I have done some more research as I found that question of input-levels quite interesting.
There seem to be at least three widely used definitions:

+ 4 dBu for professional audio (including electrical instruments like synthesizers, mixing consoles and the like)
+ 6 dBu for professional video (Europe)
-10 dBV (or -7,8 dBu) for consumer audio (USA)

The Zoom H4n's line inputs are rated +2 dBm (or +2 dBu) and hence comply with the US-consumer standard (assuming the rating is correct) but with none of the professional standards.

My Marantz CD-player is a consumer device but it still has a rated output of 2 V rms (+8.2 dBu) which is way above the rating of the H4n. That explains the original overloading (but not the distortions as I have reduced the output level during those tests).
The 2 V rms output rating of the Marantz is not exceptional, though. CD-/DVD- and BluRay- players made by Panasonic/Technics and Sony, for example, are rated just the same. Pioneer specifies their CD/DVD-player's outputs with 200 mV rms (-11,8 dBu). But a quick test with a multimeter on the Pioneer player in my household revealed just the same 2 V output voltage with a 0 dBFS signal as with all the other Japanese players. It seems not all manufacturers care much about the US-definition of 'consumer line-level'...

And the other two field recorders?
The Edirol R4's inputs are rated +4 dBu but it still gives me 6 dBFS of headroom when recording the +8.2 dBu signal from the Marantz player.
The Sony PCM-D50's inputs are rated 2 V rms (equal to +8.2 dBu) just like the CD-player's outputs. But I can still crank the input level knob down to get over 40 dBFS of headroom when recording that +8.2 dBu signal.
In other words: Both recorders offer plenty of headroom well over their specification and are good for any signal.
BTW, the Tascam DR-100, which is probably the most direct competitor to the Zoom H4n, also has inputs which are good for 2 V rms (or +8.2 dBu).

What does this all mean?
Zoom is correct in calling the unbalanced inputs 'line level' - but only for standard-compliant consumer equipment. With non-standard consumer equipment or professional equipment it will overload considerably.

I have now added this text as an explanation to my page (http://www.martin-doppelbauer.de/fie...stortions.html).

Just thought I'd mention I ended up ordering the D50, and will have it in a few days...
Thanks to all of your feedback and thanks again Martin for the samples with the Juicedlink.

I have a lot to learn about audio recording, so I'm sure the D50 will keep me happy for quite a while ;)

One thing I still would really like to ask again is about the "Low to High Impedance Matching Transformer" cable.
Is it of any use with condenser mics and the D50? If not, in what cases is this type of cable useful?

thanks
Jon.

I have never used such a cable myself but it is my understanding this will transform the output of a microphone to a high impedance for Hi-Z instrument inputs (as used in guitar amplifiers).
For field recorders (or any other device with microphone inputs) the cable is not needed.

Thanks Martin. what you are saying makes sense.
However the cable is advertised as one that "enables a microphone or microphone level device to input into the stereo 1/8" (3.5mm) mini input found on consumer recording devices".
I've also heard in the past people claiming these sort of cables improving the signal when using dynamic mics with minidisc recorders, and improving condenser mics when using mic inputs of consumer cameras (i.e HV30), but I've never heard anyone explain exactly what the transformer in these cables actually does technically.

do you think I can damage something if I connect a condenser to the D50 mic input with this type of cable?

Cheers :)

Jon, let us know your experience with the cable.
I am pretty sure you can't damage anything as this is obviously purely passive (some resistors, maybe a transformer - that's it).

I will. I'll try it first with my mini disc recorder.
But there has to be at least one person here who has tried this type of cable with a field recorder, or with a consumer camcorder, or a HDSLR, no?

Question about using external mics with the PCM-D50:

Can you have two different inputs at once? If I wanted a shotgun mic running into the mic input and a wireless lav running into the line input, would this work? Or is it an either or kind of deal?

No, for the PCM-D50 it's either the line input or the mic input.

I've used the Hosa version of this lo>hi impedence adapter, with a Rode NT3. Worked fine with HV30 and also with PCM-D50.

Thanks Tsu
When you say 'worked fine' do you mean that it actually gives a noticeable improvement over a regular non lo-hi adapter cable?

Can I use a Beachtek with the PCM-D50 to give dual XLR inputs?

I got the PCM-D50 when I bought my Z7U thanks to the $500 Sony Store credit, but I've never used it. It's been sitting in the box, unopened for almost a year. I just picked up a Canon T2i so now I need an external sound recording option, I'd like to make the PCM-D50 work.

Seems like most people in that forum recommend the Zoom H4N, but after reading this thread it looks like I'd be better off sticking with my PCM-D50. However, the XLR inputs on the H4N are really appealing.

I've got a Beachtek unit (currently at a client's site) that I could use in conjunction with the D50 I guess, but I start to wonder if I'm getting too bulky and shouldn't go with a compact solution like the H4N.

Having used neither of these devices, and based on what I'd be using it for, what do you experts suggest I do? Most of my shooting would be interviews with 1-2 mics.

Thanks!

Hi Bryan

I'm very happy with the Sony - I think it's a price performer as it's mics are really quite good for something in this price range. I mostly do music (classical/brass band) and I use it as my back-up quite often. Since you have it I would use it! Lack of XLR is the biggest issue when using it as a recorder and the Sony XLR adapter costs almost as much as the D-50. Again you aleady have the Beachtek so should be no problem. Agree it is a bit bulky but it is quite a nice unit.

I think they have a rather clever limiter built in to the Sony unit - they run a short buffer of attenuated audio and if they detect clipping they cleverly replace the clipped section with the attenuated version - works very well IMHO.

Sure, the Beachtek is great with the PCM-D50. I prefer the active Juicedlink CX231, which is even better, but anyway, the Beachtek will also give you excellent results.
Agreed, this combo will be bulkier than the H4n but it will also give you better audio quality (less noise, less harmonics).

I have no experience with non lo>hi adapter, so can't comment.