SUT - electrical theory and practical experience

@rauliruegas 

Btw, @intactaudio  : you capacitance parameter of 80pf coukld be not real to make SUT measurements as the 300k load.

as stated in the text you pulled the above numbers from, those are the actual values of the referenced phono stage cable combo not some "made up numbers" 

Normally what sees the MM stage + SUT is a load of 47k and capacitance around 200pf. Then measures arwe different that with your " choosed " parameters.

Again this is covered in the text referenced by @antinn on the first page.  It is indeed true that 47kΩ || 200pf may be a typical number, it simply represents a situation that has a good chance of being less than ideal for use with a SUT.  Gaining a fundamental understanding of the tradeoffs of the cart /SUT/phono interface goes a long way in furthering the trend of commonly occurring mistakes that historically has given SUT usage a bad rap.

Unfortuntaelly cable manafucterer almost never gives the cable capacitance but almost all are higher than 150pf and even over 200pf.

then you need a basic understanding on how load capacitance adversely effects a SUT and you also need to find a new cable manufacturer.

dave

To the notion that cartridges are “natural” current generators I would say that the general statement can only be applied to LOMC cartridges with very low internal R in relation to V output. I would also note that in a “trans impedance” stage , the first stage converts current to voltage. Thereafter and in the RIAA filter, the signal is handled as a voltage exactly as in a conventional phono stage.

In a earlier post within this thread, I made it known, I had not given too much attention to using a shortest length cable between SUT and Phon'.

As said in the earlier post, I use a cable of approx' 70cm (28 inches) 

My memory got Jogged and I recollected a few things previously learnt.

The Capacitance for the Cable I use is 57pf per metre using Manufacturer Spec.

A friend, prior to my acquiring the 70cm Cable measured an identical cable with different RCA's in a 1.2mtr length at 90pf (Memory Jog Moment).

Maybe I was focused on creating a improved Capacitance art the Interface and purchased the 70cm length to attempt to achieve this.

Ihave detected minimal differences between the Two Cable lengths in use, but this attributed mainly to the Cable RCA's.  

I would like to think that a 70cm Cable, even with a different RCA Plug is near optimised with the required 'pf' at the interface.

I hope this assists with adding a little extra support for the usage descriptions given with the owned and in use SUT's and the occasionally introduced Head Amp.  

Dearb @intactaudio  : Thank's. I know all those and certainly about capacitance but my post was because the measures in the vinatge SUT's was not with 300k-500k and I found out measured at 47k and 180pf.

That's all.

@mulveling  , yes shorter cable is better but normally audiophiles use 1m. because is the " rule " by cable manufacturers and in the other side many times the owners need that 1m. for its system SUT place/phono stage.

R.

Also, in a voltage driven conventional stage, the input load R can be thought of as the simplest form of passive current to voltage converter.