balanced amp

[emu-mode2]

hi.. i need an information about balanced headphone amps..i have an emu1212 sound card..it has balanced outputs..i had a look at internet i found tube headphone amp schematic but i couldnt find a transistor-balanced input headphone amp..i have bd139-140s and 2sk1058s irf610s..but i dont know how to convert balanced output to rca.maybe later i will make a tube amp.please help..
thanks

[wg_ski]

The easiest solution is just to use the "hot" side of the balanced output, leaving the "cold" side unconnected. Use a TRS (stereo) 1/4", and connect tip to center conductor, shield to sheild, leaving the ring unconnected. The amps in those E-mu boxes don't like to be shorted - which is what happens if you use just a normal 1/4" mono plug. Eventually the output driver chip on the cold side burns out (I have done this).

If you want to drive a simple DIY amp balanced, just choose an amp with a standard Lin topology with a differential pair input. Configure the inputs and feedback for balanced operation (consult standard op-amp app notes for how - it's easy). If you're not opposed to using op amps, hang a standard "differential to single ended" unity gain op amp stage off the input of *any* amp.

[emu-mode2]

hi..can not i use the gnd and the cold output? is not cold out same as the hot side?isnt the difference only phase?i have emu card and i have big stereo jacks but i dont know how to find cold and hot out..i think gnd is the biggest area one..but no idea about hot one

[jerluwoo]

Using a standard stereo headphone plug for both L and R channels (one plug for R and L each), then the red wire would be considered + phase and the white would be - with the shield (bare wire) as ground. An example of converting a single-ended input amplifier to balanced is in the attached file.

[emu-mode2]

gnd and cold are connected now to lm4562..it sounds good..when i connect only gnd and hot it becomes loudly and distortion..i didnt understand :S

[jerluwoo]

Line Level Analog Outputs Eight balanced 24-bit, line-level, analog outputs are provided (1-4). Output pair 4 is designated as the Monitor Output and is fed by the monitor bus of the PatchMix DSP mixer application. We suggest that you plug your speakers in here. All the analog outputs can be freely assigned in the mixer application. Special anti-pop circuitry mutes the analog outputs when power is turned on or off. Like the analog line inputs, either TRS balanced or TS unbalanced cables can be used. Balanced cables provide better noise immunity and +6dB higher signal level. The output line level can be set to accommodate the consumer -10dBV standard, or the pro audio +4 dBu standard in the I/O screen of the Session Settings dialog box. See I/O Settings. The maximum input and output line levels are matched when the input and output settings are set to the same mode (pro or consumer) in the I/O preferences screen. IMPORTANT NOTE: Do NOT use balanced audio cables (TRS) when connecting balanced outputs to unbalanced inputs. Doing so can increase noise levels and introduce hum.


This is all I could find about using the line outputs(applicable to 1212 and 1820 cards).

[AndrewT]

look up Nelson Pass site.
Most of his work is based on balanced topology.
Read up Rane and Jensen. They have numerous pages on balanced and converting from one to the other.

[emu-mode2]

hi...if i want to not use an amplifier how can i connect my headphones to my soundcard for listening stereo music? i connected the right and left channels grounds together and then connected one cable from left and one cable from right.it is not stereo enough now. when i make pan 90degrees at emu-interface nothing changes a lot..it changes a little..the music comes from both of them..pls help