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Balanced ipod lod for Toucan?

post #1 of 17
Thread Starter 

Not sure if I am posting this in the correct section or not, but I just ordered a Ibasso PB1 Toucan and wanted to know if it would be possible to make a balanced ipod lod that would connect to the Toucan or should I just stick with my SE lod i already have? If it is possible can someone provide me with the pin outs I would need?

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post #2 of 17
Quote:
Originally Posted by Dawildebeest View Post

Not sure if I am posting this in the correct section or not, but I just ordered a Ibasso PB1 Toucan and wanted to know if it would be possible to make a balanced ipod lod that would connect to the Toucan or should I just stick with my SE lod i already have? If it is possible can someone provide me with the pin outs I would need?


I asked the same question on Headfonia and here is the reply by Bebop McJiggy

 

"I think that it is a bad idea to change your iPod LOD to wire it up to the balanced input, just because you could. Maybe it would have no effect, but I think the Toucan might assume it was balanced already and not create the negative polarity signal. I don’t really know for sure, but it doesn’t seem like a good idea to me."

post #3 of 17
Thread Starter 

Thanks for the input Randius, that is good enough for me to leave it the way it is.

post #4 of 17

errmm thats a strange post from headphonia, its not even possible, the ipod does not have a balanced analogue section, you cannot have a balanced ipod LOD

post #5 of 17
Quote:
Originally Posted by Randius View Post




I asked the same question on Headfonia and here is the reply by Bebop McJiggy

 

"I think that it is a bad idea to change your iPod LOD to wire it up to the balanced input, just because you could. Maybe it would have no effect, but I think the Toucan might assume it was balanced already and not create the negative polarity signal. I don’t really know for sure, but it doesn’t seem like a good idea to me."


I dont even know what that means. if it were possible, it would be a very good idea. This way you would have the common mode rejection ratio (CMRR) all the way from the dac section, so any distortion or noise picked up along the way to the amp, would be in the most part deleted. also any distortion which is actually created by the DAC will be for the most part deleted. most modern DACs are designed and specified with this in mind and do not like you just using a single side of their balanced output, but rather prefer for a summing stage to be added after the balanced IV section. this way both phases are loaded symmetrically and even order noise including self noise in the HF is deleted.

 

the ibasso does not 'assume' one way or the other, it has both Single ended inputs and balanced inputs and both single ended and balanced outputs. if you feed it balanced input, you gain performance as mentioned above, if you feed it single ended input, it will apply a phase splitter and then give 'balanced' output, but it does nothing to get rid of noise from before the amp, only increased output voltage (swing) and CMRR from the amp section onwards.

 

I dont know what opamps the ibasso is using, but there are several, like the THS4051, OPA1632 THS4131 etc that will accept a single ended signal and output in differential mode, they will work with what you give them, but specs are always better for balanced input 


Edited by qusp - 9/19/10 at 8:14pm
post #6 of 17
Quote:
Originally Posted by qusp View Post




I dont even know what that means. if it were possible, it would be a very good idea. This way you would have the common mode rejection ratio (CMRR) all the way from the dac section, so any distortion or noise picked up along the way to the amp, would be in the most part deleted. also any distortion which is actually created by the DAC will be for the most part deleted. most modern DACs are designed and specified with this in mind and do not like you just using a single side of their balanced output, but rather prefer for a summing stage to be added after the balanced IV section. this way both phases are loaded symmetrically and even order noise including self noise in the HF is deleted.

 

the ibasso does not 'assume' one way or the other, it has both Single ended inputs and balanced inputs and both single ended and balanced outputs. if you feed it balanced input, you gain performance as mentioned above, if you feed it single ended input, it will apply a phase splitter and then give 'balanced' output, but it does nothing to get rid of noise from before the amp, only increased output voltage (swing) and CMRR from the amp section onwards.

 

I dont know what opamps the ibasso is using, but there are several, like the THS4051, OPA1632 THS4131 etc that will accept a single ended signal and output in differential mode, they will work with what you give them, but specs are always better for balanced input 


Then in your opinion, is it worthwhile to make a balanced LOD for the iPod, if possible?

post #7 of 17


Quote:
Originally Posted by Randius View Post




Then in your opinion, is it worthwhile to make a balanced LOD for the iPod, if possible?




 

Quote:
Originally Posted by qusp View Post

...the ipod does not have a balanced analogue section, you cannot have a balanced ipod LOD


Edited by g5tar - 9/21/10 at 7:19pm
post #8 of 17
For any searchers who landed on this, as I just did, you can only achieve the objective of balanced output from the iPod via an "iDAC" device like the HRT iStreamer and using the stereo RCA outs to do it because they aren't single-ended.

We need a different term because nobody considers RCA outputs balanced, but if they went straight into a headphone, then they'd be called balanced because they aren't guarenteed to be bus grounded like a single-ended headphone cable.
post #9 of 17

I though balanced means R+/R-/L+/L-? If so, RCA is not balanced in anyway.

post #10 of 17

I thought balanced is R-,R+,GROUND and L-,L+,GROUND 3 wires per channel?

post #11 of 17
Quote:
Originally Posted by BattleBrat View Post

I thought balanced is R-,R+,GROUND and L-,L+,GROUND 3 wires per channel?

You only need R+/R/L+/L- for the headphone. If I am not mistaken, (chassis) ground is usually connected to the cable shield to provide extra noise rejection.
 

 


Edited by ClieOS - 8/15/11 at 11:28am
post #12 of 17

I had these LOD's made for my Lisa III (and now L3) are they what you guys are thinking of?

DSC05010.JPG

 


Edited by BattleBrat - 8/15/11 at 12:11pm
post #13 of 17

Truly balanced does include all three (+, -, G) but for headphones there's no ground involved, thus dropping six contacts down to four for stereo.

 

So don't RCA's normally have +/- for each channel, or are the negatives from both just bus grounded?

 

BattleBrat, your LOD is definately what we're talking about. Some reason nobody really makes these in quantity?


Edited by funkmeister - 8/15/11 at 2:37pm
post #14 of 17

I dunno, I had the LOD's custom made through chinese Ebay lod makers, and I terminated them in RCA's myself. 
Next time I'm just gonna make the whole lod myself, I found the make your own lod thread that has the pin config, and everything.

and they do make them in quantity, but they are CRAZY expensive, and quite long, these two cost me ~$80 each all said and done.


Edited by BattleBrat - 8/15/11 at 3:13pm
post #15 of 17

BattleBrat, I think they are just stereo RCA.  Two channel stereo RCA is different from balance configuration.  I could be wrong, but I don't think your Lisa L3 is a balance amplifier.  The Toucan PB1 and PB2 are true balance amps.  So is the RSA SR71B.  The Lisa amps can take regular RCA L/R stereo analogue input but they are not balance input.  In order to get true balance input from a source, the only way to get it is to use a balance DAC like the Ibasso DB1/2 where it will take digital signal from a source and split the signal up for true balance output.  I doubt that the RCA output of the istreamer is balance out either.  I think they are just stereo out.  Somewhere along the signal path, the signal has to be split digitally into balance signals.  I copy the exerpt from Headroom with regard to their balance Dac.  But most balance dac follow similar typology.

 

 

"To get the most out of your balanced headphone system, it’s important to use gear that provides true differential balanced drive signals. The Ultra Desktop DAC is such a device.

With typical unbalanced audio systems, the audio is carried on a single conductor, while a shield or ground conductor is provided for the return current path. A differential balanced drive system uses two audio signals: a normal audio signal, and a matching but inverted audio signal. A ground conductor may be used as a shield, but is technically not required.

Balanced drive has long been used to reduce interference on long cable runs. But while some gear may have balanced connections externally, they are often single-ended devices internally, which are either transformer coupled or use phase splitters to create the balanced signal. These methods result in the normal and inverted audio signals to be slightly imperfect mirror images of each other, and degrades the performance.

Balanced-DriveIn a fully differential balanced drive system, a source of perfectly matching balanced signals is followed by identical, highly-matched signal paths.In the Ultra Desktop DAC the signals are created by pairs of DACs that are running in normal and inverted modes and therefore create perfectly matched signals.

A perfectly balanced phono stage could be implemented by taking the signals of either side of the cartridge coil and running the signals through identical RIAA equalization and output driver channels. The advantage of this method goes far beyond simply reducing induced noise; slew rate is doubled, some harmonic distortion components are suppressed, and a doubling of output power is realized."

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