line preamplifier suggestion???

I built amplifier with unbalanced inputs. I neeed it to drive my studio monitors. It works great for me but i would need balanced inputs. A kind of preamplifier or something preferably with some tone controls. Does anyone have a suggestion for simple circuit with pcb layout or even pcb done.
My needs are:balanced and unbalanced inputs,source selector,unbalanced and balanced outputs.
Any suggestion?

this could be done with simple resistive coupling

you are trying to use a hifi styled amp with 10k+ input imp ?

list the expected signal sources you want to switch between.

hi!
yes,it's 10k input.
i would like to switch between cd player and other unbalanced signals and also one balanced source like balanced mixer.
thanks for help
miha

since more of your sources are unbalanced and only the mixer is balanced,
use a simple unbalanced switcher like a standard hifi pre-amp
or
use a rotary switch like a Lorlin 6 x 2 and share the grounds

then just unbalance the mixer and pad the level back to -10dBu.

more ideas at DACT, Gold Point and even the Factory.
http://www.dact.com/
http://www.goldpt.com/
http://www.diyfactory.com/projects/dawmonswitch/dawmonswitch_1.htm

there is a number of ways to unbalance a signal and still keep things quiet which mixer do you have ?

i'm working mostly at concerts with diferent mixers. at home i have pioneer 600,but not always. that's why some kind of tone control would be very welcome. do you think this would be realistic without degrading the sound? maybe i should really go for a simple passive volume control. what do you think?

Most sound engineers go to great lengths to keep the frequency response of everything except EQs as flat as possible, so I would not include a "tone" control in your input selector circuit. However, I think you would find separate level trim controls for each input very useful.

To keep things simple, an ordinary 2-pole N-way rotary switch is probably sufficient. That means you would have to run the mixer output unbalanced (leave XLR pin 3 or TRS jack ring unconnected) and hope that your ground is clean.

You can buy multiway stereo switching boxes, usually with phono (RCA) ins and outs. The larger case style of those may well have enough room inside to mount trimmers on each linput line.

soon there will be a module from JLM that will achieve most of this and give a remote control so the guts can remain in the rack.
Obviously this will be active.

There is no way to do all of this in a passive unit.

The advantages of the passive unit is firstly cost and secondly simplicity.
Being very simple means the degradation to sound can be minimal.

Even if you don't know what mixer will be used a simple circuit that is adjustable can be used to UN-balance and Attenuate the signal.

If you are to use a HiFi amp or pre-amp ... one with tone defeat would be an advantage.

Although some might see it as degredation ... a quality line transformer would be good for the UN-balancing as it can also give the earth isolation you may need at these unknown venues.

Hi!
Thanks for your answers. I will unbalance and attenuate signals like Kev said. If i use monitors to mix i will have mixer with eq, so i don't really need separate hi-fi style preamp. For now,i only use monitors to know what i'm listening to.
Miha