As I mentioned, 600 was the *output* impedance of the generator, not the input of the analyzer. Orb post some samples and I would add that output impedance of sources is often frequency dependent, rising at higher frequencies.
Yeah was one of the reasons I provided the examples to show how your output covered nicely the two extremes with most products comfortably inside those limits.
I should had explained in my post, where I said x ohms
to x ohms, in those instances there is a "behaviour" where we see it is frequency dependent and why in some cases I start with a higher value, so interestingly there are a couple of products that are really stable and of those the manufacturer Ayre stand out as both their player and preamp do not fluctuate.
One aspect I should had mentioned is that I am not sure just how useful the information will be that is generated and measured because most cable analysis has not really shown why/if cables do affect sound or importantly performance behaviour (apart from the Transparent that could help where some/most/no idea products cannot deal with ultrasonics I guess).
My thoughts on this is that it depends what one is trying to show, because IMO a cable can be both passive and active.
By this I mean the use of an unbalanced cable with product A and product B that does not involve galvanic isolation/transformer-electronic floating stage/ design and implemented completely or correctly, or an isolated test and measurement setup/environment.
I am focusing on unbalanced because in theory it is a compromised implementation compared to true balanced.
So in passive I mean you could test a cable with say AP, however the AP products are galvanic isolated so any interaction from the environment and with the asssociated electronic hardware is blocked (makes sense for a test and measurement tool).
By active somehow a test would need to be designed with the cable connected between two powered products (source-or-preamp-or-power amp), with the generated signal entering product A and measuring the output in product B.
A possible alternative I was thinking about would involve some sort of passive monitoring that allows the measuring tool to be inserted in the input or output stage or a dual split from one of the connectors.
Now I am not sure if this is even feasible but would require modification of one of the two products.
A less invasive idea may be the record out on some preamps, but again this comes down to what and how the test signal is generated (by the AP or from a digital source with signal-tones on CD), and how the record out is implemented.
I really should try to explain it much better but just throwing the idea out 1st to see what Amir/Don can think of with regards to possible tests involving the unbalanced cable and critically two powered products that it will connect.
Some may be asking why this could be important but it goes waaay back to John Curl's own tests with RCA cables in 2004 or sometime like then.
I am quoting one of my posts at Stereophile where I am also a member (and also DIYAudio) that touches briefly on the conclusion and summarised pretty nicely by Bruno Putzeys (he was involved along with several other highly respected engineers in working out what JC identified).
Orb said:
Well aint the universe full of coincidence
Seemed Bruno has been dragged back into the discussion just yesterday, Steve Eddy still arguing with JC on this, and everyone else arguing as well.
Here is the post from Bruno on DIYAudio, the bold are IMO the crux of all the discussions from before.
--------------------------------------------------------------------------------
Blast from the past! SE wrote me to ask if I would come here. So:
My goodness is this thing still going on?!!
Unbalanced cables are notoriously sensitive to contact noise in connectors (what with the same connection being responsible for equalising ground potentials and providing a reference for the signal), and RCA connectors are notoriously liable to develop such trouble.
What I remember John explaining during our chat was that somehow his setup highlighted these.
The unbalanced I/O of the AP test sets are floating so such problems would not ordinarily arise.
During my measurements in 2004 -done by request of SE who wanted a second opinion whilst being embroiled in a discussion with John- I still occasionally got distortion but when that happened I always checked solder joints and cleaned the connectors which invariably solved it.
Again, in a system with non-floating I/O this might still not cut it.
So where John and I agree is that these (and some other) problems are real.
His test setup was not so much different from the kind of condition under which these cables would be normally used.
The worst thing you could say is that it did not allow proper control of all variables involved.
After all, a layer of oxide on the connector shell belongs neither to the cable, nor to the test equipment.
Same for a circulating current.
But that does not mean the readings are meaningless.
The same problems arise whenever an RCA cable (and occasionally XLR, see "pin 1 problems") sits between two boxes.
Where John and I take different routes is not in the physics but in emphasis on where to start working the problem.
I'll first try to address it electronically (design circuits which are minimally sensitive to anything a nonideal cable might throw at it).
His is first to attack the connection (use cables & connectors that don't cause problems for most circuits).
This is as literally as I can remember what we said.
Both go a long way, but for perfect results you need to do both of course.
You can't design an input that'll successfully recover an audio signal transmitted along two parallel wires, and you can't design cable that will prevent hum in an unbalanced connection with a ground loop and stamped sheet-steel pcb-mounted RCA connectors.
Now note that I didn't bother reading much of this thread. The lone fact that nearly 6 years after all this I could still suddenly be yanked back into the same discussion says something.
I hope you'll understand that I'm not going to follow up on this thread, but I hope that this reply will be helpful.
--------------------------------------------------------------------------------
Just to clarify Bruno's points, from a technical perspective oxidisation, truly floating input/output -isolation transformer, joints-contacts issues,etc are not actually part or integral to the cable even if they do affect results that may vary depending upon the rca cable.
I tend to agree with the view that the HP setup due to not having the same isolation as the APs managed to replicate the behaviour caused between two seperate audio products connected by RCA cables.
In other words cables may have different subtle affects, but they should not if audio circuit design was modified.
Of course this is just theory and as I mentioned earlier no-one has bothered to investigate further this possibility, or any of the others.
Thats my take on it anyway and I am sure many will have a different perspective.
Cheers
orb
Hope this helps but as I say I am not stating as fact this explains or proves cables sound different or importantly interact with the audio system, just that I would be interested if Don/Amir/JA/Myles/Jeff/etc could think of tests that involve testing cables while operating with two electronic audio products to see if there is some kind of interaction.
If there is some kind of interaction then other tests and setups can be considered, including those that are highly specific and designed to trigger and monitor certain parameters and responses-behaviours.
Thanks
Orb
