Line level signal to microphone input adapter

Hi,
I have found this circuit to connect line signals to electret microphone inputs.
As I have some hi grade audio 4,7uF capacitors I'd like to know if I can use them instead of the 10uF listed in the schematic

                        C1
+Line level in --||----R1----+-- +Mic level output
                          +                  |
                                              |
                              +----R2----+
                              |
  Ground (input)----+--------------- Ground (output)


R2 = 1 kohm
R1 = 10 kohm
C1 = 10 uF

Just do it. You may get less low end.

If you double your resistor values you should be fine.

NB: what is an 'electret mic input' ??

Electret mic input is a powered mic input for active microphones
It has a lower gain than traditional mic input

Can anyone tell me how this would be modified for a balanced line input?

I recently tried to make a U-pad for a Green V14 pre, using the source output impedance specified in the RME Multiface manual  (47ohm output impedance)
I estimated the input impedance of the Green V14 as 11k ohms (hopefully this is correct).

The u-pad was constructed as follows:

In comparing the sound I get, it has much less low-bass energy than the line inputs on the only other preamp I have (JoeMeek early model TwinQcs) - for example, the sustained portion of an 808 kick is much less present.

Thoughts?  Is my K-value way off?

Try 4K7, 220, 4K7.

Thanks PRR.  I will try and report back.

EDIT:  of course, I'm out of both values

PRR said:

Try 4K7, 220, 4K7.

Click to expand...

I use 3k3 150 3k3 in the EZTubeMixer.

Cheers

Ian

I use 4k99~160R~4k99 in the VP28. Many combo's will work.

jsteiger said:

I use 4k99~160R~4k99 in the VP28. Many combo's will work.

Click to expand...

And what you are aiming for is an input impedance approaching 10K, an output impedance not much more than 150 ohms and  an attenuation sufficient to ensure the input is not overloaded but not enough to compromise noise performance.

Cheers

Ian

I built one attenuator following the tips from some web (uneeda audio or something like that). Using 2x 7k5 and a 150r. U type. Looks fine when measuring a my SSL 9k pre in fuzzmeasure. Db loss is around 40.

> I use 3k3 150 3k3
> I use 4k99~160R~4k99
> Using 2x 7k5 and a 150r

Yeah, whatever is close to hand.

What caught my eye was "much less low-bass energy". While the box may claim 47 ohms output, if that comes through some golly-poly caps which don't come larger than a few uFd, a 2,047 ohm load (pad) is gonna suck bass.

10K is usually a safe load for modern gear. A large-loss U pad, most of the resistance is in the series legs. Half of 10K is, in my resistor box, 4K7, grab two. He had 47/2047 attenuation and didn't complain about overall level. Since we changed 1K to 5K, change 47 to 5 times higher. 235 ohms, but we rounded the 5K to 4K7, so round-down the 235 to 220 standard part.

The other values proposed will give 6K7 to 15K input and various losses. Any of these impedances will be more bass-friendly (from a cap-output box) than 2K047. The various losses may be fine, or not; easily tinkered after the bass is found again.

We did made this little spreadsheets for calculating PADs @german nrg-Recording.de

u-PAD Calculator

There  ls also a T & H-PAD calc made by Harpo