I've just been mulling over my options with preamp builds, specifically how to allow for balanced inputs to a pre-amp that is not internally balanced (and keep the CMR). E.g., provide balanced inputs for a B1 Korg. I've read the Jensen essay on this kind of thing and know I can use an input transformer for this purpose.
But what if there are other inputs that aren't balanced? Let's suppose I've got two balanced and two unbalanced inputs. Can I just connect all the inputs to a 4 pole selector switch and ground 'pin 3' for the RCA inputs? then feed the output of the selector into the transformer? Obviously, this would preclude any kind of attenuation of the balanced signal. (I suppose a -6dB switch could be added.) Is that OK too? Or is there some other way to do it?
Riki
But what if there are other inputs that aren't balanced? Let's suppose I've got two balanced and two unbalanced inputs. Can I just connect all the inputs to a 4 pole selector switch and ground 'pin 3' for the RCA inputs? then feed the output of the selector into the transformer? Obviously, this would preclude any kind of attenuation of the balanced signal. (I suppose a -6dB switch could be added.) Is that OK too? Or is there some other way to do it?
Riki
This is how we do the same :
https://www.diyaudio.com/community/...al-passive-preamp-with-output-buffers.384796/
We have 4 SE and 2 balanced (fully symmetrical) inputs. And we want balanced output only.
We use a 2 pole 6 position rotary switch to switch them to an audio transformer (Cinemag).
The transformer output is connected to 2x 10k pots, which then goes to an output buffer.
We did not include any 6dB equalisation between SE and BAL, as it adds too much complication.
But it can be done at the pots (by adding a fixed 10k in series for BAL) if we choose to.
Patrick
https://www.diyaudio.com/community/...al-passive-preamp-with-output-buffers.384796/
We have 4 SE and 2 balanced (fully symmetrical) inputs. And we want balanced output only.
We use a 2 pole 6 position rotary switch to switch them to an audio transformer (Cinemag).
The transformer output is connected to 2x 10k pots, which then goes to an output buffer.
We did not include any 6dB equalisation between SE and BAL, as it adds too much complication.
But it can be done at the pots (by adding a fixed 10k in series for BAL) if we choose to.
Patrick