Class D Amps?

[MJ_Sotti]

100% to what the professor said. I'm a "tube snob" again, after years of being a "preamp tube snob" and have had a number of class Ds for awhile with assorted tube emulators too...and they are loud, but I think the word is not only tone, but "body". The last 100% tube was a 70s v4b I should have kept, but I would have had to throw some bucks into it...For little stuff I'm kicking around picking up a used GB streamliner to keep in my pocket

 

[bayondai]

I think I have narrowed it down to the genz benz shuttlemax 12.2, Carvin BX1500, PF-800 or the gk fusion 800.
I have the ampeg pro 4 now with the gk neo 410 and 115 8 ohm cabs. What will compare in actual volume to the pro 4? I realize wattage doesn't mean much these days?

 

[CL400Peavey]

I think I have narrowed it down to the genz benz shuttlemax 12.2, Carvin BX1500, PF-800 or the gk fusion 800.
I have the ampeg pro 4 now with the gk neo 410 and 115 8 ohm cabs. What will compare in actual volume to the pro 4? I realize wattage doesn't mean much these days?

I would go with the Carvin BX1600. It will let you balance the power between your mismatched cabs.

 

[George Mann]

One thing to consider when looking at wattage claims is that any amp that doesn't draw more from the mains than it is rated at will not deliver the claimed wattage!

I have found that many Class-D's fall way short!

 

[dincz]

One thing to consider when looking at wattage claims is that any amp that doesn't draw more from the mains than it is rated at will not deliver the claimed wattage!

I have to disagree. Power supply capacitors provide a reserve of short-term power higher than that drawn from the mains. But specs for an amp rated for burst power can not be directly compared with those for an amp with a continuous power rating.

You can't even compare two amps' burst power ratings unless you know that both were measured with the same burst duration at the same distortion level.

 

[klejst]

Awhile back I was looking into the Orange Terror Bass 500w which is a hybrid bass amp with a class D SS section. Awesome amp and had good tones if you're into the Orange sound and I liked the easier portability of it. Found a good deal on one a while back but I was too late buying it. My search continues if I find another hot deal on one.

 

[agedhorse]

One thing to consider when looking at wattage claims is that any amp that doesn't draw more from the mains than it is rated at will not deliver the claimed wattage!

I have found that many Class-D's fall way short!

Again, let me correct factual inaccuracies here...

You are misunderstanding what the rated AC line draw means. The line draw that is screen printed on the back panel of the amp, or published in the specifications is for UL, CSA, or CE/CB Scheme (international safety standards agencies) purposes and is based on what the amp draws when operating at 1/8 of rated power (with the providion that this can be increased where the amp is designed to be normally operated at a lower peak to average ratio) into the lowest rated impedance. The reason for this is that an amp is designed to reproduce music and not steady state sine waves. The typical peak to average ratio for music is generally greater than 9dB (power) which represents the dynamics within the music. The AC line draw represents the AVERAGE power based on a typical signal with 9dB of dynamic range driven to the point of clipping.

As a numerical example, an amp that is rated at 1000 watts "RMS" into 4 ohms will be tested by the safety agencies at 125 watts into 4 ohms, and the power draw will be the quiescent (static) draw plus the rated power x efficiency. On a typical class d amp with SMPS, the static draw will be around 5 watts, the conversion efficiency will be around 80% at 1/8 power so the rated draw will be 5 watts + (125 watts/0.8) or about 135 watts.

For a typical class AB amp with line frequency supply, the overall efficiency will be roughly 30% at 1/8 rated power, and the quiescent losses will be roughly 50 watts so the calculation would be 50 watts + (125 watts/0.30) or about 450 watts.

If this is to be expressed in current rather than power, the current draw that is obtained must be corrected for power factor. In class d amps with SMPS, the effective power factor is maybe 0.9 at 1/8 power so the current draw in the above class d example is (1.1 amps/0.90) or about 1.2 amps. For the above class d example, the lagging power factor due to the primary inductance of the line frequency transformer is closer to 0.7 so the calculation would be (4 amps/0.7) or about 5.2 amps.

What this really shows is the serious improvements in efficiency (and reduction in waste heat) that have been made in recent years. This is why the amps can be smaller and lighter. Also, the mechanisms of class d have some additional improvements at very low frequencies into inductive loads that are not possible with traditional class AB amps.

I also mentioned that at the manufacturers option, an amp may use a factor greater than 1/8-power if the amp's normally intended operation is less than 9dB of dynamics, this generally applies to amps that are designed to be operated under overdriven conditions so a derating factor is often applied. For example, the Streamliner uses a different dynamics derating factor than a Shuttle because the Streamliner is designed to go into territory that is more overdriven than the Shuttle.

Hope this helps improve everybody's understanding on this topic.

 

[beans-on-toast]

In the same vein, a 15A power line rating does not really mean 15 amps. A standard 15A breaker in your power line circuit will not trip like falling off a cliff when 15 amps are drawn. There is padding built into the curves that make a breaker trip. Higher current peaks can be drawn by an amp from the line power that seemingly exceed the rating of the breaker in the panel.

 

[George Mann]

An amp is only as good as its power supply. It is technically impossible for an amp to produce more power than it is drawing in!

 

[agedhorse]

An amp is only as good as its power supply. It is technically impossible for an amp to produce more power than it is drawing in!

Correct. Rather than argue, if you read and understand what I wrote, you will see this is true and WHY you are misunderstanding this labeling concept.

An amp is not "only as good as it's power supply", it's only as good as it's weakest component... be it power supply, power amp, preamp, connectors, or whatever.

 

[dincz]

An amp is only as good as its power supply. It is technically impossible for an amp to produce more power continuously than it is drawing in!

Fixed

 

[tsokabajo]

Agedhorse,

Thanks so much for the insight and sharing your knowledge. Off hand, is the sentence below that you wrote correct or might there be a typo?

"For example, the Streamliner uses a different dynamics derating factor than a Shuttle because the Streamliner is designed to go into territory that is more overdriven than the Streamliner."

Thanks, as I was a little confused.

 

[bucephylus]

Andy, I always enjoy your easily understood posts. Hope all is going well at Mesa.

I think at least part of the issue with some of the micros is cats don't spend enough time learning how to use them. They certainly have plenty of power for most gigs; and what is left after that? Pretty much voicing; which has to be learned. Then spend your money on good cabs. I've had great luck with the Shuttle 9 into a Berg NV610 (which did look somewhat hilarious) and current "big" rig is a ShuttleMAX 12 into 2 x AE212 cabs. I promise that this rig has every bit of slam that the SVT 810 at the rehearsal space has. Maybe more.

Nothing wrong with the big old rigs, except schlep. If I had roadies doing the hoist, I'd be perfectly happy with the SVT rig. I love those. Meanwhile, the Class D developments have been the best thing to happen to bass players in the past two decades, IMO.

 

[agedhorse]

Agedhorse,

Thanks so much for the insight and sharing your knowledge. Off hand, is the sentence below that you wrote correct or might there be a typo?

"For example, the Streamliner uses a different dynamics derating factor than a Shuttle because the Streamliner is designed to go into territory that is more overdriven than the Streamliner."

Thanks, as I was a little confused.

Indeed, a most significant typo too. Thanks, will correct the original post.

 

[agedhorse]

Andy, I always enjoy your easily understood posts. Hope all is going well at Mesa.

I think at least part of the issue with some of the micros is cats don't spend enough time learning how to use them. They certainly have plenty of power for most gigs; and what is left after that? Pretty much voicing; which has to be learned. Then spend your money on good cabs. I've had great luck with the Shuttle 9 into a Berg NV610 (which did look somewhat hilarious) and current "big" rig is a ShuttleMAX 12 into 2 x AE212 cabs. I promise that this rig has every bit of slam that the SVT 810 at the rehearsal space has. Maybe more.

Nothing wrong with the big old rigs, except schlep. If I had roadies doing the hoist, I'd be perfectly happy with the SVT rig. I love those. Meanwhile, the Class D developments have been the best thing to happen to bass players in the past two decades, IMO.

Agreed.

I would also like to add that the compact bass amp market isn't standing still either. There continues to be a lot of heavy duty R&D engineering going into this class of product and the future is anything but static.

 

[bucephylus]

and the future is anything but static.

One of the few constants in life.

 

[pfschim]

Andy, let me also add my thanks and appreciation for your clear statements on these amp technology questions. Even non-techies like me can at least get a basic understanding of the technology in play as things evolve in the bass amp market. As an "old school" (and an old) player who has a certain tube bias, but also a great appreciation for lighter weight gear options, I struggle with this in practical terms all the time.

For example, when I auditioned the original Shuttle 6.0 12T combo against my (admittedly beloved) Mesa Walkabout 12, I definitely felt that the 600w (@4ohms) Shuttle 12T combo did not present the same kind of useable (not tech bench specs) volume as the 300w (@4ohm) Walkabout 12 combo, and neither did the very experienced, well respected, bass guy at a local Bay Area music store. Different format, different controls, different driver and cab, of course, but to my ears - I could not make the Shuttle reach the same clean volume levels as the Walkabout - again - To My Ears. Part of it is that the two amps are not voiced the same of course, but I walked away attributing the rest of the difference to the fact that the Shuttle was SMPS and the Mesa had a more traditional toroidal transformer.

I have heavy iron amps (Fender Studio), and I have hybrid amps (Mesa Walkabout) that I can use for gigs as appropriate, but I am currently also deep into a search for a higher wattage amp (600-1kw) for certain applications. I find that, outside of pre/power rack systems, my choices come down to hybrid designs with traditional transformers (4pro, 6pro, MPulse600, LH1000 and the like) or SMPS designs (7pro, Streamliner, Tecamp 900 etc). I'd like to lower my weight profile, but do wonder if I can get similar performance from the SMPS/Class D players as I know I can from the more traditional designs.

keep the clarity coming.

oh, I and I hope you are up to good things with the guys in Petaluma.

 

[seamonkey]

An amp is only as good as its power supply. It is technically impossible for an amp to produce more power than it is drawing in!

True statement, but power supplies can store energy and release it when needed.
SMPS can be much better at doing this than line frequency power supplies. And they are lighter and cheaper, and believe it not, more reliable.

 

[agedhorse]

Andy, let me also add my thanks and appreciation for your clear statements on these amp technology questions. Even non-techies like me can at least get a basic understanding of the technology in play as things evolve in the bass amp market. As an "old school" (and an old) player who has a certain tube bias, but also a great appreciation for lighter weight gear options, I struggle with this in practical terms all the time.

For example, when I auditioned the original Shuttle 6.0 12T combo against my (admittedly beloved) Mesa Walkabout 12, I definitely felt that the 600w (@4ohms) Shuttle 12T combo did not present the same kind of useable (not tech bench specs) volume as the 300w (@4ohm) Walkabout 12 combo, and neither did the very experienced, well respected, bass guy at a local Bay Area music store. Different format, different controls, different driver and cab, of course, but to my ears - I could not make the Shuttle reach the same clean volume levels as the Walkabout - again - To My Ears. Part of it is that the two amps are not voiced the same of course, but I walked away attributing the rest of the difference to the fact that the Shuttle was SMPS and the Mesa had a more traditional toroidal transformer.

I have heavy iron amps (Fender Studio), and I have hybrid amps (Mesa Walkabout) that I can use for gigs as appropriate, but I am currently also deep into a search for a higher wattage amp (600-1kw) for certain applications. I find that, outside of pre/power rack systems, my choices come down to hybrid designs with traditional transformers (4pro, 6pro, MPulse600, LH1000 and the like) or SMPS designs (7pro, Streamliner, Tecamp 900 etc). I'd like to lower my weight profile, but do wonder if I can get similar performance from the SMPS/Class D players as I know I can from the more traditional designs.

keep the clarity coming.

oh, I and I hope you are up to good things with the guys in Petaluma.

Good question.

There are significantly different choices made in voicing between the two amps, and there's also the different approach to the way dynamics are managed between the two power amps. These two factors alone can go a long way in explaining the differences between the perception of volume. Now what's kind of interesting, (and you can read into this whatever you want to...) is that there are more similarities between the two amps (lookig at the core approach) than there are differences (other than specific voicing differences) so looking at the marketplace the two amps fall fairly close in the way dynamics are managed (though using different mechanisms to do so). Both amps are considerably different than most other offerings.

One thing that should also be noted is that (not unlike the neo versus ceramic debates) SMPS and class D technologies have allowed designers to do things that they have wanted to do and have tried to do with heavier weight, older technologies but were unable to until this new technology arrived. That means that we can expand our horizons, and while new isn't always "better", old isn't always better either. It's important to judge new products based on their merits and what they bring to the table... and that the "good 'ol days" were not as good as most folks remember them to be.

I am totally excited to be exploring some really cool new techniques and approaches with Mesa's encouragement. I don't know what fruits will result but I am doing some pretty hard core R&D in this field and opening up some doors to additional techniques that I have been reluctant to engage until now. Of course I can't discuss any specifics at this time but perhaps in the future I can share something exciting from under the hood.

 

[agedhorse]

True statement, but power supplies can store energy and release it when needed.
SMPS can be much better at doing this than line frequency power supplies. And they are lighter and cheaper, and believe it not, more reliable.

And almost always more efficient, have a higher power factor, and lower standby current too.