Boss Katana Bass ...

[agedhorse]

To the layperson, probably nothing. From an engineering standpoint, it depends on how the amp is intended to be used. D class amps are more efficient, but they also introduce more distortion (and generally of the variety that we don't like) because of the fast on/off switching of the diodes. A/B is less efficient, but maintains hifi at higher levels.

Basically, if you have two amps rated for the same wattage, you would be able to push the A/B amp harder without distortion than the D class amp. That being said, this can be accommodated for by using higher rated class D amps but listing the capability lower so they don't go into distortion.

Class D amps have gotten a lot better than when they were introduced. If you are not diming your amp and pushing it into distortion, then sonically you wouldn't know whether it was A/B class or D Class just from listening to it.

So, if my amp was rated for actual watts and I planned to dime it all the time, I would probably want A/B Class amps. If the amp was not intended to be pushed, or used amps that were actually rated higher than what was advertised, I would probably go with D class amps for efficiency and heat reduction.

At least, that is my understanding of it.

Fortunately, none of this is true on well designed amps.

 

[Nebadon2000]

What you are missing here is that in many cases, music has gotten louder and with greater low frequency extension, or that players are demanding greater performance and low frequency extension out of smaller cabinets which decreases sensitivity compared with the “good ‘ol days”.

“good ‘ol days”. like in Mid 70's when our band needed Van with trailer to lug around equipment for large clubs on LI;

SVT with 8x10 and 18" EV folded horn, Marshall Double Stack, Actual Hammond B3 with 2 Leslies, Full double bass Drum kit, 2 Crown DC300'S for PA ETC.

 

[agedhorse]

“good ‘ol days”. like in Mid 70's when our band needed Van with trailer to lug around equipment for large clubs on LI;

SVT with 8x10 and 18" EV folded horn, Marshall Double Stack, Actual Hammond B3 with 2 Leslies, Full double bass Drum kit, 2 Crown DC300'S for PA ETC.

Yup, pretty much!

 

[mbell75]

What you are missing here is that in many cases, music has gotten louder and with greater low frequency extension, or that players are demanding greater performance and low frequency extension out of smaller cabinets which decreases sensitivity compared with the “good ‘ol days”.

I wish music had gotten louder out here. These days, even bars are increasingly having a sound guy and volumes are kept at levels you can easily talk over. But Im in Southern California where almost every bar or small club is near residential areas and neighbors complain. Last venue I played, there was a huge apartment complex literally in the same parking lot like 500 feet away. The music was so low that you could carry on a conversation not far from the stage and it was a venue that holds like 300 people. I could have literally played it with a practice amp that had a direct out. On a positive note, the mix sounded great, unlike venues with no sound guy where amp volume wars are far too common and peoples ears are ringing after two songs.

 

[Redbrangus]

There have been multiple iterations of Fender Rumbles. My understanding is that the smaller models were Class AB until Version 3 was implemented, but I'm no expert.

I have one first-generation Rumble that I like and another that I don't care for at all. They're both Class AB, so I don't credit the circuit topology for anything about the difference in the way they sound.

 

[BruceG63]

What you are missing here is that in many cases, music has gotten louder and with greater low frequency extension, or that players are demanding greater performance and low frequency extension out of smaller cabinets which decreases sensitivity compared with the “good ‘ol days”.

Thank you thats something that I havent taken into consideration.Back in the early 80s I bought a Mesa D-180 and a 215 cab that I think was loaded with 400 watt EVM 15Ls[correct me if im wrong on the speakers Mesa used].That cab had very high sensitivity as 1 night our monitor amp quit and we used the D 180 to run monitors and an old Traynor 100 watt tube amp for my bass amp.That 100 Traynor head pushed that Mesa cab loud enough to keep up with a pair of 100 watt halfstacks.You might have trouble doing that with 15 cabs nowadays.

 

[BruceG63]

I have officially joined the club! Excellent amp, my favorite yet, love everything about it. Posted more details in my NAD thread.

Is that the Katana 110?

 

[agedhorse]

Thank you thats something that I havent taken into consideration.Back in the early 80s I bought a Mesa D-180 and a 215 cab that I think was loaded with 400 watt EVM 15Ls[correct me if im wrong on the speakers Mesa used].That cab had very high sensitivity as 1 night our monitor amp quit and we used the D 180 to run monitors and an old Traynor 100 watt tube amp for my bass amp.That 100 Traynor head pushed that Mesa cab loud enough to keep up with a pair of 100 watt halfstacks.You might have trouble doing that with 15 cabs nowadays.

The EVM-15L’s are good for about 200-250W mechanically from 50Hz and up in the common cabinet tunings.

 

[agedhorse]

There have been multiple iterations of Fender Rumbles. My understanding is that the smaller models were Class AB until Version 3 was implemented, but I'm no expert.

I have one first-generation Rumble that I like and another that I don't care for at all. They're both Class AB, so I don't credit the circuit topology for anything about the difference in the way they sound.

Pretty much correct. There is some ambiguity regarding V2 and I don’t have any docs to sort that out.

 

[mbell75]

Is that the Katana 110?

Yes!

 

[mbell75]

There have been multiple iterations of Fender Rumbles. My understanding is that the smaller models were Class AB until Version 3 was implemented, but I'm no expert.

I have one first-generation Rumble that I like and another that I don't care for at all. They're both Class AB, so I don't credit the circuit topology for anything about the difference in the way they sound.

Very likely. I just know there is no way the V3 Rumbles are A/B at that weight. The Rumble 40 1x10 is only 18 pounds while the Katana 60 1x10 is more than twice as heavy at 37 pounds. Thats one downside to A/B vs Class D and Ive owned both amps, but I'll take the better tone with way more variety and more power on the Katana over the Rumble all day long.

 

[agedhorse]

The V3 is class D.

 

[67goat]

Fortunately, none of this is true on well designed amps.

Not exactly. It is still true. That is the very nature of the designs of the different amps. The question is whether the amp use case will drive the amp to the point where it would happen, and if so, if it will be noticeable.

While it is true from a theoretical standpoint that a class D amp would generate more distortion, what does that mean practically? If we look at the powerball, for example, if you bought 10 tickets, you would increase your chances of winning by a whole order of magnitude. That sounds really good, but in reality, you would still have 1 in 30,000,000 odds. Practically speaking, 10 tickets are not really better than 1 in this case. By contrast, you have a 1 in 15,300 chance of being struck by lighting. So even is D amps always had 2x (just making a number up) distortion, if that 2x distortion is not noticeable to the human ear, does it matter? No.

I do think that modern amps that are well designed around their anticipated usage it is more a matter of weight and heat than of sonic properties in most cases. I do not make choices on amps (guitar or otherwise) on the class of amp it uses. Does it sound good the way I intend to use it? If the answer is yes, then the amp is good.

 

[agedhorse]

Not exactly. It is still true. That is the very nature of the designs of the different amps. The question is whether the amp use case will drive the amp to the point where it would happen, and if so, if it will be noticeable.

While it is true from a theoretical standpoint that a class D amp would generate more distortion, what does that mean practically? If we look at the powerball, for example, if you bought 10 tickets, you would increase your chances of winning by a whole order of magnitude. That sounds really good, but in reality, you would still have 1 in 30,000,000 odds. Practically speaking, 10 tickets are not really better than 1 in this case. By contrast, you have a 1 in 15,300 chance of being struck by lighting. So even is D amps always had 2x (just making a number up) distortion, if that 2x distortion is not noticeable to the human ear, does it matter? No.

I do think that modern amps that are well designed around their anticipated usage it is more a matter of weight and heat than of sonic properties in most cases. I do not make choices on amps (guitar or otherwise) on the class of amp it uses. Does it sound good the way I intend to use it? If the answer is yes, then the amp is good.

I can think of many examples of class D amps that have lower distortion than class AB amps.

There are designs where a specific type of distortion is intentionally generated within a power amp (this goes for class AB and D equally), to achieve a particular tone/feel or texture. That's a specialty within amp design/engineering.

 

[Plastalmonus]

The V3 is class D.

I’ve read a few sources that say that the 15, 25, and 40 are Class AB and only the 100+ are Class D.

Example:
The Fender Rumble Dilemma

@Linnin seems to be the go to guy for Rumble info.

Also in the NoTreble review the sub-100 amps are listed as ‘Solid State’ whereas the 100+ say Class D. I notice this is the same way Boss describe their power section.

Fender Redesigns Rumble Series Bass Amps for 2014

 

[agedhorse]

I was talking about the larger Rumbles, I should have been more clear.

 

[mbell75]

I’ve read a few sources that say that the 15, 25, and 40 are Class AB and only the 100+ are Class D.

Example:
The Fender Rumble Dilemma

@Linnin seems to be the go to guy for Rumble info.

Also in the NoTreble review the sub-100 amps are listed as ‘Solid State’ whereas the 100+ say Class D. I notice this is the same way Boss describe their power section.

Fender Redesigns Rumble Series Bass Amps for 2014

I can’t see how anyone is making an 18 pound 1x10 A/B amp. The Katana is 37 pounds. Besides, every place that sells them from Amazon to MF says they are Class D. AFAIK, solid state can be used with any power section. Also, aren’t all non tube amps solid state? If the smaller amps are solid state, what’s that make the Rumble 100, 200 and 500? Digital? They aren’t SS and they aren’t tube. Maybe that’s a question for the Rumble club.

 

[agedhorse]

There is also a hybrid SMPS/class D option that saves weight.

 

[Redbrangus]

I can’t see how anyone is making an 18 pound 1x10 A/B amp. The Katana is 37 pounds.

Without actually knowing anything (*), I'm going to suggest that a substantial portion of the Katana's relative portliness might be due to the cabinetwork. At that relatively low power level, it's hard to imagine there's a substantial weight difference between a conventional linear power supply and a SMPS, which is what I think you're probably referring to when you get off into the Class D/Class AB distinction. Of course, if it's a regular driver rather than a neodymium one, that could also contribute to the weight difference.

Also, marketing jargon mixed with sales hype can sometimes lead to such mystifying statements as "the amp has a solid-state preamplifier and a Class D power section". Are we to infer that the power section is Class D implemented with tubes? Or did someone tell the copywriter that Class D is digital? Anyhoo...I think this concern with what Fender amps used which circuit topology is somewhat mystifying, given you've chosen something else that ticks all your boxes. Good for you!


(*) Since when has that ever stopped someone from opining on TB?

 

[67goat]

I can think of many examples of class D amps that have lower distortion than class AB amps.

There are designs where a specific type of distortion is intentionally generated within a power amp (this goes for class AB and D equally), to achieve a particular tone/feel or texture. That's a specialty within amp design/engineering.

Yes, if the A/B amp is built to a lower quality or for a different specification. I can build a super-efficient internal combustion car and a super inefficient battery powered car were the gas powered car will be more efficient. That does not make gas powered engines as efficient as battery powered motors. And that's not how people talk about things when we say one design is more efficient or noiseless than another design. They talk about comparing equivalent examples of the two designs, not a better version against a lower quality. (I am specifically talking about when determining whether a design is more efficient, etc, than another. I am not talking about comparing two actual amplifiers - where people often do compare a higher quality version of one against a lower quality of the other.)

Two amps built (not overbuilt) to the same specs for the same purpose and of the same quality of design, a D Class amp will, in fact by design, create more distortion at peak rating than an A/B amp. Whether or not some manufacturers design specifically around class D distortion is irrelevant to that fact. Also it doesn't prove anything anyway. In the 90s Fender designed solid state amps around their distortion, but nobody liked it.

It is also true that the type of distortion in D class amps is of the type that is generally not something people want or enjoy. That is not the same thing as saying there is no use for it. There are lots of things that are generally not sought after in most situations, but fit perfectly in specific situations