In series, I assume. Is there a way to test for the ideal value in this regard. If matching the impedance, as suggested, would you expect a difference in sound? I assume that capacitance is not much of an issue due to drive current available from the output.
You can measure the output impedance of the preamp by varying the load.
Then subtract this from cable impedance to get value for Rout (series).
Just try first,
Patrick
PS Try teflon cables as well.
Then subtract this from cable impedance to get value for Rout (series).
Just try first,
Patrick
PS Try teflon cables as well.
OK.
I am always hesitant in soldering cables, but i notice that the Lemo's have crimps. Do you have to buy a crimping tool to do this properly?
I am always hesitant in soldering cables, but i notice that the Lemo's have crimps. Do you have to buy a crimping tool to do this properly?
The far end loading to match the characteristic impedance must use a capacitor in series with the resistive load.
The combination should be adjusted to suit the frequencies you want to pass through the far end.
This "loading" is only there for the VHF and UHF that might be getting in. It is NOT for the audio signal.
See Cordell and Ott.
BTW,
I have experimented with unshielded star quad for interconnect.
I can wrap the star quad interconnect around transformers and mains cables and anywhere else close to my Live equipment and cannot detect any change in the amplified output signal.
The star quad is a DIY using 4 cores from CAT5. I tie the four ends to a door knob and twist them up manually as I work away from the door. 3m is the longest I have done, but longer is possible.
DO NOT use a group twisting method !!!! Don't think that a drill can substitute for hand twisting. Just look at the machines invented for cable twisting to see the efforts that Manufacturers go to to avoid the straining that drill twisting would involve.
The combination should be adjusted to suit the frequencies you want to pass through the far end.
This "loading" is only there for the VHF and UHF that might be getting in. It is NOT for the audio signal.
See Cordell and Ott.
BTW,
I have experimented with unshielded star quad for interconnect.
I can wrap the star quad interconnect around transformers and mains cables and anywhere else close to my Live equipment and cannot detect any change in the amplified output signal.
The star quad is a DIY using 4 cores from CAT5. I tie the four ends to a door knob and twist them up manually as I work away from the door. 3m is the longest I have done, but longer is possible.
DO NOT use a group twisting method !!!! Don't think that a drill can substitute for hand twisting. Just look at the machines invented for cable twisting to see the efforts that Manufacturers go to to avoid the straining that drill twisting would involve.
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I have some work to do. I will start with trying Mogami and the Belden that Euvl suggested as well as looking into adding a series resistor to the preamp output.
For those interested.
http://www.canare.com/UploadedDocum...phone Cable Perfrmance and Specifications.pdf
http://www.canare.com/UploadedDocum...phone Cable Perfrmance and Specifications.pdf
Buzz,
RFI may also be a contributor to the differences. That extra capacitance and/or better shielding may be a contributor to the changes you hear. Why don't you try adding a small capacitance across the diff terminals at the amp input connectors and retest the cables.
Just a thought.
Dave
RFI may also be a contributor to the differences. That extra capacitance and/or better shielding may be a contributor to the changes you hear. Why don't you try adding a small capacitance across the diff terminals at the amp input connectors and retest the cables.
Just a thought.
Dave
I need to figure it out. The change was simply to dramatic. The paper i linked did show the Mogami and Canare to be excellent at rejecting noise, but i would not think the Belden 1800f was poor in this regard. I am willing to try anything.
though , I think Super Cable Cookbook is worth reading ...... then proof the concept(s)
😉
I like to add a 47pF at the signal input socket direct and very short leads from hot to barrel.
This interacts with cable and source inductance to create a 2pole filter that is very effective at vhf and uhf. Costs almost nothing.
I recent soldered an 805 smd 47pF NP0 direct from Hot to Barrel just spanning the tiny gap across the insulator. Must be the lowest inductance I have achieved for this RCA filter.
Now that I have managed that, I can fit a 2M2 smd 805 across the insulator gap. This to minimise input offset voltage when the cable is disconnected.
This interacts with cable and source inductance to create a 2pole filter that is very effective at vhf and uhf. Costs almost nothing.
I recent soldered an 805 smd 47pF NP0 direct from Hot to Barrel just spanning the tiny gap across the insulator. Must be the lowest inductance I have achieved for this RCA filter.
Now that I have managed that, I can fit a 2M2 smd 805 across the insulator gap. This to minimise input offset voltage when the cable is disconnected.
Just revisited this thread after quite some time - prompted by the fact that I have got going on building my F5X.
Hope the F5X preamp gets going again.
Hope the F5X preamp gets going again.
I just have all the mechanical parts after one year's delay, and am slowing getting back to DIY.
The F5X Pre is among the top 3 of the priority list, but I do want to finish my DAO headamp first.
Will keep you informed of any progress.
Patrick
The F5X Pre is among the top 3 of the priority list, but I do want to finish my DAO headamp first.
Will keep you informed of any progress.
Patrick
> What is top 2 on your list
The DAO, and a secret project not yet know to the public. 🙂
I do want to see more of the 50+ F5X Power Amp being finished first before we do another big one like the pre.
AND I do have someone who volunteered to take over manufacturing the mechanical parts from Mark's factory.
So it will be interesting to see how far we get in 2015.
Patrick
The DAO, and a secret project not yet know to the public. 🙂
I do want to see more of the 50+ F5X Power Amp being finished first before we do another big one like the pre.
AND I do have someone who volunteered to take over manufacturing the mechanical parts from Mark's factory.
So it will be interesting to see how far we get in 2015.
Patrick
It's amazing how long it takes some time, especially when you are attempting to do it for a final time. Everything requires more precision and patience. Hope you are doing well. Thanks for all you have done.
The lack of progress has more to do with personal issues this year.
It was a eventful and at times very difficult year.
So I am glad that I am finally getting back to have some fun with my numerous unfinished projects .....
Patrick
PS You still owe me the test for the simple speaker protection board ...... 😉
It was a eventful and at times very difficult year.
So I am glad that I am finally getting back to have some fun with my numerous unfinished projects .....
Patrick
PS You still owe me the test for the simple speaker protection board ...... 😉