Conference hips::uk_audioo

    
    I don't know about the real specs, but there's some information in this
    month's HFN/RR (where they review the Arcam Delta 150 NICAM tuner).
    
    From this article, it appears that the NICAM system works like this:
    
    - sample audio signal to 14 bit resolution (can't remember sampling
    frequency, might be 38Khz)
    
    - batch up sets of 32 14 bit samples.
    
    - based on the highest-amplitude sample in the batch, decide on a
    "scale factor", and scale each sample down to 10 bits by this factor.
    The scale factor is tacked on the front of the block, and is used by
    the receiver to reconstruct the 14 bit data at the correct amplitude
    level. This technique allows high resolution for low amplitude signals,
    and lower resolution for high amplitude signals.
    
    The article then briefly explains how this digital signal gets put onto
    the video carrier, but I don't really know enough about signal
    processing to understand how that works. The upshot of all this is that
    the audio signal has somewhat less resolution than CD.
    
    The article made some interesting points. The author made some
    cassettes from TV programs to listen to in his car. He said they
    sounded very strange when played without any visual cues as to what was
    actually going on. He complained in particular about spot mics being
    used and causing voices to appear in funny places in the resultant
    sound mix (although it sounds natural when you can see what's happening
    on the screen).
    
    Trevor

    How much is the Acrcam Delta 150 Nicam tuner?
    
    I have a Stereo video, but it's not Hi-fi quality.  i could use
    the auxiliary input to record TV in stereo.  The replay sound quality
    would be very inferior to that broadcast (although still in stereo).
    
    My cassette deck would be up-to the job, but I guess it would get
    tiring syncronising the audio to the visual recording when playing
    back!  (plus I would have to swap tapes at 45/60 mins max).
    
    Hmm?   
    
    Also, why do people buy NICAM televisions?  Must sound great live, but 
    surely the digital signal is lost when a program is recorded on a 
    normal (non-NICAM) video, and the television reverts back to normal
    sound?
    
    And another thing...  Why have both a NICAM tv and NICAM video?  Surely
    only a stereo TV would be required to monitor the stereo output (in the
    absence of a real Hi-Fi with auxiliary inputs).
    
    What do you think?
    Rob.

> 
>     How much is the Acrcam Delta 150 Nicam tuner?
>
    	350 pounds
    
>     
>     Also, why do people buy NICAM televisions?  Must sound great live, but 
>     surely the digital signal is lost when a program is recorded on a 
>     normal (non-NICAM) video, and the television reverts back to normal
>     sound?
    
    Yes.  Perhaps people aren't too worried about not getting NICAM on
    videos. 
    
    >      
    >     And another thing...  Why have both a NICAM tv and NICAM video?  Surely 
    >     only a stereo TV would be required to monitor the stereo output (in the 
    >     absence of a real Hi-Fi with auxiliary inputs).
    
    I agree - I think the best approach would be to have a NICAM VCR with a
    good tuner in it so that you can both record and watch NICAM if you
    want. You lose the ability to record one NICAM program and watch
    another as the same time in stereo, but who cares about that ?
    
    Of course, if you have a crappy old telly, and have recently bought a
    non-NICAM VCR (like me), you may favour replacing the TV first.
    
    Trevor

    �350 for JUST the audio tuner?  Gulp.
    
    I would have expected about �100
    
    Does the NICAM signal get lost when recorded on a normal video though?
    Rob.

Ah, it's not just an audio tuner, but a video tuner as well.

ARCAM say that the audio/video circuit is of sufficiently high quality, that
it will improve the video signal by removing the audio signal from it.

Therefore, you should get a better picture. If you already have a video/TV,
then this extra tuner is cheaper than getting a NICAM video/TV, given the
low resale cost of older videos.

That doesn't mean to say I'm buying one!

	�350 just for a NICAM tuner seems an awful lot of money. For an extra
fifty quid you could get a HiFi NICAM VCR.

	I don't think that I could persuade my financial controller but my 
feeling is that a non NICAM TV and two HiFi NICAM VCRs would be the best way to 
set up a system. There are many occasions when you are part way through
watching a video and then have to stop so that you can watch another programme
in real time. With this set up you could record two programmes and be watching
a third. Or even heaven forbid use it for copying video tapes! 

	I think that unless you are really strapped for cash that buying 
anything other than a HiFi NICAM VCR is a very big mistake. Don't forget that 
like a TV you are going to be stuck with it for several years, the resale value 
is very poor so the justification for replacement is ordinarily irrepairable 
breakdown.

Nigel 

BTW apropos a previous note as regards recording the NICAM information on a non 
NICAM VCR. Even if it does (which I doubt) there would be no way of retrieving 
it if you played it back on a NICAM set.

>>	�350 just for a NICAM tuner seems an awful lot of money. For an extra
>>fifty quid you could get a HiFi NICAM VCR.

If you find a �400 NICAM HiFi VCR that sounds any good, let alone as good as
the Arcam, you'll be fortunate.  For that matter, if you find a �400 non-NICAM
VCR that sounds any good, I'll be surprised.  TVs and VCRs don't seem to be
designed with decent sound in mind.


>>BTW apropos a previous note as regards recording the NICAM information on a
>>non 
>>NICAM VCR. Even if it does (which I doubt) there would be no way of
>>retrieving 
>>it if you played it back on a NICAM set.

If you have a HiFi stereo VCR, you can connect the stereo output of the tuner
to the audio inputs of the VCR, and the audio outputs of the VCR to the inputs
of the TV.  That should do it.

Nick

    I recently (last 6 months) have bought a NICAM TV and a HIFI NICAM
    VCR. The TV came first and I was very pleased with the sound
    capabilities so when it came time to replace the Video I decided to
    opt for the Panasonic VF-B65 (there is mention of this in another
    note). In the previous note it was said that "TVs and VCRs don't seem
    to be designed with decent sound in mind" but I'm sure anyone else who
    owns either this or the B70 video will disagree as the sound quality
    when played through a Hi-Fi is superb.  
    
    I am very impressed with my set-up , on reflection I would probably not 
    have bought the NICAM TV if I had knew I was going to buy the VCR but 
    what's done is done and I certainly won't need to upgrade either in the 
    near future.
    
    
    							Geo.

Unfortunately, we've not heard a view from people who have tried both a
�400 NICAM video and the �350 Arcam NICAM tuner.

I've no doubt that the video sounds impressive (especially when compared
to normal television), but the impression I got was the Arcam used *VERY*
high quality circuits.

As Arcam already produce high quality budget equipment, then I think they
are doing the same here.

Mark.

Re .7

>If you find a �400 NICAM HiFi VCR that sounds any good, let alone as good as
>the Arcam, you'll be fortunate.  For that matter, if you find a �400 non-NICAM
>VCR that sounds any good, I'll be surprised.  TVs and VCRs don't seem to be
>designed with decent sound in mind.

All HiFi VCRs that I have heard sound great, it's all in the specifications for 
VHS HiFi sound, it has as wide a dynamic range as CD and for the anti-cd 
purist is of course an analogue medium. The HiFi sound is depth multiplexed 
onto the VHS tape on top (or below) the visual information. It is laid down 
using the same helical scan head that the picture is. The sound on 
non-HiFi VCRs is awful whether they cost more or less than �400. The linear 
soundtrack is smaller than on an audio cassette if it is split into two for 
linear stereo it becomes even worse. There is no hiss on HiFi that was not 
there on the source material. It must of course be played back through a decent 
audio system for best results.

>>BTW apropos a previous note as regards recording the NICAM information on a
>>non 
>>NICAM VCR. Even if it does (which I doubt) there would be no way of
>>retrieving 
>>it if you played it back on a NICAM set.

>If you have a HiFi stereo VCR, you can connect the stereo output of the tuner
>to the audio inputs of the VCR, and the audio outputs of the VCR to the inputs
>of the TV.  That should do it.

I suspect that we may be talking at cross purposes here. If it is recorded on a
non-NICAM HiFi VCR it will not have a HiFi stereo soundtrack so there is no way
that it could be played back in stereo although it would have a HiFi
soundtrack. If it is a non-NICAM, non-HiFi then even if you replay it in a HiFi 
VCR it will not be able to replay anymore than was originally recorded. I
suspect that HiFi VCRs without NICAM will disappear from the market, after all
the cheapest NICAM HiFi VCR is now �370. 

Nigel 

I've had a Hi-fi video for a few years now and am very pleased with it, the
sound quality is sooper and makes me feel like I'm in the cinema even if I
do need a magnifying glass to see the TV screen.

However, the big problem with this format is tape dropouts and general
degradation which causes *extremely* irritating buzzing and 'fluttering'
noises. This is particularly noticeable when hiring virtually anything
other than recently released videos. Many's the time I've had to switch
back to linear mono sound because of this interference.

Do NICAM VCRs suffer in this respect? Also how do NICAM VCRs actually
record the sound? Do they record sound in encoded or decoded form
or both? If decoded, is it in the hi-fi format in which case I guess they
will be just as susceptible to the interference.

Steve.

I think .-1 has it slightly wrong.

NICAM is a way of getting the stereo information from the TV Aerial. Any
HiFi Stereo video recorder can record from it. This is why Arcam can supply
a NICAM decoder.

I know what you mean about the interference with sound. It does seem that
the tape has to be 'exactly right' for it to sound good. I've had a few tapes
where I've had to move to mono sound. Even tweaking the HiFi tracking control
didn't do much.

Mark.

In other words, a NICAM VCR is merely a Hi-Fi stereo video with a NICAM
decoder built-in?

So when I said that a NICAM VCR would be just as susceptible to the noise,
I was in fact, slightly right.

Steve.
;^)

re .10:

>>All HiFi VCRs that I have heard sound great, it's all in the specifications
>>for 
>>VHS HiFi sound, it has as wide a dynamic range as CD and for the anti-cd 
>>purist is of course an analogue medium.

Well...  I'd agree a VHS HiFi VCR makes a far better job of the sound than it
does of the video, but I don't find the sound 'great'.  I don't think it has
anything close to the resolution of CD, though I may be wrong here; it's just
an impression from listening.  Comparing HiFi VHS against a cassette is
interesting.  To me, the VHS sound seems more 'accurate', perhaps because of a
flatter freq response, but I prefer listening to the cassette, hiss and all. 
Especially with classical stuff, even more with piano.  That's without Dolby,
by the way.  Not sure what the pecking order would be if I used noise reduction
on the cassette.


>>There is no hiss on HiFi that was not 
>>there on the source material.

I don't agree.  There's not enough to worry about, but there is some.  I
imagine it's from the record/replay electronics rather than the tape.


>>It must of course be played back through a decent 
>>audio system for best results.

I'd like to think mine qualifies...


>>>If you have a HiFi stereo VCR, you can connect the stereo output of the tuner
>>>to the audio inputs of the VCR, and the audio outputs of the VCR to the
>>inputs
>>>of the TV.  That should do it.

>>I suspect that we may be talking at cross purposes here. If it is recorded
>>on a
>>non-NICAM HiFi VCR it will not have a HiFi stereo soundtrack so there is no
>>way
>>that it could be played back in stereo although it would have a HiFi
>>soundtrack. If it is a non-NICAM, non-HiFi then even if you replay it in a
>>HiFi 
>>VCR it will not be able to replay anymore than was originally recorded. I
>>suspect that HiFi VCRs without NICAM will disappear from the market, after all
>>the cheapest NICAM HiFi VCR is now �370. 

In my description above, the separate tuner does the NICAM decoding, and then
passes a two-channel audio signal to the HiFi VCR for recording.  On tape it
isn't NICAM-encoded; it's just a stereo videotape.  NICAM isn't involved once
the signal leaves the tuner.


I for one am not planning to buy another VHS VCR.  While the sound quality is
passable for its purpose, the video quality is abysmal.  I haven't looked
closely at S-VHS but the little I have seen doesn't suggest the basic problems
have been fixed.  And I'm fed up with buying eight- to ten-quid videotapes to
get marginally acceptable results.

Nick

    Hmm,
    But surely (based on a previous reply), a non-nicam VCR can record the 
    incoming signal (digtally encoded bit and all).  Then use the external 
    decoder (a la Arcam) to extract the NACAM encoded signal, passing sound
    to expensive Hi-Fi (you must have one of those since you're reading
    this!) and picture minus sound to the TV/monitor.
    
    As for picture quality on VHS.  Yeah I agree the picture isn't
    brilliant.  I blamed the tapes I buy for �3 each, perhaps it's the
    format.  
    
    Is the sound present in the VHF TV output from the Arcam decoder? (i.e.
    does it remove it?)
    
    If so, perhaps the picture is improved if you use the decoder to remove the
    analogue soundtrack before the video.  Thus eliminating interferance of
    sound on picture.  Trouble is were back to having the decoder before
    the recorder (could buy two of them)!
    
    The other expensive alternative to improve picture quality is to have a
    monitor and to use the <mumble> video output leads from the VCR (thus
    eliminating two tuner circuits during tape playback).
    
    e.g.                                                            VHF from
    		<mumble> format		            ++++++++++++++++ video rec. 
    	Monitor  ============\                      +Arcam         +__________
                             or ====================+              +
        TV ___________________/    pic output:      ++++++++++++++++
            VHF signal in coaxial    picture(prob still includes NICAM code)
                                     sound removed?      \\
                                                          \\
                                                          Hi-Fi stereo sound
    
    Anyone know about this?
    
    Rob. "who's just guessing".

re .15:

>    But surely (based on a previous reply), a non-nicam VCR can record the 
>    incoming signal (digtally encoded bit and all).  Then use the external 
>    decoder (a la Arcam) to extract the NACAM encoded signal, passing sound
>    to expensive Hi-Fi (you must have one of those since you're reading
>    this!) and picture minus sound to the TV/monitor.

No, I don't think this'll work.  I seem to remember the NICAM-encoded audio is
present in the RF signal, so you can extract it at the tuner's FM decoder
stage, but once you've decoded the FM to get a mono audio signal you've lost
the information required for NICAM decoding.  It's rather like making a mono
recording of an FM stereo broadcast; you can't get the stereo signal back
because you didn't record either the RF signal or audio L-R signal, only the
audio L+R signal.

    
>    Is the sound present in the VHF TV output from the Arcam decoder? (i.e.
>    does it remove it?)

I don't know if the Arcam has an RF output; if it does it'd certainly include
audio.  But audio will certainly not be present in the video output - there's
nowhere for it to go.  If it does have an RF output, I wonder if it passes the
NICAM information through?  I guess it has to, in case it's passed to a NICAM
TV.

    
>    If so, perhaps the picture is improved if you use the decoder to remove the
>    analogue soundtrack before the video.  Thus eliminating interferance of
>    sound on picture.

Arcam make much of the fact that audio and video are separated as early as
possible.  This means audio- and video-specific optimisation can be applied,
giving higher video, as well as audio, quality compared to typical TV or VCR
practice.  So if you use your TV as a monitor you may well get better a picture
than if you used its own tuner.

>    The other expensive alternative to improve picture quality is to have a
>    monitor and to use the <mumble> video output leads from the VCR (thus
>    eliminating two tuner circuits during tape playback).

I was kind of assuming this.  Modern TVs usually have video inputs, so they can
be used as monitors.  Certainly running through multiple tuners is a no-no. 
Personally, I'd like to use a professional broadcast monitor - you don't get
high light levels, or a flat screen, but the colour shading accuracy would be
wonderful.  I dread to think what one would cost, though.

Nick

    RE: .-1
    
    Hi Nick,
    I thought that the NICAM signal was actually transmitted as part of the
    picture image, mono 'normal' sound being separate.  So, a normal video
    wouldn't do anything with the NICAM signal except record it, as it does
    the rest of the picture.

I thought it had its own subcarrier, separate from both the mono audio and
video channel.  But anyway, if it's buried in the video signal, VHS doesn't
have enough bandwidth to waste on information that isn't visible.  It'll
certainly make a dog's breakfast of it, if its treatment of the picture is
anything to go by.  

Nick

Just the put the cat well and truley among the pigeons consider this...
    
    I'm considering upgrading the visual side of my A/V system.
    
    Currently
    
    	o Phillips Matchline TV (2xScart + audio out - NO Nicam).
    	o Pretty naffy Hitache video (Not Hi-Fi quality).
    	o ALSO one of those awfully nice 16" SONY monitors (sitting on top
    of my home PC). I would really like to use this as a TV as the
    picture quality is fantastic (Though the screen is a bit small).
    This is the same a the badge eng. DIGITAL Trinitron 1024x800 monitor.
                                                    
    So - does anyone know if the ARCAM thingy produce a 1V 60Hz signal
    suitable for use with such ?
    
    		Rik
    
    PS As an aside, the old 19" VAXstation colour monitors can be had for a
    very cheep price (�400-00 ish ??) from Rockhall (or EPP / Idle
    Materials) this would make a nice large monitor.
    
    
    

The NICAM digital signal is encoded using DPFSK modulation onto a sub carrier
that is around 6.23 Mhz (if memory serves - the MAPLIN magazine ran a detailed
article about a year ago that has all the real figures and equations - I can
look it up if you like).

This Sub-carrier is therefore just above the 6.0 Mhz FM sound subcarrier that 
is used for the mono sound.

NON-NICAM VCR's (and TV's) have narrow filters that separate out the video and 
sound sub-carriers (prior to recording in case of the VCR) - hence they loose
 the NICAM subcarrier. 

I believe that true NICAM recorders (not the cheap one, which records the decoded signal using
 normal analogue - the small print points out that the recorded sound is stereo
 but NOT hi-fi) have different filters and can record the encoded NICAM 
 subcarrier signal - ie the recording is effectively digital.

THUS, if you play a true NICAM VCR recording/recorder into a NICAM TV, the TV's
NICAM light comes on and it's decoder decodes the sound - as well as being 
available from the Audio sockets on the VCR.

The reason for having both a NICAM TV and a NICAM VCR is so that you can listen
and watch a live NICAM transmission at the same time as you record another one
also in NICAM!

> I believe that true NICAM recorders (not the cheap one, which records the decoded signal using
>  normal analogue - the small print points out that the recorded sound is stereo
>  but NOT hi-fi) have different filters and can record the encoded NICAM 
>  subcarrier signal - ie the recording is effectively digital.
    
    Would such a device be VHS-compatible ? Or would the on-tape format
    have to be different ?
    
    Trevor

Does anyone know anything about the NICAM kit that maplin sell. No doubt not as good
as the arcam, but at only 130 pounds it might be worth trying.

As a more general question can you get good hi-fi from kits?....

    � As a more general question can you get good hi-fi from kits?....
    
    In theory yes in practice I don't know.
    
    Both Crimson and Linsey Hood produce(d) amplifiers but I've no idea how
    good they are. I did once build an amp out of an RS catalogue spec
    sheet. I didn't sound at all bad considering how cheap it as (<�30).
    
    To misquote a couple of amp designers                            
    
    	``An amplifier is a power supply with a gain.''
    
    	So spend you money on a high quality transformer and a couple of
    enourmous capasiters.
    
    Now, my turn with the trivia topic, which amp designers have I
    misquoted above, which company(s) do they represent and what were the
    original quotes.

Hi,

I have built the MAPLIN NICAM tuner.

It is based on the Toshiba chip set, and
comprises 4 PC boards, all of which are high quality, double sided glass fibre 
with plated thru' holes.

Wiring is minimal, comprising ribbon cable for DC control signals and screened
coax for signal lines.

It provides 16 preset channels with optional IR remote control. Outputs are
composite video and audio. UHF Tuner is a high quality unit using SAW filters -
it was noticably better that the tuner in my TV.

Sound quality is pretty good, but I would recommend not using the IR volume
control as it uses some op-amp circuitry which is not very hi-fi - and it
increases distortion measurably (0.01%)

Automatic switching between FM and NICAM sound is provided, with manual overide..
NICAM mode indication is provided (stereo, dual language mono), with push
button selection of special (ie non-stereo) modes.

Physically, it is a midi sized box of reasonable quality, but not up to the
standard of fininsh of commercial units. It requires an outboard regulted 12v
AC adapter.

To build it, you need have a decent soldering iron (preferable a 60W 
TEMPERATURE CONTROLLED iron (eg Weller TCP) with a fine bit, and you need to
know ho to weild it properly. Test equipment needed is only a multimeter, since
all the critical RF stuff in the UHF tuner is pre-aligned. There are a couple
of cores to set but these can be done by watching/listening to the FM sound and
video outputs on a TV or monitor. (you can feed the sound & video outputs back
into your VCR and then use a normal TV if yours doesn't have the right inputs)

If you want any more info, call me on 844-3293

Rgds, Dave

    Somewhere else, I responded to a note about NICAM decoders, but I'm
    blowed if I can find where! It must be that time of year again. 
    
    Anyway, the story so far. Back in 1984 I bought a hi-fi VHS recorder,
    mainly for sound recording, as it offered an extremely good
    price/performance at that time. Since the arrival of NICAM
    transmissions in Wales last year I had been looking at the options for
    upgrading the recorder. The alternatives were:
    	- a Cambridge decoder at around �230
    	- a new video at anything up to �500+
    	- modifying a surplus panel.
    
    I opted for a surplus panel available from SENDZ Components of
    Shoeburyness for �15. That was about three weeks ago. I built a
    power supply, modified the panel and took a signal from the IF panel
    of an old TV and it worked O.K.
    
    I've since taken a signal from the VCR. It works O.K. on BBC 1, but it
    seems the NICAM signal is weak on the other channels and is
    causing some distortion. Time to get the old 'scope out and do a bit of
    waveform watching!
    
    I have technical details if anyone wants to experiment.
    
    Peter
    
     

    Or you could have bought my Arcam Nicam Tuner when I was selling it last
    year, Peter...
    
    (Too late now - I've found a reuse for it!)
    
    Steve