Computer-to-AMP-to-Speaker connection (w/ diagram)

Hi, my dad had an old computer he’s trying to boost the sound on, rather than take my suggestion to change the sound card or buy different speakers, he’s more fond of the idea of having a “tiny amp” that could “grow with his needs as he changes computers” So I’m the tech, but he’s the retired engineer so I’ve been trying to make his fantasy come true (as cheaply as possible).

I’ve found an amp, for not much (LINK) however everything I come up with possibly has a Line in jack, but has, at BEST a pair of RCA outputs on the back(more commonly it will have Terminal clips that are meant to bite down on bare speaker wire. (I don’t want to strip the speaker wire bare). They were obviously designed to pump juice out of an i-pod signal or what have you to a normal size speaker. Only, I have just his aging 2.1 computer speaker set to work with which only has the standard 3.5 mm headphone jack style plug.

This problem never got any easier for me until I finally just drew something out on paper. (HERE)

So while I’m sure everything would connect this way, I’m unsure of the effects of all these connections as far as noise and also if the sound could be properly controlled from the computer mixer area in the sound properties. My apologies for the poor handwriting, I just need to know if it would work or not, Thanks

Wait, you want to use an amp to boost the signal going into a set of amplified computer speakers? If so, not a good idea.

There should probably be a way to just go into the computer’s sound settings and boost the levels of the signal it outputs, which should be all you need. In the computer’s sound settings, look for either an EQ and turn up the levels some, or look for a “loudness” setting or something similar.

Does your father have a regular home stereo system he might be able to use instead of these amplified speakers?

Oh, and if they’re not amplified speakers, then they were only designed to take a typical headphone/lineout signal level, and would not sound good and/or last long if you were to amplify the signal.

In the very old days, computer sound cards included an AMPLIFIER to drive speakers - a SPEAKER OUTPUT. The card may have also had a “Line Out” (pre-amp level) capability. Some cards had jumpers to change the output socket from line out to speaker out. Or there may be two sockets.
In the not so old days, until now, computers only have LINE OUT, and you MUST have an external AMPLIFIER for the speakers.

( My point is I am confused by “old”. Since when ? Its 2013 … when did the speaker output go missing ? “several life times ago”!)

The OP says the speakers are 2.1 . 2.1 would mean 'stereo plus woofer".
This is the modern speaker system, it would include its own amplifier… ?? Surely.
But the drawing shows the simple speakers.

According to the drawng -
So it looks like the case of driving unamplified speakers using a line out from the computer which only has line out ? So add the amplifier…
Or, the problem may be connecting a speaker out to a line in .
This is where the older computer is connecting to modern speakers.

Speaker outputs put the signal into CURRENT.
Line outs put the signal as voltage.

So line in’s only read the VOLTAGE, they do not allow a current flow.
With no current flow, the voltage of speaker outputs is pathological - its clipped by the amplifiers voltage supply, and it becomes a mess .

There is a circuit you can by from electronics shops to convert the speaker output to “line input” voltage signal.

Hi guys, sorry to confuse, I was short on time with the drawing, the speakers really are powered and come with a sub-woofer although the rig is rated for 25W, my dad did readings on them and concluded it was 9W total (either RMS or a limitation set by the included A/C adapter). This a picture of the set aka Cyber Acoustics 3080. There must of been a re-design on them because most the pictures show this set in black with extra pieces.

I date this computer around 02-or 03, for me that’s ancient. The “sound card” I refer to is actually integrated on the MB. It has three outs which off the top of my head I can’t name only the colors of the inputs which are " pink (probably mic), Green in the center (typically speaker/headphone out) and a blue connector last (no clue). The amp btw, is in the link and plugs into the wall to amplify a signal although this device like most computer gear runs off D/C so I would think it COULD be used in a car if you only had two speakers to run it to. Not my intended application though.

And just to say it, I’ve already been through all the menus and boosted the loudness slightly as suggested by “V” prior to posting this.

light blue is the line in jack.

First, there is no problem plugging from a headphone output to a line input. One just needs to take care that the headphone output isn’t turned up high enough to exceed the voltage capacity of the line input. Generally, if that happens, you hear distortion. So, if it sounds crappy, turn it down.

Second, are these POWERED computer speakers? (As most are.) If so, don’t follow your plan. Just get newer, louder powered computer speakers. (That’s probably the best solution in any case.)

If the speakers are passive (that is, if you don’t have to plug them into a 110V outlet), then yes this will work as long as you use the correct Y adaptor.

The correct Y adapter should be labeled “Stereo to mono Y adapter”, like this one from Radio Shack.

Ah crap, should have reloaded the page before answering. This is not a solution, given that the speakers are powered.

The first question to answer is whether the old computer’s outputs are weak, or the speaker system is weak. Obviously, if the latter, he needs a new speaker system. The easiest way to test this is to try the speakers with some other gear you have more confidence in, like an iPod or a smartphone. If they’re loud enough, then all you need is a line level signal boost, something like this or this.

Note: A 12 dB gain is somewhere from twice to four times as loud. (“Twice as loud” is subjective. Many academic sources treat a 10dB gain as twice as loud, but some people report that a 6dB boost sounds twice as loud. 6dB is twice the amplitude; 12dB is four times the amplitude.)

Your first advice is the best, get a real piece of sound hardware on the computer instaed of the crappy bare-basics motherboard sound card. Even if you manage to amplify that, it’ll be crackly and nasty. You can buy USB hardware for this, but since his computer is so old it doesn’t have USB2 so that probably won’t work very well if at all.

I also agree with the other posters that it’s… strange to want to use an external amp to amplify a set of speakers that already includes an amp. I don’t see how that could possibly produce good results.

And yes, a computer from 2002 is ancient. What parts of it are that old? Surely the HD at least has been replaced between 2003 and now, right? I personally don’t see the point of upgrading a heap like that. Buy a new computer, then worry about the audio situation.

Hey all, just wanted to finish up on this thread, thanks for all your feedback and links. Although the science of sound still baffles me I leanered a good bit technology-wise from taking on this issue.

However, in the end my dad ended-up wearing the full-fledged “tech troubleshooter’s hat” and also revealed to me that he had the exact same set-up on the his primary computer (now he tells me).

So he ended-up doing some testing with the known good set-up vs the suspect set-up and ultimately ended-up ripping the volume control attenuator out of the “primary” speaker. Problem solved, he just controls the volume with the mixer and the sound recovered to it’s original volume output levels. I don’t really feel so stupid since it was one of the originally suggested replacements I gave him. Although, I did wonder what would have happened if I would have boosted the weak sound signal through an amp to raise the volume now that I know it was his attenuator that was faulty. Shorter speaker life? Spontaneous combustion? Anybody? :rolleyes: