Sometimes wiki is an excellent source of information, in this case however it is not.
Guitar tube amps for probably the last 40 years generally have very large power transformers as do solid state. While I know a popular mod is to increase the size of the transformer, in most cases you're already dealing with a pretty large, high quality transformer.
The primary reason tubes sound the way they do in guitar, and there is a lot of speculation and debate as well as theories that are widely accepted, is in my opinion plate voltage. The sonic difference you hear between analog chips, digital chips verse tubes is the massive difference in voltage driving the tubes and your signal.
Lets say you want to start a fire and you can use kerosene or gasoline.
Essentially the chips are running on kerosene, the tubes on gas. Once you identify the specific character of this power difference, you realize there's hardly a difference at all. What "they" call warmth is really just the sound of more voltage driving your signal so it has a bit of a richer sound. The notes like to decay more evenly and tend to be a bit denser. The more obvious and primary differences you hear are due to the tone stack design, the speakers and the cabinet. One of the most common traits of tube amp designs that I don't often see in solid state or digital is "natural" frequency modulation. This occurs from the bandwidth footprints of the preamp, power amp and speaker sections interacting with one another.
More or less you get a bit of a wah-wah sound. In some cases it's really potent, others it's more mild but ultimately, it can be recreated in any amp with the right circuitry. It can also be recreated by a single circuit be it used in the preamp stage or the power amp stage. I've successfully done it in both.
If you really want your solid state to sound like a tube amp, upgrade your power transformer, mod your preamp's tone stack and build your own boutique overdrive pedal.
If you fiddle with these circuits enough, you can pretty much get the sound of any tube amp and well beyond. In my opinion, tube amps are really just a sales gimmick at this point. Before long, digital will dominate the market as it's more versatile and affordable. The claim that tube costs more to build is pretty much rubbish. For you or I to build a tube amp, sure. For a corporation buying parts in massive quantity, their tube models probably only cost 10-15% more to build than their solid state. Meanwhile, the profit they make off those tube amps are literally 10 times what they make off the solid state.
So, they dumb down the solid state amps like Marshall switching from the HFX to the DFX. They also like to use economy sized cabinets with the solid states so they sound thinner and sharper. The tube heads always come with full sized cabinets.
Switch your solid state to a full sized cabinet with higher quality speakers. That upgrade alone will allow a $300 S.S. head to rival a $1200 tube head.
Sorry, complete rubbish - valves amps cost LOAD's more to build than solid state ones, it's ludicrous to suggest otherwise. The biggest cost is transformers, valve ones need to be MUCH larger (as valve amps are so inefficient), and they require two of them instead of one.
Some people like the low quality sound from valves, you can't make a transistor sound that bad - but valve distortion is gradual and even harmonics, transistor amps are sudden and harsh odd harmonics.
There are many great sounding transistor guitar amps, and they don't 'dumb them down', valve cabinets have to be stronger due to the much higher weight they carry.
Some people like the low quality sound from valves, you can't make a transistor sound that bad - but valve distortion is gradual and even harmonics, transistor amps are sudden and harsh odd harmonics.
There are many great sounding transistor guitar amps, and they don't 'dumb them down', valve cabinets have to be stronger due to the much higher weight they carry.
Johnny,
Any chance that you have some arguments that support this outrageous claim?
jd
you dont need two tubes.
Edcor makes a 15 watt output transformer for $17
The cabinets dont need to be much stronger just a good base for the transformers.
a 2n6678 weighs more than a 9 pin tube
as for the gradual harmonics a or a simple relaxation oscilator fed by the audio singal or a reverb which is then fed to a double balanced fet mixer will give you those steady harmonics. Thats one of the biggest problems in heterodyne design. the output of an rf mixer gives you both original signals which become parasitic then it gives you all the way up to the 8th harmonic and sometimes even higher along with their reciprocal. this unfortunately removes the original signal. solution? use a simple fet audio mixer to mix the original signal back in with the harmonics. you probably wont want more then the second harmonic so a filter can be placed on the output of the diode mixer.
eitherway i think your going to get in over your head doing a whole amp instead of something smaller than can be plugged in between the amp you have and the guitar like an effects pedal is.
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Have you scoped the output waveform before and after the added transformer while run into clipping? Back in the day when I was playing my Hofner alternately through a Fairchild tube power amp and a SWTP Tigersaurus solid state, I was scoping them. The waveforms were very different when overdriven. The SS amp just clipped off top and bottom, creating harsh harmonics (and getting very loud). When the Fairchild was overdriven, the waveform buckled at zero cross, literally crunched, creating warm, low order harmonics. I have no idea why the tube amp buckles at zero cross, if it's the nature of the tubes, the tranny, or what?
Marty
Marty
Tubes sound they way they do because the electrons have to travel though a vaccum and that has a soft attack so smoother highs. If the plate voltage is in the sweet area for the tube, then the tube is fast, but the attack is slow so low harshness on highs.
Solid state devices, except for MOSfet and FET, have a fast attack and produce harsher sonics unless the circuit design is good. Also, great sounding Hi-Fi amps use pretty expensive out transistors that are usually higher impedance and slower attack, faster speed devices, so smoother sonics.
Older guitar amps like VOX used the transformer driver circuit and had fantastic tube like overdrive.
Tube out stages crunch in the middle because the whole circuit is being overloaded, it is both the tubes and the reflected crunch back from the secondary of the out transformer.
I re-stored a Gibson BR-1, 1946, last month, and every guy that came in went right over to that amp drooling, proof is in what was used on what hit songs....
Solid state devices, except for MOSfet and FET, have a fast attack and produce harsher sonics unless the circuit design is good. Also, great sounding Hi-Fi amps use pretty expensive out transistors that are usually higher impedance and slower attack, faster speed devices, so smoother sonics.
Older guitar amps like VOX used the transformer driver circuit and had fantastic tube like overdrive.
Tube out stages crunch in the middle because the whole circuit is being overloaded, it is both the tubes and the reflected crunch back from the secondary of the out transformer.
I re-stored a Gibson BR-1, 1946, last month, and every guy that came in went right over to that amp drooling, proof is in what was used on what hit songs....
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Interesting points. As I remember, an output transformer setup is designed to match the impedance of the speaker, which is frequency dependent near resonance, so it really can't be done well on a bass amp. A normal solid state amp has a low output impedance. Sounds like this could make a huge difference in dampening factor, keeping control of the cone in a high Q box, with very audible differences.
Regarding the reflections back from the transformer, I'm thinking of two sources, impedance mismatch between the secondary and the speaker, and over-driving the iron core. Both would be frequency dependent, no? Adding dollars (iron) to the tranny would reduce the second factor, but not the first?
Please excuse me if I'm off the rails here, I haven't worked in this particular area since 1974
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Regarding that off the wall post about "hearing voltage", I can see how someone might come to that conclusion. High voltage devices have to be driving transformers, low voltage devices usually aren't. That's got to introduce a whole pile of variables in matching and the nature of distortion, of course having nothing to do with voltage as such.
Marty
Interesting points. As I remember, an output transformer setup is designed to match the impedance of the speaker, which is frequency dependent near resonance, so it really can't be done well on a bass amp. A normal solid state amp has a low output impedance. Sounds like this could make a huge difference in dampening factor, keeping control of the cone in a high Q box, with very audible differences.
Regarding the reflections back from the transformer, I'm thinking of two sources, impedance mismatch between the secondary and the speaker, and over-driving the iron core. Both would be frequency dependent, no? Adding dollars (iron) to the tranny would reduce the second factor, but not the first?
Please excuse me if I'm off the rails here, I haven't worked in this particular area since 1974
.Regarding that off the wall post about "hearing voltage", I can see how someone might come to that conclusion. High voltage devices have to be driving transformers, low voltage devices usually aren't. That's got to introduce a whole pile of variables in matching and the nature of distortion, of course having nothing to do with voltage as such.
Marty
Interesting suggestions. Ive started making a couple tube amps(12k5 tube version of Zen), and so far my experience confirms that transformers certainly do make the sound more musical. I have a problem with distortion at the high volume end for my simple amps though. Sound is sweet till it does that;( I think what i need is tone controls and tone stack circuits. Any suggestions would be appreciated.
Hi Chris,
I've slotted the amp and guitar build as a summer activity so I'll resume work on those then. The preamp is the big part of the project (Ampeg VH140 clone) and I have that nearly finished.
Good that it's still going. If you have a spare transformer, perhaps you could try the mod, too (one speaker with the transformer, one without, AB testing). It's easily reversible, but you might decide to keep it anyway.....
Chris
Well, recently we (me and Dad) have been trying to make a soft clipping circuit for the power amp side. The idea is that when the signal comes within 10V of the power supply rails, it begins to attenuate the signal into the power amp. The result should be a clipping waveform similar to that of valves... All on a 2" square bit of stripboard.
We haven't got it completely working yet, but more progress shall be made tonight.
We haven't got it completely working yet, but more progress shall be made tonight.
FET's... or maybe some back to back diodes, perhaps even in the feedback loop of an opamp... maybe... ish
Hmmmm...
These hybrids sound interesting. The problem for me is that I'm young and restless - putting valves into the mix would mean lots of money spent replacing valves. So, for now, I'm trying to make a completely SS amp sound valvey...
Interesting development today...
I added a few turns of my own wire on to the transformer, to give approx 2.5V output. This I fed to a slave amp (using windings instead of earthing removes ground loop problems), through an old pair of PA speakers. Nice sound. Very very loud, when needed (well, 2x12" at 100W, what's expected?).
Chris
These hybrids sound interesting. The problem for me is that I'm young and restless - putting valves into the mix would mean lots of money spent replacing valves. So, for now, I'm trying to make a completely SS amp sound valvey...
Interesting development today...
I added a few turns of my own wire on to the transformer, to give approx 2.5V output. This I fed to a slave amp (using windings instead of earthing removes ground loop problems), through an old pair of PA speakers. Nice sound. Very very loud, when needed (well, 2x12" at 100W, what's expected?).
Chris
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