Has anyone used a class D amp for guitar? I am curious about using something like the TA2024 for a small practice amp. I did a bit of searching and could not find any information on how it sounds and takes being overdriven.
It's a really bad idea to over drive ANY solidstate power amp - and you should certainly never do so with a Class D one.
Class D has completely "invaded" electric bass amplification but mainly because lots of players use hundreds or a thousand watts or so and get most if not all their sound at the preamp level and through the speakers. The size and weight reduction is a big factor. Class D would make a fine guitar practice amp so long as you follow the same plan in getting the sound, athough the interplay between tube output stages and speakers is usually given a lot more consideration for guitar.
I understand the advantage of class D for bass, you need a lot of clean power to make a lot of sound. But with guitar the amp overloading is a part of the sound generation. And no, it is not any worse if a solid state amp gets overdriven as long as you are happy with the sound.
I have made a few guitar amplifiers running class AB in the past but have no experience with Class D when they hit their maximum output capabilities.
My preamp section will have it's own distortion signature but let's face it, at some point in time the output stage will be driven beyond maximum. Just the nature of guitarists. The question is what does it do to the sound?
I have made a few guitar amplifiers running class AB in the past but have no experience with Class D when they hit their maximum output capabilities.
My preamp section will have it's own distortion signature but let's face it, at some point in time the output stage will be driven beyond maximum. Just the nature of guitarists. The question is what does it do to the sound?
The overdrive performance of class D amps is pretty much Bad, meaning basically there is nothing to be desired there. Without having actually tried it a lot I'd say the conventional triangular wave carrier / comparator type modulation schemes will give the mildest clipping, but I doubt it's going to be a sound you want. With the cartloads of signal level overdrive circuits being done for guitar I seriously doubt you could beat the sound with a clipping class D amp. It probably wont kill your amp, but it will probably make you want to turn it down.
From my experience with small class-d amps; when they are driven into hard clipping they produce a sharp clicking sound on top of the heavily distorted audio signal.
Not the least bit desirable.
Not the least bit desirable.
That sounds like something especially a self oscillating circuit would do. IIRC Marshall once did a push-pull transistor guitar amp with an output transformer. I suppose you could add a transformer in the output of a class D output stage, even split it apart into two push pull section with N devices, with the feedback coming off the transformer. Maybe you could fiddle with the shape of the carrier to try simulating the compression of hard driven tubes. It could get pretty fancy. By the time you were done you'd probably have most if not all of a tube amp, at whatever output capacity. 🙂
You can build a practise amp with a class D amplifier. Why not a TA2024? Only thing is, it's stereo.
If I was going to do this, I'd run it into a regular efficient guitar speaker in an open back cab A small Celestion or Jensen. Two in the case of a stereo amp. I'd buy a Sansamp or other DSP amplifier emulator/effects pedal (Behringer V-amp?) and use it as a front end. I'd fiddle with the main volume control between the Sansamp and the class D so that you couldn't overdrive it.
That's probably not quite what you had in mind, but it would probably give you the most satisfactory outcome.
w
If I was going to do this, I'd run it into a regular efficient guitar speaker in an open back cab A small Celestion or Jensen. Two in the case of a stereo amp. I'd buy a Sansamp or other DSP amplifier emulator/effects pedal (Behringer V-amp?) and use it as a front end. I'd fiddle with the main volume control between the Sansamp and the class D so that you couldn't overdrive it.
That's probably not quite what you had in mind, but it would probably give you the most satisfactory outcome.
w
I was just cruising EBay for a small amp to throw in a box as a practice amp. A guy I work with is retiring and I was going to throw something together for him since he liked an amp I built years ago.
Not really planing to do much development, have a few ideas on the preamp, people have done a lot of work since I played around with the stuff. I just thought if I could shed a few pounds of transformer weight he might appreciate it. Just looking for 10w to put into a 8 ohm speaker.
Did some reading on the TA2024 and got the impression it would start to distort but continue putting out power. Some of what I read makes me think it might be the protection circuitry that causes some of the funny sounds. I think I may pass on giving it a try for mow.
So now I was thinking of a TDA2030 or possibly a TDA2005 in bridged configuration. Then I can spend my time playing with the preamp section.
Not really planing to do much development, have a few ideas on the preamp, people have done a lot of work since I played around with the stuff. I just thought if I could shed a few pounds of transformer weight he might appreciate it. Just looking for 10w to put into a 8 ohm speaker.
Did some reading on the TA2024 and got the impression it would start to distort but continue putting out power. Some of what I read makes me think it might be the protection circuitry that causes some of the funny sounds. I think I may pass on giving it a try for mow.
So now I was thinking of a TDA2030 or possibly a TDA2005 in bridged configuration. Then I can spend my time playing with the preamp section.
It certainly is, I've never met (or heard of) anyone who likes the unplesent sound of a solidstate output stage clipping - apart from the fact you're VERY likely to kill the amp as well (and the speakers).
Fender transistor amps commonly had circuitry to prevent clipping, as does my class D PA amp.
If you want distortion in a transistor amp, use ovedriven preamp stages.
This is where we have to disagree, though. I've heard of many recordings made with small amps like Pignose 7-100, LM386 variations etc. and that's solely SS power amp overdrive. In most amps, when cranked, PA clipping is inevitable and still there are numerous recorded (pun intented) usages of SS amps by many pro musicians. Besides all that, there are also some SS designs that focus on creating soft clipping in the power amp - albeit these examples are rare and most of the SS power amps do indeed clip rather nastily.
Still, there's enough contradictory in performance of various SS guitar amp designs that you really can't make a rule of thumb out of SS power amp clipping sounding bad.
Yet, I think a class-D amp will have much less possibilities to modify the circuit to clip in a pleasing manner - even less when it's on an integrated chip.
Still, there's enough contradictory in performance of various SS guitar amp designs that you really can't make a rule of thumb out of SS power amp clipping sounding bad.
Yet, I think a class-D amp will have much less possibilities to modify the circuit to clip in a pleasing manner - even less when it's on an integrated chip.
Yes, we'll have to agree to disagree 😀
Many recordings use solidstate amps, but they don't drive them in to clipping - they use solidstate in preference to valve to get much higher quality.
The guitarist that had me build him an amp after I lent him mine went the tube route buying small fender amps and the like. He was not really happy till he played through mine, He was so impressed that he had some of his buddies try it and they wanted some also. I did not want to get into making a lot of them and ended up selling my original and made a practice bass amp for myself.
I used to have the schematic of it but that was about fifteen years ago and I have just a vague idea of what I did for the power amp.
The amp put out about what the speaker could handle, being an open back cabinet the speaker would physical compress the sound without overheating. Whether the amp lost its feedback and then its dampening factor giving the speaker a ballsier sound I can not say. Should have played with it more. As long as the speaker can handle the power and the excursion it does not care if the amp is in clipping.
Now if you design an amp without profit in mind then you might end up beefing up the output transistors so that they can take the maximum power and current through them. The transistors do not care if they are operating in their linear region or in clipping. All they care about is their safe operating area.
In fact if the transistors are in clipping they are operating in switched mode and they have less voltage across them. They are probably happier that way if they can take the current. The power supplies were also not that stiff, giving compression when needed. I tend to oversize the diodes so it is a question of the transformer taking the heat. If it can the amp does not care if it is in clipping.
More than anything that amp was just a happy accident the result of parts I just had laying around. One thing I did not have in it is any protection networks because it was built robustly. Using a chip amp may cause some issues when it is overdriven but the guy I am building it for more than likely will not crank it up that far.
I've played around with output transformers for a while. Even tried it with my little tripath amplifier. I find that, while they don't make a massive difference to the sound, they do bring SS a step closer to the valve sound.
I use a Boss ME-20 pedal to provide distortion and stuff, and it sounded really good. Went pretty loud, too. I didn't have a problem with SS distortion: the amplifier stayed clean for as loud as I wanted it (being a teenager, that wasn't exactly quiet). So I declared it good. I even made a pre-out for my guitar amp (class AB combo), so it could run the tripath amplifier aswell, resulting in more power!
Chris
Why overdrive class D
Class D has been around for decades. I have an old PYE broadcast quality limiter, designed in the early seventies to be devoid of distortion. Why want to overdrive class D ?. It is a bit like buying a Jag and driving it into a brick wall.
Get more power than you need and choose the overdrive style you want in the pre-amp, tube, FET, tranny Fuzz etc.😉
Class D has been around for decades. I have an old PYE broadcast quality limiter, designed in the early seventies to be devoid of distortion. Why want to overdrive class D ?. It is a bit like buying a Jag and driving it into a brick wall.
Get more power than you need and choose the overdrive style you want in the pre-amp, tube, FET, tranny Fuzz etc.😉A well designed class D amplifier should be able to handle clipping - this means that the engineer designing it took careful consideration of thermal issues. What I'm saying is, a class D amplifier isn't necessarily afraid of clipping, so long as there's adequate cooling. What does cause a class D amp to fail is overvoltage, because the switching mosfets will fail from the voltage spike.
Now, why would you ever want to overdrive a SS poweramp section anyways? It's not a good sound. As someone else suggested, just get all of your overdrive from your preamp section and you'll be fine.
Now, why would you ever want to overdrive a SS poweramp section anyways? It's not a good sound. As someone else suggested, just get all of your overdrive from your preamp section and you'll be fine.
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