geofex, KG's website, Aiken Amps' website, and other places, and from my own twiddling and tweaking, I think a lot of the difference between tube amps and solid-state amps come from: 1. Soft clipping in single-ended stages, namely, the preamp gain stages. AFAIK, this comes from a tube's non-linear operation when it's near cutoff. That can be emulated with JFETs. 2. Duty cycle modulation. All it requires is two cascaded stages, each of which clips assymetrically. That can be emulated with cascaded JFETs. 3. The tone coloration that comes from the interaction between the power tubes, output transformer, and speakers. That can be approximated by using an output transformer together with power transistors or power MOSFETs in push-pull. From what I've read, the way to increase the output impedance of a power transistor is to input the signal into the emitter or source, rather than the base or gate. I just might try putting these components together some time. I wonder if it'd be cheaper than making a tube amp of the same wattage? BTW, my buddy Darren finally located and bought a Vox Defiant. That is one hell of a fine-sounding solid-state amp! Not that it proves any of my theories, though. It doesn't use any of them. Shea

4/19/2003 8:13 PM

Shea

If the main differences between tube guitar amps and ss amps are soft-edged clipping, frequency response (such as a mid hump and a high-end rolloff), and second-order harmonics, then there is no reason why those differences shouldn't show up in a recording no matter what the recording process is.

Think about it: if the sound coming out of a tube amp is down 3dB at 10k, a solid-state recording rig isn't going to boost the signal coming out of a tube amp back up 3dB at 10k unless it does the same thing to solid state amps, in which case the two amps will still sound different at 10k. If an 800hz note comes out of the tube amp colored with audible 1600hz harmonic, then a solid-state recording device isn't going to surgically remove the 1600hz.

From what I've read on Ampage, Geofex, KG's website, Aiken Amps' website, and other places, and from my own twiddling and tweaking, I think a lot of the difference between tube amps and solid-state amps come from:

1. Soft clipping in single-ended stages, namely, the preamp gain stages. AFAIK, this comes from a tube's non-linear operation when it's near cutoff.
That can be emulated with JFETs.

2. Duty cycle modulation. All it requires is two cascaded stages, each of which clips assymetrically. That can be emulated with cascaded JFETs.

3. The tone coloration that comes from the interaction between the power tubes, output transformer, and speakers. That can be approximated by using an output transformer together with power transistors or power MOSFETs in push-pull. From what I've read, the way to increase the output impedance of a power transistor is to input the signal into the emitter or source, rather than the base or gate.

I just might try putting these components together some time. I wonder if it'd be cheaper than making a tube amp of the same wattage?

BTW, my buddy Darren finally located and bought a Vox Defiant. That is one hell of a fine-sounding solid-state amp! Not that it proves any of my theories, though. It doesn't use any of them.

Shea

4/20/2003 12:33 AM
Bernt	Digressing, but don't we always . I don't think tubes per se gives you 'softness' or 'musicality'. I once hooked up a tube-base square-wave generator to a wide-band oscilloscope (a perfect thing to do on a rainy day when there's nothing on the telly...), and I saw a nice square-wave. I have also built tube pre-amps that sounded like Fuzz Faces when overdriven. I also own a big "luggable" transistor-radio from the sixties, with interstage- and output-transformers, which gives a very nice, soft tone when I hook up my guitar and overdrive it. Which leads to one thing that Shea touched: I think the output-transformer in tube-amps is underestimated when it comes to tone-shaping. Off track again, but kindest regards, Bernt.

4/20/2003 12:33 AM

Bernt

Digressing, but don't we always

.
I don't think tubes per se gives you 'softness' or 'musicality'. I once hooked up a tube-base square-wave generator to a wide-band oscilloscope (a perfect thing to do on a rainy day when there's nothing on the telly...), and I saw a nice square-wave. I have also built tube pre-amps that sounded like Fuzz Faces when overdriven.
I also own a big "luggable" transistor-radio from the sixties, with interstage- and output-transformers, which gives a very nice, soft tone when I hook up my guitar and overdrive it.
Which leads to one thing that Shea touched: I think the output-transformer in tube-amps is underestimated when it comes to tone-shaping.
Off track again, but kindest regards, Bernt.

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