impedance mismatched ?

Audio Aero Capitol Mark 2 running directly into amplifiers via balanced outputs has a output impedance of 100 ohms.
My VTL 750 REFERENCE amplifiers balanced input impedance is 137 ohms. Is this a impedance mismatch which could possibly cause a audible [20 feet away] hum to result when using 1 meter balanced Interconnects? when using the RCA outputs and RCA inputs with same components as above [same impedance specifications for RCA also] their is absolutely zero hum. And yes the XLR pin configuration has been confirmed as being correct on my balanced Interconnects for these components. was suggested could be a ground loop causing the hum but when plugged all 3 components into a power strip the hum still remains, even if floating all the grounds with cheater plugs.
The input impedance is actually 137,000 ohms, which is typical for a tube amp. The high ratio of amp input to source output that you have is what you want in this situation.

I suspect you have a broken connection inside your balanced cable at the connector since the RCA doesn't hum.
hello Herman I believe your correct I checked the information again the specifications actually says input impedance 137kw is this actually same as 137k ohms? Thanks
What brand of cables are they? I've had a number of balanced cables that really weren't balanced and hummed like crazy. They were just coaxs with XLRs stuck on the ends.
they are XLO SIGNATURE 2 they don't hum when used in my friends system. Interesting note when I connect from the balanced players outputs using a XLR to RCA adapter and a RCA terminated Interconnects to the amplifier their isn't any hum problem?
The XLR introduces one more ground plane, so now you have the grounds from two or more outlets (the amps) and the grounds in the XLR cables creating a grid with loops.

The RCA's ground the signal to chassis only while the XLR's bond to equipment, so the RCA's break the grid (even though they're more prone to picking up common mode noise, their main advantage is not creating a ground plane).

XLR's reject common mode noise and can create ground loops, especially if the equipment they're connected to are on dedicated circuits.
Looks more & more like a system ground loop. OTOH the 100->137kOhm connection looks good on paper.
Excuse my stating the obvious but, why not stay with rca OR try plugging the cdp into another outlet, with & without floating the ground -- just to check. In a similar situation (but with barely perceptible hum), I plugged the cdp's into a different outlet and REDUCED the noise (but you've probably been there & done that...)
Note that I use a pre & short rca IC for the cdp... Cheers
ok player returned for service they didn't find a hum problem with the balanced outputs player returned today still has the hum problem with balanced outputs.
Plug player into outlet on entirely different circuit which is original to the house 1985 construction the hum didn't change its the same. If its a AC ground loop how do you prove it is? Have a magic cable ground break devise for the cable TV already installed. Can someone explain if 3 circuits are all grounded at the same point as the entire house is ground at how is a ground loop possible?
Yee Ha, an opportunity to use the new reference thread:
Video & Audio: Power, Ground, EMI, Noise in Cables.

Can someone explain if 3 circuits are all grounded at the same point as the entire house is ground at how is a ground loop possible?

Mejames, what you have is the classic "pin 1" problem in pro-audio balanced systems. Perhaps I can sum it up by suggesting for *your* system, you use RCA and thereby create an unbalanced system. Trade your nice XLRs. Since you currently have a problem with a balanced line, your distance is 1m and you don't have an extreme environment (EMI, theater, stadium etc.) then there is not much to gain by running a balanced system and a lot to lose. Often, a high end balanced input uses an active (op-amp) circuit to provide a matching virtual impedance for the cable while providing high common mode rejection (CMR) (unlike tubes typically) and all grounds conform to a star ground or better. I don't think you can achieve this without modifying/soldering your current system (either cables, equipment or both).
Try a shielded coaxial cable with foil (for EMI) and braid (for hum) read about them at Coaxial Cables and Applications (Belden)

The most important reference is for you is:
7. Equipment Wiring - Internal to Electronic Equipment
7.1. The "Pin 1 Problem"
The "Pin 1 Problem", refers to a means of EMI pickup in audio equipment related to connections to Pin 1 - the ground pin - of an XLR connector. The reference work on this subject is [2] by Neil Muncy of Toronto, Ontario. Pin 1 of an XLR connector, of course, is the pin used for the cable shield connection. In general, the "Pin 1 Problem", refers to the connection of shields to audio equipment and how connector contact "Pin 1" is internally grounded.
... The "Pin 1 Problem" manifests itself as noise induced into the circuitry of audio and video equipment that then appears on its outputs. In brief, the problem occurs when the circuit grounds are shared with the input and output connector shield grounds. When this occurs, common impedance coupling, as discussed earlier, causes the electrical noise picked up in the shield to be transferred to the electronic circuits.
Why is this so?:
3.3.3. Grounding the Shield
An actual connection to earth plays no part in EMI shielding effectiveness. The ideal EMI shield forms a continuous conductive layer around those items that it protects as shown in Figure 3-3. In the case of twisted shielded pair cable, normally terminated with an XLR, clearly there is an opening in the shield at the connector. By connecting the shield to the ground of the equipment case the continuity of this shield is improved, however, clearly it is far from perfect as the conductors are clearly exposed. In the case of coaxial connectors such as BNC’s, the shield makes a circumferential connection to the cable connector and that in turn makes a circumferential connection to the panel mounted connector providing 100% coverage of the inner conductor. In the case of coaxial cable, we have 100% shielding throughout the length of the interconnect and we have a ground loop that is formed between the send and received ends. This has always been one of the difficulties of the single ended transmission system used for video. In the case of audio equipment, the shield is never grounded at both ends to avoid this ground loop problem. At the high operating frequencies of video, maintaining the characteristic impedance of the transmission line (usually 75 ohms) and high frequency shielding are more important than maintaining the ground system integrity.
For your tube equipment with its high input impedance and sensitivity note:
5.4. Separation and Routing
For further reading see:
2.1. The Isolated Star Ground" and the background explanations of
" Circuit Ground", " Shield Ground", and " Equipment Ground"
Followed by:
2.3. Ground Loops
And then before you hire the electrical contractor read:
8. Case Study - Getting the Installation Right
8.1. Power and Ground Systems at The Hamilton Place Theatre
Ignore most concentrate in particular on:
8. Case Study - Getting the Installation Right
8.1. Power and Ground Systems at The Hamilton Place Theatre
When done (whew!) skim the various posts where Subaruguru and others talk about power wiring. Pick cable to match your budget, but at least consider some form of braided 3 or 4 conductor cable or conduit.

One last note, due to power problems I have, I am using GFIs and I'm currently installing a 220VAC feed into a 2000VA Sola constant voltage transformer to create a 110VAC circuit and a virtual isolated ground. This goes to two Isobar12 with dual EMI/RFI Filtering (40 & 80dB) between equipment outlets. One to supply my MLs, DVD etc. and the other for power amps etc. I think I have found filtering each piece of equipment relieves many noise problems and reduces the need for more exotic power cables, but I do need to test more before getting on a soap box (LOL). One should use at least braided shield power cords to reduce their effects on other equipment.

Ok that is enough *noise* by me!
I was surfing last night and saw a company which sells a XLR to XLR with pin #1 lifted to avoid the famous pin #1 problem I will post there site address soon.