Can line in, mic in, DI in be the-same circuit but just different padding and sound the-same?

[canidoit]

I am trying to figure out whether I should patch my line-ins and DI ins on the patchbay as I have been using Mic ins pretty much to feed anything to my pre-amps. I would simply lower the signal being fed to get the correct gain staging on the pre-amp if the mic input was too hot at minimum.

I read somewhere that the Warm Audio did their line-ins cheaply on their 73 line, as all they did was pad their mic ins for the line-in feature instead of having a separate transformer for it.

Does that really matter? Wouldn't you still get the-same sound from using the mic-in and also have the option for different tones using the impedence switch?

Thank you.

 

[CJ]

Try and see

There are many different pad circuits, T pad, H pad,

Sometimes the sound gets darker when you put the signal through resistors. But you can add bypass caps across the resistors to compensate.

 

[pucho812]

I currently have a few diy pieces where I just padded the line inputs and have it on a mic/line switch. Same signal path after the switch, otherwise a separate connection. Never been a problem.

 

[ruffrecords]

Combining mic and line in using a switched pad is very common and has been used by mixer designers for over 70 years. The first instance of it I know of is in a Universal Audio all tube console. In my own designs I use a line input pad consisting of a pair of 3K3 resistors and a 150 ohm resistor which gives an attenuation of 33dB and an input impedance of 6.6K which is fine for most sources. Most decent mic pres will have an output noise of around -90dBu with the gain set to 33dB so noise is not generally an issue. You can use 4K7 or 5K1 resistors if you want to be closer to the nominal 10K line input impedance but you will lose anther 3 or 4dB in level and worsen the noise by the same amount.

This technique is not really suitable for a DI where you need an imput impedance of about 1Megohm because the attenuation would be so geat the noise would be terrible.

Cheers

Ian

 

[Whoops]

I am trying to figure out whether I should patch my line-ins and DI ins on the patchbay as I have been using Mic ins pretty much to feed anything to my pre-amps. I would simply lower the signal being fed to get the correct gain staging on the pre-amp if the mic input was too hot at minimum.

Like Ian said, padding down a Line Level signal to mic level signal is easy enough, I use a 40dB pad, Ian uses 33dBs which is also fine. Both Line Level and Mic Level are "Low impedance signals", that makes it pretty easy

But a DI input, Direct Injection for an Instument with Passive pickups or Piezo pickups will need a minimum of 1M input impedance, and that you can't do just with a simple resistor network passive PAD, best way would be to have a buffer, or use the JLM FET DI kit:

https://www.jlmaudio.com/shop/fet-di.html?display_tax_prices=1

 

[canidoit]

So I guess, it's safe to say, I don't really need to add the line ins to the patchbay as the sound quality differences are not really substantial when using the mic-ins instead. I thought the difference was more inferior quality such as high noise or distortion that I might not hear due to poor hearing or accumulative effects when mixing.

Thanks everyone!