Run amplifiers from battery + a DC-DC step up

[Buzzyll]

Hey! I have these sure electronics amplifier: Sure Electronics' webstore 4 x 100 Watt Class D Audio Amplifier Board - STA508 and

Sure Electronics' webstore 2 x 100 Watt 6 Ohm Class D Audio Amplifier Board - TDA7498

I am currently using it in a 3way homebuild "portable" active outdoor speaker.. I run the amplifiers from 2x 12V 70ah car batteries in series. I use a voltage step down converter to run some parts that requires 12V (example my active crossover). I would like to push the amplifiers as high as possible.

I was thinking to add a voltage step up converter and give the amplifiers 30V instead. Currently I have the whole system fused on a 10A, and I have not exceeded that when I max it out. This fuse thing bothers me a litte, since with 24V in and <10A I only get <240W into the system, can not really see why this is happening.

Is this voltage step up plan stupid? Or will it provide me with more power to the amplifiers -> higher SPL. I was for example thinking to use this 400W boost converter: 400W Step-up Boost DC-DC Converter Constant Current Power Supply Module 665380129408 | eBay

Thanks in advance.

 

[Viennatom_new]

Make sure to buffer the 30V rail as good as possible using electrolytics. So you can get the peak power requirement for the booster down and the battery too will be happier to provide average power more continuously instead of short peaks of very high current.
Also, you ll have to take care of the booster's regulation loop with the right half plane zero in continuous mode. If it responds to a output voltage sag by increasing the duty cycle, at very first it will charge up the inductor with higher current and provide LESS energy to the output rail.

 

[JonSnell Electronic]

Why not add another battery.

 

[Buzzyll]

Why not add another battery.

Another battery will bring it up to 36V and I am a little afraid that the 4x channel amplifier will not be able to handle it, since it says 30V max. And there could also be some problems fitting another battery in the box.

 

[Buzzyll]

Make sure to buffer the 30V rail as good as possible using electrolytics. So you can get the peak power requirement for the booster down and the battery too will be happier to provide average power more continuously instead of short peaks of very high current.
Also, you ll have to take care of the booster's regulation loop with the right half plane zero in continuous mode. If it responds to a output voltage sag by increasing the duty cycle, at very first it will charge up the inductor with higher current and provide LESS energy to the output rail.

Thanks for reply.

You mean I should add capacitors after the booster to help it handle the peaks? I do not understand what you mean about "booster´s regulation loop". If you have the time maybe you can give me a schematic over how you mean I should have it wired, including the capacitor.

If I decide to use the booster the plan is to have the batteries in parallell instead, so I can get rid of the step down. So the booster will go from 12V to 30V. I forgot to point that out in the first post.

 

[JonSnell Electronic]

Two 12volt and one 6volt will do the trick.
24 plus 6 is 30.
Most older tractors used two 6volt batteries and they are still available through many dealers.

 

[Buzzyll]

Two 12volt and one 6volt will do the trick.
24 plus 6 is 30.
Most older tractors used two 6volt batteries and they are still available through many dealers.

True! That is a good option. The good thing with the booster is though, that I could if needed use only 1 battery, when the need of Ah is low. To add another battery will definitely work. The question still remains, will it also work with the booster or is a bad idea? I know about the efficiency lost but lets put that aside.

I actually have this booster at home, so if I just go and plug it in and take the system up to 30V, will this work well, or is there some parameters I have missed?

 

[29285]

I would expect that the audible difference between 24V and 30V supply comes close to 2dB. Not worth the effort imho
.

 

[cbdb]

Agreed, and you can use one battery to get the 12 volts you need, don't need the step down. Since a car battery can easily source 100 amps putting caps to help with current may be a waste of time. Smaller caps right at the amp rails might be good if you have long/smaller gauge power cables between batteries and amp to make the current delivery faster.

 

[tapestryofsound]

I run a 100 watt @ 4 ohm mono Class D power amplifier rated @ 3 amps with two 12 volt 10 amp batteries wired in series to give 24 volts. The difference between 12 and 24 volts is a lot more head room with far higher signal to noise ratio, no hiss and no bass burping. That's about it, and I reckon pushing it to 30 volts would indeed be pushing it. I listen to music in a confined space, so my rig runs at a fraction of its true capacity, meaning complex bass transients are nearly always clearly defined. Hope my example helps.

tapestryofsound

 

[Viennatom_new]

I would expect that the audible difference between 24V and 30V supply comes close to 2dB. Not worth the effort imho
.

1.938 dB electrically, acoustically less difference due to power compression, maybe 1.85 dB or 1.9dB ..

 

[Viennatom_new]

Thanks for reply.

You mean I should add capacitors after the booster to help it handle the peaks? I do not understand what you mean about "booster´s regulation loop".

If you do a converter, you should really know what a regulation loop is otherwise you should not do a converter.

 

[doctormord]

1.938 dB electrically, acoustically less difference due to power compression, maybe 1.85 dB or 1.9dB ..

How is this NOT close to 2dB, as voltwide stated? 🙄

You don’t know his speakers but do a wild guess on numbers, i don’t get the point here as well. Beside this, not knowing the boost converters bandwidth gain/phase but talking about RHP zero problems doesn’t help at all.

Just saying.

If you do a converter, you should really know what a regulation loop is otherwise you should not do a converter.

He is saying:

I was thinking to add a voltage step up converter

To add (a ready made) converter, not to build one from scratch.

 

[Buzzyll]

If I understand correctly the flaws with the booster is that it will have a hard time with the powerswings? This because of the nature of the booster. When the amplifiers suddenly drains more power, the booster will first give out less power instead of more because of the capacitors? And when the booster has "catched up", the power drain needed may be over, which will of course affect the sound quality and performance. Is that at the right direction of understanding?

If you do a converter, you should really know what a regulation loop is otherwise you should not do a converter.

He is saying:

To add (a ready made) converter, not to build one from scratch.

Exactly, I am not planning to make my own step up converter. I want to add a ready made to the my system. ViennaTom - are you only talking about creating one (from scratch) or is your comment about the one I linked in my first post?

How is this NOT close to 2dB, as voltwide stated? 🙄

You don’t know his speakers but do a wild guess on numbers, i don’t get the point here as well. Beside this, not knowing the boost converters bandwidth gain/phase but talking about RHP zero problems doesn’t help at all.

Just saying.

If it is of interst this is the speakers I use:
2x Bass: Eminence Delta 15C, 15" Speaker 400Watt/4Ohm, 48Hz - 4kHz
2x Mid: 8" mellanregister - Celestion TF-0818MR
4x Tweet: Diskanthorn - Monacor MPT-016

 

[Viennatom_new]

@doctormord: I was just kidding with some decibel commas. Please don't kill me, ok? Sorry, another joke based on your nick.... ;-)

@Buzz: sorry - misunderstanding. Having worked my whole life as a PSU engineer, almost for the last 2 decades every time when someone said, he 'll "add" or "use" a converter to reach a certain voltage / power level, this meant he would design and implement it into his or his team's latest model / product.

 

[Viennatom_new]

Quote: "When the amplifiers suddenly drains more power, the booster will first give out less power instead of more because of the capacitors? And when the booster has "catched up", the power drain needed may be over, which will of course affect the sound quality and performance. Is that at the right direction of understanding?"

No, not exactly. The situation is that the musical signal will define the currently consumed input power for the amp, which - in case of Class D - is almost independent of the DC rail voltage. So higher rail voltage on Class D means less average current consumption for the same music output. (With Class AB for example, the input power for the amp would depend on music signal AND DC rail voltage, with even more power being wasted as the rail goes higher. Higher rail voltage on Class AB would mean about equal current in that case.)
Next is that the booster - (if you mean a step up converter - there are other topologies for this application too ) - will need some time to respond to a sag or surge at the output DC rail. In continuous mode, it will even do the opposite for the very first time and only catch up after some time as the inductor current needs time to find it's new equilibrium. The capacitors at the boosted DC rail are there to help you during this time - they are your friend.