I am just a starter in guitar amp design and need to know what are the requirements. To say the truth I am not any musician. I looked on youtube and most serious study of the subject is this.
It shows all the myths developed about the guitar tone but I remain with more questions than answers. What I think for sure, the sound of the paper of the speaker plays the major importance, as the harmonic table of an acoustic guitar or of violin does. How really the sound of an amp plays any role?
@JMFahey is the expert as he designs and builds guitar amplifiers for a living, but what I understood from it, is that guitar amplifiers are often deliberately driven into clipping, so their clipping behaviour will influence the sound, and that they often have output impedances high enough to influence the quality factor of the loudspeaker. In fact, they sometimes have a knob to tune the output impedance to whatever the musician likes. Besides, there are tone controls influencing the sound.
If you have a look to the documentary, the musician tries out comparatively different types of bias, rectifier, output tubes, input tubes, tone controls and shows that there is no significant difference. At the end he tries out SS amp with diy controls as head and switches to other speakers, tube heads, I can hear only speaker sound difference.
When I see George, "Tubelab" who designed dozens of tube amps in 50 years and still looking for a better one, I get astonished why not design better speaker diaphragm.
When I see George, "Tubelab" who designed dozens of tube amps in 50 years and still looking for a better one, I get astonished why not design better speaker diaphragm.
It’s a great video, it’s like a PhD research project in tone! The amp does have a tone, he shows that in this video, the conclusion the “tone” is not in any one component, but is related to the signal path architecture. This is why when at the end and he is toggling between amps and his effects pedal fishing box it sounds the same. Speakers and cabinets make a huge difference, because they are last stage before you ears; the final step in the signal path. In hindsight it’s quite intuitive!
Guitar, guitar effect pedals, guitar preamps and poweramps and finally guitar speakers are all part of the musical instrument that shape the tone and all are equally important. Today, you can have all of it (sans the guitar) in one integrated device with a headphone output but the principle still applies, sculpting the tone in building blocks.
As a guitar player:
Yes they do.
My post here largely refers to valve guitar amps as that's what I that's what I use.
Different amplifiers make a huge difference to guitar tone. True when paying (relatively) undistorted, truer still when the amp is overdriven into output stage distortion, and even truer when the amp has a dedicated higher gain distortion channel, where preamp distortion is generally dominant compared to power stage distortion.
In a distortion channel, different manufacturers "voice" their amplifiers differently. As the signal passes through the various gain stages lows are cut - usually in the earlier stages. Distorting a large low frequency signal tends to make the amp "fart out" as it dominates the signal. And throughout the gain stages higher frequencies are controlled too: distorting a signal will generate higher harmonics; too much high-frequency content can make the amp sound "fizzy" and harsh. There is no one right answer to this: different guitarists and manufacturers hear (and voice differently.
"Farting out". "Fizzy and harsh". Great subjective terms! Its the balance of lows and highs in the final signal. Sounds like an EQ problem, and in a way I suppose, it is. But it matters more where that EQ / voicing is applied, as the signal passes through the various stages of non-linear amplification. Just slapping an EQ on the end of the gain channel doesn't suffice. (There is generally EQ there for the player, but I'd argue that the (usually fixed) voicing of the gain stages themselves has a bigger effect).
Then there is the nature of the distortion itself. In general, a solid state amplification stage will transition from clean to clipping harder than most valve/tube - say - so the harmonic content of that distortion will differ. But that is not to say that all valve amplifiers sound the same, and all solid-state amplifiers sound the same.
Clean channels are less different, tonally. You'd expect that, as the amplifier is now just making the signal bigger. But even there, tone-shaping/ voicing can be different between manufacturers.
There's other factors in valve amplifiers: tube rectification (and the resulting voltage sag as the amp is driven) can affect tone,, and the amount of negative feedback around the output stage affects the tone too.
As I said earlier: what I have scribbled out here applies to valve amps; I have far less experience with solid-state guitar amps. I have no doubt that it is just as possible to engineer a great sounding solid state amplifier - the task is the same, after all. But I've not found one yet, though in truth I'm not really looking..
As others have mentioned, effects pedals, speakers, cabinet construction (open- or closed-back) also make a big difference. And DSP modellers are rapidly becoming the great game changer here as well. But I'll not go there: the OP asked about guitar amps...
Cheers!
Ant..
Yes they do.
My post here largely refers to valve guitar amps as that's what I that's what I use.
Different amplifiers make a huge difference to guitar tone. True when paying (relatively) undistorted, truer still when the amp is overdriven into output stage distortion, and even truer when the amp has a dedicated higher gain distortion channel, where preamp distortion is generally dominant compared to power stage distortion.
In a distortion channel, different manufacturers "voice" their amplifiers differently. As the signal passes through the various gain stages lows are cut - usually in the earlier stages. Distorting a large low frequency signal tends to make the amp "fart out" as it dominates the signal. And throughout the gain stages higher frequencies are controlled too: distorting a signal will generate higher harmonics; too much high-frequency content can make the amp sound "fizzy" and harsh. There is no one right answer to this: different guitarists and manufacturers hear (and voice differently.
"Farting out". "Fizzy and harsh". Great subjective terms! Its the balance of lows and highs in the final signal. Sounds like an EQ problem, and in a way I suppose, it is. But it matters more where that EQ / voicing is applied, as the signal passes through the various stages of non-linear amplification. Just slapping an EQ on the end of the gain channel doesn't suffice. (There is generally EQ there for the player, but I'd argue that the (usually fixed) voicing of the gain stages themselves has a bigger effect).
Then there is the nature of the distortion itself. In general, a solid state amplification stage will transition from clean to clipping harder than most valve/tube - say - so the harmonic content of that distortion will differ. But that is not to say that all valve amplifiers sound the same, and all solid-state amplifiers sound the same.
Clean channels are less different, tonally. You'd expect that, as the amplifier is now just making the signal bigger. But even there, tone-shaping/ voicing can be different between manufacturers.
There's other factors in valve amplifiers: tube rectification (and the resulting voltage sag as the amp is driven) can affect tone,, and the amount of negative feedback around the output stage affects the tone too.
As I said earlier: what I have scribbled out here applies to valve amps; I have far less experience with solid-state guitar amps. I have no doubt that it is just as possible to engineer a great sounding solid state amplifier - the task is the same, after all. But I've not found one yet, though in truth I'm not really looking..
As others have mentioned, effects pedals, speakers, cabinet construction (open- or closed-back) also make a big difference. And DSP modellers are rapidly becoming the great game changer here as well. But I'll not go there: the OP asked about guitar amps...
Cheers!
Ant..
What I retain from the explanation,
"Clean channels are less different, tonaly."
The sound of the diaphragm paper is the major actor with less than 10% for the tone of the power amp.
I am still in doubt when I see Tubelab is struggling to design his Nth amp after 50 years, with no mention to which speaker it needs to mate it with. As if the amp is 100% of the tone.
"Clean channels are less different, tonaly."
The sound of the diaphragm paper is the major actor with less than 10% for the tone of the power amp.
I am still in doubt when I see Tubelab is struggling to design his Nth amp after 50 years, with no mention to which speaker it needs to mate it with. As if the amp is 100% of the tone.
Why don't you start a thread about making your own guitar loudspeaker diaphragm then? Questions about Tubelab can best be asked to @Tubelab_com
Take the alinico magnet speaker for example.
If I had to design the power stage, I would choose open loop single pentode 6L6GC. Why?
The alnico magnet material has very stiff acoustic character that in mid frequencies when the VC provokes acceleration, the alnico pole piece provides the VC more reactive force than soft iron. Even though Eminence uses steel for pole piece it is not acoustically as hard.
By this, the person who chose this expensive speaker needs very high presence as horns have.
The class A biased pentode, magnetizes the output transformer, when a negative going voltage on its gride decreases the current, the magnetic field collapse, spits electrons in the VC overcoming the high inductance of the VC. This fiers acceleration along with the alnico's reaction results very high presence. On the other hand when the gride voltage increases, the pentode will pull more current from the voltage supply , instead of electron spit the speaker sees voltage and decides accordingly the current it would pass through, resulting less presence. Hence, the player by choosing the direction of scratch can modulate the presence.
If I had to design the power stage, I would choose open loop single pentode 6L6GC. Why?
The alnico magnet material has very stiff acoustic character that in mid frequencies when the VC provokes acceleration, the alnico pole piece provides the VC more reactive force than soft iron. Even though Eminence uses steel for pole piece it is not acoustically as hard.
By this, the person who chose this expensive speaker needs very high presence as horns have.
The class A biased pentode, magnetizes the output transformer, when a negative going voltage on its gride decreases the current, the magnetic field collapse, spits electrons in the VC overcoming the high inductance of the VC. This fiers acceleration along with the alnico's reaction results very high presence. On the other hand when the gride voltage increases, the pentode will pull more current from the voltage supply , instead of electron spit the speaker sees voltage and decides accordingly the current it would pass through, resulting less presence. Hence, the player by choosing the direction of scratch can modulate the presence.
Hi Hayk,
As I think about it, that sounds sort-of right. On the video you linked, I would say that sounds there were not particularly high-gain by today's standards. I'm sure you will have discovered other videos on this with people demonstrating far higher gain tones.
Modellers and DAWS can load IR responses for different cabinets and speaker types, often with varying mic types and positions. And for the pedal board user, there are standalone IR loader pedals to do the same trick. Not sure if I would build it into an amp though, unless you were going to take a direct out from the amp to the PA / recording interface ((bypassing any speakers), or if the amps speaker system was a full range, flat response (FRFR) type.
Cheers!
Ant
As I think about it, that sounds sort-of right. On the video you linked, I would say that sounds there were not particularly high-gain by today's standards. I'm sure you will have discovered other videos on this with people demonstrating far higher gain tones.
This is quite commonly done already
Modellers and DAWS can load IR responses for different cabinets and speaker types, often with varying mic types and positions. And for the pedal board user, there are standalone IR loader pedals to do the same trick. Not sure if I would build it into an amp though, unless you were going to take a direct out from the amp to the PA / recording interface ((bypassing any speakers), or if the amps speaker system was a full range, flat response (FRFR) type.
Cheers!
Ant
Part of my "problem" stems from my ADHD powered brain that changes its mind before I can finish one. True, I have made lots of guitar amps over a period of 60 years, and they weren't all tube amps. There were some long periods of time when I didn't make any at all, and even a few years when I didn't even own a guitar. Did they all sound the same? NO.
There were three different time periods in my life when I made guitar amps. From age 10 through 20 I started making amps from parts taken from dead TV sets. I even sold a few of them to buy some parts like a 'real" guitar speaker. At age 15 I got a job in a TV repair shop fixing TV's, and at 17 I was running the service department in the largest Olson Electronics store in the country. All my earnings went to build stuff, from guitar and HiFi amps to music synthesizers.
At 20 I got the job at Motorola making more money than I could spend, so I quit building amps and concentrated on primitive 8 bit computers and music synthesizers powered by those computers. My Hagstrom had been stolen and I had no guitar. I played the synths through a Kustom K-200 PA amp that I got cheap because it was "unrepairable." It did take a lot of parts to fix it. I made clones of all the SWTPC amps, as we got the silicon free by filling out sample request forms. I used some of them for guitar amps but most went for home and mobile HiFi amps. This was in the 70's so my shagmobile Chevy van had 9 channels of Tigers!
By about 1990 my home HiFi rack contained Carver and Phase Linear stuff and I was content with it. I still had my first car a 1949 Plymouth which still ran fine. A friend and habitual junk collector saw it and proposed a trade, some of his "stuff" for my old car. I went to see his old junk and found a Scott 272 tube amp and matching tuner, so the trade was made. After fixing the old Scott, it promptly kicked the Carver stuff right out of the rack and I haven't built or listened to a solid state amp since.....except for one which is still being developed.
Take several different amps and play them at a volume level that's maybe 25% of its rated power output so it is not being pushed into the distortion zone. There are still from one to three (or more) tone controls that can alter the tone of each amp. Every amp builder has the freedom to choose the component values that gives him the "tone" he wants. Tahe two identical amps, change the value of a few caps in one of them, and it won't sound the same as the other. Push that amp into distortion and compare it to something similar also pushed into its nonlinear region and there will be differences. No two tubes will distort exactly the same way. Two "identical" output transformers could have subtle differences, but the real variable element here is now the speaker.
Most guitar speakers have their resonant impedance peak within the guitar's frequency range. At resonance that "8 ohm" speaker could be 30 ohms or more. No two will be exactly the same, and the depth and frequency of the peak is affected by that cabinet, and any other speaker in that cabinet.
The real variables are not the amps. Yes, every amp is different, especially when pushed out of its linear operating region. No two guitars are the same. Identical pickups aren't. But....
....Many years ago I had dragged a DIY solid state guitar amp I had made using a "Lil Tiger" 20 watt power amp and a DIY SS preamp copied from something I had reverse engineered into a classroom at adult education night class along with my guitar and proceeded to demonstrate my ability to crank out Magic Carpet Ride, or some other popular 60's or 70's tune when an older guy came up to me and said "gimme that thang." Without turning a knob, he cranked out some really neat country guitar pickin that I did not even think could come out of my guitar and amp. No two guitar players are even close to the same. Even when playing the same note in the same song in the same style, there will always be differences in dynamics.
Now, what do I want to build? Well for one, I have no problem building just about anything with electronics. From cell phones and two way radios to simple circuits, I can do it. Speakers, cones and cabinets, I would not know where to begin. I have seen some of the rocket science simulations used to model the air flow and flame front travel in modern automotive cylinder heads and come away amazed. Want to make the world's best speaker, go learn how to do that stuff. It's way beyond me. I have learned from experience that even the wood used in the cabinet makes a difference. MDF has no sound. It's dull and lifeless, which some prefer. OSB is brighter, plywood, brighter still, and yellow pine has a distinct tone all its own which diminishes when covered in Tolex.
We had a boss who told his mechanical engineering team to design a plastic housing for a police and fire walkie talkie. He stated that he would pour lighter fluid on it, light it on fire, wait 1 minute, toss it into a muddy puddle, then drive over it with the front and rear wheels of his Ford Explorer. He would then extract it from the puddle, dunk it into a bucket of water for cleaning, and it better work. I watched the official demo and the radio performed as expected. This happened over 10 years ago, I'm sure that modelling tools have improved further still.
I tend to play my guitar through my PC today, but I need to make a guitar amp or three while I still can. Shaky hands and table saws are not compatible. Those shaky hands don't play the guitar so well today either, but part of that is lack of practice. Right now, I am mostly playing 60's surf music since that's what I learned on, but that may change. There is no "one size fits all" guitar amp, but I will try to make something that I will use.
Since persistent bad weather has limited my outdoor table saw time, I have come up with a shortcut suitable for trying out some experiments. I found this old Crate amp in my shed. It looks rather nasty, but maybe it will clean up. I relieved it of its chip amp guts and ordered a suitable chassis from Amazon that will contain a tube amp. Not sure if the 10 inch speaker works yet though.
Attachments
What he did was turn every knob up to full clockwise (which is bad, that's not where you get different and more playable tones), and then he posted the video on youtube which uses lossy compression that removes all the smaller differences in the sounds because it doesn't think you need to hear them (and if the video was recorded with a phone, it was already lossy compressed once). The differences in speaker FR is something that lossy compression algos think should be mostly left intact for you to hear, which is why you hear that.
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You need to try out some guitar amps in a place where its quiet so you can hear (i.e. not in a noisy guitar center). There are 4 guitar amps here at the moment, and each one can drive the speaker cab of any other one. There is a Blues Jr. with an Alnico Celestion, there is a Marshall 18-watt with a Ferrite magnet Celestion, there is a sold state amp with an 8" Eminence speaker, and Mesa Boogie MkIIc with JBL speaker.
The amps themselves all sound different; the speakers sound different too. The amps can be adjusted in and played in different ways. And certainly they are best played with the knobs not turned up fully CW. It isn't just about things like choice of 6L6, EL84, etc., either. Everything affects the sound, including the guitar cable (because of its capacitance interacting with pickup inductance), if the cabs are flat on the floor or tilted back, the player, etc.
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there are myriad numbers of drivers that can be used, most don't change the 'sound' by that much either
this stuff is designed to reproduce, not color
Not necessarily true for guitar speakers. They are ribbed differently to control cone breakup modes, they use paper surrounds for a less hi-fi sound, they have different intentionally shaped FR, etc. Of course the cabinet has a lot of effect on the sound too. Many cabinets are designed to be light weight (open or closed back), but they can resonate badly. Best not to stuff them with damping material, better to brace the inside of the cabinet (I use maple, a tone wood for that).
Even without distortion, HF finger noise on the strings could be unpleasant. It would be like listening to high definition lip smacks and tongue clicks in singer. Good technique can help but not completely eliminate since the strings have to be touched.
I currently have about 22 guitar amps (almost all that I have built) and 10 different speaker cabinets, along with another 15 or so raw drivers and about 20 electric guitars. Each and every component has its own sound, though some are more similar to others if they are of similar design. They each exhibit their own clean and distorted characteristics - they are designed to do exactly that - be different from each other.
Guitar speakers are not intended to reproduce sound - they are intended to sound in very particular ways, and as a result, have very different synergies with different cabinets, driver combinations, amps, tubes, and guitars, among myriad other components.
It is useful to think of electric guitars and amps as one instrument with two components that can have significant effects on the combined sound. If the goal is to make one amp sound the same as another, there are a lot of ways to make that happen, or at least, appear to happen. That is reductionist in my view, and does not accurately reflect the reality of the many ways that electric guitar players can change the sound of their rig.
Guitar speakers are not intended to reproduce sound - they are intended to sound in very particular ways, and as a result, have very different synergies with different cabinets, driver combinations, amps, tubes, and guitars, among myriad other components.
It is useful to think of electric guitars and amps as one instrument with two components that can have significant effects on the combined sound. If the goal is to make one amp sound the same as another, there are a lot of ways to make that happen, or at least, appear to happen. That is reductionist in my view, and does not accurately reflect the reality of the many ways that electric guitar players can change the sound of their rig.