well this might also fit in this section....
Does anybody knows anything - or has some schematics related to speaker cables that have avtive shielding ....something related to canceling capacitances or something...
i am interested in this thematic - i have a double coaxial speaker cables that might be used to try this method....
Does anybody knows anything - or has some schematics related to speaker cables that have avtive shielding ....something related to canceling capacitances or something...
i am interested in this thematic - i have a double coaxial speaker cables that might be used to try this method....
I have worked with equipment, from a different field, That had to drive analog signals 20-30' down a cable. We used a double shielded cable. The inner shield was driven by a low power amp driving the same signal as the signal line. The outer shield was a gnd'ed shield. The theory here is that the signal line is in effect "cascoded" by the inner shield. With almost the same potential from the signal line to the inner shield, there is no charge, no capacitance. The inner shield amp had to deal with the capacitance to the grounded shield. Although not a perfect amp, or as accurate as the signal amp, it provides a 98% improvement for the envirenment of the signal carrying line.
thanks FLG, well, i have only one shield .....
i wonder what Audioquest is doing with their cables and also Synergestic Research with their Active Shielding.....that is the reason...
i have only one shielding - so i can't make Your suggestion work....but i think that something similar is what they are using but i am not fully sure.....
any other suggestions - or something how to modify this first one ...
i wonder what Audioquest is doing with their cables and also Synergestic Research with their Active Shielding.....that is the reason...
i have only one shielding - so i can't make Your suggestion work....but i think that something similar is what they are using but i am not fully sure.....
any other suggestions - or something how to modify this first one ...
sunrise said:
What they do with their Active Shielding is something known as "marketing".
If you want a decent shielded speaker cable, try four mini-GR-8 with all shields in parallel and all cores in parallel. The equivalent capacitance will be about 120 pF/ft, or about .001 uF for an 8 foot run. Series inductance will be about 18 nH/foot, or about 150 nH for 8 feet, low enough even for difficult loads. Series resistance will be about 20 milliohms for 8 feet.
It turns out shielded speaker cables can help under some circumstances such as noisy RF environments, perhaps because less junk is coupled back to the feedback loop.
Audioquest tried it.
Art Dudley of Stereophile wasn't impressed: "My belief is that their 'dielectric bias' system, which I wound up removing and leaving in my desk drawer, has no influence on their performance one way or the other."
http://www.stereophile.com/cables/804aq/index.html
Art Dudley of Stereophile wasn't impressed: "My belief is that their 'dielectric bias' system, which I wound up removing and leaving in my desk drawer, has no influence on their performance one way or the other."
http://www.stereophile.com/cables/804aq/index.html
PrestonTom - i do want to get rid of anything that might affect the sound in my cables - that also includes RFI..... 
but i also wants to get rid of the capacitance that speaker (or interconnect) cable has.....
That is why i want to make something that will insert the signal also on the shielding in order that i loose that capacitance - that is done (from the informations that i have) by using some opamp and some kind of circuit and very low currents....
i don't know how this circuit is looking so i need somebody that has some experience with this problem to help me with the circuit
i don't want to invent some circuit that is completely new but to use the technology that people use in the situations where they want to get rid of those pharasythic capacitances in speaker (or interconnect) wires if those wires are coaxial types.....
edit: phn....what Audioquest did is intersting too but i don't think that they want to get rid of that capacitance of the cable - they were thinking probably to build something like people use for anthena's on TV sets...but i am also not sure how this circuit is looking to.....sorry...that is why i have asked if anybody know this too.....
first what i want to do is to get rid of the capacitance of the cable.....first thing ....
but i also wants to get rid of the capacitance that speaker (or interconnect) cable has.....
That is why i want to make something that will insert the signal also on the shielding in order that i loose that capacitance - that is done (from the informations that i have) by using some opamp and some kind of circuit and very low currents....
i don't know how this circuit is looking so i need somebody that has some experience with this problem to help me with the circuit
i don't want to invent some circuit that is completely new but to use the technology that people use in the situations where they want to get rid of those pharasythic capacitances in speaker (or interconnect) wires if those wires are coaxial types.....
edit: phn....what Audioquest did is intersting too but i don't think that they want to get rid of that capacitance of the cable - they were thinking probably to build something like people use for anthena's on TV sets...but i am also not sure how this circuit is looking to.....sorry...that is why i have asked if anybody know this too.....
first what i want to do is to get rid of the capacitance of the cable.....first thing ....
o.k. - so far i have found that i need unity gain opamp that be stable at unity gains, that will have reasonable slew rate and that will be able to work on high input voltages (up to +/-40 or 50V)
the schematic is attached...
can anybody help me with the opamp....
it needs to withstand the voltage at the output of the power amplifier (lets say that amplifier is arround 50-70W), it needs to be unity gain stable and also have rail-to-rail input/output topology or at least common mode input voltage range and output swing in the voltage range of the signal from the output of the power amp.....
the schematic is attached...
can anybody help me with the opamp....
it needs to withstand the voltage at the output of the power amplifier (lets say that amplifier is arround 50-70W), it needs to be unity gain stable and also have rail-to-rail input/output topology or at least common mode input voltage range and output swing in the voltage range of the signal from the output of the power amp.....
Attachments
I cannot see how you can remove the capacitance.
I probably oversimplify things here. But you can only lower the capacitance, and when you do you increase inductance.
Capacitance you have to deal with in the active components. And then you have the capacitance load of the loadspeakers. The latter should alone make whatever capacitance of your cables irrelevant.
I probably oversimplify things here. But you can only lower the capacitance, and when you do you increase inductance.
Capacitance you have to deal with in the active components. And then you have the capacitance load of the loadspeakers. The latter should alone make whatever capacitance of your cables irrelevant.
www.iop.org/EJ/article/0957-0233/17/11/004/mst6_11_004.pdf
phn - look at this link above....this is how they do it with instrumentation....the problem is that i have higher input signal in loudspeaker cables....
that is why i need that partucular opamp (discrete or integrated doesn't matter).....
the capacitance of the cable is still there - you can't remove it physically doing this way but at least you do not have the voltage to charge that capacitor....
the use it in signal trasmission and in measuring eqipment - i want to use the same principle in speaker cables and in interconnect cables....
i need suggestions what to do with that opamp i need - for interconnect cables it is simple - but for the speaker cables i need opamp that can work with +/-50V input signal for my power amplifier.....
phn - look at this link above....this is how they do it with instrumentation....the problem is that i have higher input signal in loudspeaker cables....
that is why i need that partucular opamp (discrete or integrated doesn't matter).....
the capacitance of the cable is still there - you can't remove it physically doing this way but at least you do not have the voltage to charge that capacitor....
the use it in signal trasmission and in measuring eqipment - i want to use the same principle in speaker cables and in interconnect cables....
i need suggestions what to do with that opamp i need - for interconnect cables it is simple - but for the speaker cables i need opamp that can work with +/-50V input signal for my power amplifier.....
The problem with coax only concerns high-bandwidth transfer. We talk gigahertz here. It's misfortunate that DVD-A and other formats are called high resolution. That's nothing but marketing. Audio is the same low-bandwidth world it has always been. You are chasing ghosts here for all I care.
"Power chips" like the LM3886 easily handle +/-50V.
"Power chips" like the LM3886 easily handle +/-50V.
o.k. but i have learned from my experience that when working in audio you have to chase some gosts from time to time.....
i don't care - i want to see if this thing will affect the sound.....
LM3886 can handle +/-50V at the input....i will see that in datasheets....if this is true and if they are unity gain stable than i have solved my problem..
i don't care - i want to see if this thing will affect the sound.....
LM3886 can handle +/-50V at the input....i will see that in datasheets....if this is true and if they are unity gain stable than i have solved my problem..
Radio frequency coaxial cables are normally low capacitance units
As they will need to receive frequencies up to 1 Gigahertz travelling inside..you can imagine how problematic will be capacitance in that sittuation...losses will be enormous.
They are, normally, low impedance cables..so, the pre-amplifier will need to work in a very low impedance and the amplifier input will need some resistance to ground to match.
Have you tried Radio frequency cables?
Distance from the inner conductor related to the shield is very big...resulting very low capacitance.
regards,
Carlos
As they will need to receive frequencies up to 1 Gigahertz travelling inside..you can imagine how problematic will be capacitance in that sittuation...losses will be enormous.
They are, normally, low impedance cables..so, the pre-amplifier will need to work in a very low impedance and the amplifier input will need some resistance to ground to match.
Have you tried Radio frequency cables?
Distance from the inner conductor related to the shield is very big...resulting very low capacitance.
regards,
Carlos
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.