Sound Card

[bikedave]

I just have a quick question which is probably very easy to answer. I will be running my HT off of my laptop. However, I am using a pro amp for my subwoofer. The output voltage from the headphones is obviously not enough for the proamp so my question is, is the output from an external USB soundcard enough for a proamp? I've looked all over and at specs for different soundcards and I can't find conclusive information.
Thanks for your help.

[ThomasW]

I seriously doubt a laptop soundcard would have enough drive voltage for a prosound amp.

I don't know about external soundcard since I run mine into a preamp...

This is probably one of those situations where you need to email tech support and ask about any external soundcard you're interested in ....

[bikedave]

Ok, so chances are need to pick up a preamp. Can you recommend an economical one since I am just getting in?
Thanks

[ThomasW]

Describe the system configuration you want to use..Is this for stereo or multi-channel?

[Operandi]

I would suggest an external soundcard with digital out that you can then feed a HT based pre-amp or receiver with a dedicated sub output.

[Hdale85]

Either that or one of the nice M-Audio outboard sound cards? Like the firewire ones or something but honestly your best bet is going to be feeding a digital signal to a preamp. You should also explain what you feel is ecinomical.

[bikedave]

Well, at this point I am just trying to get a strong enough signal to my Carver Pro amp to drive my XJ-15 Sonosub. I'm a little new at all this so forgive my ignorance. I always assumed that line level meant like the headphone output. But I now know better. With my current setup I have a signal coming from my computer, into an active crossover, into the poweramp. But with everything turned up as high as it will it is just too weak. Thats when I found out that I needed up to a 3V output into the amp. So, I called Creative to ask about the output voltage of their sound cards and all they could tell me was that their higher power external models consume 500mV so probably wouldn't output enough. I'm just building up my system now, so I've got a heavy old amp driving my mains which runs fine off of the headphone out, but pro-amp just needs more i guess. Thank you all for your help and interest. Any ideas what I should be looking for as far as minimum voltage to feed the proamp?

[ThomasW]

Any ideas what I should be looking for as far as minimum voltage to feed the proamp?

Look at the owners manual, there should be a line drive voltage spec. Usually it's between 1 and 2 volts

[bikedave]

Here are what the specs say as far as sensitivity...
They also say it can be increased to .775mV by installing a jumper on the main board. It kinda implies that the jumper is located on the board so I will have to check that out.

[ThomasW]

The jumper thing is cool. Give it a try and see what happens.

Getting even .775mV out of a soundcard maybe asking too much.

[bikedave]

Ya, that's what I am beginning to wonder, I may have found a small preamp which will boosts a very low signal up to 500mV so I may have to give that shot first just to see if it makes a difference before finding a higher power preamp. I do have a BFD, do those bump up the total signal any, beside the bandwidths which I choose?

[ThomasW]

I may have found a small preamp which will boosts a very low signal up to 500mV so I may have to give that shot first just to see if it makes a difference before finding a higher power preamp.

That's 2/3rd the minimal level needed.

I do have a BFD, do those bump up the total signal any, beside the bandwidths which I choose?

The FBD shouldn't be used to create much other than 'unity' gain, that being signal level in = signal level out. Otherwise you run the risk of clipping it, and that's not a good thing...

[bikedave]

I understand what you are saying. So, there seems to be quite an array of preamps available. Will a mic preamp work or is that input too sensitive. I'm looking at a Behringer MIC800 for example.

[bikedave]

Preamp

So, I got a Gemini PA preamp, got all excited, ran from my computer into that, into my crossover, to the proamp. Turned it all on and slowly started raising the levels, expecting great things. I didn't hear hardly a thing. The amp wasn't even recognizing a signal. The only way I can get it to boost anything is to use the phono input but then it terrible sound quality because its probably overdriving the phono input. How in the world do I get to line level, i thought the preamp was supposed to do it??? I'll post the specs to the preamp if anyone is interested:

SPECIFICATIONS

INPUTS SENSITIVITY/IMPEDANCE
Mic............................................... .................................................. .1mV / 3 Kohms
Phono............................................. ............................................3mV / 47 Kohms
Tape,Tuner,CD, Aux............................................... .......................150mV / 22 Kohms

OUTPUT/IMPEDANCE
Tape Rec............................................... ......................................150mV / 3 Kohms
Pre Output............................................ ......................................max. 11V / 1 Kohms

TOTAL HARMONIC DISTORTION
Mic............................................... .................................................l ess than 0.02%
Phono............................................. ..............................................less than 0.04%
Tape,Tuner,CD, Aux............................................... .................less than 0.01%

SIGNAL TO NOISE RATIO
Mic............................................... ..........................................more than 70dB
Phono............................................. .......................................more than 90dB
Tape,Tuner,CD, Aux............................................... .............more than 100dB

GENERAL
Frequency Response.......................................... ........5Hz - 30 KHz +0, - 3dB
Bass.............................................. ............................................+/-12dB at 100Hz
Midrange.......................................... ................................................+/-9dB at 1KHz
Treble............................................ ......................................+/-12dB at 10KHz
Loudness.......................................... ...............................+9/0/+9dB at 100/1K/10KHz
Mute.............................................. .................................................. ........-20dB
Power............................................. ............................120V or 230V, 50/60Hz
Power Consumption....................................... .............................................15W
Dimensions........................................ ...........................483mm x 45mm x 248 mm

[ThomasW]

Not sure what the problem is. I do know you don't want to use the phono circuit since it contains special EQ contouring.

Have you listened to the laptop output through headphones? Perhaps it's defective.

At this point I'd start a process of elimination. Take another source TV, Walkman/Ipod, standalone CDP or DVDP, send a signal from one of those through Aux input on the Gemini.

[Dennis H]

Something isn't hooked up right or isn't working right. It says it will output up to 11V with a .15V input. Are you sure you're hooked to the pre out and not the tape out?

[bikedave]

Hmmm... ya I definitely have it on one of the two sets of RCA preouts. I'll try using a few different sources and see if that makes a difference. The headphone out on my computer is fine and has worked great with other sets of speakers or headphones. I'll have to do a little more experimenting. With a 150mV sensitivity I guess I wasn't expecting to run into this kind of trouble. What kind of preamps are you guys using? Thanks for the resonses.

[ThomasW]

What kind of preamps are you guys using? Thanks for the resonses.

Ayre K5-xe

[---k---]

I plan on trying to take some measurements today. Tell you what, I'll hook my old USB Soundblaster live up. If it works, it is your's for the price of shipping.

[---k---]

Well, I just tested it for Dave. I hooked up my laptop to my to my Behringer EP2500 using a Creative Soundblaster Live External soundcard:

http://us.creative.com/products/product.asp?category=1&subcategory=206&product=10702

I used an RCA-->XLR cable, and it played just fine. I'm listening to some music full range through my sub right now. It is amazing how good my big sub sounds full range.