Class D Amps

[KJung]

I really would like to find one that worked for me just because I'm getting older and i am tired of carrying the heavy stuff. So here's the question. I use a rack mount sans amp as a pre I love it and won't change that anytime soon so pre amp doesn't matter.I also have an ampeg 810 for big shows and I play a 7 string with two lower strings. So out of all the class d amps including heads with power amp inputs and class d power amps what amps would you guys suggest I try that has enough power for occasionally pushing an 810 with enough headroom to be able to use the full range of my bass? I have already tried the eden and the swr golight stuff, they weren't powerful enough and they are the only ones Ive seen in stores in my area and could try before buying.

Sounds like some of you guys know your stuff so help an old guys back out with some suggestions. Just from reading other posts I'm already curious about the ampeg7.

For bang for the buck, a nice hi powered class D/SMPS PA type power amp with nice hi pass capability would be the thing. It would unfortunately put you into a three space rack, but it would be very lightweight. I know nothing about the different executions of PA amps, but the key for bass amplification is the input gain structure (so that your preamp is nicely matched to get optimum output) and the hi passing control (since you will want to control the deep low end of that amp, which is done for you with all in one bass amps. Lots of threads on this. You might want to ask in the fEARFul threads, since many of those guys use big PA amps to drive those big 8ohm cabs with enough power.

For the smallest, most neutral, most powerful platform for running effects or an additional preamp, hard to beat the TecAmp Puma 900. Tiny head, slams hard, not cheap. With the new full featured pedal Sans AMP VT coming out, you could fit everything in a little bag and get every tone you could think of out of that rig. IMO. The GKMB800 is also very impressive for pure slam, but has a bit stronger voice than the Puma. Half the price though!

 

[father of fires]

I just like a weighty note and I play amps that give me that. Whether it's weighty in the power amp, weighty in the preamp, or weighty in the power supply I couldn't care less about the technology behind it. All that matters is the low e punches you in the gut.

People like to blame old versions of things for crappy reputations of technology. What about crappy reputations of those spouting "truths"? I think engineers give players too much credit and don't limit their amps to settings that only sound good.

I can make an SVT sound thin and a Markbass sound huge. It's all in the execution.

 

[Mark Reccord]

This may be the general consensus but I sold my Big iron SS amps about a month after I bought a GK MB800. Its lightning quick, has a very tight bottom and I would bet that in a blindfold test most ppl could never tell the difference.

This sonic signature translates to the lower powered MB amps as well. I've owned an MB500 for about 16 months and when I bought it I demoed a used 800rb in the store alongside the MB500. The MB500 sounded every bit as tight and fast as the 800rb down low and it doesn't lose that character even when you get into the limiter. Into my Berg AE112, it's a tone monster, right down to the low B. They've done their homework. I'd also expect the same level of performance out of anything agedhorse has designed. As an EE with experience in the industry myself, it's easy to tell that Andy really has his poop together from his posts here.

We didn't try anything other than a toroid transformer, as our engineer thought the toroidal would be the best choice given the sound I was after and EMF concerns. Honestly, I am but a humble bass player and when we get to the engineering side of things, I'm certainly not on the same level with the experienced engineers that participate on this site. After I do the industrial design on a product, my job then becomes explaining, as best I can the characteristics in tone and feel that I am after to my engineering team and then evaluating the designs that they bring to me. Any comments I make are simply based from my 30+ years of experience as a bass player and from hundreds of hours of playing and critical listening to the amp design as it progressed. I ask lots of questions and try to decipher what I can, but I leave the engineering work to those infinitely more qualified than I.

I spent the first part of my engineering career in the high end home audio business working for a small manufacturer who has since gone under (stupid recession!) The primary product was a 3-way active loudspeaker system where we used single ended 300B tube amps for mids and tweeters and Bryston 2B modules for the woofers (all on one chassis). It had 4 output transformers and 2 big power transformers. After a bunch of calculations and a bunch of listening tests, we came to the conclusion that any potential sonic benefits of EI transformers were easily outweighed by the weight, lack of efficiency and EMI radiation of the things, so we went with toroids all around.

 

[grendle]

tried a bherenger, peavey and a crown. still lugging my class a/b samson around. through my rig there was a very noticeable loss of mids with the class D amps. would love to save the weight but cant deal with the loss of tone. YMMV.

 

[DrumsAndBass]

I cast my vote in favor of Class D amps. I recently bought an Aguilar Tone Hammer 500 and gigged with it. Like many others, I've read thousands of words here on TB about the pros and cons of Class D. I very recently used my TH 500 (with my Class AB plugged in nearby) with my fEARful 1515/66 bass cabinet on a gig. I enjoyed all of the same fat, clean, warm and round tones as my Class AB amp. The TH 500 did not heat up at all and I was actually asked to turn down my stage volume - which I did. I used to think that a Class D amp would not be able to cut it for me but I was really wrong about that. It did not leave me wanting for more bass tone and volume for a 4 hour Reggae gig.

 

[KJung]

tried a bherenger, peavey and a crown. still lugging my class a/b samson around. through my rig there was a very noticeable loss of mids with the class D amps. would love to save the weight but cant deal with the loss of tone. YMMV.

'Loss of mids with a class D amp'

Edit: Didn't mean to be a bit snarky here, and I don't question what you are hearing. However, it would not be due to amp topology. Probably due to different gain structures on those amps, different hi passing, and possibly different volume taper design, making them sound quite different with the same preamp settings and/or master volume settings.

 

[dincz]

'Loss of mids with a class D amp'

Or with any PA power amp for that matter!

 

[agedhorse]

It takes more than electronics 101 to design switchers

Understatement of the day!

 

[agedhorse]

But there remains that question, and I'm dope enough to ask it...if there is truly no difference based on power amp topology alone, why do people report hearing differences, even with the power amps our sound running friends like to use?

Excellent question actually.

I think that in some cases there are significant differences, but the differences are mor often due to hearing defects in a particular implimentation rather that the topology itself. When a power amp does not sound good, or suffers from a particular artifact, what you are really hearing is the defect (or possible a particular design choice) rather than purely the topology itself.

Usig Jerrold's example of premature current limiting, this is (or was) primarily a designer imposed limitation that was used for a particular reason (size, weight, cost???) rather than something inherent it the technology itself. A more robust design could shift the current limit threshold up above where it's an issue and that artifact then disappears.

It comes back to the decisions made during the design, the applications engineering rather than the raw technology itself.

 

[agedhorse]

Frankly, there are quite a few really solid executions of SMPS/class D bass amps on the market. Each one has made their own design choices because each manufacturer has their own tonal goals. The overall tone of each amp may be very different even though all use a SMPS/class D platform. There are also some poor class D bass amps on the market, suffering from some of the same problems that others have mentioned. IMO, it has to do with design choices rather than the SMPD/class D topology itself.

It's really unfortunate that some of the early SMPS/class D amps were pretty poor performers, thay left a bad taste in people's mouths and fueled the stereotype that no longer holds true today (for the most part, with the quality manufacturers anyway).

 

[Bob Lee (QSC)]

A SMPS is constantly switching back and forth between on and off and tends to behave in a very linear manner as the volume goes up. A heavy transformer is always on

No, that's incorrect. A typical SMPS creates high frequency AC for its power transformer. A line-frequency power supply uses line-frequency AC for its power transformer. Neither transformer is "always on" but instead requires alternating current; transformers do not pass DC.

 

[seamonkey]

It's really unfortunate that some of the early SMPS/class D amps were pretty poor performers, thay left a bad taste in people's mouths and fueled the stereotype that no longer holds true today (for the most part, with the quality manufacturers anyway).

You could go back to the late 60's and there were some poor designs of SS amps. Same thing, constantly repeated here that SS sucks because of some bad amp design choices way back when. At the same time there were good designs for the technology of the '60s time, but that's not what people either had access too our bought.

And actually it's still that way with class-ab, and their power supplies, and active devices of choice.
They are bad designs.
Some would think shoving in a component or transformer because some past design had it good would make a copy design good. It doesn't automatically make a new design good.
And there's good designs.

Between a good class-ab and good class-d amp part - there really are no difference sonically. The trade offs and comparisons should be made elsewhere.

 

[JimmyM]

People report hearing differences between power cords, too.

Right, but the difference is power cords are easily proven not to make a difference

 

[JimmyM]

Excellent question actually.

I think that in some cases there are significant differences, but the differences are mor often due to hearing defects in a particular implimentation rather that the topology itself. When a power amp does not sound good, or suffers from a particular artifact, what you are really hearing is the defect (or possible a particular design choice) rather than purely the topology itself.

Usig Jerrold's example of premature current limiting, this is (or was) primarily a designer imposed limitation that was used for a particular reason (size, weight, cost???) rather than something inherent it the technology itself. A more robust design could shift the current limit threshold up above where it's an issue and that artifact then disappears.

It comes back to the decisions made during the design, the applications engineering rather than the raw technology itself.

Good answer, actually! There's a big size/weight/cost war going on with bass micros these days, so maybe that's what I'm hearing with them. Wish I had more equipment here to test out that idea. I think I'll move next door to Tom Bowlus

 

[DrumsAndBass]

What amplifier designs are coming up relative to bass guitar amps ? Are people working on new designs ?

 

[HolmeBass]

This is not correct. Maybe true for others, but not for the WTX260. trust me on this one

I agree, Eden's manual specifically lists different output wattage based on input voltage. People in Europe get more output from their WTX-260's than us in the US.

I will add further to the consensus: I don't find any inherent sound or issue with class D power amps and their weight-saving SMPSs. I have the WTX-260 and aside from one time when it smoked, it's been a workhorse (although the DI is on the fritz, need to get it serviced...) and even backed up a Mesa M2000 at a fairly loud rock gig. I turned the main volume way up and that little sucker hung in there like a champ. I was surprised, actually.

My main rig is now a Genz Benz Shuttlemax 9.2 and it is an excellent amp. Loud as heck, really. I would use it for metal pumping 2x 8 ohm 410's (or for real death, 2x 8 ohm 810s or 412s, muahaha!) and I shudder to think of how loud it would be.

 

[grendle]

'Loss of mids with a class D amp'

Edit: Didn't mean to be a bit snarky here, and I don't question what you are hearing. However, it would not be due to amp topology. Probably due to different gain structures on those amps, different hi passing, and possibly different volume taper design, making them sound quite different with the same preamp settings and/or master volume settings.

I did try and get along with them, my back likes the weight difference for sure. i run my bass into my tuner, into my pre, then power amp into my cab. Definatly different gain structures with all three of those and my current amp. played with each one for a few days, the crown sounding the closest to my samson, but still nothing in the mid range presence. lots of lows and highs and plenty of power just still sounded hollow. been my experience with class D heads and power amps. their passable i guess, just not for me and the tone i go for.

 

[agedhorse]

What amplifier designs are coming up relative to bass guitar amps ? Are people working on new designs ?

The industry is always working on new designs and refinement of existing technology as new components become available.

 

[Blackjax]

Carvin BX500 is an great 500 Watt Head good down to 2 Ohms. Endless (almost too much) choices for EQ/Tone adjustment. This is my pick in the Bang for the Buck category.

I've been wondering this lately and a discussion about Class D amps seems like a place to ask. What others in the class are good to 2 ohms?

 

[KJung]

I've been wondering this lately and a discussion about Class D amps seems like a place to ask. What others in the class are good to 2 ohms?

Not many. Genz has the Shuttle Max 12.2, which would be my choice if I had to run below 4ohms. Two separate power amps, each 4ohm minimum, so functionally '2ohm safe'.

The TecAmp Bonafide and Puma1000 are similar dual power amp design.

Finally, the Glockenklang Blue Soul can be special ordered to be 'safe' down to 2.67 ohms (i.e., 3 x 112 or a 4ohm 410/8ohm 210, etc.). However, you lose some power at 4ohms.