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headless car audio pre-amp

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adown

Member
Hi All,

I would like to build a preamp for my Ipod and Sirius radio, to run into the line level inputs of the amp in my motorcycle and have a volume control. I thought I found a preamp circuit, but I have a question for you. I know if I plug my ipod into my home stereo from the earphone jack and control the volume from the Ipod it will distort. How can I boost the signal, and have a volume control without distorting the preamp signal feeding the amps. Car stereos have aux iinput that will do this, but I don't have the room, or the need for the head unit. I will need a four volt signal into the amp, but I am completely confusing myself with this volume thing.

I have seen store bought preamps with a gain control, but that's for matching the source output to the amp input circuitry, not really a volume. please set me straight.
 

Sceadwian

Banned
An Ipod or Sirius radio should feed a line level input easily... Ipod definitely the output is meant to drive headphones. The Sirius might require a preamp. The reason your home stereo distorts when you turn the volume up on the ipod is because you're over driving the stereo's pre-amp. It sounds like the actual output of whatever audio system you're using on the bike is the problem not the input levels.
 
Well if his amp needs a 4V input then we have a problem because the maximum output of an iPod is 2.5V peak with a 1kHz sine wave. You may need a preamp for the iPod in ordre to drive your amplifier unless, you use the audio out from the 30 pin connector used to interface the iPod with the computer. This output is only 1.5V peak with a 1kHz sine wave. Building a preamp for this connector would be much easier.

I do know that in most car sterios that have iPod interface capability, they use the USB port to send control data to the iPod and get audio data from it as well.
 

Sceadwian

Banned
Dragon Tamer, it's possibly a misunderstanding of terminology, line-level inputs for commercial audio equipement .447 volts peak to peak, professional audio is 1.7 volts peak to peak, per Wikipedia. Germany is slightly higher at 2.19. If the voltage is outside that range it's not line-level, it's just an input and at this point undefined, so there's no way to answer the question until the required voltage levels are mentioned by the original poster.

If the voltage levels start and end can't be defined there is no possible way to recommend an appropriate pre-amp.
 
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adown

Member
Thank you for your input. That Ipod output is Max, and not a clean enough signal to amplify. I will take the audio out of the 30 pin connector. I have seen the head units with Ipod controllers, but don't have the room or use for a head unit. I am going to be running an 8" sub, two 6x9's and an 800w amp in a Harley Batwing fairing. Todays car audio pre amp/ line drivers provide as high as 24db of gain to an amplifier. I actually found a preamp kit with volume and separate tone controls providing up to 20db of gain for $22.00. I usually prefer to build electronics, but I don't think I can even purchase the components for that, let alone design and etch a board. Once again, thank you for you input and time. Have a great day, adown
 

audioguru

Well-Known Member
Most Helpful Member
An 8" speaker is a woofer. A 10" and bigger can be a sub-woofer.
Oh. You want a sub-woofer on a (hee, hee) motorcycle?? Then wear sealed headphones.
 
An 8" speaker is a woofer. A 10" and bigger can be a sub-woofer.
Oh. You want a sub-woofer on a (hee, hee) motorcycle?? Then wear sealed headphones.

Why can't he put a sub on his motorcycle? We have a right to put rediculusly large subs in our cars, he also has a right to put a rediculusly large sub on his bike. 800W is a pretty big amplifier though to be demanding that much power from a little motor cycle battery. The amps in my car only total 350W, 250W sub amp and a 100W amp

As for what adown stated about the iPod connector, if you use the audio out from the 30 pin connector you can also use the same connector to charge your iPod. For me at least, this has caused some problems with noise getting into the circuit. I suspect it was from the power supply not having enough current for all the devices attached so I'm working on this issue now. Just something to keep an eye on.
 

audioguru

Well-Known Member
Most Helpful Member
But you can't close the windows on a motorcycle then the very loud sound system (and the noisy exhaust) will wake dead people for miles.
Maybe the rider needs 800W because he is deaf?
 

Sceadwian

Banned
Isn't there a problem with voltage on Bike's anyways? I thought most of them were 6 volt systems? Then again I don't know, maybe those bigger touring bikes I see use 12 volt systems, but if it's six volt power output is gonna be a problem.
 
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