Max input level of a PC soundcard?

There is no standard for it.

It all depends on the analog VGAs of the particular audio card and the mixer setting. The mix. input can typically take the levels up to 100mV, and the line input is up to several volts.

There was no datasheet on

I did that! The signal of 10Vrms kills the mic. input.

Why transistors? One good opamp would do.

Many audio cards do have the electric power at the mic. input, so you can feed the preamp from it.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

He talks about 1.5Vpp. That really doesn't sound right to me. AFAIK this whole area on the laptop is supplied with only 3.3V.

BTW I was pleasantly surprised by the dynamic range I got. And not so pleasantly surprised that the only way to remove hum (other than notching) is an audio transformer. Or if you have to measure below 20Hz a powerline transformer that has two individual secondaries.

I thought so :-(

Specsmanship also does not seem to be a strength in that field. I guess none of those guys has ever worked on a defense or medical design.

Ouch! That's a lot of volts.

It's easy. Opamps aren't that good on a single alkaline that has dropped to 1.3V. No problem with transistors. Of course this only makes sense if I know that I never need more than 50mVpp or so.

Mine offers 2.6V. Not much to write home about and it begins to collapse the millisecond you load it with only a few hundred microamps. Also, the

I hear "dBu" and immediately think: "dB above 1 microvolt per meter". But I don't think audio and radiofrequency field intensity mix very well.

-mpm

I'd say it should be good for "line in" levels at the "line in" input. ;-)

I've heard somewhere that this can go to .7 or 1VRMS; I'm sure you or someone could look up the standard for "audio line level" or some such. If you're building a 20-40dB preamp, then you could just clamp its output at 1.4VPk or so if you're paranoid or anything. ;-)

Good Luck! Rich

Hmm, that would mean I need two AAA cells. Dang. But for some reason my card starts to clip at 10mVrms. Thing is, I will use that on other people's (client's) PCs as well so I want to play it safe.

No idea why mine clips so early. Maybe they have some kind of PGA on there. Probably buried in a driver and there is next to nothing in documentation. In the good old days PCs were extensively documented. Nowadays you get a packing list and numerous lawyer pages, that's it.

Mine tops out at about 80mV rms. (1dB compression point)

Interesting. That is quite a few dB difference there. Maybe a PGA is involved but I guess in the absence of a standard or at least some documentation I won't know :-(

No s*it!?

Way I look at it is that the bottom noise end is bound to be a uV or so (20kHz bw ) and the makers are always keen to point out their 100dB DR, hence max' in has got to be in the 100mV area but yes, if there's a volume slider lurking somewhere in the mutiple layers of soundcard baggage, then all bets are off.

Yep, and I can't even easily find out how many bits my chip has without opening the laptop. Just sez Vinyl AC'97 on the puter. There are half a dozen of those, some 18, some 20 bits. Would be kind of cool to know when doing filtering and stuff through it. Or maybe I should buy a USB codec that has good docs. If there is one ....

Are you sure you have a line input and not a mic input?

No idea. There is an utter lack of documentation, like usual with computer stuff these days. But I have a hunch that it is a mic input because one channel carries 2.6V at a few hundred uA which I guess is for an electret mike. So does a 10mVrms clip level sound normal in that case?

Boy I wish they'd document things like IBM used to.

Late at night, by candle light, Joerg penned this immortal opus:

The mic input is a lot more sensitive than the line input. BTDT, you need to open up the advanced sound controls and select the active input. Most laptops have only mic inputs, tip is signal and ring is power (5 Vdc) so if you nees stereo inputs you're in a bind. Whichever you choose make sure to select "no sound" unless you want it fed back to the output.

Download Winscope or something similar and generate externally a signal and watch when it starts to clip.

- YD.

The max? perhaps 0 dBV? I expect to see normal levels of 0 dBm (with maybe

There are, and almost all of them are semi-pro and pro audio. Check your local guitar shop for in information starter, then the internet for better price / performance equipment. RMA Hammerfall specs out pretty good.

Should have done that yesterday when I was in the Bay Area but I was pretty bushed after a noise fixing job down there and if I had left one hour later I'd have been stuck in traffic even worse.

Out here they don't have them thar newfangled electrical stuff. But you could buy a nice fiddle, along with a matching saddle, boots, spurs, horse feed and all that.

Well, Rich pointed to a web site that explained the color code and it confirmed what I think Graham had suspected. It's a mic input, not line level, whatever that means.