Home |
Search |
Today's Posts |
#1
|
|||
|
|||
Balanced Line Implementation
Does anyone here have any specific thoughts on the means of implementing
balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway |
#2
|
|||
|
|||
Graham Holloway wrote:
Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway Here are two resources I found useful. If you are looking for simple implementation I have recently been toying with the burr brown DRV134 and INA 137 and have found them excellent for my purposes. http://www.jensen-transformers.com/an/an003.pdf http://www.dself.dsl.pipex.com/ampin...d/balanced.htm Brian |
#3
|
|||
|
|||
Brian Allen wrote:
Graham Holloway wrote: Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway Here are two resources I found useful. If you are looking for simple implementation I have recently been toying with the burr brown DRV134 and INA 137 and have found them excellent for my purposes. http://www.jensen-transformers.com/an/an003.pdf http://www.dself.dsl.pipex.com/ampin...d/balanced.htm I see that Doug Self hasn't learnt how to design for equal inverting and non-inverting input impedances on his differential input circuits. Graham |
#4
|
|||
|
|||
Pooh Bear wrote:
Brian Allen wrote: Graham Holloway wrote: Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway Here are two resources I found useful. If you are looking for simple implementation I have recently been toying with the burr brown DRV134 and INA 137 and have found them excellent for my purposes. http://www.jensen-transformers.com/an/an003.pdf http://www.dself.dsl.pipex.com/ampin...d/balanced.htm I see that Doug Self hasn't learnt how to design for equal inverting and non-inverting input impedances on his differential input circuits. Graham Hi Graham, which topologies are you refering in D. Self's site? Are you talking diferential or common mode input impedance? He notes that the differential input imp. is non-equal on some of the layouts, sacraficing it for common mode input imp. equality. Does the 'superbal' circuit (fig 12) not provide equality on both though? Brian |
#5
|
|||
|
|||
"Pooh Bear" wrote in message ... Brian Allen wrote: Graham Holloway wrote: Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway Here are two resources I found useful. If you are looking for simple implementation I have recently been toying with the burr brown DRV134 and INA 137 and have found them excellent for my purposes. http://www.jensen-transformers.com/an/an003.pdf http://www.dself.dsl.pipex.com/ampin...d/balanced.htm I see that Doug Self hasn't learnt how to design for equal inverting and non-inverting input impedances on his differential input circuits. Graham Either figure 12 or figure 13 look OK to me... |
#6
|
|||
|
|||
"Graham Holloway" writes:
Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. You can find some general information on this field at http://www.epanorama.net/links/audiopro.html#wiring and lots of links to circuits for on this field at http://www.epanorama.net/links/audiocircuits.html#diff -- Tomi Engdahl (http://www.iki.fi/then/) Take a look at my electronics web links and documents at http://www.epanorama.net/ |
#7
|
|||
|
|||
In article ,
"Graham Holloway" wrote: Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway Simple op-amps will do this if you're not looking for common mode rejection of more than a couple of volts. The output should unbalanced if you're using coaxial cable with a single center conductor, but the input still mostly balanced. There are some exotic double shield cables for very long runs (much longer than a house). Two amps drive the same signal to the center conductor and the inner shield. The center conductor then sees a lower load capacitance so it degrades more slowly. The end of it needs to be terminated in some way to maintain noise rejection. Check an electronics book. |
#8
|
|||
|
|||
Karl Uppiano wrote:
"Pooh Bear" wrote in message ... Brian Allen wrote: Graham Holloway wrote: Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway Here are two resources I found useful. If you are looking for simple implementation I have recently been toying with the burr brown DRV134 and INA 137 and have found them excellent for my purposes. http://www.jensen-transformers.com/an/an003.pdf http://www.dself.dsl.pipex.com/ampin...d/balanced.htm I see that Doug Self hasn't learnt how to design for equal inverting and non-inverting input impedances on his differential input circuits. Graham Either figure 12 or figure 13 look OK to me... I've never seen them actually implemented in any audio gear. Fine in theory Figs 9 and 10 are classic examples of poor design though. Widely seen in many pieces of kit though. Fig 10 looks like it's from a Soundcraft Spirit Folio. It iseasily fixable though. In Fig 9 change R2 and R4 to 3k3. This will give equal loading on both legs with a balanced signal. The scaling of values can be used to work this 'trick' for any gain. You end up with some oddball values - easily fixed by a series or parallel arrangement of resistors. Neve used to - probably still do - have custom resistor packs made for this topolgy. I've improved the Fig 10 style arrangement to at least offer symmetrical impedances in the '+4' setting. Graham |
#9
|
|||
|
|||
Pooh Bear wrote:
Karl Uppiano wrote: "Pooh Bear" wrote in message ... Brian Allen wrote: Graham Holloway wrote: Does anyone here have any specific thoughts on the means of implementing balanced lines, ie. transformers, discrete circuits using IC op-amps, dedicated driver and receiver IC's, etc. I need to buffer other audio circuits and I have yet to find anything that I feel I can confidently use as I have never done this before. Graham Holloway Here are two resources I found useful. If you are looking for simple implementation I have recently been toying with the burr brown DRV134 and INA 137 and have found them excellent for my purposes. http://www.jensen-transformers.com/an/an003.pdf http://www.dself.dsl.pipex.com/ampin...d/balanced.htm I see that Doug Self hasn't learnt how to design for equal inverting and non-inverting input impedances on his differential input circuits. Graham Either figure 12 or figure 13 look OK to me... I've never seen them actually implemented in any audio gear. Fine in theory Figs 9 and 10 are classic examples of poor design though. Widely seen in many pieces of kit though. Fig 10 looks like it's from a Soundcraft Spirit Folio. It iseasily fixable though. In Fig 9 change R2 and R4 to 3k3. This will give equal loading on both legs with a balanced signal. Doesn'this then match the differential input impedance, but then unbalance the common mode input impedance? This is what I measure when I tested it, in fact it matched table 3 in D. Selfs article. Wouldn't the common mode input impedance matching be more important because the whole reason for balanced circuitry is to use the common mode rejection for noise reduction. With audio signals having plenty of signal typically we are not worried to much about exactly matching the differential input impedance. Or am I mistaken and the differential input impedance matching is more important? Brian The scaling of values can be used to work this 'trick' for any gain. You end up with some oddball values - easily fixed by a series or parallel arrangement of resistors. Neve used to - probably still do - have custom resistor packs made for this topolgy. I've improved the Fig 10 style arrangement to at least offer symmetrical impedances in the '+4' setting. Graham |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Power Filtration | Audio Opinions | |||
Power conditioner or power cord or something else | Audio Opinions | |||
FS: Tube Driver 16V RMS balanced tube line driver | Car Audio | |||
Where are those Wascally Weapons of Mass Destwuction??? | Audio Opinions | |||
A balanced line driver for MIDI synth racks | Pro Audio |