Seeking your real world class D amp head comparison and experience

[IvanMike]

It really depends so much on the individual player's tastes as well as the application (music type, instrument and playing style). There is quite a difference between the D-800/800+ and the WD, you should try to get some time with both to see what you might prefer and when you might choose one over the other.

That definitely makes sense. Couple of related questions:

Is the Q on the semi parametric mid bands of the D-800+ the same as the Q for the fixed frequencies on the D-800? (i.e., Is it possible to replicate the precise functionality of the high and low mids of the D-800 on the D-800+?)

Second, did you approach the different amps with specific design goals? In other words I don’t imagine that you put together a circuit and said “gee that one sounds good let’s use that.” I imagine you had a finished product in mind for each of the flavors of the series. If I understand correctly the WD-800 is kind of supposed to be in the direction of the walkabout (which is an amp that I have no experience with), while the TT-800 is focused a little bit more on like sounding like a 400. Is that correct? And more to the point, what was the design goal of the D-800? Was there a specific tone you were going for from the beginning?

thank you very much for your participation in this thread. The education has been interesting and I’m always fascinated by amplifier design.

 

[agedhorse]

The Q's of the active mid and parametric mid filters are all in the same ballpark.

The design goals for the different models were very different and quite targeted. Some features are common to all models, like 2 ohm stable drive capability, linear acting gain/volume control tapers aux in and headphone out, deep switch, DI but some features are very much unique to the model.

D-800: Straight forward amp, mild tube emulated O/D with some of the legacy featured just done a little bit differently. A more neutral amp with the voicing control that does multiple things simultaneously. Size and weight was an important feature in this amp.

D-800+: Same as the D-800, but with 2 sweep mid controls plus bright switch and effects loop.

WD-800: This amp is heavily inspired by the Walkabout, shares a single tube preamp, 3 band parametric eq, passive mid, more heavily voiced, damping control, also includes additional rear panel features including the first USB power port included on a bass amp. There was an extensive thread that was the basis for many of the decisions made when designing the amp.

TT-800: This 2 channel amp is the combination of two "TB favorite" preamps, the first being the Subway D-800+ series but with the inclusion of tube gain stages and only a single sweep mid control. The second preamp was heavily inspired by the Bass 400/400+ preamp but again with refinements and updates strongly influenced by another TB thread on the Bass 400. The enhancements included smoother control tapers overall, more usable tone stack eq (better turnover frequencies, greater range and the ability to operate with a flatter midrange if desired). This amp also contains damping control management but is done differently to track better the effect of the Bass 400's output transformer on the damping via an impedance selector switch. It's a 2 channel amp with a separate DI that follows the channel switching, as well as a tube driven post DI and a pair of effects loops that can also double as insert points for external preamps. This model also has the USB power port.

As you can see, very much different strokes for different folks.

 

[Taffronaut]

TC BAM200 into a PhJ 27 cab for jazz gigs. I want as little colour and features in the amp as possible especially for when I'm playing acoustic upright. There's no drama and the TC fits into my bag. Replaces my old 100W combo. I looked at Markbass but prefer this rig instead.

 

[MultiScaleMale]

The Q's of the active mid and parametric mid filters are all in the same ballpark.

The design goals for the different models were very different and quite targeted. Some features are common to all models, like 2 ohm stable drive capability, linear acting gain/volume control tapers aux in and headphone out, deep switch, DI but some features are very much unique to the model.

D-800: Straight forward amp, mild tube emulated O/D with some of the legacy featured just done a little bit differently. A more neutral amp with the voicing control that does multiple things simultaneously. Size and weight was an important feature in this amp.

D-800+: Same as the D-800, but with 2 sweep mid controls plus bright switch and effects loop.

WD-800: This amp is heavily inspired by the Walkabout, shares a single tube preamp, 3 band parametric eq, passive mid, more heavily voiced, damping control, also includes additional rear panel features including the first USB power port included on a bass amp. There was an extensive thread that was the basis for many of the decisions made when designing the amp.

TT-800: This 2 channel amp is the combination of two "TB favorite" preamps, the first being the Subway D-800+ series but with the inclusion of tube gain stages and only a single sweep mid control. The second preamp was heavily inspired by the Bass 400/400+ preamp but again with refinements and updates strongly influenced by another TB thread on the Bass 400. The enhancements included smoother control tapers overall, more usable tone stack eq (better turnover frequencies, greater range and the ability to operate with a flatter midrange if desired). This amp also contains damping control management but is done differently to track better the effect of the Bass 400's output transformer on the damping via an impedance selector switch. It's a 2 channel amp with a separate DI that follows the channel switching, as well as a tube driven post DI and a pair of effects loops that can also double as insert points for external preamps. This model also has the USB power port.

As you can see, very much different strokes for different folks.

Great post and worthy of the second bookmark I've ever used on TB

 

[Drummerboy2]

After reading through the responses, let me provide both information and background behind the different power amp topologies and especially the transition period that some (or even many) manufacturers struggled with in their efforts to get to where we are today.

For background and a little history, I am an EE with 40 years of design experience, I have designed plenty of lead sled power amps (both tube and solid state) including bass amp models GBE-400/600/750/1200, plus designs used in the pro audio market. I started the transition to class D almost 20 years ago while I was designing products for pro audio, and I joined up with ICEPower (Bang and Olufsen at the time) as they were the one development group that was ahead of the curve (in hindsight by a wide margin).

At the time, there were several serious and notable attempts at class D in both pro audio and bass amplifier markets, specifically the Crown K2 which was pretty successful and probably the most reliable of the bunch, but used a line frequency power supply which was heavy and resulted in only a modest reduction of weight. It was fanless however as it used the entire chassis/faceplate as the heatsink. Peavey also developed a line of class D amps which was the DECA line (digital energy conversion amplifier), it may have been the most clever of the bunch as it combined an SMPS with the class D power amp to create a much lighter weight package. The downside of this implementation is that there were a lot of unpredictable, seemingly random failures, but when they worked they were impressive for the time (especially using through hole components). The other notable class D amp was GK's 1200SEB from the 1980's, but this too suffered reliability problems. The problem with all of these pioneering amps wasn't the understanding of the principles, the technology or even the implementation (all 3 were developed by skilled engineers), but the limitations of the parts and the tools necessary to do in depth analysis of the performance boundaries. Semiconductors were quite slow back then, and speed is necessary for successful (both sound quality and reliability) audio applications. As the SMPS (switchmode power supply) markets evolved, this drive the development of more advanced semiconductors, as well as the integration of essential synchronization and drive functions into highly refined IC's. This is what opened the door to making class D successful.

During this time, I studied many possible ways to decrease the weight of bass amps but every time I revisited class D, I came to the conclusion that it wasn't quite ready for prime time. Therefore, I focused my attention on power supply transformer design (and materials) and chassis structures using heat treated aluminum and the Neo-X 400 was the first amp using this technology (400 watts RMS into 4 ohms, weighing 16 pounds, the same power amp module and transformer would also support 600 watts RMS, but never went into production because the speaker models of that era weren't up to the task). Like other designers, we were looking for intermediate steps.

As SMPS became more reliable and more standardized in their designs, the next step for some manufacturers (Walter Woods, MarkBass, Peavey, etc.) was to combine SMPS with a conventional linear power amps to create lighter weight packages. In my case, I took the Neo-X 400 amp and replaced the line frequency power supply with an SMPS that was designed in house. The result was the NeoPak 3.5 (released 2005-2006) which was 500 watts RMS into 2 ohms and weighed 8.5 pounds. There was also a follow-up NeoPak 750 watt model designed, but ICEPower's new class D platform was about to change all of that.

I had been working with ICEPower on some pro audio powered speaker designs for a large touring pro audio speaker/amplifier company and attended a presentation by B&O about their new little division that was pioneering combined class D and SMPS technology that for the first time was fully integrated together (meaning that the SMPS and class D sections worked together, with feedback between the two sections), this feedback included automatically changing or adapting the switching frequencies to optimize performance and efficiency. They also developed unique integrated driver electronics and specialized protection to eliminate some of the most common failure modes that class D was prone too. I received samples of the new modules and built up the same amp both conventionally as well as with the new technology and came to the conclusion that it was in fact a very robust, high audio quality solution. The only problem was the cost, but in the end it was the most viable solution (by a mile) available that allowed a manufacturer of MI gear to offer a 3-5 year transferable warranty with confidence. I designed these modules first into a touring pro audio powered speaker product (can't mention the brand, but they are still in business with essentially the same product line 15+ years later), and then set out reinventing our bass amp product line starting with a smaller 300 watt at 4 ohm model that was the (2007) Shuttle 3.0 which was the first (successful) bass amp that used this new technology and remained essentially unchanged through Fender's shut down of Genz Benz in ~2014. The sound quality problems were gone, the reliability was as good or better than the best linear amps, and IMO this was the point that ICEPower, in spite of the higher cost, became the "gold standard" of SMPS/class D platforms.

Being involved early on, and understanding what was going on under the hood of these designs, I was able to exploit some of the additional hidden features that were present in this platform to further improve performance and reliability, receiving a patent (assigned to KMC Music and Fender) for this in 2012 which allowed for critical off sheet designs to move forward, and are still in use today. Some of these concepts evolved from the older modules to the newest modules, but understanding the evolution of the technology, how and why it evolved, simply allows a designer the freedom to focus on superior applications based on the technology. Some designers have done great jobs with this, some not so good, track records are important.

Now, regarding the "class D" debate, with good implementations SMPS and class D technology can IMO and IME deliver exactly the same (or BETTER) performance in a smaller, lighter package. Yes, better, because there are things that we as designers wanted to do with line frequency power supplies (specifically regulation or active rail support) that were either impractical or way too costly without SMPS technology. I explored this with the NeoPak 3.5 (which has some of this same technology) and came to the conclusion that this was the next big step forward as it reduced one of the biggest challenges in designing with line frequency supplies. I also built up identical bass amps, the only difference being the power supplies and the power amp topology. With good implementations the differences could be made imperceptible in double-blind listening and play tests. The bonus is that I was now free to be able to tweak parameters that were impossible in conventional designs which became another evolutionary step in the process of developing new bass amps. Also, this means that if a manufacturer of a bass amp discontinues an amp, it doesn't mean that a proprietary part becomes no longer available. I can still support the Shuttle 3.0 now and into the future, large quantities of current parts are still available off the shelf. This is no longer true of the NeoPak (as an example) as there are a few SMPS parts that are no longer available (though I can still generally repair them, at some point this may no longer be true). I know there are a lot of amps out there using proprietary parts that haven't been available for quite some time, in many cases there are simply no workarounds and the amp can not be repaired. This is not true of ANY product using an ICEPower module, which I believe is a very real world, meaningful benefit to owners of such amps.

I am not alone in this journey, there are other bass amp designers that I know of who have similar history, similarity in their approach and have come to the same conclusions regarding the ICEPower platform. Experience and knowledge really do make a difference, experienced designers seem to be more successful in this regard. Each designer has different tonal tastes, makes different design choices for a variety of reasons. This is one reason why none of these amps sound the same, each one reflects the personality of the principle designer and the design team of their respective companies.



That would be the WD-800, which was designed from the start to take the Walkabout concept forward by improving performance, reducing weight, adding requested features and eliminating the things players found frustrating or bothersome. There was an entire thread on this development process, TB members contributed freely to the process and the result mirrors closely what the majority of TB players wanted.

So from what I'm reading here, most of the smaller Class D amps are using the ICE Power Modules from B&O? The only difference between those are just the front ends/preamp portion of the amps are different? These are popular with the High End Home Audio amps along with Hypex. The Crowns have developed their own Drivecore version which I like a lot.

 

[Passinwind]

So from what I'm reading here, most of the smaller Class D amps are using the ICE Power Modules from B&O?

B&O sold off ICEpower several years ago, FWIW.

 

[Al Kraft]

So from what I'm reading here, most of the smaller Class D amps are using the ICE Power Modules from B&O? The only difference between those are just the front ends/preamp portion of the amps are different? These are popular with the High End Home Audio amps along with Hypex. The Crowns have developed their own Drivecore version which I like a lot.

IME using common components or modules doesn't mean there is no difference in design implementation...and subsequently unit performance. Many common core type elements/components have a basic functionality that at a first order look is easily understood by its specs. However, these components can easily offer additional capability when integrated into an overall circuit by someone who is very familiar with the component's design.

If we step outside of class D for a moment and just think about class AB (tube or SS), most amplifiers have a high degree of common components (many may be identical) but are voiced and perform very differently. The trick here is to appreciate the total design of the circuitry as a system and not overly focus on one component/module/sub-assembly. While the preamp matters a lot IMO, what can be done with a common power module may differ with with degree of deeper understanding of that module's inherent and latent capabilities.

 

[Drummerboy2]

IME using common components or modules doesn't mean there is no difference in design implementation...and subsequently unit performance. Many common core type elements/components have a basic functionality that at a first order look is easily understood by its specs. However, these components can easily offer additional capability when integrated into an overall circuit by someone who is very familiar with the component's design.

If we step outside of class D for a moment and just think about class AB (tube or SS), most amplifiers have a high degree of common components (many may be identical) but are voiced and perform very differently. The trick here is to appreciate the total design of the circuitry as a system and not overly focus on one component/module/sub-assembly. While the preamp matters a lot IMO, what can be done with a common power module may differ with with degree of deeper understanding of that module's inherent and latent capabilities.

The reason I had asked those questions was because of the Aguilar Tonehammer 500 video showing the ICEpower 250ASX2 module and then just adding their Preamp to it. That's all I saw done in the assembly of the amp and the installation of these two boards. Aguilar Amplification NYC Shop Tour - YouTube

 

[agedhorse]

IME using common components or modules doesn't mean there is no difference in design implementation...and subsequently unit performance. Many common core type elements/components have a basic functionality that at a first order look is easily understood by its specs. However, these components can easily offer additional capability when integrated into an overall circuit by someone who is very familiar with the component's design.

If we step outside of class D for a moment and just think about class AB (tube or SS), most amplifiers have a high degree of common components (many may be identical) but are voiced and perform very differently. The trick here is to appreciate the total design of the circuitry as a system and not overly focus on one component/module/sub-assembly. While the preamp matters a lot IMO, what can be done with a common power module may differ with with degree of deeper understanding of that module's inherent and latent capabilities.

This is a good description of what goes on under the hood of different amps.

 

[agedhorse]

The reason I had asked those questions was because of the Aguilar Tonehammer 500 video showing the ICEpower 250ASX2 module and then just adding their Preamp to it. That's all I saw done in the assembly of the amp and the installation of these two boards. Aguilar Amplification NYC Shop Tour - YouTube

It’s more than the parts, its about the specific application of the parts too.

 

[Al Kraft]

The reason I had asked those questions was because of the Aguilar Tonehammer 500 video showing the ICEpower 250ASX2 module and then just adding their Preamp to it. That's all I saw done in the assembly of the amp and the installation of these two boards. Aguilar Amplification NYC Shop Tour - YouTube

Fair enough...and that is a cool video. The trick comes in how those modules are actually used relative to their full set of capabilities within the overall circuitry.

An easy to understand example (albeit a bit over-simplistic) would be if you took the exact same preamp tube and installed it in Mesa Carbine and a Mesa WD-800. Same amplifier company, identical part number tubes, and possibly even the same part number tube receptacle, but the preamps will sound entirely different.

While how those circuits use the tube's capabilities is likely quite different, someone watching a recording of you installing the tubes would say they look identical. They'd be right about how it looks, but totally wrong in assuming both preamps would sound the same because a key part is the same.

 

[sunbeast]

Epilogue:

i’d like to thank everybody who participated in this thread and hopefully it continues to grow. I ended up having a long behind the scenes conversation with Al Kraft which was also extremely helpful and we talked about several brands.

I was surprised to find out that there are very few Mesa dealers in Connecticut. I had to go to one about 40 minutes away and it turned out that a guy I knew owned the shop, which was very cool. It took a while for us to recognize each other behind the masks and behind years of weight gain and hair loss. Well, his hair loss, mine was gone a long time ago.

I got a chance to try the Trace Elf both through a mesa 15 & the trace 2 x 8. I plugged into the Mesa 2 x 10 for a second but tried to stick to one cabinet for the amp demos. In stock he had a mesa D 800 and a mesa WD 800. Both really good sounding amps. If he had a D 800+ it would have been a lot tougher to make a decision. I ended up going home with the WD 800. In the future I might have to ask him to order me a D 800+. The amps are definitely voiced a little bit differently and they are both really good flavors.

Despite everything I said about wanting something really small in the beginning, I found that in its little carry-on bag the Mesa is incredibly portable and I’m pretty sure I can walk in with my bass and that slung over my shoulder and carry a cabinet.

back at home I was able to do direct comparison in real time by plugging the mesa WD 800 into a Bag End 15 and Bag End 12 while I put my Demeter 201s into one channel of the QSC 1602 driving an identical stack of bag end speakers. (Everyone should have 4 cabinets).

I liked the Demeter tone a little bit better but I was able to get pretty close to it with the Mesa. The Demeter was a touch more open and kind of had a little bit more tube compression sort of. But its mids are voiced very differently. - Both sound really good. plugging the Mesa into all four cabinets and running it 2 ohm mode I found it to be every bit as loud as the QSC with both channels driven. It was also just as loud running against one channel of the QSC into to cabs in 4 ohm mode. I’m glad people clued me into the idea that the master and gain are linear because it was kind of counterintuitive not to be at maximum volume at around 12 o’clock and then run into clipping.

I’m still experimenting with the controls of the WD 800. It is really capable of a lot of different feels if you mess with the high pass filter, the adjustable dampening factor, the gain, and the passive mids. Combining those with the bass and treble shelving controls and the semi parametric 3 band mid range (total range 80-5k with considerable overlap between controls) allows you to do a lot with smaller adjustments on the active EQ section than you might normally be used to.

Like I said, I really was torn between the tone of the WD 800 and the D800. In many ways they are very similar but the WD definitely seems more complex & aggressive while the D 800 sounds a little bit more polite. The shape or whatever they call the global tone control/Instant smiley face eq knob only found on the 800 and 800+ is actually a really good one. The deep switch sounded a little boomy but not awful, and it certainly did exactly what it should. The 800 doesn’t have a bright switch but the 800+ does. However, I think the reason I would want an 800+ would be for the high pass filter. That’s actually really useful just from a tonal perspective alone and messing with that and the bass control knob is a lot of fun. I can see how it would interact very well with the deep switch as well. Even without those two extra amenities (and a couple of back panel extras) the D 800 was a very impressive little amplifier. If that’s what was available to try I certainly would have gone home with it.

The Trace elf was exactly how people describe it. Not exactly fantastic tone, but not terrible. Definitely would not have a problem being heard playing that head. It’s a little dirty and a little heavy on the mids but it is like a baseball bat hitting you in the skull. It’s also surprisingly loud. The store owner and I kind of joked about the fact that I could fit into the side pocket of the gig bag for the Mesa where you normally store the cord. It seems like an excellent little thing to have as an emergency back up amplifier. I may have to get one just because it is so darned impressive.

Now I’m really just faced with a problem. What do I do with my heavier gear? I did mess around with the auxiliary input on the Mesa and compared it with the effects return on the Mesa and they seem to enter the circuit at about the same point, post EQ, pre master gain and I think pre-damping factor control. At least that’s how it sounds. As such, I was able to plug my Avalon straight into the power amp which worked wonderfully. I can see myself Jonesing for the demeter tone and just throwing that & my super filter into a little two space rack bag and using the Mesa as a power amplifier. I don’t suppose they make one space rack bags? Hah.

there was a really funny moment yesterday when I threw the lids on my rack which is a four space calzone, (Joe Calzone by the way is an excellent drummer although he hits really hard. I have had the pleasure of playing with him a few times.). I brought that 45 pound rack downstairs, came back upstairs and picked up the little 6 pound or so head sitting on top of my cabinets. I plugged one of my basses in and was much more confident that I had done the right thing.

Nice! I still need to try a WD- I picked up a TT last year as a longtime Mesa fan who loved the 400+. I really dig the amp voicings so far, but like many of us haven’t had the opportunity to gig (or even rehearse at band volume) with it yet. That is where previous few Class D heads I owned tended to fall flat (lacked punch/dynamics and became tonally “congested” when pushed) vs the other heads I had to compare with (granted this was several years ago and the tech and implementation has clearly improved) so I am very curious to get to really put it through its paces. My volume needs are definitely less extreme these days though, so even if it doesn’t quite slam as much as my other amps I still see it sticking around just because it sounds so good!

 

[fdeck]

B&O sold off ICEpower several years ago, FWIW.

Their loss.

 

[Jeff Scott]

Just to add some visuals to this Class D discussion.

Walter Woods Eletracoustic Super

MarkBass LM II

MarkBass F1

Aguilar Tone Hammer 500

 

[Drummerboy2]

Fair enough...and that is a cool video. The trick comes in how those modules are actually used relative to their full set of capabilities within the overall circuitry.

An easy to understand example (albeit a bit over-simplistic) would be if you took the exact same preamp tube and installed it in Mesa Carbine and a Mesa WD-800. Same amplifier company, identical part number tubes, and possibly even the same part number tube receptacle, but the preamps will sound entirely different.

While how those circuits use the tube's capabilities is likely quite different, someone watching a recording of you installing the tubes would say they look identical. They'd be right about how it looks, but totally wrong in assuming both preamps would sound the same because a key part is the same.

Yes, I get that. I was just asking about the same Icepower modules being used in quite a bit of bass amp brands and that the Preamp side in those is the only difference. I know the design of the preamps to extract the potential of the power modules is the difference for the voicing of the amps and what they can do. Just like my Crown XLS amps, change the preamp and you get a whole different sounding system, sometimes better sometimes worst. With my experience with Class D amps they do tend to sound a little bright at first but after hours of use they then sound a lot better with that initial brightness gone, but this was with home audio using Home audio Class D and Pro amp Class D amps.

Yes, I agree. You can use the same tube/s with same parts but the way the supporting circuit is designed you will get different sounds from the same tube. Change the Voltages on the Plate and with the way it's biased will have an effect on the sound.

Class D has come along way, specially in the last 6-7 years. I have a buddy that had Hypex Mono blocks in his home system and heard this about 9 years ago when I went to visit him. I could never get used to their sound, they had a bright edginess to them and when pushed hard it was hard for me to sit and listen to them. Now, when I bought my Crown XLS 1502 Drivecore amp, at first it didn't sound too good bright and I was thinking of sending it back. I let it run with music for over 100 hours and when I came back to listen the next weekend, it sound way better and nothing like what it sound when I first put it in the system. I liked this amp so much I bought another Crown XLS but it was the 2502. I really like the sound of these newer class D amps

I had been thinking about getting a nice bass preamp and running the XLS 1502 with my bass setup but I like my Carvin BX1500 so much, I really don't want to change it out but I still may try that experiment down the road just to see.

So for me, I think I will never go back to regular Bass amps again. I love the light weight and high power output of the newer amps and my back loves it too!

 

[agedhorse]

Break-in doesn't happen in any measurable way with class D power amps. Ears and perception are a huge variable however.

 

[Drummerboy2]

Break-in doesn't happen in any measurable way with class D power amps. Ears and perception are a huge variable however.

Yes, I know this as well. But my ears don't lie and there is/was a difference that not only happened one time. It was repeatable with others having the same experience.

 

[MultiScaleMale]

 

[Al Kraft]

With my experience with Class D amps they do tend to sound a little bright at first but after hours of use they then sound a lot better with that initial brightness gone, but this was with home audio using Home audio Class D and Pro amp Class D amps.

I'm not aware of any specific type of break-in with a class D amp that would cause its tone to change. However, I do know that our ears/brain tend to adapt to new things over time (e.g. a change in how something is voiced). This can lead to us hearing them differently.

 

[Drummerboy2]

I'm not aware of any specific type of break-in with a class D amp that would cause its tone to change. However, I do know that our ears/brain tend to adapt to new things over time (e.g. a change in how something is voiced). This can lead to us hearing them differently.

I wasn't in the room to listen for a whole week and came back the following weekend and just saying what I heard. It was mostly the Brightness that was gone and the amps was more open, it surprised me as well.

I knew another person complained about the same Crown XLS amp sounding bright/congested so he just used it for subwoofer duties. I told him to run in it with the system for a week without sitting and listening to it. I didn't tell him nothing about my results but just as a suggestion to do what I did with no additional info. He told me the same thing I noticed and was surprised as well, before I even told my experience. I have read the same thing with the Hypex Class D amps as well but I never personally heard this happen with the Hypex.

BTW, I did see a post here earlier today about another member wanting a list of amps that did not use the ICE Power Modules in them, this was posted in 2019. He was complaining about the amps that used the ICE Power Modules sounding bright. I never experienced this when I did try some other Class D bass amps, I either liked the voicing or not. I did settle on the Carvin BX1500 because it came the closest to the sound of the Carvin B1000 that I liked so much for my taste and at a very good price.