mute circuits

[sakis]

many of our sources like CD players - tuners feature mute circuits in the analog audio outs .

I presume that the specific mute circuits are installed there to avoid digital and/or other noises to come out in the analog line out .

i wonder if those circuits beyond the benefit of muting do they have any effect in the sound quality since are directly involved in the signal path

opinions are welcome

regards sakis

[sakis]

ok ...here we go

i also noticed that in a technics tuner except the muting circuit there is also a lot of filtering in the out ....

its a simple tuner that the sound comes out from a humble AN 7470 this we have to take as a fact ....not much you can do about that ... beyond that there is a astronomical 15nf capacitor that goes from signal to ground and a coil of some nh in series with the signal

removed the muting circuit totaly then removed the 15nf capacitor and replaced that with silver mica 300pf

now the radio doesnt mute any more while searching for a station ( not really importand since all your required stations are in memory ) and also while changing from memory one to memory two there some kind of not really loud pop noise .

though high become by far more crisp and clear ....then sound stage become more real and as about the low end didnt seen much eventhough i beefed up the capacitors in the output of the AN from 3.3 mfd to 10 mfd plus 100nf styroflex bypass

any comments ????

[sakis]

one other thing ....i would be more pleased if in the out a small relay existed than transistors that interfere with the signal ....

this i can try first thing in the morning with a CD player ...

i ll let you know

[currentflow]

Originally Posted by sakis

ok ...here we go

i also noticed that in a technics tuner except the muting circuit there is also a lot of filtering in the out ....

its a simple tuner that the sound comes out from a humble AN 7470 this we have to take as a fact ....not much you can do about that ... beyond that there is a astronomical 15nf capacitor that goes from signal to ground and a coil of some nh in series with the signal

removed the muting circuit totaly then removed the 15nf capacitor and replaced that with silver mica 300pf

now the radio doesnt mute any more while searching for a station ( not really importand since all your required stations are in memory ) and also while changing from memory one to memory two there some kind of not really loud pop noise .

though high become by far more crisp and clear ....then sound stage become more real and as about the low end didnt seen much eventhough i beefed up the capacitors in the output of the AN from 3.3 mfd to 10 mfd plus 100nf styroflex bypass

any comments ????

Hi Sakis,

Are you sure that 15nF capacitors aren't part of the FM de-emphasis circuit? The series coil in this type of tuner is usually present to reduce the residual 19KHz stereo pilot tone component. This was particularly important in the days of tape recording as the pilot tone, unless adequately filtered, would beat with the recorder's tape head bias oscillator, creating some ugly whistles.

If the above situation is the correct, your 330pF would likely result in the audio sounding too bright.

I am often surprised by manufacturers using transistors as (shunt) mute switches. Surely their non-linearity destroys audio quality?

Regards,
Steve

[DigitalJunkie]

Removing the muting transistors can help with sound,but you need to somehow ensure that the "clunks and pops" are still muted,or it can do ugly things-A small relay is commonly used instead. I've re-purposed the existing muting transistor(s) to trigger the relay(s),it's pretty simple.

[sakis]

this is what i thought also relay would be by far better ... i mooving to this direction soon ....


as about the cap yes ....high sounds too bright but on the other hand 15nf in the signal out is too much .... will look to go higher may be up too 1000pf but not 15nf

thanks guys ..... will play arround a Sony cd player and keep you posted


( clunks and pops ....i could live with a few of these if my sound is getting a lot better !!!! )

[underwurlde]

Among the long list of improvements for the Marantz CD players is the removal of the muting transitors....

Andy

[currentflow]

Originally Posted by sakis

as about the cap yes ....high sounds too bright but on the other hand 15nf in the signal out is too much .... will look to go higher may be up too 1000pf but not 15nf

This has got me thinking. If the tuner sounds dull, could it be that it was designed for the US market? They use 75us pre/de-emphasis, while in Europe it's 50us. A tuner designed for US use might possibly sound dull when used in Europe.

If the de-emphasis is based on a 75us CR time-constant, changing to the European standard would mean changing the filter capacitor to 10nF. Just a thought.

Regards,
Steve

[janneman]

Originally Posted by currentflow

This has got me thinking. If the tuner sounds dull, could it be that it was designed for the US market? They use 75us pre/de-emphasis, while in Europe it's 50us. A tuner designed for US use might possibly sound dull when used in Europe.

If the de-emphasis is based on a 75us CR time-constant, changing to the European standard would mean changing the filter capacitor to 10nF. Just a thought.

Regards,
Steve

You can use a muting relay two ways: in series with the signal, where it closes after the mute delay, or from signal to ground where it opens after the mute delay. The last method is best since it doesn't have the relay in the signal line. Since all sources have a series output resistors, shorting the signal to ground during the mute does no harm.

jd

[sakis]

Originally Posted by janneman

You can use a muting relay two ways: in series with the signal, where it closes after the mute delay, or from signal to ground where it opens after the mute delay. The last method is best since it doesn't have the relay in the signal line. Since all sources have a series output resistors, shorting the signal to ground during the mute does no harm.

jd

WELL....dont really think so ....i think that having a resistor to ground as termination in a line outpout signal is a diferent story than a transistor providing ground fro muting .... the idea is not to have anything messing arround with your signal

---- then again if i go for relay mode i would go fro shorting to ground than interrupt the line out signal ....

----- yeap i presumed that mods like that will be present in the marantz cd mod list ....BUT THE ALL THREAD IS WAY TOO LONG TO READ ...

thanks jan and others nice to see you arround ....will do some testing any day now and see what goes on

kind regards sakis