| dunderchief |
So I'm a member over at elitecaraudio.com and we first started a conversation about using a tube amp in the car for powering a set of horns. Obvious problems with high voltage and SMPS's came up. Eventually it was mentioned that an array of batteries could be used to gain the voltage needed for the B+. After that the conversation turned more to batteries in general, and then to using batteries to power a Class A design.
I might add that this is not a simple passing comment or discussion. The people involved are willing to go to most any legth to improve sound. This isn't a "3 more db out of my sub" situation.
So I guess I'm asking for opinions and suggestions on using an array of batteries to create the rails for a class A amp. It seems that the Aleph X uses +- 15V rails. As far as I can figure this means you'd need 3 cells @12V each. You then halve it and regulate it down to the needed 15V per rail.
Taking power straight from a battery seems to circumvent a huge amount of the problems found in mobile audio design. Noisy power supplies suck. So I'm just looking for ideas, suggestions, the perfect way to do it. That sort of thing. Thanks in advance.
Oh yeah, one more though. I was under the impression that a pair of Aleph X channels was about $1000 to make. How much of this would be involved in the power supply and how much in the actual gain stages and such? |
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| fr0st |
It would be more sensible to build a decent SMPS. You have to make one to charge 36v worth of batteries anyway. In Car audio theres not much you can do to avoid then. Spend your time looking into making a better SMPS rather than huge battery arrays.
Google for low noise SMPS and you'll probably find something half decent. Whether it need to be linearly regulated is up to you. |
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| Eva |
You can put the SMPS in one side of the vehicle and the amplifier in the other side, any radiated EMI fields will attenuate proportionally to the distance squared and conducted EMI is easily attenuated with LC filters down to the noise floor
Anyway, a car is full of things working in a SMPS fashion, for example the alternator
Most head units and CD changers also include SMPS inside them
CD transports tend to use PWM to drive its motors and the signal read from the disc by the laser pickup is pure RF so this is also comparable to a SMPS in some ways |
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| Circlotron |
| quote: | Originally posted by dunderchief
It seems that the Aleph X uses +- 15V rails. As far as I can figure this means you'd need 3 cells @12V each. You then halve it and regulate it down to the needed 15V per rail. |
I did a few source-follower choke loaded class A's a while back. I thought they might be relevant to what you want because they will swing an output voltage of double the supply voltage.
http://www.diyaudio.com/forums/show...2377&highlight=
http://www.diyaudio.com/forums/show...6338&highlight=
Hope you find it useful. |
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| dunderchief |
| Yes, I'm aware that cars are filled with SMPS, and that the obvious sollution is to simply build one, which I have done before. But, I wasn't looking for other options, I'm looking for opinions on the one stated above. Once again, we're willing to go to all lengths here. |
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| jackinnj |
| quote: | Originally posted by fr0st
It would be more sensible to build a decent SMPS. You have to make one to charge 36v worth of batteries anyway. In Car audio theres not much you can do to avoid then. Spend your time looking into making a better SMPS rather than huge battery arrays.
Google for low noise SMPS and you'll probably find something half decent. Whether it need to be linearly regulated is up to you. |
If you want low noise SMPS go to the Linear Tech website (www.linear.com) and look to the LT3439, look at application note 70, etc.
LTC has a series of low noise switcher chips which can be used as gate drivers. You can order right off their website if you are buying less than 500 parts.
It has been suggested that you use a sine oscillator at 100kHz as a low noise driver for an SMPS -- you can drive a "rough" BJT amplifier to drive the primary of a transformer. While you could certainly do this it's a little tricky to get it to "start" and much less efficient than the slew controlled SMPS chips. referenced above.
What's the ambient noise level in the vehicle anyway ? -- even in a MB 500S or Bentley any benefit to class-A would seem to be obviated by the ambient noise. |
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| dunderchief |
| The amps would be used in competition. The Car would not be running. |
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| Cesar |
| Im planning to build the ESP smps, seems simple, but Im not sure about the transformer (Turns, AWG, measures, etc.) Can anybody help me with this? Maybe one who has made it. I can get the thoroidal cores easily, but I think EI type may give it more power. |
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| Volenti |
| quote: | Originally posted by dunderchief
The amps would be used in competition. The Car would not be running. |
I was under the assumption that non-commercial amplifiers wern't allowed in competition?
What event/class are you competing in? |
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| dunderchief |
| I'm in contact now with IASCA and a couple other people about exacty what can be used. |
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| Luke |
Hi dunderchief
how bout this one from Andrea Cufolis site.
Maybe bridge a couple if u need more power, but dont know how well the batery will cope with tha sort of drain. |
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| jackinnj |
| quote: | Originally posted by Cesar
Im planning to build the ESP smps, seems simple, but Im not sure about the transformer (Turns, AWG, measures, etc.) Can anybody help me with this? Maybe one who has made it. I can get the thoroidal cores easily, but I think EI type may give it more power. |
this interactive worksheet will get you steered in the right direction.
http://www.tech-diy.com/smps_xfmr.xls
there are other links here:
http://www.tech-diy.com/smps.htm
once you know the average current, peak current, inductance, you can decide on the core size and wire to use --
if you are going to invest the time and money in building an SMPS don't bother with the SG3524/LM3524 switching chip -- its first generation, noisy, voltage control only -- to its credit it's cheap ($0.40) and ubiquitous but there are much better switcher chips out there. |
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| sma |
| anyone have the LOW NOISE SMPS schematic or kit? |
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