ECN Forum Forums Technical Discussion Re: Computers and the Internet Amplifier For PC Speakers

I found two Fisher cabinet style speakers at a yard sale for $20.00. Three speakers in each cabinet. They work fine.
I want to find an amplifier so I can use them with my PC. The speakers are Fisher Model # DS-825, 8 ohm, input power 10-100 watts, crossover? 1.5/6 khz.

I found this "Pyle" mini amp on Amazon and I am not sure if it will work. Here is the link.

http://www.amazon.com/PCA2-40-Watt-...mp;ie=UTF8&qid=1310926253&sr=1-2

Any help or suggestions appreciated. Thanks John

That should do it.

I got a nice amp at Goodwill for a few bucks tho.

Greg,
Goodwill? I had no idea. I have never been inside a Goodwill store. My wife goes to all those type stores. I thought it was just clothing?
I just happened upon the speakers as I was driving by a house.


Will the 40 watt output from the mini amp, drive the 10-100 watt speakers enough to improve the sound verses PC speakers? Will it be loud enough?

I guess I could find another used/old stereo amplifier instead and get the 100 watts instead of the 40 watt? But the 40 watt is available right now. $45.00
Whats your suggestion? I hope I am making sense with these questions?

Thanks Very Much..........John

It all depends on how close that is to actually being 40 watts. My guess is it will probably be OK. "100 watts" in the olden days was usually a fantasy. I am driving some pretty big "disco era" speakers with a pretty modest amp. The actual silicon is pretty cheap these days.

Thanks Greg.

Greg,

I got the 75 watt model for a few more bucks. Found out afterwards it is 4 ohm amplifier and my speakers are 8 ohm. Manufacturer says no problem and so does the community forums. Your take? Yes? No?

4 ohms would allow you to put 2 (8 ohm) speakers in parallel on the same channel.

I read a little about that amp you were looking about and it is 40w "max" whatever that means and the consensus is that is really about 8w RMS. Unless you are in the Hollywood Bowl that may still be plenty. There has been so much lying going on in the amp business, for so many years, it is not clear how much power is really enough.
If something has a heat sink about half as big as a beer can on each channel, I figure it is big enough for me.

The 40 Watt Power Amp's Data shows 40 Watts Max into a 4 Ohm Load.
If this Power Amp drives an 8 Ohm Load, the Max will be 20 Watts.

Now, if this Amp can continually push that 20 Watts into the Woofer (largest Speaker) via a Digital'ish signal, that will be quite thumpy!

Unless you really want "noticeable" Low Frequency response, the 20 Watts per Channel - 2 Channel Output from this Power Amp should be fine.

As mentioned by Greg, the RMS "Actual" (continuous) Power Output for this Amp is 8.0 Watts into a 4 Ohm Load - which loosely translates to 4 Watts into an 8 Ohm load.

From the looks of the Amp's design, I would say this RMS Power would find it's way into the Mid-Range and Tweeter Drivers most of the time - with the Transient Max Power pulsing the Woofer for very short bursts.

Hopefully the High End (Tweeter) Driver has a proper Crossover!
Power Amps with low output Power ratings tend to fry Tweeters (Tweeters resonate "easier" with very simple Crossovers and low power amps).
Cheap-'o Capacitors exacerbate the issue - until the Cap pops!

For fun... to "clean up" the signal leaving the Sound Card, Pre-Amp the signal with a 10 Octave Graphic Equalizer.
Bypass the E.Q.s on the PC (i.e.: Windows Media Player's Equalizer) by placing all the slide pots at the center "0" position.
Only Equalize the signal through ONE EQ! Things begin to sound very crappy when Two or more EQ's are working on the same output signal!

This just in...
I just noticed the power Amplifier you obtained is rated for 75 Watts into a 4 Ohm Load.
This should give you around 38 Watts Peak into your 8 Ohm Loads (Speakers), with a continuous RMS Power of around 9 Watts. Again, these are "Per Channel" ratings.

There are many different Tweaks which may be applied to an Audio System... some are intense (read: lotsa' $$$), others are quite modest (read: realistic, with good quality sound, not lotsa' $$$).

Good luck with your Digital Audio Quest!

-- Scott

Forgot this...



These are the "Roll-Off" points for the Mid Range Driver's Crossover settings.

In a Nutshell, the "1.5 kHz" is the Low-End Rolloff Frequency for the Mid Range Driver, as set by the Crossover design; and the "6 kHz" is the High-End Rolloff Frequency.

The Crossover will "Bandpass" the range between 1.5 kHz and 6.0 kHz through the Mid Range Driver (the "middle" Speaker in each Enclosure).

Frequencies < 1.5 kHz become attenuated at the Crossover, and will be Low-Passed through the Woofer Driver - via the Low Hz Crossover section (if included...).

Frequencies > 6.0 kHz become attenuated at the Crossover, and will be High-Passed through the Tweeter Driver - via the High Hz Crossover section.

-- Scott