Directionality in digital = impedance mismatch

This is my first post. It's great to participate given members' knowledge and experience. I have a little story to share which may encourage some feedback. My system is as follows:

* Amp: Manley 100W monoblocks (Svetlana winged C 6550 x 2)
* DACPRE: Monarchy M24 (Amperex Mullard 6DJ8 1976 A-frame x 4)
* Speakers: Harbeth SHL5 (special edition)
* Transport: Denon DCD-1500AE (SACD player)
* A/C: isolation transformer for sources
* Interconnects: Monster 400mk2 + Monster Coax digital (75 ohm)
* Speaker cable: OFC free generic copper cable (spades + bare)

David Manley is a very good friend, so he recommended most of the components above (apart from the Denon, which he said was rubbish). Nonetheless, the system is excellent and competes with others that cost much much more. Very involving and "foot-tapping".

Here's a funny story: after a few months of using the system, I discovered that my directional Monster coax (75 ohm) was connected in the wrong direction (arrow pointing to Denon). So i decided to "correct" the direction and reverse the cable (arrow pointing at DACPRE).

Result #1: timing of music "gone", foot-tapping disappeared, image became fuzzy, vocals move rather than center, and one of the Amperex 6DJ8 starts whistling and squealing at random intervals (with or without music).

Action: I blame the 6DJ8 and win two eBay auctions for Tesla and Amperex replacements. Then, after 2 frustrating days, it hits me (the damn coax cable). SO I REVERSE THE MONSTER COAX into the "wrong" direction (arrow pointing at Denon).

Result #2: MAGIC. The wrong coax cable direction makes everything "correct". Music gets back weight, timing, presence, etc... . Some may argue that this was caused because coax cable was "burnt-in" the wrong direction, hence, needs time to burn in correct direction. Seems that tube whistling has gone too.

Well I don't think so (apart from the die-electric theory). I blame the poor interfacing of equipment, especially mid-fi products such Denon. It seems it took two wrongs (wrong cable direction + bad Denon coax output) to reach a neutral state.

Morale of the story:

1. Mid-fi gear (i.e. Denon) is crap: I presume that the Denon does not have a decent coax interface, hence, must have either a coupling transformer (CC Poon) or reversed cable grounding to match impedance.

2. Mid-fi gear can ruin the rest of a high-end system through power interference and interface mismatches.

3. Buy a great transport (used) rather than new mid-fi transports. That's what Manley says anyway ("get the cheapest Meridian 2nd hand and you'll be fine")

4. With properly matched hi-fi gear, cable shouldn't matter. It seems cable only matters when there are electrical problems that need to be addressed.

Who shares these views, who thinks otherwise?

I don't see the need for exotic cable with properly matched components.
You cable coax might be damaged (got bent severely?) - it seems you may have ground loop issues getting onto the coax and messing up the digital signals or the clock signal (jitter). Get a new coax it is cheap.

I'd also check to makes sure all gear is grounded (three prongs) and no cheater plugs (your A/C isolation transformers might be the problem - meaning your gear is floating - this means ground loops flow along the digital coax which goes to common).

Don't be so hasty to assuem Denon is crap. It coudl be a combo of factors.
Red, You are welcome to the small pile of Monster cables I accumulated before I knew any better... That's not really fair, 20 some years ago they were the only game in town. Thank goodness that changed... I recommend you revisit those lessons of yours from time to time.
I completely agree with Shadorne's comments.

I would add that I believe that the reason many (but not all) cables are specified with a directionality is that the shield is only grounded at one end. Depending on the overall configuration of your particular system, in terms of grounding, signal return paths, ac return paths, ac neutral, the impedances and/or leakage paths between all of these to the chassis of each component, etc., all of which obviously is difficult to analyze, it is conceivable that your particular system may require a grounded shield on both ends of the cable, or, perhaps less ideally, the reverse orientation that you found worked satisfactorily.

-- Al
Red, You are welcome to the small pile of Monster cables I accumulated before I knew any better... That's not really fair, 20 some years ago they were the only game in town. Thank goodness that changed...

Good point. Ordinary cables were cheap in the bad old days. Even the best Monster cables look like cheap crap today. If you know better then you will definitely want to get something much more expensive...have a good dealer help you select a good sounding replacement and get rid of that "Denon crap" while you are at it!
I've tried many 'audiophile' digital cables over the years, they do sound different. Until you try, you'll never know. AES/EBU, RCA, coax and I2S all sound different from one another as well, also depends on what your DAC and transport are optimized for.
Thanks to you all for your helpful feedback. I just bought a 1m MIT Digital Reference Cable from a fellow A'goner. I will test once cable arrives and post my findings.

As for ground loop entering, here's the situation:

Isolation transfomer-connected gear = Denon + DACPRE
Direct AC connection = monoblocks

Q) Do you think noise can STILL enter the system?