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A simple audio question
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laura woodswalker



Joined: Oct 06, 2007
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Location: valley forge pa
Audio files: 10

PostPosted: Mon Feb 15, 2010 8:57 pm    Post subject: A simple audio question Reply with quote  Mark this post and the followings unread

Since people post on every imaginable topic here, I hope y'all won't mind if I ask a simple question about a dumb problem.

My son has an old laptop, maybe 5 years old...I want to use it to stream Shoutcast while I'm working in my home office. For a speaker I would like to run an audio cable from the laptop to my Peavey KB2 keyboard amp.

I tried this and it worked great the first few times. Now I'm getting nothing but static on my amp. I bought a new cable with an 1/8" and a 1/4" jack. So connection shouldn't be the problem. As for the Amp...it works fine when I plug my keyboard into it & take it to jams. As for the laptop output...it sounds fine with headphones.

So, as far as I can tell, every component of the system is functioning OK. So what could my problem be?

Thanks
Laura

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Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Mon Feb 15, 2010 9:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

I bet Sherlock Holmes would deduce it to be a cable failure. Weird on a new one but I had a new one go bad once right out of the box. I'm trying to imagine how there could have been any damage to your laptop or amp. Check that the cables are fully inserted and wiggle them to see if you get crackles of sound.

Other than that, perhaps a signal level incompatibility or volume adjustment is causing problems. Try that stuff and tell us what happened.

Les

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laura woodswalker



Joined: Oct 06, 2007
Posts: 419
Location: valley forge pa
Audio files: 10

PostPosted: Wed Feb 17, 2010 5:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
I bet Sherlock Holmes would deduce it to be a cable failure. Weird on a new one but I had a new one go bad once right out of the box. I'm trying to imagine how there could have been any damage to your laptop or amp. Check that the cables are fully inserted and wiggle them to see if you get crackles of sound.

Other than that, perhaps a signal level incompatibility or volume adjustment is causing problems. Try that stuff and tell us what happened.

Les


Hi Les!
Thanks for replying, but the problem was there before I bought the new cable. I originally used a 1/8 jack with a socket adaptor that hooked up to a stereo cable with 2 1/4 jacks for 2 of the amp inputs. (the amp has 3 inputs, an effects loop, etc.) The first few times I used this it worked great! Then the static started. That's why I bought the new cable.

Laura

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Stream Operator


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PostPosted: Wed Feb 17, 2010 5:40 am    Post subject: Reply with quote  Mark this post and the followings unread

OK Laura, thought about it some more. When I do this with my guitar amp I have to keep the volume of the computer really low or it is freakishly loud in the amp's output volume. This is because headphones are +/- 5 V signals IIRC and guitars are more like +/- 0.2 V. That's a signal level incompatibility.

Can you determine the signal level of your amp's input connection? That might tell us something useful.

Les

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laura woodswalker



Joined: Oct 06, 2007
Posts: 419
Location: valley forge pa
Audio files: 10

PostPosted: Wed Feb 17, 2010 3:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
OK Laura, thought about it some more. When I do this with my guitar amp I have to keep the volume of the computer really low or it is freakishly loud in the amp's output volume. This is because headphones are +/- 5 V signals IIRC and guitars are more like +/- 0.2 V. That's a signal level incompatibility.

Can you determine the signal level of your amp's input connection? That might tell us something useful.

Les


OK you won't believe this!!!

I turned on the amp this morning. Got the usual static with high-pitched pulses. (I don't know how to determine a signal level.) Generally it doesn't matter what volume it's at...all I get is static. (as I said, at first it had worked.)

I fooled with the computer's volume settings and the winamp volume settings & guess what.... IT WORKED!!!! Actual music came out of my Amp!!

I don't know how to explain this, cause I'm sure I had fooled with volume levels before in the course of my experimentation.

But THANKS!!! Very Happy Very Happy Very Happy Very Happy

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Stream Operator


Joined: Oct 13, 2007
Posts: 5978
Location: San Antonio, Tx, USA
Audio files: 258

PostPosted: Wed Feb 17, 2010 4:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yeah i was kind of thinking along those lines and I see you got the hint... Next thing to do is to characterize the output at different volume levels. Set the computer for low and sweep the amp volume, then step up the computer and repeat. Soon you will have mapped out a two dimensional scan of the possible volume settings that work. Or not, just a suggestion. Congrats!

Les

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