Class D Amps

[JimmyM]

Originally Posted by Hounddog

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.

Maybe. Extra wattage does seem to help to that end. Never played that one, though.

[Hounddog]

Originally Posted by KJung

god help us

This made my Day.

[modulusman]

Originally Posted by KJung

Don't understand what you are saying here. I do agree that the WTX260 was probably the worst class D execution ever done (although the preamp is quite nice sounding). Low power (even considering its low power rating), and horrible limiting. However, again, there is NO reason to treat 'class D' watts different from 'class H' watts, or class 'A/B' watts.

I agree. What ever you do don't use the mute unless you want to hear a very loud pop. One of the biggest POS Eden ever manufactured.

[R Baer]

Originally Posted by Bob Lo

Enlighten us,Roger, on how that translates into performance,if you would please.

Sarcasm, noted, but why not. Installed into our amp, the switch mode power supplies we tried felt a bit more immediate. Like a faster attack to the note. It also made the amp sound just a bit brighter, which seemed to increase a bit at higher volumes. The toroidal transformer on the other hand, added a bit of cushion to the attack of the note that felt a bit like what players refer to as "tube sag" as the volume got louder. It was also a hair warmer sounding. To my hands and ears, the toroid had a bit more body to the note as the volume increased.

These are only the perceptions of myself and my design team in trying both SMPS and a large toroidal transformers in our particular design and the differences were definitely subtle enough that some players wouldn't hear a difference. Keep in mind also, that just about every component decision can affect the sound and feel of the design in some manner. If I had been going for a little punchier, brighter sound, I would have gone SMPS. As it was, I was looking for a warmer sound with a bit of tube amp like compression going on and I found that the toroidal transformer delivered on that a little better. Pulling out my crystal ball, I can see a point in the not too distant future when the price of copper and fuel for shipping will render the big heavy transformers obsolete due to the enormous cost of actually putting of of these into a bass amp.

[greggster59]

The Ampeg SVT-7PRO is a 1000 Class D amp (rated as such, anyway) with a tube pre amp. Sounds pretty good to me and weighs about 15lbs.

[JimmyM]

Originally Posted by R Baer

Sarcasm, noted, but why not. Installed into our amp, the switch mode power supplies we tried felt a bit more immediate. Like a faster attack to the note. It also made the amp sound just a bit brighter, which seemed to increase a bit at higher volumes. The toroidal transformer on the other hand, added a bit of cushion to the attack of the note that felt a bit like what players refer to as "tube sag" as the volume got louder. It was also a hair warmer sounding. To my hands and ears, the toroid had a bit more body to the note as the volume increased.

These are only the perceptions of myself and my design team in trying both SMPS and a large toroidal transformers in our particular design and the differences were definitely subtle enough that some players wouldn't hear a difference. Keep in mind also, that just about every component decision can affect the sound and feel of the design in some manner. If I had been going for a little punchier, brighter sound, I would have gone SMPS. As it was, I was looking for a warmer sound with a bit of tube amp like compression going on and I found that the toroidal transformer delivered on that a little better. Pulling out my crystal ball, I can see a point in the not too distant future when the price of copper and fuel for shipping will render the big heavy transformers obsolete due to the enormous cost of actually putting of of these into a bass amp.

Geez, I hope not!

[Passinwind]

Originally Posted by R Baer

Installed into our amp, the switch mode power supplies we tried felt a bit more immediate. Like a faster attack to the note. It also made the amp sound just a bit brighter, which seemed to increase a bit at higher volumes. The toroidal transformer on the other hand, added a bit of cushion to the attack of the note that felt a bit like what players refer to as "tube sag" as the volume got louder. It was also a hair warmer sounding. To my hands and ears, the toroid had a bit more body to the note as the volume increased.

These are only the perceptions of myself and my design team in trying both SMPS and a large toroidal transformers in our particular design and the differences were definitely subtle enough that some players wouldn't hear a difference. Keep in mind also, that just about every component decision can affect the sound and feel of the design in some manner. If I had been going for a little punchier, brighter sound, I would have gone SMPS. As it was, I was looking for a warmer sound with a bit of tube amp like compression going on and I found that the toroidal transformer delivered on that a little better. Pulling out my crystal ball, I can see a point in the not too distant future when the price of copper and fuel for shipping will render the big heavy transformers obsolete due to the enormous cost of actually putting of of these into a bass amp.

Roger, did you try any E-I or C-core transformers while you were at it?

[agedhorse]

Originally Posted by BogeyBass

The sacrifice is that most of them are chip amps and there is a thermal limit to chip amps.

and a many use the same power section which has been developed by the same company and then the advertised company has used their own preamp design in front of it.

The actual power of a single section is only 180 watts, then 2 power modules are ran in a bridged configuration for 360 watts.

making most of the "400"to "500" watt market

out of the 180 watts just about 120 of it is useful, the other part is cracking distortion that sounds horrible,

So because of thermal limits minimum load for most class D is only 4ohms and even at 4ohms depending on the design of the chassis. Even a 4ohm load will run them close to overheating.

so if you like running multiple cabinets, or plan on adding more in the future you have to be aware of this and buy higher ohm cabinets. if unaware of this when adding more speakers you have to buy and spend more money on completely different cabinets. Majority of use full cabinets being 4ohms, pairing 2 of them for a 2ohm load is impossible

Because of the built in protection devices built into the chip, if they overheat the signal will just be shut down. usually in the middle of a show.

with ratty light power supplys, depending on the player if your use to digging in they are rather lacking in tone.
Shut down often in the middle of shows, and modern PCB construction makes them impossible to repair, other than replacing the whole board that has failed and continues to fill land fills with toxic trash.

but hey most players only really need 180 of that 400 watts they think they are using, and most use single cab applications.

most the problems are not found, aside from overheating and a few models that constantly fail and have to be repaired.
Just do a search for the most failed/cracking class d's out there and dont buy them.

Sir, much of what you are stating here is both inaccurate and completely false. This comes from a lack of understanding about the technology and how it works. It is a dis-service to those trying to understand this technology and why it works.

Before you dismiss me as a class D techno-geek, I am an experienced engineer and have designed many large class AB/G/H, and D amps, as well as both line frequency and SMPS. Properly designed, there is no difference in performance which is why almost all of the big pro audio touring amps these days are a combination of SMPS and class D. Reliability and performance is as good or better than line frequency power supplies and class AB/G/H lines they replaced.

[R Baer]

Originally Posted by Passinwind

Roger, did you try any E-I or C-core transformers while you were at it?

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.

[dukeorock]

My Genz ShuttleMax's replaced the very nice lead sleds I'd been using previously. The sleds weighed around, heck I dunno, 50+lbs. The Genz weighs under 7lbs. I got the Genz for performance reasons...I had no issues schlepping the sleds...The Genz is a better amp for my uses and had nothing to do with weight, though after a couple years of touring these amps, I'm not exactly bummed that they weigh so little

[TinIndian]

I know two things; I'll never turn my Streamliner 900 loose and I'm never going back to a "traditional" head.

[RS66LB]

Originally Posted by KJung

No compromises at all. These heads have been around for years. All bass heads sound different. There a midrange voiced 'heavy heads', and there are small heads that hammer huge down low. There is not 'class D' sound IMO and IME. And, more importantly, the SMPS power supplies (which is really what makes 'small heads small') have significantly improved over the last 6 or 7 years.

The only thing they won't do is sound like an all tube amp pushed hard. Of course, neither will a 40 pound version of a solid state head.

lol -was about to answer when I read your post -couldn't have said it any better, have a great day.

[Jerrold Tiers]

To be perfectly fair....... with a transformer, there is NO LIMIT to the power throughput other than the impedance of the wires (inside and outside of the transformer), and the fuses/circuit breaker.

With a switchmode supply, there ALWAYS is a current limit..... If you want, you can make that limit stupidly huge, so that something else will limit the current, but that costs money.

Some of the original issues with SMPS probably come down to those current limits. (the problem is always the protection circuits, isn't it!!?) Issues with "weak low end", lack of "punch", etc, etc, etc. Most of the stuff that folks associate with SMPS in audio amps.

In more recent times, this issue has gotten quite a bit better.... the parts used have improved a lot, and folks have become considerably smarter about using them.

An SMPS that truly acts like a transformer? So far I've not seen one, but I have seen some come close. It will happen.

[agedhorse]

The SMPS in our NeoPak 3.5 was designed from the ground up to emulate our line frequency supply (though under the heavy load there were no line frequency harmonics... an improvement). When you overlay the impedance curves, they were virtually identical in sag envelope as well as impedance. It does make sense because the energy storage was very similar as was the impedance of the HF transformer plus chokes. In practice, I could not tell the difference between either power supply on the amp (it was a class AB power amp).

[seamonkey]

Ah, but that's what happens when you study SMPS engineering. Build it, test it, make adjustments and re-engineer it.

If another builds one, and it sucks, then they blaim the technology and forever saying it sucks and isn't ready yet.

High end A1 prime audio is using SMPS designed by engineers who know what they are doing. It takes more than electronics 101 to design switchers

[JimmyM]

Andy, you realize that the amount of knowledge you specifically have on the subject, plus the enormous amounts of good will and respect you've earned as a big cheese at Genz Benz, makes it hard for most of us to argue with you and not look like dopes

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?

Again, certainly not slamming micro technology. I think I've bought enough micros to prove that I like the format

[4-string]

People report hearing differences between power cords, too.

IMO, differences or not, micros are so good now that buying anything else makes no sense at all to me personally. I have never been able to tell that micros have something tonally going on that they all have in common. Maybe I'm just blessed with mediocre ears.

Different story for the all-tube guys of course.

[KJung]

Originally Posted by JimmyM

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?

Again, certainly not slamming micro technology. I think I've bought enough micros to prove that I like the format

For a fews of reasons:

1) As Jerrold and others (including me) have said, this WAS true back in the day, and it is hard to 'not listen with your eyes' once something has become 'common knowledge' over years.

2) SO many times, this is based on someone listening to 2 or 3 amps and then attributing the difference between those amps to the wrong thing. So someone plays a DB750 and then a Markbass F500, and concluded 'well, the big amp has a lot more bottom' so class D amps must all sound 'quick and punchy but without the big slam'. They don't take into account wattage differences, designers tone goals, hi passing, preamp voicing and a million other things. Kind of similar to back in the day when players would play a Ric and then a P Bass and conclude 'neck throughs have more sustain and bolt-ons have more punch'

3) Front of house guys.... I have never heard a front of house guy believe there is a differece in the slam or whatever of a current SMPS amp and the old iron... not once. Most of them are so excited about their new rack of Crowns or whatever that you can't shut them up about them! That being said, just like a great player who doesn't really take time to understand gear, there are many front of house engineers (very good ones) who really don't know much about the actual workings of the gear.

4) Talking to older repair techs... 'yeah, this new stuff sucks'. Same in all categories. You typically stick with what you understand and replace a lack of experience and knowledge of recent improvements with disdain! I'm of the age where I unfortunately understand this.

IMO and a lot of IME. Again, if you blind listening test 20 amps, with different power amp topologies, I would be very comfortable predicting that NO ONE could identify the amp topology beyond random chance... period.

In your case, where you love your SVT, you are completely correct saying that no other amp really sounds and feels like it. However, that is true of other tube amps, or big iron solid state amps, or micro's. All amps sound different for hundreds or reasons. Nothing sounded like my heavy Glockenklang either... until Glockenklang made a class D version with a very high quality class D/SMPS module and identical preamp!

[KJung]

Originally Posted by R Baer

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.

It would not surprise me if a given engineer has more expertise with some designs versus others, and like the rest of us, has preferences. Not suprising also that there would be strong preferences, especially if you just kind of 'attached' a class D/SMPS module to a preamp for a quick test. From what I understand, there is a LOT more to it to really dial that in.

Lots of ways to get a good tone, and for a new, small start-up amp manufacturer, it would not be surprising to me if you couldn't get to 'better' performance more quickly with older technology.

That all being said, I think there will always be a place in the market for an amp like yours. 2ohm operation, lots of features, high wattage, moderate weight, and some unique features like your 'transformer based tube drive', etc., etc. I agree that for some, the feel of a nice chunk of metal when you pick the unit up is 'impressive and comforting'! NOTHING wrong with that.

[Nephilymbass]

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.