Re: Digital / Analogue Voice Recorder


Advid wrote:
> ...does a Digital Voice Recorder (dictaphone ect) have a better signal to
> noise ratio than an analogue voice recorder ???

Not necessarily.

> ie NO tape hiss as there is no tape (or moving parts) ....

The tape hiss has nothing to do with moving parts. The tape hiss
exists because there are random variations in the orientation of
the magnetic particles on the tape.

But tape is but one source of noise, and there are many others,
some are irreducible.

There's noise inherent in the electronics themselves, whether
the recording method is digital or analog. There is noise intrinsic
in the microphone (probably one of the major sources of noise
limiting low-level reocrdings.

And while tape-based recorders have tape noise, a digital recorder
must/will also have noise, whether it is the signal-correlated
quantization noise resulting from a bad implementation of the
analog-digital conversion stage, or it's the uncorrelated noise due
to dithering.

> I want to use one to monitor very low external noise levels....
>
> My Olympus analogue/tape device records OK but there's too
> much hiss and background noise - I have to filter it out using
> PC software....

As long as you insist on using these little voice recorders, which
are NOT designed for the purpose, you're going to be stuck with
the noise problem.

> Just wondering if digital would produce better sound levels.....

No, not intrinsically.

What you need to understand is that the noise levels are dependent
in both analog or analog units, by the amount of storage available
and the amount of time you want to record. THat may seem surprising
and not at all intuitive but, in fact, the amount of storage or the
amount
of data, whatever ytou want to call it, sets the limits of the dynamic
range you can capture, all other things being equal (like bandwidth).

It means that if you have tiny little tape cassettes with not much tape
in them, you have to run the tape very slowly, and tiny tapes at low
speed have lots of noise, becuase there's not enough data storage
to capture wide dynamic ranges (that means difference between loud
and soft signals) well. If you want to record soft sounds, you can't
record loud, because the loudspegnals would overload the tape
and severely distort. If you want to record loud, you can't record soft
becuase of the inherent tape noise.

Implement it in digital, and you have the same problems: low data
storage (memory) means that you can't assign a lot of bits to the data,
and you end up with the same limitations as analog.

This is why low-noise recordings are made, in the analog world, with
wide tape passing at relatively high speeds past the tape heads. It's
why low-noise recordings are made with digital recorders using high
sampling rates and wide samples widths with lots of memory.

Now, add to that the fact that most of these little voice recorders
are
most assuredly NOT designed for what you have in mind: they are
designed for just the opposite: high sound levels and limited signal
bandwidths. They're designed to be heald a few inches away from the
mouth while someone is speaking in a clear, normal level. The
desitgners deliberately don't care about noise, in fact, to make them
as small and as cheap as possible, they make design compromises
which make the noice worse. They don't for example, use a high-
frequency erase or bias signal, which leaves the noise on the tape
worse than it otherwise could be. But it's not important for what they
are used for.

If you want to record very low sound levels, you need equipment suited
to the task. That means low-noise microphones, that means quiet
electronics with a carefully configured gain structure to maximize gain
and minimize noise (two conflicting requirements). An Olympus voice
recorder, digital or analog, or a digital dictaphone is about the worst
choice for such a purpose. Getting rid of your analog one and
replacing
it with a digital one is NOT likely to make much difference. If, for no
other reason, the microphones used are pretty awful, they're noisy
becuase they don't have to be quiet, and quiet microphones can be
as large or larger than the entire recorder AND will cost MUCH more
than the entire recorder.

.

Relevant Pages

  • Re: Tom Scholz on Why Digital Sucks ... again
    ... With an analog system, the shape of the ... nasty nature of digital clipping) ... magnetic tape is not consistent, but depends on the recorder and tape. ...
    (rec.audio.pro)
  • Re: Frako Capacitors for a Studer B67
    ... MRL tape and I intend to acquire a millivolt meter so that I can ... Play back the level-set tone ... the level mismatch between recorder and soundcard. ... suppose I've a one in a thousand chance of that clearing up the noise. ...
    (rec.audio.pro)
  • Re: Image noise
    ... Think of it as a microphone, a pre-amp, and a not-too-good tape ... recorder is a bit hissy and records some static. ... noise recorded is completely overwhelmed by the signal. ...
    (rec.photo.digital.slr-systems)
  • Re: Digital / Analogue Voice Recorder
    ... >> ...does a Digital Voice Recorder have a better signal to ... >> ie NO tape hiss as there is no tape ... > But tape is but one source of noise, and there are many others, ... > the recording method is digital or analog. ...
    (rec.audio.tech)
  • Re: tascam hd-p2 + gracedesign lunatec v3 + rode nt4 stereo mic ?
    ... significantly less noise and distortion. ... very specialized preamp, and perhaps choose a particularly quiet mic. ... And if you just amplify a low level recording, ... better than what's in the recorder as well (or maybe not - it's a few ...
    (rec.audio.pro)