Hi,
Just wondering how I could improve the connection between my home made preamp and its external 9VDC power supply choosing a better cable, but I do not know by what criteria to choose it.
Generally speaking I like to oversize elements and I would like to use a good cable suitable for that purpose.
Shielded or not?
Thanks for any addressing.
Just wondering how I could improve the connection between my home made preamp and its external 9VDC power supply choosing a better cable, but I do not know by what criteria to choose it.
Generally speaking I like to oversize elements and I would like to use a good cable suitable for that purpose.
Shielded or not?
Thanks for any addressing.
More information needed, eg schematics for both power supply and preamp and a photo so that the layout is visible. What is the supply current? What kind of connector do you want to use? Screened cable might be worthwhile in some circumstances and a circular cable might suit some connectors better.
Given it´s a 9V powered preamp that alone is a HUGE performance limiting factor.
ANY cable will be competent enough in that duty, that woukd be the least of my worris.
Very much doubt any shielding is necessary.
As mentioned above, we need the preamp and supply schematic, and a picture or two to show layout.
Hope we are not seeing the birth of yet another cable thread.
So sorry if I just realized I asked the question in a misleading way and thank you for your appreciated replies.
My question is actually much simpler: I want to know what is the state of the art for DC transfer between separate power supply and preamp.
In other words, if the DC cable from the electrical point of view and from the point of view of interferences (does it produce any?) is preferable to be coaxial rather than a flat one, or a shielded flat one, optimal cross section and if it still needs to be shielded and if affirmative then where the screen is connected, etcetera.
No seed of discussion about the sound of DC interconnect cables...
Or... why not?
If from the global electrical point of view the energy transfer respects the state of the art of the knowledge then also the reproduced sound will consequently be good, or not?
P. S.: the preamp is a passive LDR one that I simply mounted, not created. Thank you
My question is actually much simpler: I want to know what is the state of the art for DC transfer between separate power supply and preamp.
In other words, if the DC cable from the electrical point of view and from the point of view of interferences (does it produce any?) is preferable to be coaxial rather than a flat one, or a shielded flat one, optimal cross section and if it still needs to be shielded and if affirmative then where the screen is connected, etcetera.
No seed of discussion about the sound of DC interconnect cables...
Or... why not?
If from the global electrical point of view the energy transfer respects the state of the art of the knowledge then also the reproduced sound will consequently be good, or not?
P. S.: the preamp is a passive LDR one that I simply mounted, not created. Thank you
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A passive preamp implies no power is used by the preamp, so what is the power supply energising?
BTW the 'state of the art' for your specific circumstances depends on the questions I first posed. It sounds like the 'art' you are seeking is aesthetic, not so much electronic; if so only you can decide.
If you want a meaningless application of 'state of the art' then use triple shielded coaxial superconductors chilled to near absolute zero degrees which will provide the lowest impedance between supply and load, contribute the least Johnson noise (thermal electron noise) and not act as an antenna to either radiate or receive EMI / RFI into or out of the power supply and/or preamplifier.
BTW the 'state of the art' for your specific circumstances depends on the questions I first posed. It sounds like the 'art' you are seeking is aesthetic, not so much electronic; if so only you can decide.
If you want a meaningless application of 'state of the art' then use triple shielded coaxial superconductors chilled to near absolute zero degrees which will provide the lowest impedance between supply and load, contribute the least Johnson noise (thermal electron noise) and not act as an antenna to either radiate or receive EMI / RFI into or out of the power supply and/or preamplifier.
A more down-to-earth answer, right?
I'm sorry for telling you, but (if I have correctly understood what you mean, since this is not my mother tongue) I don't see any need to bother with extremes.
Otherwise I could say that I understand everything, and that's that any cable "not too thin and not too big" is fine if there is no "audible" interference, otherwise a shielded one is better.
The "passive" adjective was used in the sense of "no gain", but since LDR stands for "Light Dependent Resistor" then a power supply does seem needed.
I've no idea about what is the supply current.
I like these connectors Free shipping 5set GX16 GX16 4 4P 4Pin 16mm Male&Female Wire Panel Connector plug Circular Aviation Connector Socket Plug|plug connector|plug socket connector4pin wire - AliExpress, but maybe it is only an aesthetic reason.
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I'm obviously not up to date as I wasn't conscious that LDR's have become fashionable in passive preamps. LDRs have been used for many decades (since at least the 1950s) as level control mechanisms. Probably the main use long ago was in signal compressors which are devices used to control or regulate the level of audio signals, particularly in broadcast and recording applications. They've generally fallen out of favour in professional equipment, except for some idiosyncratic devices, because they are inherently fickle and somewhat capricious, at least as implemented years ago.
From a pragmatic point of view, a properly designed implementation of LDR volume control would not be susceptible to external limitations such as that imposed by power supply leads because a competent designer would ensure that it wasn't. Indeed if the LDR design is susceptible to external interferences not much can be said about the specific power supply or cable requirements without knowing the susceptibility weaknesses of the particular LDR design.
Having said the above, I would probably use a star quad microphone cable from manufacturer such as Canare, Klotz, Belden. The screen should be grounded at the power supply end only and the (+) and (-) conductors configured in diagonally opposed pairs. This is the 'practical' state of the art in creating immunity for the conductors to external influence by RFI / EMI, and also a benign coupling between the supply output and load, i.e. mitigating the effect of the cable on the both power supply's and LDR's behaviours. I'm sure others can contribute different insights based on practical experience of passive preamps with LDRs.
From a pragmatic point of view, a properly designed implementation of LDR volume control would not be susceptible to external limitations such as that imposed by power supply leads because a competent designer would ensure that it wasn't. Indeed if the LDR design is susceptible to external interferences not much can be said about the specific power supply or cable requirements without knowing the susceptibility weaknesses of the particular LDR design.
Having said the above, I would probably use a star quad microphone cable from manufacturer such as Canare, Klotz, Belden. The screen should be grounded at the power supply end only and the (+) and (-) conductors configured in diagonally opposed pairs. This is the 'practical' state of the art in creating immunity for the conductors to external influence by RFI / EMI, and also a benign coupling between the supply output and load, i.e. mitigating the effect of the cable on the both power supply's and LDR's behaviours. I'm sure others can contribute different insights based on practical experience of passive preamps with LDRs.
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Ok, then there´s no amplification, no active elements, the LDR itself is NOT fed anything from the power supply, then there is no interaction whatsoever.
The preamp (LDR) is not fed from 9V, it is not fed at all.
I guess DC powers a LED shining on the LDR, and you have some means of varying it for volume control.
ANY unshielded single conductor cable will do, you are only passing 0 mA to, say, 10 or 20mA feeding that Led.
If anything, be careful where/how you ground that power supply, a poor choice might introduce some supply ripple and contaminate your grund.
But that´s a layout problem, not a cable one.
Again: we NEED the schematic, both of the preamp and supply.
If you already built a prototype, show a picture, we might detect some layout problem.
No, PLEASE 😛
State of the art is a piece of insulated copper wire.
Thay´s an erroneous but sadly very common belief.
Similar to: "silver is a better conductor than copper (true), so wiring my amp with silver wire will make it sound better" NO.
Short explanation: quality, sound and performance come from DESIGN, and only partially from PARTS, as long as they are competent enough for the job.
But to DESIGN you need KNOWLEDGE and EXPERIENCE, both of which take YEARS and EFFORT to acquire, so some think the short path is using expensive/exotic parts.
Sadly it´s not so.
The connectors are fine (I think they are called aviation plugs), and if I were making an external supply for something I would use the same. There are more expensive, prettier ones from Limo and others, but functionally for your application I don't think they are better.
Point of view very informative for me: thanks for saying that.
So very interesting: best answer for me.
That's exactly what I was interested in knowing: thank you so much!
Glad to hear you say that.
Great answer (I'm very serious): thank you so much!
Here I do not agree.
Also because you only quoted the last part of my statement which instead in its entirety is: "If from the global electrical point of view the energy transfer respects the state of the art of the knowledge then also the reproduced sound will consequently be good".
I think that the above statement is true: and therefore I do not believe that if the energy transfer did NOT respect the state of the art of the knowledge then the sound could be "better".
Really I think it's a bit difficult for this to happen.
(Quote bold is mine)
Yep, this is precisely the matter.
May be that any part - even if exotic - could not compensate for a design error in any way, I agree.
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Use an opto coupler instead of LDR.
Use DAC if needed.
No noise introduced.
Use a metal box suitably earthed to protect from radiation.
And do the math, use a device with a high interference rejection ratings.
Use DAC if needed.
No noise introduced.
Use a metal box suitably earthed to protect from radiation.
And do the math, use a device with a high interference rejection ratings.
Cable specialist such as Belden, Whirlwind, et al, will be thrilled that they can cut their inventories from thousands of specialist cables to just a few lines based on universal bundles of pieces of insulated copper wire.
😀
But weren't just you the one who described another extreme about state-of-the-art before? 😛
Seriously, I liked that answer because it is so basic and for this very reason it makes the concept a lot constructive for me.
On the other hand your first answer - as already said - was also extreme, but unlike this one it wasn't equally constructive in its own way IMNSHO.
As matter of fact a so "basic" concept as "State of the art is a piece of insulated copper wire" although it is certainly extreme it is also a starting point to which you can add further and subsequent elements that you have learned and which then constitute scientific knowledge, while "your" extreme was definitive and did not allow any possibility to add anything else except to put in doubt its presumed "scientificity".
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