The need for shielding depends on what you plan to use for an enclosure. If you have a full metal enclosure, you can probably get by without shielding.
The purpose of a shield is to block electrostatic fields from contaminating your signal (this energy is capacitively coupled into your circuit). The need for a shield is determined by the strength of your signal, the strength of the garbage fields floating around, and the level of signal quality you wish to maintain. Generally, the smaller the signal, like a microphone or a phono cartridge, the more attention you should pay to shielding. Most would agree that without a full metal enclosure your inputs should be shielded. There are also those that will insist your wires float in free space, are insulated with calendared rhino horn, and are surrounded by tons of exotic metals... shields are cheap.
While capacitive coupling does increase with frequency, you should not dismiss the need for shielding just because audio is low frequency.
Twisting wires is whole 'nother story. Moving (changing) magnetic fields will induce voltage in a wire. Twisting in done to mitigate the effects of stray magnetic fields. Were you to X-Ray a twisted pair of wires, you would see many small "eyes" or loops. The magnetic field "cutting" these loops induces voltage. Without any twisting, a magnetic field would see one large loop, and it will induce a voltage. When the wires are twisted the fields see many small loops... the trick is that half of these loops are reversed. So a whole series of voltages will be induced, but; half of them are of opposite polarity and they tend cancel out. Is it perfect? No. Does it work? You betcha! There are many exceptions of course.
This street go both ways... wires are also twisted so that they don't radiate a large coherent magnetic filed. This is done in AC wiring throughout most things.
Should you twist your wires? Sometimes, looks cool too!
EDIT: Why is it so hard to type in little boxes???????
The purpose of a shield is to block electrostatic fields from contaminating your signal (this energy is capacitively coupled into your circuit). The need for a shield is determined by the strength of your signal, the strength of the garbage fields floating around, and the level of signal quality you wish to maintain. Generally, the smaller the signal, like a microphone or a phono cartridge, the more attention you should pay to shielding. Most would agree that without a full metal enclosure your inputs should be shielded. There are also those that will insist your wires float in free space, are insulated with calendared rhino horn, and are surrounded by tons of exotic metals... shields are cheap.
While capacitive coupling does increase with frequency, you should not dismiss the need for shielding just because audio is low frequency.
Twisting wires is whole 'nother story. Moving (changing) magnetic fields will induce voltage in a wire. Twisting in done to mitigate the effects of stray magnetic fields. Were you to X-Ray a twisted pair of wires, you would see many small "eyes" or loops. The magnetic field "cutting" these loops induces voltage. Without any twisting, a magnetic field would see one large loop, and it will induce a voltage. When the wires are twisted the fields see many small loops... the trick is that half of these loops are reversed. So a whole series of voltages will be induced, but; half of them are of opposite polarity and they tend cancel out. Is it perfect? No. Does it work? You betcha! There are many exceptions of course.
This street go both ways... wires are also twisted so that they don't radiate a large coherent magnetic filed. This is done in AC wiring throughout most things.
Should you twist your wires? Sometimes, looks cool too!
EDIT: Why is it so hard to type in little boxes???????
OK, using shielding, how can you ground at only one end. Each of the 2 inputs comes in on an rca jack, and need the center signal and the ground (outer case of rca jack) to the briangt lm3875 amp board.
The amp board has two connection points to solder for each of the two lines, one is signal, one is ground.
I understand that if you ground the shield at both ends you cna have ground loops, but how do you make the two lead connections for each channel if the shield is not used as the ground?
The amp board has two connection points to solder for each of the two lines, one is signal, one is ground.
I understand that if you ground the shield at both ends you cna have ground loops, but how do you make the two lead connections for each channel if the shield is not used as the ground?
I just used about 5 meters of Audioquest copperhead interconnect analog wire. I am sure that many will say this was overkill, especially considering the price, but I did it mostly just to see if there would truly be a difference...and I believe that there is.
I used plain shielded cable before for the (amp) output signal and regular copper before for the (amp) incoming input signal, and there really is a difference.
Also, I am using the same copperhead wire to interconnect my cd player to the amp itself which means that the signal is carried throughout its entire jouney on the same exact type of cable.
I honestyl would not do it again because the cost was prohibitive. Its kinda the difference between buying the 50k speaker package vs. the 75k speaker package when the audible difference is "very little".
Now that it is in there though, I am happy to see that there is at least an impovement over my last amp and it was fun!
Now you heard the word!
I would suggest trying some cardas cable from the percy high end catalog!
Dominick
PS-I will post pics soon!
I used plain shielded cable before for the (amp) output signal and regular copper before for the (amp) incoming input signal, and there really is a difference.
Also, I am using the same copperhead wire to interconnect my cd player to the amp itself which means that the signal is carried throughout its entire jouney on the same exact type of cable.
I honestyl would not do it again because the cost was prohibitive. Its kinda the difference between buying the 50k speaker package vs. the 75k speaker package when the audible difference is "very little".
Now that it is in there though, I am happy to see that there is at least an impovement over my last amp and it was fun!
Now you heard the word!
I would suggest trying some cardas cable from the percy high end catalog!
Dominick
PS-I will post pics soon!
Aluminum foil also works. Wrap it around the signal wires and then connect it to the safety/chassis ground. Also make sure all metal parts are connected to the safety chassis/ground. Don't forget about heatsinks, standoffs, potentiometer cases, even the metal plate on large bridges. I am currently testing my gainclone under fluorescent lights in the same room with 2 computers, only a trace of noise when no input connected and volume turned all the way up.
A few weeks back I did a little experiment of replacing the input cables in one of my clones with cat 5 (all 8 strands) with the coloured ones as positive and whites as negs, with aluminium foil wrapped around these, then teflon plumbers tape to keep it neat and tight.
At first I tried it on only one channel, without the foil earthed, this was way better than the std cabling, lower noise floor and hum, which are both very easily revealed by my high efficiency drivers. So regular cat 5 rejects noise pretty well.
I then tried it with the foil wrap earthed as well, the result as expected was even better, in fact dead quite.
My conclusion is cat 5 works a treat, and the foil wrap makes it better still, I feel that if possible it is best to eliminate all noise from the system, so the amp can get on with the job unimpeded.
Of course this is easier said than done.
Chatting to a friend who is an electronics/audio repairer builder guru, now retired, his comment is that all noise and interfence has flow-on effects right up through the frequency range and often the defects in sound we hear are not recognised for what they really are, which is a mixing and attenuation of noise sources at low levels, his feeling is attention to fine detail pays dividends even though sometimes you can't quite put your finger on what is better or why just by listening. In other word good sound is the result of a myriad of small details taken care of.
He's pretty clear that controlling even low level oscillation in chip amps is really important and this can easily enter the system through the input leads and it won't show up till the music is playing, but often the level is low so when mixed with the signal can be heard to discern, although it is easy to see on an oscilloscope, but its there doing its damage to the overall sound.
I'm nowhere near clever enough to properly decode and apply all of what he has told me, but I guess 50 yrs or so in the field means he has a good basis to work from, so all noise is out and good cabling is a cheap form of sonic insurance!
At first I tried it on only one channel, without the foil earthed, this was way better than the std cabling, lower noise floor and hum, which are both very easily revealed by my high efficiency drivers. So regular cat 5 rejects noise pretty well.
I then tried it with the foil wrap earthed as well, the result as expected was even better, in fact dead quite.
My conclusion is cat 5 works a treat, and the foil wrap makes it better still, I feel that if possible it is best to eliminate all noise from the system, so the amp can get on with the job unimpeded.
Of course this is easier said than done.
Chatting to a friend who is an electronics/audio repairer builder guru, now retired, his comment is that all noise and interfence has flow-on effects right up through the frequency range and often the defects in sound we hear are not recognised for what they really are, which is a mixing and attenuation of noise sources at low levels, his feeling is attention to fine detail pays dividends even though sometimes you can't quite put your finger on what is better or why just by listening. In other word good sound is the result of a myriad of small details taken care of.
He's pretty clear that controlling even low level oscillation in chip amps is really important and this can easily enter the system through the input leads and it won't show up till the music is playing, but often the level is low so when mixed with the signal can be heard to discern, although it is easy to see on an oscilloscope, but its there doing its damage to the overall sound.
I'm nowhere near clever enough to properly decode and apply all of what he has told me, but I guess 50 yrs or so in the field means he has a good basis to work from, so all noise is out and good cabling is a cheap form of sonic insurance!
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