Electronics > Projects, Designs, and Technical Stuff
Headphone Amp front end design.
(1/4) > >>
Jbliss:
Hi All,

I am designing a headphone amp with two line level balanced stereo inputs.
I need to design a small front end active summing mixer that sums the two stereo signals to a Left and Right bus which then feed the headphone amp section of the circuit.
I would like the ability to adjust the volume of the two signals, so I can create a mix of the two stereo inputs.
My question is what would be the best way to attenuate ? I have realised it is quite difficult to attenuate a balanced stereo signal precisely with a potentiometer. Here are some of the options I have thought of

Option 1;
Attempt to attenuate Stereo Balanced signals with 4 Gang Potentiometer.

Option 2;
Use a line Receiver (INA2134) to convert to a single needed signal then attenuate

Option 3;
Look at the use of digital pots (Would prefer not to due to more PS rails and micro)

Let me know that you think, all of these options could be terrible ideas
really appreciate any help.


 
Conrad Hoffman:
I'd go with attenuation after the input stage. If you have enough drive, you can use a fairly low value attenuator, thereby reducing thermal noise. I'd go with a stepped attenuator, as good pots are expensive and hard to find.
Jbliss:
Hi Conrad,
Thanks for your quick reply, Silly question but what part of the input stage are you referring to ?
Jbliss:
Option 4;
Using line receivers at input convert to single ended signal then use a VCA (THAT 2181) to adjust volume.
Richard Crowley:
Option 1 - 4 Gang Potentiometer
This seems like the most unlikely.  Acquiring/making a 4-gang pot (or DIY stepped attenuator) with decent tracking will be fiddly, expensive and time-consuming.  unnlikely to have a positve cost/benefit ratio unless there is some other requirement (like precision cablibration,etc.) that you did not mention.

Option 2 - Line receiver and conventional pots
This seems like the simplest, most straightforward, and highest cost/benefit ratio.  It would certainly be my first choice.

Option 3 - Digital pots
Maybe.  Seems more fiddly to design/construct and operate than Opt.2  Not clear what benefit it would have over Opt.2  This (and ALL) the options need some kind of balanced to unbalanced scheme.

Option 4 - Line receivers and VCA
Same disadvantages as Opt.3

I believe @Conrad Hoffman was recommending Opt.2
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod