Do I need a pre-amp?

[jwl2]

Hello,

I am trying to figure out if I need a pre-amp or not. I have received different answers from different manufacturers, so I would like your help in understanding why I would need/want one. What I am trying to do is connect regular speakers to a computer (sound card).

I bought an AMP, but it was DOA so I am in the process of shopping for an AMP to use with the equipment below. It is on another thread, but so far the leading contenders for a new AMP are ADCOM GFA-535, ATI AT602 and Emotiva UPA-200.

I have a Klipsch Promedia DD5.1 preamp/decoder, but I am not sure if that will work as a pre-amp for this type of equipment. If you know, please let me know.


Here is the equipment I am using

Polk Monitor 40 Series II
Polk PSW10
HT Omega eClaro (PC sound card)
If needed, I have a Klipsch Promedia dd 5.1 preamp/decoder




Thanks!

J

 

[BoredSysAdmin]

Your Klipsch Promedia dd 5.1 preamp/decoder is the pre-amp and yes it will be needed. Imagine scenario - your soundcard driver resets its settings and windows start-up sound plays at 100%. Without pre-amp it could play at same 100% volume to amp and then to speakers. depend on amp it could permanently damage your ears and speakers.

p.s: If I were you - I wont spend so much on amp, but save money to get better speakers.

 

[ImcLoud]

I would get this...
Dayton Audio APA150 150W Power Amplifier 300-812

Its integrated so it gives you a more convenient volume control than your pc, Class A/B, has plenty of power for your speakers, is on sale rite now for $30 off {first time I ever seen them on sale}and if you ever decide to buy new speakers and want more power these are bridgeable so you can just buy another one and have 150 X 2, but honestly 75x2 is going to be more than enough for any speaker you have rite in front of you, you really only need 20 watts max.
I own a few of these, its a very good amp, sounds the same as any of the Emotivas, it was actually designed by them they used to call it BPA1 http://www.sonicflare.com/_photopost_data_500_3003emotiva_bpa_1_med-med.jpg

Them Polks are 89db sens, so you only need 25 watts to get to 100db at 3 feet with 3db headroom!!!! http://www.crownaudio.com/elect-pwr-req.htm

 

[JerryLove]

You have only one source.

A pre-amp can serve two purposes for you.
1. Volume control (as pointed out: you cannot rely on only the computer there)
2. splitting out the .1 for the subwoofer (though you could use the crossover control on the sub if you wire that way)

I'm using a Sony 5.1 AVR from 1997 as a pre-amp for my computer gear. I think pawn shops want like $30 for it.

*edit* It could also serve the third purpose of being a DAC.

 

[jwl2]

Does it make any difference if the sound card RMS value is 2.8Vpp/2Vrms?
-assuming I find a technical solution preventing windows from automatically raising the volume to 100% on boot.....although I am somewhat skeptical on this because it does not do this with computer speakers.

 

[Grador]

Does it make any difference if the sound card RMS value is 2.8Vpp/2Vrms?
-assuming I find a technical solution preventing windows from automatically raising the volume to 100% on boot.....although I am somewhat skeptical on this because it does not do this with computer speakers.

It's more an issue of the possibility of this happening than saying it will happen. I've accidentally raised the volume on my computer to a fairly high level, when you're using speakers with a preamp this isn't an issue, but if you feed that signal strait into an amp you can/will damage the speakers.

If you're really fine with that risk, there is nothing preventing you from going strait to an amp.

 

[jwl2]

What is the pre-amp do that prevents that from happening? Also, are you saying that your speakers could handle the volume you set because you gradually raised the volume, but that if that level was turned on instantly, that it could be damaging?

 

[Grador]

There are two ways a preamp could prevent this from being an issue:

1) Since volume control on many sound cards degrades sound quality, it is probably best to set the computer volume and max and use the preamp to control volume. It's far more difficult for the preamp to accidentally be turned up all the way, and literally impossible for some arrant software to do it.

2) If you are still going to use your volume control on the computer you can set the preamp such that max volume on the computer is still a manageable output level. This gives you control on your computer and protection for your amp/speakers.

Also, are you saying that your speakers could handle the volume you set because you gradually raised the volume, but that if that level was turned on instantly, that it could be damaging?

I have no clue where you got this from. No

Edit for further explanation:
the UPA-200 only requires 1.1 volts to achieve full output into an 8 ohm load (per their specs). If you throw a 2 volt signal at it you'll not only be sending 100% of the polk's rated input power [which is dubiously high], but an extremely heavily clipping signal. This is likely to destroy those drivers extremely quickly.

Edit 2 with more research: the AT602 is even worse, requiring only .9 volt for full power.

Clipping kills

 

[jwl2]

Let me see if I have this straight - the volume setting on the computer determines the voltage sent to the amp. 100% volume on the sound card will send 2 volts to the amp. Sending 2 volts to the AMP is like telling the AMP to play at 100% - which will blow the speakers. With the pre-amp in the middle, it does not matter if the computer is set to 100% volume because pre-amp determines the volume to the AMP. Do I have all of this correct?

It was mentioned that when Windows reboots, the volume is reset to 100%. If that is true wouldn't there be a lot of people blowing up their computer speakers? We know this does not happen, so I am trying to understand why this would be different for regular speakers. Please explain.

 

[Grador]

Let me see if I have this straight - the volume setting on the computer determines the voltage sent to the amp. 100% volume on the sound card will send 2 volts to the amp. Sending 2 volts to the AMP is like telling the AMP to play at 100% - which will blow the speakers. With the pre-amp in the middle, it does not matter if the computer is set to 100% volume because pre-amp determines the volume to the AMP. Do I have all of this correct?

Mostly correct. The only thing a little off is that the 2 volts to the amp will try and have the amp play well above 100% [around 200% for the amps I found specs for]. This cause a lot of distortion that is all but guaranteed to destroy the speakers.

It was mentioned that when Windows reboots, the volume is reset to 100%. If that is true wouldn't there be a lot of people blowing up their computer speakers? We know this does not happen, so I am trying to understand why this would be different for regular speakers. Please explain.

I've already addressed this, and you need to reread what was said.

Imagine scenario - your soundcard driver resets its settings and windows start-up sound plays at 100%.

It's stated as a possible scenario to display what could possibly happen. Additionally think about every computer speaker you've ever seen, they all have volume controls don't they?

I have had a program screw with my windows volume settings before. If this happens just once with with your soundcard strait to a power amp you can say goodbye to all your equipment.

 

[jwl2]

OK, that makes sense. Ordered the cables for the pre-amp. Thanks all.

 

[sterling shoote]

I think you would be served best with a control amp, perhaps a preamp/processing type such as the Sony TA-E9000ES. You will need to buy one off of ebay since these have not been made for awhile. All of your source components can plug into this unit like turntable, computer, CD player, DVD player, etc. And, at some later date you can add speakers and additional power amps for surround sound. With a control amp you can also integrate a passive sub into your system as the control amp will properly adjust crossover from mains to sub. Of course a digital pre/pro allows for music sourced from computer without the need of an external dac. All you will need, if the pre/pro does not have a USB input is a USB to S/PDIF converter. In addition to functions like source selection and volume the control amp will also accommodate recording from one source component to another which has a recording capability such as a CD recorder, reel to reel recorder, cassette deck, or DAT recorder. Tone controls have been largely replaced these days by digital sound-fields. The TA-E9000 has a plethora of these tone controls are not easily accessed. I do not miss tone controls. Finally, there are some digital pre/pros out-there which have a lot of video processing capability and the latest movie codex but these amps are very expensive and can become obsolete quickly. I prefer to get the latest movie codex and video processing from the BluRay player. It seems a more economical route to the latest and greatest.

 

[jwl2]

sterling shoote - I saw your response, but I am not sure I understand. The only thing being connected is the speakers to the computer and I have both the AMP (on order) and the pre-amp. Can you explain what you meant?

Thanks,

J

 

[sterling shoote]

Look at the specs for a contemporary preamp/processor also known as a control amp such as one from Emotiva. You will see functions which you will realize are convenient, important, or those you would like to have after you recognize the system you are putting together is not very accommodating or versatile.

 

[Grador]

He wants computer speakers, versatility isn't really important. What you are suggesting is severe overkill, overly expansive, and oversize for the intended purpose.

 

[sterling shoote]

He wants computer speakers, versatility isn't really important. What you are suggesting is severe overkill, overly expansive, and oversize for the intended purpose.

He did not say computer speakers, he said regular speakers. That implies passive speakers which require amping. There's nothing overkill about it. The control amp is simple way of incorporating a computer to be used as a source component in a high fidelity stereo system. A receiver or integrated amp could also be used. Get one of these with with digital processing and a digital converter is not necessary. With most newer models there will be a USB port which will also eliminate the need for USB to S/PDIF conversion. At any rate if the idea is to enjoy computer audio from the home theatre then yes the preamp or preamp function is necessary.

 

[Grador]

Speakers to be used only on a computer are computer speakers in my book, which has been the implication from the beginning. He already owns a preamp that will work just fine, I have no clue why he'd want to spend more money unless he decides that the sound card isn't high enough quality.

Given my responses so far you couldn't grasp that I was aware he was using passive speakers?

 

[sterling shoote]

Speakers to be used only on a computer are computer speakers in my book, which has been the implication from the beginning. He already owns a preamp that will work just fine, I have no clue why he'd want to spend more money unless he decides that the sound card isn't high enough quality.

Given my responses so far you couldn't grasp that I was aware he was using passive speakers?

I'm not trying to "grasp" anything you are saying. I responded to you as a courtesy. Remember, a forum is an exchange of ideas, which includes discussion of possibilities. There's no need for you to become argumentative about what constitutes a " computer speaker". Computer speakers have long been defined as active desktop designs which usually require nothing more than RCA stereo output from the computer's internal sound card. At any rate the OP can certainly discern what posts here have helped him see a satisfactory solution. He certainly does not need you telling me what he wanted to know. He can do that himself. Being knowledgeable of several paths to a destination is always a good idea, not to be thwarted by some-one's particular notion for the ideal route. It's why I began my original reply with the words " I think you would be be served best". There is plenty of room here on this thread for a multitude of ideas on the matter, not just ones which you have concluded the OP wanted. Also, for a beginner, if indeed the OP is a beginner, what he wants to know may not be all that he needs to know to make a good decision. Having comments from all those with experience or informed opinions in the matter, I'm sure you agree, is better than limited opinion or discussion. Most of all, forums like this are first and foremost entertainment and the sharing of like interests. There really isn't any place here for argument over matters so inconsequential. It kinda sucks the fun right out of it. This is not overall very important in the big picture, just a temporary distraction from the inevitable contemplation of our mortality.

 

[Grador]

I agree with what you're saying, and my initial post of disagreement was for the OPs benefit, showing how my opinion was different than yours. I disagree though on the definition of computer speakers being an unimportant argument. I used the phrase to mean a method of use and it was integral that my definition be understood for my statements to make sense.

Finally, if he didn't already own a preamp I would probably agree with you, but I never recommend people spend money to replicate functionality they already have unless a specific need is determined.