Upon the suggestion of Leadbelly and shanx, I've opened a new thread to explore what I don't know about instrument amps and how they should differ from hifi amps. Two of the attributes discussed were electrical characteristic tolerance and environmental indifference. I would like to examine these more closely and learn the methods used to obtain them. More on that later...
The first question that puzzles me is why the members above agree an instrument amp works better as an integrated unit. Many musicians use FX units to output a signal that is strong enough to reach a good level of amplification without the waveform being changed further by introduced amplifier characteristics. These FX units have amazing flexibility and can create exactly the sound you want so why introduce any further influence. I don't really understand the need for tone controls on the amp when you have them on the instrument and FX unit. Same goes for the clipping, reverb and presence controls. If we take a guitar with a full FX palette as the working example, where do we want to set the input sensitivity on the amp?
The first question that puzzles me is why the members above agree an instrument amp works better as an integrated unit. Many musicians use FX units to output a signal that is strong enough to reach a good level of amplification without the waveform being changed further by introduced amplifier characteristics. These FX units have amazing flexibility and can create exactly the sound you want so why introduce any further influence. I don't really understand the need for tone controls on the amp when you have them on the instrument and FX unit. Same goes for the clipping, reverb and presence controls. If we take a guitar with a full FX palette as the working example, where do we want to set the input sensitivity on the amp?
Random brain dump of musical instrument amp facts:
Traditional tube guitar amps had preamp and power amp running off the same unregulated power supply. This allowed for more grunge and distortion that might have been considered desirable.
Power amps for guitar are often designed with a high output impedance as guitar speakers seem to sound better that way.
The volume requirement for electric guitar is more like PA than hifi. Power is usually limited by driving the power amp into hard clipping. The speaker must be matched to the amp such that both can withstand this, and the power amp has to clip cleanly without sounding too bad. (Bonus points if it can allow the clipped signal to soar outwith the supply rails, as most tube amps could.)
On the basis of these last three points, some people argue that the power amp is part of the instrument.
The traditional tone controls on a Marshall guitar amp gave a flat response when bass and treble were set to 0 and mids to 10. All the normally used settings gave a bass and treble boost with scooped out midrange.
The input sensitivity for guitar amps and effects is traditionally similar to the consumer -10dBV standard.
Many guitarists nowadays will run a digital effects unit like the Fractal Axe-FX or Line6 Pod straight into the house PA. Rackmount power amps for guitar have been available since forever. During the metal era, a rig with separate rackmount preamps, FX and power amps was sought after, but now there is a retro craze and everyone seems to want tweed covered things.
Traditional tube guitar amps had preamp and power amp running off the same unregulated power supply. This allowed for more grunge and distortion that might have been considered desirable.
Power amps for guitar are often designed with a high output impedance as guitar speakers seem to sound better that way.
The volume requirement for electric guitar is more like PA than hifi. Power is usually limited by driving the power amp into hard clipping. The speaker must be matched to the amp such that both can withstand this, and the power amp has to clip cleanly without sounding too bad. (Bonus points if it can allow the clipped signal to soar outwith the supply rails, as most tube amps could.)
On the basis of these last three points, some people argue that the power amp is part of the instrument.
The traditional tone controls on a Marshall guitar amp gave a flat response when bass and treble were set to 0 and mids to 10. All the normally used settings gave a bass and treble boost with scooped out midrange.
The input sensitivity for guitar amps and effects is traditionally similar to the consumer -10dBV standard.
Many guitarists nowadays will run a digital effects unit like the Fractal Axe-FX or Line6 Pod straight into the house PA. Rackmount power amps for guitar have been available since forever. During the metal era, a rig with separate rackmount preamps, FX and power amps was sought after, but now there is a retro craze and everyone seems to want tweed covered things.
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Thanks for the input. I would like to address a few points before we continue. I've noted the predisposition of using tubes for instrument amps. Is this primarily for their soft clipping behavior or are there other benefits over solid state? We have seen solid state designs with a strong 2nd harmonic characteristic so I don't count this as an automatic plus for using tubes. Ditto for high output impedance; distortion from low damping can be dialed in FX. If an amp can reproduce a square wave cleanly and not misbehave, there is little reason to overdrive it so wouldn't it be more advantageous to make a dynamic, accurate and quiet amp and leave all the other stuff to the FX unit and instrument controls? If clean amps similar to what I've described above become the new paradigm we would want at least a 10V peak input before clipping. Anyone else agree with my point of view?
Could you perhaps clarify what you are attempting to achieve?
You are asking questions on a broad subject, and from them it would appear (a) you are not familiar with MI amp design, either tube or SS; (b) you are not familiar with performing using an MI amp (your tone control question); (c) you want very specific design parameters (your 10V example).
This is a vast topic!
You are asking questions on a broad subject, and from them it would appear (a) you are not familiar with MI amp design, either tube or SS; (b) you are not familiar with performing using an MI amp (your tone control question); (c) you want very specific design parameters (your 10V example).
This is a vast topic!
To paraphrase R. Aspen Pittman, "It's not that tubes sound better, it's that they feel better." Tube amps have what is called touch response. There is no stomp box that gives that to a solid state amp. Separate power and preamp setups don't have as much as a normal guitar amp because the preamp's power supply does not move around in response to the power delivered to the speaker. This is something you don't necessarily hear, but you feel it when the guitar is in your hands.
An amp with 10V of headroom on the input would not be "pedal friendly", meaning that it would not sound good with overdrive pedals. There are bass amps like that, but they don't sound good for guitar.
An amp with 10V of headroom on the input would not be "pedal friendly", meaning that it would not sound good with overdrive pedals. There are bass amps like that, but they don't sound good for guitar.
Good to see you here leadbelly. Right, what I'm trying to determine is if there is a possible market for a universal amp. An amp that can function well as an instrument amp and also play music credibly.
Thanks for your input Loudthud, so if I'm understanding you correctly, tube amps have less signal processing lag or put another way, they're faster? There are solid state designs that approach a 200V/uS slew rate so I think even this advantage can be addressed by design. WRT to 10V of headroom, keep in mind we have all the clipping and output control on the FX unit so all we need to ensure is a low output impedance, high current drive signal generator on that box then then amp can be as pristine as we want. I've experimented with a decent hifi integrated amp on a middle pickup only Strat feeding a timefactor and found the dead silence behind the glassy sounds quite intoxicating. It couldn't do everything that well but with some smart design, I imagine it could. That's my pursuit here.
Thanks for your input Loudthud, so if I'm understanding you correctly, tube amps have less signal processing lag or put another way, they're faster? There are solid state designs that approach a 200V/uS slew rate so I think even this advantage can be addressed by design. WRT to 10V of headroom, keep in mind we have all the clipping and output control on the FX unit so all we need to ensure is a low output impedance, high current drive signal generator on that box then then amp can be as pristine as we want. I've experimented with a decent hifi integrated amp on a middle pickup only Strat feeding a timefactor and found the dead silence behind the glassy sounds quite intoxicating. It couldn't do everything that well but with some smart design, I imagine it could. That's my pursuit here.
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It all depends on the type sound/feel you want, it seems like you are leaning more towards the FX, amp sim direction, which already have tons of offerings on the market, so incoporating tube(s) into the mix is nothing new... what would make your design stand out? But why are we discussing a potential commercial product on a diy forum?
No, I don't want an amp sim, I want an amp with no character sound of its own so the FX unit can provide all the variation. If there are 'tons' as you say, would you point me to an instrument amp that has no character sound of its own and is also suitable for hifi? If you can do that, I would thank you and this thread would be resolved but if you can't, I think this is a worthwhile discussion. My use of 'market' was to describe a collection of diyers potentially interested in this project, not to indicate a commercial venture. Scopeboy, what is meant by the clipping soaring out with the supply rails and how do we measure this?
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Loudthud has a scope plot of this effect as his avatar so I will let him explain. Then the rest of you can fight over whether it is musically significant. 🙂
I also recommend Rod Elliott's articles on instrument amplifiers:
Musical Instrument Amplification
Valves - Clipping
Rod's solid-state guitar amp is not a million miles away from the Marshall Mosfet ones.
http://sound.westhost.com/project27.htm
(there may be a few others that I forgot)
I once spent some time playing a Strat through one of my half-finished Blameless power amps. It was... clean. 🙂
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If you want an amp that had no characteristic sound of its own, then you will trade off touch sensitivity to a degree, I believe. To achieve that type of flatness, is more likely using a power amp with a higher damping factor, but there are amp designs in both SS and tubes that use lower damping factors and also sound very good for audio. It's harder to get good control of the speakers at higher (PA) volumes, and that is why PA systems with tubes were more difficult to EQ properly.
Electrovoice has a guitar speaker series that is really quite flat in response,little coloration and high wattage. A good candidate for the sound driver. I think geofex offers a 100W kit for power amp with low damping, and again importance is given to the thing handling peaks gracefully, being servicable.
Electrovoice has a guitar speaker series that is really quite flat in response,little coloration and high wattage. A good candidate for the sound driver. I think geofex offers a 100W kit for power amp with low damping, and again importance is given to the thing handling peaks gracefully, being servicable.
Many of the top names in the MI market offer rack mount PA's that could easily be used for hifi, such as Marshall, Mesa, Carvin, the list goes on... that's what they were designed to do, all the signal processing, fx are done before the PA's input - these are pretty "clean" amps. As for the amp sims, there are many hardware not software offerings from Fender, VOX and Peavey, etc.
I think there are a number of factors that explain why many guitarists prefer tube amps. One factor, which I don't think has been mentioned so far, in this thread, is that as a result of tubes drawing grid current when overdriven (and also because tubes have a so-called 'self-rectification' effect) various decoupling and bypass capacitors in the circuit get transiently charged with some DC while the amp is played. This temporarily shifts the bias point of various stages in the amp, giving a dynamic characteristic to the harmonics in the overdriven sound (sometimes called 'swirl'). In the extreme, however, the same effect causes 'blocking distortion' - which is generally considered unpleasant by most guitarists.
Many effect boxes try to emulate, or simulate, what a tube amp does naturally, and can sound 'processed' to many guitarists.
For (loud) live playing, the interaction between the output tubes (invariably pentodes - not in triode mode) and the speaker, via the output transformer, also seems to be an important part of how the instrument feels to the player.
Having said all the above, if an absolutely 'clean' sound is what is wanted then a solid state amp can do that very well.
Many effect boxes try to emulate, or simulate, what a tube amp does naturally, and can sound 'processed' to many guitarists.
For (loud) live playing, the interaction between the output tubes (invariably pentodes - not in triode mode) and the speaker, via the output transformer, also seems to be an important part of how the instrument feels to the player.
Having said all the above, if an absolutely 'clean' sound is what is wanted then a solid state amp can do that very well.
Yes. Rod Elliott chose not to emulate this "swirl" in his solid-state design, but others have done it. I built a Fender-style preamp using discrete JFETs that showed similar dynamic bias shifts to the all-tube version, and it can also be done by adding a few extra diodes to the opamp version.
The Rod Elliot article posted by scopeboy was quite helpful to me in getting up to speed, thanks. I hope Louthud does as suggested because I'm not really clear on the benefits of having rails flying up or down when the waveform is controlled by the FX unit. I guess my desire for separating everything has become apparent now so the only plausible box combination that might interest me is amp/speaker and there has to be a bloody good sonic reason for it. I have heard a Crown PA amp play audio recordings. It was not anywhere near hifi and it is supposed to be sonically superior to Marshall heads. So, what I've learned so far is that I am looking to do what has been done before but not really that well. What's a short list of clean MI amps? Has anyone ever looked at or published their FR and distortion profiles like is typically done on stereo gear?
A Marshall head is a sound generator. It distorts hell out of the electric guitar and alters its frequency response radically, then it blasts the speakers with a useless damping factor that lets them throb and resonate out of control.
You can't compare it to a Crown PA amp which is a sound reproducer. It is designed to just take the input signal and make it bigger, while running clean and maintaining control of the speaker. Yes, the Crown has more distortion than many hi-fi power amps, but that small amount of distortion doesn't even begin to be relevant in musical instrument land.
If you thought the Crown was bad, you should try playing your favourite recordings through the Marshall. Then for good measure plug a Les Paul directly into the Crown. 🙂
You are certainly looking to do what has been done before, but I wouldn't be so quick to judge the quality of the existing stuff. Try plugging into a Fractal Axe-FX hooked up to a Crown Macro-Tech amp and a wall of 4x12s, and get back to us. 🙂
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I think the root of the answer has to do w/ the people purchasing them. Most guitar players are old fashioned and superstitious. They want exactly the amp their guitar hero used. They chase this mythical "tone" that they can never quite reach... The guitar player forums are full of such funny posts about tone and swoosh and swirl and crunch, and air, etc. (and everyone probably has a different idea in their had about what those words mean). If they spent a minute learning what actually produces those sounds and went about reproducing them logically, I think 80% of them would be on the same page as Terrences.. Use FX and plug in to the PA w/ the rest of the band.
But, young person wants to sound just like their favorite band who uses this specific amp. Goes to guitar store saying they want to sound just like this band.. Guitar store sells them an expensive tube amp.. Player happy, store happy, tube amp manufacturer happy.. The cycle continues.
(I ordered custom wound pickups for a friend for xmas, and dealing w/ the pickup winder was strange.. we spoke different languages.. I wanted something w/ x magnets and y average mv output and z frequency response...
The winder only spoke in air and shimmer and sparkle and boom, etc.. )
But, young person wants to sound just like their favorite band who uses this specific amp. Goes to guitar store saying they want to sound just like this band.. Guitar store sells them an expensive tube amp.. Player happy, store happy, tube amp manufacturer happy.. The cycle continues.
(I ordered custom wound pickups for a friend for xmas, and dealing w/ the pickup winder was strange.. we spoke different languages.. I wanted something w/ x magnets and y average mv output and z frequency response...
The winder only spoke in air and shimmer and sparkle and boom, etc.. )
What seaker did you use? As already noted, if you want a clean amp, all you need is an ordinary hi-fi or PA amplifier. A hi-fi amp will be clean as a whistle, and most modern PA amps will be too. But speakers are not.
Guitar speakers have a very narrow and non-flat frequency response, which sounds great with guitar but is useless for hi-fi. PA speakers tend to be quite basic too, and very often sound terrible when trying to reproduce wide-band hi-fi.
If you want a system to work equally well for guitar and hi-fi then you need a clean amp (hi-fi or PA) and a hi-fi speaker. That's the hi-fi task sorted. Then you need an FX unit that has enough EQ to recreate the familar sound of a guitar speaker (which the hi-fi amp+speaker will have no trouble reproducing).
Thanks Merlinb and wicked1 (great names to drop together BTW). I was thinking along the lines of a full range speaker or high bandwidth MI driver. They're simple, not too perfect, responsive and if boxed properly can be voiced to taste. I don't think many hifi drivers are sufficiently rugged and perhaps not very exciting. Ditto for a perfect hifi amp. I believe in the random interaction of resonance peaks for creative purposes but what is key is having the amp able to do double duty. The speaker(s) can be the flavor, all we need to do then is switch them out to taste or have another set working in the background. WRT the MacroTech, I'll look for one used but this diy so why not clone it or make something better?
Yup. The Eminence Beta series are perfect for applications like this. And as you pointed out, the power amp is interchangeable, bearing in mind Elliott's points about output impedance and clipping behaviour.
Also some more commercial products similar to what you are planning 😉
MINI-BRUTE II
Home | Jazz Guitar Amplifier: Henriksen Jazz Amp: light, powerful, inexpensive, small, jazz guitar amplifier
Atomic Amplifiers - Products
Also some more commercial products similar to what you are planning 😉
MINI-BRUTE II
Home | Jazz Guitar Amplifier: Henriksen Jazz Amp: light, powerful, inexpensive, small, jazz guitar amplifier
Atomic Amplifiers - Products
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