Line level mixing

[rochest126]

I upload my circuit diagram,can it is appeared?

 

[Mooly]

Not appeared 🙂

Follow the instructions. Click "Go Advanced" and then "Manage Attachments".

 

[rochest126]

this is circuit picture.I means is when mute control switch to left,Q1 can turn-on slowly.And ,the signal on LineInp1 fade out.

 

[rochest126]

Not appeared 🙂

Follow the instructions. Click "Go Advanced" and then "Manage Attachments".

Thank you! There are two Submit Reply button in reply page,I must to press below one.

 

[Mooly]

Like this.

 

[rochest126]

Like this.

Thank you! 🙂

 

[Mooly]

Your welcome 🙂

 

[Mooly]

I'm not so sure the transistor would fade the signal as you want. It would tend to conduct fairly quickly as the base-emitter junction come into conduction probably introducing a lot of audible distortion in the transition period. Even FET's do that to some extent.

C5 and C7 are far to big. If you need them at all then somewhere around 10 to 47pf is suitable.

Edit... and C6

 

[godfrey]

this is circuit picture.I means is when mute control switch to left,Q1 can turn-on slowly.And ,the signal on LineInp1 fade out.

When the mute control is switched to the right, it short circuits the 10uF capacitor. The high current can cause a small arc in the switch. After many switchings, the switch contacts may be damaged.

It may be better to move the 10K resistor like this:

 

[godfrey]

I'm not so sure the transistor would fade the signal as you want. It would tend to conduct fairly quickly as the base-emitter junction come into conduction probably introducing a lot of audible distortion in the transition period.

Yes. An LDR (light dependent resistor) would be better for fading.

 

[Mooly]

Yes. An LDR (light dependent resistor) would be better for fading.

That's a good idea.

I remember in Elektor (probably 25 years ? ago) a circuit to blend L and R channels on an FM tuner to reduce hiss and it used opto coupled FET's (8 pin DIL I think). I've never seen any such devices (that I can remember) since.

 

[rochest126]

o,my mistake!
But ,use LDR for fading?It is unimaginable for me,if it is must to dimming a lamp?

 

[Mooly]

This will give you an idea for LDR's
http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp.html

(Muting is easy with transistors, fading is not)

 

[ODougbo]

A little off topic - but never saw this before: Audioplex Technology 72W Stereo-to-Mono Mixer | MONOMIXER 200 | Audioplex Technology

 

[DF96]

That will be a hybrid - used for many years in old analogue telephones, and related to directional couplers used in radio.

 

[forart.eu]

Sorry to revive this old 3ad, but we (a non profit organization) need a fully-passive "mixer" that does an L+R and can manage both balanced and unbalanced audio.

Something like the Australian Monitor's "Mixed Up" (that is quite expansive, check it out: http://www.australianmonitor.com.au/products/product/mixed-up) but with just 2 XLR-combos as inputs and a balanced/jack as out.

It would be great to have an opensource/DIY project for this kind of tool.

Thanks in advice.