|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
In Reply to: Re: The Importance of Audio Measurements posted by jj on November 20, 2002 at 20:45:51:
Well, I just tried it. I put the preamp on Disc, turned the preamp gain all the way up (in steps, just to be safe; of course, there was some broadband hiss at full volume), and tapped the phono cables. Couldn't hear any result from the tapping out of the speakers.I also tried my headphones through the headphone jack of a tape deck (my preamp has no headphone jack), and could hear nothing from the tapping, but the gain isn't really very high in that case, though more than adequate for music.
I imagine the effect would be measureable, but in this case, I couldn't hear it.
____________________________________________________________
"Nature loves to hide."
---Heraclitus of Ephesus (trans. Wheelwright)
Follow Ups:
Wow, even I would have expected it from the Phono cables, but certainly not the regular interconnects - impedance is too low.I've done this on an oscilloscope numerous times, especially with unterminated teflon cables, it's easy to see the results - until you put a low impedance(resistance) load on them, then it's gone.
Isn't the standard phono input impedance 47 kilohms?
____________________________________________________________
"Nature loves to hide."
---Heraclitus of Ephesus (trans. Wheelwright)
Yep, 47k is it.
Some call for 47K input. Some don't. Some call for rather orders of magnitude less.And a few (does anyone know if any of those old ceramic THINGS are still out there) expected something like 2.2 meg.
JJ - Philalethist and Annoyer of Bullies
I have a Grace F9E.The Quad preamp is spec'd for a phono input impedance of 47K, with a choice of adding in 180 pF capacitance, which would be in addition to whatever the phono cables had. The extra capacitance introduces a roll off in the FR, about 5-6 dB at 16K if I recall, which generally sounds way too dark. In any case, the phono cable I tapped on is on the outside the TT, a Denon DP-60L, which Dougman says is fine, BWT. If I tap the cartridge or tone arm, of course I can hear something.
Now, if I had a low output moving coil, which requires more gain, perhaps I would hear something. Quad used to have different input modules available for moving coils, and they may still be available.
2.2 meg? Gee, my Radio input is only 1 meg; CD input .5 meg; the rest are about 100,000 ohms (varies somewhat with the input sensitivity, which is adjustable). I really don't know anything about the availability of ceramic cartridges or replacement needles.
____________________________________________________________
"Nature loves to hide."
---Heraclitus of Ephesus (trans. Wheelwright)
The lowest of the two impedances the cable see, is normally the source impedance, say 1kOhm for MM, down to 2 Ohm for MC.The source impedance load down the cable's generator, which is a high impedance generator.
Microphones often have 600 Ohm source impedance and low levels, making this cable microphonic effect audible.
Preamps and CD players have from a few Ohms to 2kOhm source impedance, but much higher levels, and thus relative less audible effect of microphonic cables.
I have no idea what the source impedance of a Grace cartridge is.What sort of magnitude are cable microphonics?
____________________________________________________________
"Nature loves to hide."
---Heraclitus of Ephesus (trans. Wheelwright)
Ole is correct. The Grado cartridge is low Z.
Well, I do own a Grado cartridge, but I no longer use it. They are supposed to maintain their FR pretty well into various capacitances, as I recall.I currently use a Grace F9E. Is it low impedance, too?
____________________________________________________________
"Nature loves to hide."
---Heraclitus of Ephesus (trans. Wheelwright)
I don't think so.
This post is made possible by the generous support of people like you and our sponsors: