Solid State Power Amp Classes? Need help

[rsf1977]

I'm looking to get a solid state power amp for my axe-fx modeller to power (2) 4x12 guitar cabs. I'm new to solid state amps and I noticed they all seem to use different class amps, like:

• Crown K1 - Class B amp
• Crest CD 1500 - Class D amp
• Carvin DCM1500L - Class AB amp

Are there any that are more suited for this application then others? Are some just a bad idea?

 

[Metaltastic]

I'm really not certain about different power classes, but I am pretty certain that the most ear-pleasing variety of solid-state amplification is MosFET technology; I don't know of any current MosFET power amps currently available (at least, none that are remotely affordable), but I'd vote scouring ebay for a Tubeworks Mosvalve (MV-962) or Hafler/Digitech (they were sold as both) G150! (the G150 is the better option IMO, as it has a dedicated output for running it in bridged mono, though I guess since you're gonna use two 4x12's that isn't an issue unless one of the cabs has a passthru output)

 

[rsf1977]

well in case you aren't familiar with the axe-fx it has tube power amp modelling so if the units above color the sound like a tube amp, i'm not really looking for anything that sounds tube-y since i'm already producing that part of the equation. Basically, looking for a flat response full range power amp that will represent whatever signal the axe puts out as faithfully as possible. I play really low in drop-A so it needs to be able to handle some bottom end tightness more then usual.

 

[rsf1977]

bump

 

[tarnationsauce2]

Class D is best for low frequencies. Extremely efficient and low heat generation but piss-poor sound at higher frequencies (usually filtered out). Ideal for live sound subwoofers. Usually high power 100+ watts.

Class B is somewhat efficient and gets fairly hot. But has some unpleasent distortion (crossover distortion) at lower volumes. When ran hard the crossover distortion is too little to hear. Not suitable for musical applications, except maybe concert level stuff or for a megaphone.

Class A is not efficient and generates a lot of heat and consumes energy, even at idle. This class has no crossover distortion and is very linear. An audio purist's amplifier. Class A can also have reliability issues due to the excessive heat. When class A is pushed distortions appear more gradually (great for mic-pres). Usually lower power 100w or so.

Class AB is somewhere between class A and B in efficiency and heat generation. At lower volumes it operates in class A mode and when pushed hard switches to class B mode. This class is probably most common in stereo amps. Pretty reliable and distortion is low right until the point of clipping, then it is suddenly clips with a harsh sound. Higher power 100+ watts.


So if you are relying on your modeler for all the mojo sound and plan on running your amplifier in the linear region at all times (turn down if you ever see clip LEDS), I would use a class AB amp.

 

[rsf1977]

thanks for the info. My Carvin DCM1540L is class AB. I have my doubts about it being the best solution after reading a lot about failures and being on the cheaper end of the spectrum. Any suggestions for some AB amps out there?

 

[rsf1977]

what about Class G & H any thoughts on those?

" Class G: The power supply voltage in thee amps changes from a lower level to a higher level when larger output swings are required. This is accomplished by utilizing a single class AB output stage connected to two power supply rails by a diode, or a transistor switch. For the majority of program material, the output stage is connected to the lower supply voltage, but it automatically switches to the higher rails for large signal peaks. One other approach uses 2 class AB output stages, each one connected to a different power supply voltage. The strength of the input signal determining the corresponding signal path."

 

[Wolfeman]

In guitar applications, class AB is usually the way to go, it works out well. tarnationsauce2 pretty much explained it in a way everyone should understand.

 

[Wild Hades]

Class D is best for low frequencies. Extremely efficient and low heat generation but piss-poor sound at higher frequencies (usually filtered out). Ideal for live sound subwoofers. Usually high power 100+ watts.

What frequencies are you talking about, concerning the high filter? According to Bode graphics and the specifics (Hypex models i.e.), class D power amps seems to start filtering at 15-20 KHz depending on the load, which is pretty much non-influent for guitar sounds, considering the frequency response of the cabinet...
Am I missing something?

 

[Notuern]

I would try to find a TubeWorks MosValve.
I own one, and its great for this kind of stuff.. it doesnt colour the sound that much, but it still adds somewhat of a tube-warmth to it even though its SS.

 

[aortizjr]

For SS MosFET's are probably the best at simulating tube-like response which works for your typical pre-amps.

The AxeFX is a whole new thing that does tube modeling really well. So you will probably want the most "uncolored" amp you can get.

I would personally go Class-D with a switchmode power supply for the light weight and less heat. Guitar is mostly low mids and mids anyway so Class-D will be perfectly fine. 15-20K who cares on guitar? Especially at loud ass live volumes! Not to mention the THD even then is probably still .01 vs. .001. Speakers, especially guitar speakers, have THD's much much higher than that. Speaking of which, guitars speakers won't even respond to anything above 7Khz.

I would also check out Carvin. All their new poweramps are super light weight and sound great! They also have a tube poweramp if you want to go that route as well.

EDIT: Just saw you are already looking at Carvin haha.

As far as power, I am using a GSP1101 with the little Crate Powerblock (rated at 150Watts 8Ohm) and it is more than enough power. Killer little rig. Not quite my Powerball, but good enough for smaller gigs/rehearsal.