"Jim Lesurf" wrote in message

In article
, Arny
Krueger
wrote:
"Jim Lesurf" wrote in message

In article
, Arny
Krueger wrote:


I think the lesson is that economies of scale can be
quite impressive. The development, tooling and sales
costs don't increase that much when the sales double.

Tell me about it! I'm trying to find a UK supplier who
will sell small quantities of items like Toko-type
low-pass filters! Countless similar filters are in all
kinds of tuners, etc.

Must be legacy technology. The FM tuner in my Sansa
Clip+ can't have many coils, given that they fit the FM
stereo tuner (biggest weakness - no dedicated antenna
terminals), a computer (with DSP), EPROM (firmware), two
banks of gigabytes of RAM, headphone amps, jacks, color
display, pushbuttons and a battery in less than a cubic
inch.

So how does it filter/suppress the 19kHz pilot tone and
the remains of the 38kHz DSBSC after stereo demodulation?

Good question. Obviously, it could be done with active filters. I direct you
to the data sheets for the relevant chips which are online. I'd study it
myself right now but I'm off to a gig this morning.

In article ,
Jim Lesurf wrote:
Must be legacy technology. The FM tuner in my Sansa Clip+ can't have
many coils, given that they fit the FM stereo tuner (biggest weakness -
no dedicated antenna terminals), a computer (with DSP), EPROM
(firmware), two banks of gigabytes of RAM, headphone amps, jacks, color
display, pushbuttons and a battery in less than a cubic inch.

So how does it filter/suppress the 19kHz pilot tone and the remains of
the 38kHz DSBSC after stereo demodulation?

Maybe like my old Quad FM3 tuner - don't bother to?

--
*If you don't like the news, go out and make some.

Dave Plowman London SW
To e-mail, change noise into sound.

"Jim Lesurf" wrote in message

In article
, Arny
Krueger
wrote:
"Jim Lesurf" wrote in message

In article
, Arny
Krueger wrote:


I think the lesson is that economies of scale can be
quite impressive. The development, tooling and sales
costs don't increase that much when the sales double.

Tell me about it! I'm trying to find a UK supplier who
will sell small quantities of items like Toko-type
low-pass filters! Countless similar filters are in all
kinds of tuners, etc.

Must be legacy technology. The FM tuner in my Sansa
Clip+ can't have many coils, given that they fit the FM
stereo tuner (biggest weakness - no dedicated antenna
terminals), a computer (with DSP), EPROM (firmware), two
banks of gigabytes of RAM, headphone amps, jacks, color
display, pushbuttons and a battery in less than a cubic
inch.

So how does it filter/suppress the 19kHz pilot tone and
the remains of the 38kHz DSBSC after stereo demodulation?

It appears that all audio signal processing is done in the digital domain:

http://read.pudn.com/downloads159/doc/710424/Si4706.pdf

Please see page 15 for listing of external components required (a bypass
cap on the power supply).

In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:
Must be legacy technology. The FM tuner in my Sansa Clip+ can't have
many coils, given that they fit the FM stereo tuner (biggest
weakness - no dedicated antenna terminals), a computer (with DSP),
EPROM (firmware), two banks of gigabytes of RAM, headphone amps,
jacks, color display, pushbuttons and a battery in less than a cubic
inch.

So how does it filter/suppress the 19kHz pilot tone and the remains of
the 38kHz DSBSC after stereo demodulation?

Maybe like my old Quad FM3 tuner - don't bother to?

The diagram I have for the FM3 shows it using an MC1310 followed by a pair
of active LP filters. (The FM4 seems to use the Toko type '21 filter
modules. But I don't know the filter shapes for these as they don't give a
part number I could trace to any of the Toko sheets I have.)

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article , Arny
Krueger
wrote:
"Jim Lesurf" wrote in message



Must be legacy technology. The FM tuner in my Sansa Clip+ can't have
many coils, given that they fit the FM stereo tuner (biggest weakness
- no dedicated antenna terminals), a computer (with DSP), EPROM
(firmware), two banks of gigabytes of RAM, headphone amps, jacks,
color display, pushbuttons and a battery in less than a cubic inch.

So how does it filter/suppress the 19kHz pilot tone and the remains of
the 38kHz DSBSC after stereo demodulation?

It appears that all audio signal processing is done in the digital
domain:

http://read.pudn.com/downloads159/doc/710424/Si4706.pdf

Please see page 15 for listing of external components required (a
bypass cap on the power supply).

Thanks, I'll have a look.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article ,
Jim Lesurf wrote:
So how does it filter/suppress the 19kHz pilot tone and the remains
of the 38kHz DSBSC after stereo demodulation?

Maybe like my old Quad FM3 tuner - don't bother to?

The diagram I have for the FM3 shows it using an MC1310 followed by a
pair of active LP filters. (The FM4 seems to use the Toko type '21
filter modules. But I don't know the filter shapes for these as they
don't give a part number I could trace to any of the Toko sheets I have.)

My early FM3 caused real problems when recording to my A77. Had to fit a
filter to it.

--
*Virtual reality is its own reward*

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:
So how does it filter/suppress the 19kHz pilot tone and the
remains of the 38kHz DSBSC after stereo demodulation?

Maybe like my old Quad FM3 tuner - don't bother to?

The diagram I have for the FM3 shows it using an MC1310 followed by a
pair of active LP filters. (The FM4 seems to use the Toko type '21
filter modules. But I don't know the filter shapes for these as they
don't give a part number I could trace to any of the Toko sheets I
have.)

My early FM3 caused real problems when recording to my A77. Had to fit a
filter to it.

I haven't analysed the filter but it doesn't have an obvious 19k 'trap'.
Just looks like a standard 3rd order LC design for a low pass. I'd expect
the 1310 to leak fair amounts of 19k, etc. That's why the 600s used a Toko
filter, and perhaps why the FM4 does as well!

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article ,
Jim Lesurf wrote:
My early FM3 caused real problems when recording to my A77. Had to fit
a filter to it.

I haven't analysed the filter but it doesn't have an obvious 19k 'trap'.
Just looks like a standard 3rd order LC design for a low pass. I'd
expect the 1310 to leak fair amounts of 19k, etc. That's why the 600s
used a Toko filter, and perhaps why the FM4 does as well!


ISTR it being said the recorder should have the filtering - perhaps
switchable - rather than restricting the tuner audio output? For say mono?

--
*A clear conscience is usually the sign of a bad memory *

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Dave Plowman (News)
wrote:
In article , Jim Lesurf
wrote:
My early FM3 caused real problems when recording to my A77. Had to
fit a filter to it.

I haven't analysed the filter but it doesn't have an obvious 19k
'trap'. Just looks like a standard 3rd order LC design for a low pass.
I'd expect the 1310 to leak fair amounts of 19k, etc. That's why the
600s used a Toko filter, and perhaps why the FM4 does as well!


ISTR it being said the recorder should have the filtering - perhaps
switchable - rather than restricting the tuner audio output? For say
mono?

Clearly some makers/designers have thought that. :-) However my own view
is that it should be the tuner that suppresses anything that isn't intended
as audio from appearing the outputs. If nothing else, some people can hear
19kHz. And having a lot of ultrasonics isn't very kind to following
amplifiers, etc.

Personally I liked the Yamaha method. Have an active null to cancel out the
19k pilot, then use a Toko filter flat to about 17kHz to ensure good
behaviour up to 15k but still cut down the ultrasonic hash.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Dave Plowman (News)" wrote

ISTR it being said the recorder should have the filtering - perhaps
switchable - rather than restricting the tuner audio output? For say mono?


It was a licensing requirement for recorders fitted with Dolby B noise
reduction that they include a 19kHz notch filter and a low-pass filter to
remove the 38kHz sub-carrier and sidebands. Some high-end domestic
recorders, reel-to-reel and cassette, made the notch filter switchable,
though most domestic cassette decks didn't bother.

David.