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Old 24th February 2008, 02:47 PM   #1
jtaytay is offline jtaytay  United Kingdom
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Default TA10 and car battery - crackling sound

I'm using 2 TA10s as power amps with a Musical Fidelity pre-amp. Having used the supplied plug in power supplies, I wanted to try a car battery and did this today. Both TA10s use the same battery, but there's a crackling sound in both speakers when the volume goes up. It seems to coincide particularly with louder lower frequency sounds. But for that, the sound is crystal clear, dynamic and promising.

Can anyone tell me why the crackling is happening? As I say, it happens in both speakers. I've tried changing the power cables from battery to amps to rule out problems there. The pre-amp has it's own seperate power supply. If I didn't know better (and I don't!) i'd think they were shorting.

I'm very keen to experiment with what clean battery power will add to the mix, but i'm worried that if I continue to experiment without getting rid of the crackles I'm going to do some damage.

Suddenly occurs to me, in case it's relevant, I use each amp to power one speaker. I do this by taking that amp's left and right channels to feed the higher and lower frequencies of each speaker. I've done this on the basis that should give a little more more power. Don't know if this introduces earthing issues etc.

Thanks

Chris
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Old 24th February 2008, 06:43 PM   #2
Puffin is offline Puffin  United Kingdom
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What you are hearing is distortion due to insufficient current getting to the chip. The batteries are 12v ? What ah are they ?

I found that the only successful way of using a battery with my modded Sonic Impact amps was to use a 30 ah, 12v car battery.(and it was only powering one amp) You should also use some caps (say 20 - 30,000uf) to store some energy and smooth the battery power.

By the way batteries are inherently noisy !

"Noise figures for a lead-acid suggests they're not all that quiet under load...

Links to this thread here.

Those battery noise plots are much like mine. Glad to see them.

Batteries are very quiet until you put a load onn them, then they are noiser than most AC supplies."


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The above are posts from the Diyaudio site."Noise figures for a lead-acid suggests they're not all that quiet under load...
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Old 24th February 2008, 09:04 PM   #3
jtaytay is offline jtaytay  United Kingdom
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many thanks for the reply Puffin. I couldn't follow any link to the source you cited nor did I find it when I searched. Could you give the link again.

I am interested in knowing more as I'm intent on getting the best sound from my system within my money constraints. As I've said, I've got very little knowledge of electronics. Having said that, after reading your post, I'm more confused now than before. While the link to the other article you mentioned may shed light, could you help with the following where I'm confused:

1. I've seen references to people using car batteries with extremely good results. I've also seen references to items like DACs (altmann springs to mind) and other tripath amps (Red Wine Audio) where designers and users swear by battery (including car batteries) as a clean source of power, yet you say they are inherently noisy?. How can this be if others prefer battery power? If only some car batteries supply such clean batteries, how is it possible to know which ones are best?

2. you say it's distortion due to insufficient current. Would this be so, if, as in my case, the nature of the 'distortion' doesn't change with volume when I turn off one of the amps. It still appears at a similar level of volume. Would this be consistent with insufficient current, if it doesn't seem to change when one amp is no longer being powered?

Also, the power supply that came with the TA 10s was rated at only 3.5 amps. My battery is 12v 45AH. Until the crackle starts, the sound doesn't appear to be anything but very clear and free from distortion ie there isn't a gradual increase in distortion according to volume, more an all or nothing distortion on certain low frequency notes when volume high enough.

Chris
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Old 24th February 2008, 09:54 PM   #4
Eva is offline Eva  Spain
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You seem to be describing straight clipping. Remember that you can't get any loud with 12V and conventional hi-fi speakers.

BTW: Be careful with ground loops when more than one amplifier module share the same signal source ground and power supply ground.
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Old 25th February 2008, 03:51 AM   #5
jtaytay is offline jtaytay  United Kingdom
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I'm sure it's not clipping Eva - with the normal power supplies I've gone louder and know what the amp sounds like when it loses quality and distorts/clips. So, I'm wondering about the ground loop suggestion. I've been looking elsewhere on this forum and mention was made of earthing the battery. I remember having a similar problem once before when using my two TA10s without a pre-amp, and a particular DAC (Art Dio).

I'd like to try earthing the battery. I know I take a cable from negative terminal, but where do I connect it to to provide the earth?

Also, is there likely to be any problem with my bi-amping arrangement in principle? ie each amp (jumpers set up to be power amp) feeds the high and low inputs to one speaker (so, for example, the left channel goes to upper and the right channel to lower frequencies). To do this, I use two adapters on my preamp to double the phono socket outputs and provide the same signal going to the left and right phonos for each amp. Could this arrangement lead to earthing complications? If so, beside the battery, should I look to try earthing this set up elsewhere.

Chris
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Old 25th February 2008, 03:33 PM   #6
Puffin is offline Puffin  United Kingdom
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Here is the link.

Sonic Impact 5066 Parts List & Modifications

I just occured to me that my speakers are really sensitive and only need about 1 Watt to go loud. I have alos used a PS with 13.8v which gives more power.
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