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On 13/11/2018 18:00, Adrian Tuddenham wrote:
N_Cook <diverse@tcp.co.uk> wrote:
On 13/11/2018 10:59, Adrian Tuddenham wrote:
Dave Platt <dplatt@coop.radagast.org> wrote:
In article <5bea2452$0$25659$e4fe514c@textnews.kpn.nl>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:
On 13-11-2018 0:18, Adrian Tuddenham wrote:
Oscillating a bit somewhere?
That's what I was thinking, but why only on the left channel? Both
recorders behave the same way.
Spread in components, differences in layout causing parasitic caps an
inductances
to vary, take your pic.
Possibly there's some occasional switching noise on a digital or power
trace, which is coupled more effectively into the left-channel analog
trace going to the ADC? The left-channel trace might actually be
acting to shield the right-channel trace from some of the noise.
That could be the sort of thing that is happening - but I wonder why it
comes on after about a second's delay?
Demonstration at:
www.wrightshardware.co.uk/Other/DR0002_0276.wav
....beware loud clicks!
Any chance of cutting a couple of traces and jumpering/swapping left and
right to see if the problem swaps channel or stays the same?
I really don't want to go butchering it, I'mrelying on it quite a bit
for location recordings.
The mystery ticking noise I had long ago was with magnetic tape car
cassette player, no record function, would overlay ticks on pre-recorded
tapes.
A small bit of ferrite/magnet buried in the pinchwheel rubber was the
cause there.
I've had that happen with a car cassette player, the tapes got worse and
worse until one day I found the cause.
Do you use batteries or what used to be oddly called "battery
eliminators" to power the recorders?
In article <1ny79x7.wl3ij9kcn7mqN%adrian@poppyrecords.invalid.invalid>,
Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote:
That's what I was thinking, but why only on the left channel? Both
recorders behave the same way.
Spread in components, differences in layout causing parasitic caps an
inductances
to vary, take your pic.
Possibly there's some occasional switching noise on a digital or power
trace, which is coupled more effectively into the left-channel analog
trace going to the ADC? The left-channel trace might actually be
acting to shield the right-channel trace from some of the noise.
That could be the sort of thing that is happening - but I wonder why it
comes on after about a second's delay?
Demonstration at:
www.wrightshardware.co.uk/Other/DR0002_0276.wav
...beware loud clicks!
Looking at that file, I see three sets of noisy impulses... two
negative-going and one positive-going. They're present in both
channels - similar but not identical waveforms in the two channels.
There's a very sharp leading edge (rise time is two or three samples)
and then a much slower fall, with some ringing. The signal takes
about 40 milliseconds to fall back to zero, and then overshoots.
This doesn't look like a one-sample error on the digital-storage side
of things - it's not just a brief impulse. It appears to me that
something is spiking the input to the ADC pretty hard, and that this
glitch is getting into both ADC inputs. The fact that the pulse and
ringing is slightly different, between the two channels, suggests that
it's not just a single sample of bad data in the ADC being blurred out
by the ADC's filters.
Is this .WAV exactly as it came out of the recorder, or did you adjust
it (e.g. gain-boost for visibility) in any way?
On Monday, November 12, 2018 at 11:50:19 AM UTC-5, Adrian Tuddenham wrote:
I have two Tascam DR-05 recorders and they both exhibit the same
phenomenon: when they are recording complete silence, there are faint
irregular ticking noises on the left channel.
This occurs when using an external circuit which disconnects the
internal mics, but the circuit only needs to be plugged in, not
connected to anything, for it to happen. If there is any sound on the
channel, the noise immediately stops, but re-starts about one second
after complete silence returns.
To be clear, this doesn't happen when using the internal mics?
What sort of "external circuit" are we talking about?
If it only happens when recording silence, wouldn't that be easily
mitigated with post production software?
But if it's a design problem, I would try adding an osc signal above
audible frequencies at low levels right at the input jack. Should have no
effect on the recorded audio and may be enough to keep the phenomenon
from happening. If there's no room inside the Tascam, maybe you can add
it to the external circuit.
John-Del <ohger1s@gmail.com> wrote:
On Monday, November 12, 2018 at 11:50:19 AM UTC-5, Adrian Tuddenham wrote:
I have two Tascam DR-05 recorders and they both exhibit the same
phenomenon: when they are recording complete silence, there are faint
irregular ticking noises on the left channel.
This occurs when using an external circuit which disconnects the
internal mics, but the circuit only needs to be plugged in, not
connected to anything, for it to happen. If there is any sound on the
channel, the noise immediately stops, but re-starts about one second
after complete silence returns.
To be clear, this doesn't happen when using the internal mics?
That is correct - or at least I have never noticed it. I'm guessing it
is because:
1) I never use the internal mics for professional work and rarely use
them at all.
2) When I do use the mics, nowhere is quiet enough to show up the
effect.
3) I would record from the mics with the gain at a level where just the
pre-amp noise floor prevented the effect.
What sort of "external circuit" are we talking about?
I tried it with a 'double-ender' 3.5mm screened jack lead about a foot
long, with nothing connected to the far end. The effect also happens
with the same lead plugged into a passive mixer and also on a longer
lead with a built-in 12dB attenuator, fed from a powered mixer
I have also used a passive distribution box with separate L and R inputs
(P.O. 315 jacks) taking line level from the mic pre-amp (floating and
battery-powered) and delivering signals to two 3.5mm output plugs, one
attenuated by 12 dB and one by 24 dB for the two recorders.
If it only happens when recording silence, wouldn't that be easily
mitigated with post production software?
I had to do that on one occasion, but it is time-consuming taking out
the clicks by hand. I would rather tackle the problem at source if at
all possible.
But if it's a design problem, I would try adding an osc signal above
audible frequencies at low levels right at the input jack. Should have no
effect on the recorded audio and may be enough to keep the phenomenon
from happening. If there's no room inside the Tascam, maybe you can add
it to the external circuit.
...or add a bit of hiss to dither it.
...or add a sub-audio signal.
...or never turn the recording gain right down and let the pre-amp noise
floor take care of it..
\
I haven't looked to see if new software is downloadable for that model -
but I suspect this is more likely to be a hardware fault.
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
I have two Tascam DR-05 recorders and they both exhibit the same
phenomenon: when they are recording complete silence, there are faint
irregular ticking noises on the left channel.
This occurs when using an external circuit which disconnects the
internal mics, but the circuit only needs to be plugged in, not
connected to anything, for it to happen. If there is any sound on the
channel, the noise immediately stops, but re-starts about one second
after complete silence returns.
I have two Tascam DR-05 recorders and they both exhibit the same
phenomenon: when they are recording complete silence, there are faint
irregular ticking noises on the left channel.
This occurs when using an external circuit which disconnects the
internal mics, but the circuit only needs to be plugged in, not
connected to anything, for it to happen. If there is any sound on the
channel, the noise immediately stops, but re-starts about one second
after complete silence returns.
try connecting an audio signal generator do create say a 1 kHz sine tone.
slowly drop the level.
at some level the clicks will start.
observe the tone during the clicks for clues. Does the tone change in anyway due to the clicks?
Also with the external input connected to nothing, do the clicks change depending on if the external input is open vs shorted or terminated?
These recorders often apply a few volts of DC power to the input to power mics.
Put a scope on the input line and see if the spikes are actually present on the input line. Or connect the input to another audio input that you can listen to , do the spikes come OUT the audio input?
If you apply a small DC signal to the input through a current limiting resistor , will that stop the spikes? Try both polarities?
Is there a schematic available?
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