Anyone still prefer Class A/B amps over Class D?

[fdeck]

And the tone my class D's have.... well lets just say that I predict an extinction level event for class anything else.

I also play through Class-D amps exclusively these days, but I think if we've learned one thing about bass gear in the past 60 years, it's that nothing goes extinct. There are still people producing variants of practically every topology of bass amp ever made. Even if there were no technical reasons to produce new Class-AB gear, there would still be demand from bassists, and marketing reasons to serve that demand.

 

[Coolhandjjl]

I've gotten to the point where I care more about the preamp stage than the power stage. I use IEM's for every gig, and I leave the volume knob on my amp at zero. With the IEM earbuds in I can't hear the amp even if I want to.

I *feel* the low end through the PA though, and I like that a lot. And when it comes to big systems, one of the advantages of class D and its variants is power draw--they generally pull much less power than equivalent class AB amps when making an equivalent amount of noise. So if I can walk into a venue knowing that I only need 200 (electrical) amps of power to make the same noise that I would need 1000 (electrical) amps for, then I'm way ahead. Then there's less weight to truck around, which means fewer trucks, fewer crew to move them, etc etc.

Tom

Pro Sound Touring companies are going to, or have gone to, Class D. If their set-ups sounded crappier, they wouldn't be doing it en-masse.

 

[blindrabbit]

I find there is too much within-class variability for me to make sweeping generalizations about preferring one over another...it just isn't valid. Instead, I'll readily talk about specific amps that I love, and those cover all sorts of different "classes" - Aguilar TH350/500, Aguilar DB751, Traynor YBA-200-2, Traynor Dynabass 800...

 

[wateroftyne]

I got my first class D, what.. 13 years ago? I then spent the best part of a decade buying the next new class D, and the next, to try and find what was missing from my tone - and the whole gigging experience.

Then I realised: whenever I used provided backline that was class A/B, that magic component was always 'there'.

So I bought a Walkabout, and latterly a Handbox R-400. Almost class-D form factor, with analogue tone. I'm sorted.

 

[JimmyM]

Pro Sound Touring companies are going to, or have gone to, Class D. If their set-ups sounded crappier, they wouldn't be doing it en-masse.

"Crappier" is not the word I'd use, but I do know plenty of sound techs who would prefer to use the heavier stuff but they can't argue with the weight and storage savings.

 

[wateroftyne]

Pro Sound Touring companies are going to, or have gone to, Class D. If their set-ups sounded crappier, they wouldn't be doing it en-masse.

I don't think the pro touring companies are using the off-the-shelf ICEPower modules you generally get in bass heads.

 

[FingerDub]

To be clear, I did not intend this thread to become a D v. A/B thread, and which one might be better. I only wanted to know why some might prefer A/B.

When people here post gig rigs and such, it seems that class D amps are in a lot of pictures. If there is any difference, it seems that class D amps are sooo close in performance to class a/b that I wonder why people still have bigger amps.

I gigged my Hartke HA4000 head last week, and I noticed it felt warm on the top right side of the amp. Never felt that with my TC BH250, but I loved the way it sounded. It got me wondering.

There has been some interesting opinions so far, especially about the note hitting harder with a class A/B head or the "envelope". I can tell you I much prefer the Hartke head, but then again, the BH 250 isn't as full featured.

I guess I feel that class D heads are now the majority, and it seems that most people here have had at least one experience with a class D head.

I'm no electronics expert, and have mostly just had amps for the power until a few years ago. I never cared about amp features, except for the contour knob on my very first big boy Hartke head back in the 90's.

Is there any science rooted in the idea that class A/B amps hit harder? Do they provide more current or something?

 

[hennessybass]

I'm kind of with what @JimmyM said - I prefer amps that sound good. Good being subjective - meaning I prefer amps that sound good to me.

I have owned and gigged a lot of all tube, hybrid, SS, and class D amps. What cabs you are using make a huge difference in how an amp sounds and plays - lot's of other factors too.

The Thunderfunk TFB800 (all SS) is probably the best amp for me as far as a total package kind of thing- tone, feel, power, and every other check box item in the world a gigging bassist could possibly need. I gigged an AMP BH420 for a long time, and also a TFB550... all in the family.

I think my '77 Bassman (all tube) is probably the most musical, expressive, and my favorite amp to play - but it has some limitations - which is mostly convenience stuff.

As far as class D, I've never really found one I love. I settled with the TH500 - and that's what I mostly gig with. It's a good amp.

 

[bassbully]

Like I was telling my guitar player last night. I would haul a Peavey TNT around since for the money they sound great and are a killer amp. I also reminded him "killer" is also what they do to your back....we laughed. I will stick with class B please.

 

[Doner Designs]

By the way, in terms of clean tone and low disrtortion, class D as a principle is technically inferior to A/B. There is a good paper on the QSC homepage explaining the mid and high frequency compromises still inherent in class D.

Is this at all compensated for by headroom (500w class ab vs 1000w class d for example)?

 

[GroovinOnFunk]

Probably anyone that favors tone over convenience, and is unwilling to compromise the former for the latter, would prefer class A/B amps over class D.

 

[prowla]

Pro Sound Touring companies are going to, or have gone to, Class D. If their set-ups sounded crappier, they wouldn't be doing it en-masse.

I'm not sure about that - I've been to gigs where the sound was pretty grim.

The worst one I recall was Marilyn Manson at Brixton, where I honestly couldn't identify the songs which were being played over the PA before the band came on.

 

[lowfreqgeek]

I'm not sure about that - I've been to gigs where the sound was pretty grim.

The worst one I recall was Marilyn Manson at Brixton, where I honestly couldn't identify the songs which were being played over the PA before the band came on.

Do you seriously think this was directly due to the topology of the power amps?

 

[agedhorse]

I'll add a caveat; Classes B and C are NOT for audio amplification. Class B is more efficient than A or A/B, but it has significantly more crossover distortion as the signal passes from positive to negative and back. Class C is for RF applications.

Class A is the most inefficient, but also the lowest distortion. A/B is the trade-off between distortion and efficiency. That has nothing to do with how much power is delivered, how dynamic the power is delivered, how it interacts/reacts to the load, etc.

Class b (by the common definition) is certainly very common in audio, where each half of the output stage conducts for as close to 180 degrees as is practical. In reality, there is always variations if output stage conduction angle, but the LEAST amount of crossover distortion is where the handoff at zero (voltage) crossing is at exactly 180 degrees.

Where there is crossover distortion present (remember that the feedback loop can mask of hide much of the presence), the output stage is operating in class C (or less than 180 degrees conduction angle)

The difference between Class AB, B and C is purely based on conduction angle, AB is slightly greater than 180 degrees, C is slightly less than 180 degrees and class B is exactly 180 degrees.

Now this definition is further clouded by the fact that under a reactive load, the voltage and current are not exactly in phase, so you can have current present at zero voltage because of the phase angle of current to voltage.

 

[agedhorse]

I find there is too much within-class variability for me to make sweeping generalizations about preferring one over another...it just isn't valid. Instead, I'll readily talk about specific amps that I love, and those cover all sorts of different "classes" - Aguilar TH350/500, Aguilar DB751, Traynor YBA-200-2, Traynor Dynabass 800...

But of course!!!

 

[agedhorse]

"Crappier" is not the word I'd use, but I do know plenty of sound techs who would prefer to use the heavier stuff but they can't argue with the weight and storage savings.

At this point, I don't know a single one who prefers the heavier amps... those few "holdouts" have been bypassed for folks who were better equipped to handle the real world and get down to mixing the show rather than remembering the "good 'ol days which" weren't at all as good as they fondly recalled. I was there, I lived those days and no way would I go back. That doesn't mean that I don't look back at some of my lead sled designs with fondness, but also recognize that there are almost no customers left for them.

 

[Doner Designs]

Are there any Class A bass amps out there? I'm guessing maybe the SVT and similar? What about SS or Hybrid Class A? Just curious - you don't seem to hear much about them if they do exist.

 

[pfschim]

Probably anyone that favors tone over convenience, and is unwilling to compromise the former for the latter, would prefer class A/B amps over class D.

this is a pretty loaded statement IMO/IME. To say that those who don't agree with your choice of amp are'nt as dedicated to tone is pretty condescending.
Personally, I do love my all tube amp (Fender Studio), and have truly loved me some other tube amps in my day, but they are not superior in any way to my class D hybrid (Demeter VTBP-800) when it comes any of the common non-measurable/unquantifiable tone descriptions we bass players come up with to describe what we hear or feel when we play.
Over 45 years of gigging I have used just about every common brand of tube amp. Great stuff for sure (mostly), but they are not automatically better amps than well designed class D gear.

 

[agedhorse]

I don't think the pro touring companies are using the off-the-shelf ICEPower modules you generally get in bass heads.

Then perhaps you might not know the whole story behind the technology and its adopters...

I did in fact design some IcePower class D pro audio powered speaker products that were used in the touring industry. Can't discuss this, but absolutely they are out there, and in the thousands.

 

[agedhorse]

Are there any Class A bass amps out there? I'm guessing maybe the SVT and similar? What about SS or Hybrid Class A? Just curious - you don't seem to hear much about them if they do exist.

Nope, not at all. Maybe that's why you don't hear about them