Originally Posted by IngoT
So my idea would be to use a direct HDMI A/V connection to the second HDMI input of my beamer (please remind that the first HDMI input remains occupied by the Marantz) anf to use the HDMI Audio output for connection to the Marantz. As dave7 already suggested, the composite video connection to the TV set is only needed for on-screen menu purposes with the DX-5, not for regular watching and might be plugged off if not needed.
If your projector has two HDMI inputs, this arrangement will give better picture quality (because the signal from the DX-5 is not going through any extra connectors and circuitry) and better sound quality (because the HDMI Audio Output has lower jitter than the HDMI A/V Output).
There are only two points to watch for:
a) When the HDMI Audio Output is connected to an active HDMI input on your processor, the Analog Audio Outputs will be turned off. Normally all that is required is to select a different input and the HDMI Audio Output will be turned off and the Analog Audio Outputs will be turned on.
b) I'm assuming that the composite video connection would go to a small (eg, 18cm) LCD monitor. Please refer to the other posts on the page for ideas on how to avoid the introduction of extra noise from its power supply.
Originally Posted by IngoT
As for the idea to insulate the cable receiver by a Jensen VRD-1FF, it is a HDTV HDD recorder that uses a kind of F-type satellite connector and requires a return channel for firmware upgrades and other stuff. It was installed by a technicial from the cable distributer, works fine and I think I will not touch it.
Others on this forum may have more experience with this than I do, but satellite and cable connections are well-known for causing hum problems due to the extra ground connections. The Jensen is designed to isolate the ground connection and solve these problems. I don't see why it wouldn't work in your situation. I'm sure that it is a bi-directional device, fully capable of sending information back to the service provider.
Originally Posted by IngoT
However the Jensen page brought another idea, although a little off-topic now: I have a minor hum from the main speakers feeded by the Mark Levs only when signals from the Mararntz are played back (i.e multichannel). This is an old phenomenon with my system, also the Marantz's predecessors suffered from it. It is not caused by the DX-5, you can plug off everything from the Marantz AV7005 and it remains as long as the AV7005 is connected to the No. 326S. A few years ago I tried some cheap 1:1 transformers to insulate, the hum was gone and the good sound too. From your experience as an engineer, can you comment on the audiophile qualities of the Jensen Iso-Max transformers (i.e. CI-2RR or PC-2XR) ?
a) The Jensen transformers are probably the best sounding transformers you can get.
b) Even the best transformer will degrade the sound. Therefore I would try to solve the problem directly rather than put a "band-aid" on it.
Since you live in Germany where Schuko plugs are used, it is critical to properly orient the AC power cord on every single piece of equipment in your system. This will not only help to reduce (or eliminate) the hum, but also improve the sound quality noticeably.
If the hum still persists, it is probably the result of ground loops. The major cause of ground loops is the use of three-wire grounded power cords. This is a cheap way to ensure compliance with international safety standards. A better way is to use double-insulation and two-wire power cords with no AC safety ground.
(Ayre components are double-insulated. We only include three wire power cords to ensure that they are connected with the proper polarity to give the best sound quality. However, this doesn't work with Schuko plugs, and you will need to make some measurements to see which way is correct.)
In the US, one can purchase "cheater plugs" that disconnect the AC safety ground. These not only can eliminate hum problems, but if your entire system is "floated" with no AC ground connection, it will provide noticeably better sound quality.
NOTE!!! Using cheater plugs can kill you. Just like lightning can kill you. So if your stereo fails in such a way as to connect the AC mains voltage to the chassis, and you simultaneously touch the stereo ground at the same time you touch a cold water pipe, you could be seriously injured or killed.
The chances of this are about 100,000,000:1, but it can happen -- mostly with crappy equipment where the AC connections are made with spade lugs instead of soldering them, or with cheap Chinese transformers that are shoddily made.
If you die because you used cheater plugs, don't sue me!
I have all of my gear floated and have had for over ten years. In fact the house I'm living in now is the first one in thirty years that even had grounded outlets anyway! Many people will try to scare you and say that everything must be connected to the AC safety ground. Well, that is baloney. Look at any Japanese receiver and they all have two-wire AC cords.
And the fact of the matter is that if *any* of your connections are single-ended, it is impossible to get rid of all the hum if you also have AC safety ground connected. (Unless you use audio isolation transformers, but that degrades the sound and is expensive.)
I have my flame-proof suit on, so now everyone can tell me how stupid I am....