# generating a 10mVpp signal from computer

I have an input to a system that requires a 10mVpp max signal. I have to use my computer to input it due to constraints out of my control. I am well aware an audio card cannot go down that low. I have several attunators, one active and one passive (just a potentiometer and some resistors).

no matter what I do I cannot get the signal to go that low. I have also tried introducing a digital amplifier (just some high quality digital speakers with an audio out) into the system between the computer and the attenuators but had no success.

Where can I go next? what other information can I provide to help.

I am running audacity on a dell optiplex 760 (my computer) and it has the manufacturers audio card in it. I did some quick research and it seems most built in audio cards have about 46Ohm impedence. I couldn't find info on my exact card. It maxes out its output at about 3Vpp and starts to struggle keeping its output stable below 150mVpp.

I am also using a probe master 20:1/200:1 active attenuator (model 4231) and a homemade potentiometer attenuator.. about as simple as it sounds.

ANY help is appriciated.. this is stumping several of us and we are unsure of where to go next.

• Is Ohm's law not working for you? A simple resistor divider should be able to provide an arbitrarily low signal. If the frequency is very high you may get capacitive feed through from poor layout/wiring but you don't say what kind of signal you are trying to attenuate. May 2, 2016 at 19:43
• This should be simple. If your voltage divider does not work, there's an underlying issue. Please draw a systems diagram so we can see what you're trying to do, and where you're attaching the probe, and such things.
– pipe
May 2, 2016 at 19:50
• What's wrong with your sound card? A 16-bit sound card set to 1Vrms output at full scale (2.828 Vpp) should have a resolution of about 43 uV. a 10 mVpp signal would be generated by numbers in the range of -116 to +116. May 2, 2016 at 19:52
• so it turns out it must have been a quality issue.. although I am still unsure why I was getting absolutely nothing through the potentiometer (yes its wired correctly and has a large bandwidth.. its a unit that has has passed through production and has been used in other applications so I would hope it works! haha). I finally found someone with a high precision handmade attenuator used for ham radios.. and it worked flawlessly. Lesson learned would be when in doubt about integrity, get high quality parts ;) thanks! May 2, 2016 at 21:10
• The attenuator that finally worked was similar to this JFW industries inc model 50TA-007 BNC May 2, 2016 at 21:10