Amplifier mute control

Ron H

Joined Apr 14, 2005
7,012
Hello,

I have looked at the datasheet.
The transistor can be ommitted.
The NE555 when powerd at + 5 Volts will drive the mute directly.



Greetings,
Bertus
I haven't seen any evidence that he has a 5V supply. He could still run the 555 off +12V and use a voltage divider to get 0-5V. Looking at the mute control equivalent circuit, I suspect that Vcc would work just fine for muting.
I notice that no one (including me) has corrected the STB input on the schematic. As I explained in post #10, it needs to be connected to Vcc to turn the device ON.
 

bertus

Joined Apr 5, 2008
20,061
Hello,

A 5 Volt stabelizer is easy to use.
The STB signal can be tied to it too.
The power supply can be higher than for more output power.

Greetings,
Bertus
 

Ron H

Joined Apr 14, 2005
7,012
Hello,

A 5 Volt stabelizer is easy to use.
The STB signal can be tied to it too.
The power supply can be higher than for more output power.

Greetings,
Bertus
Why would a 5V regulator be better than a transistor?
The schematic on p.6 of the datasheet is in error. The STB pin needs to be tied to Vcc, not to +5V. See my post #10, and Fenris's post #13.
 

Thread Starter

Fenris

Joined Oct 21, 2007
288
Hi Chaps

The STB pin is to the Vcc. This is what got the amp working. The mute is taken to 0V and the amp becomes active (got a little mic with pre-amp hooked up)

I'm still running at 12VDC

Simply disconnecting the mute from 0V mutes the amp.

At the moment I'm having problems with my bread board I think. The 556 circuit has packed up as has a 555 timer I tried to run to get the signal. I'll be back as soon as I get it going :/

Heres the schematic with the STB corrected as per Ron's post.

regards

Fenris
 

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Thread Starter

Fenris

Joined Oct 21, 2007
288
Hi chaps

Found this circuit for mute control of a different chip but I think it may still be relevant for what I am trying to do. Currently I am still having trouble with my timer circuits :/ Which is just plain silly! So tomorrow, build a 555 circuit that works, build the level shifter as shown and fingers crossed stage one of the 'grande experiment' will be complete.

regards

Fenris
 

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Thread Starter

Fenris

Joined Oct 21, 2007
288
Hi chaps

I am pleased to say that the level shifter is indeed the answer. I have a 555 circuit running the level shifter and all I need to do now is set it up as per the current 555 circuit with 1M pot that I use in the voice mod :)

Thanks for all the input and help thus far!

Hi Bertus just caught your post. ;)

regards

Fenris
 

Thread Starter

Fenris

Joined Oct 21, 2007
288
Hi Bill

Well at this stage with this chip the amp consists of 7 components, The timer 5, the level shift 5, and the pre amp for the mic is a 741 with a round 5 parts to it. So thats 22 components at this time. The mute is very audible in it's action so I don't know if I can do anything about that so that may entail extra bits?? I need a volume control between the pre amp and the amp to.

I think the next stage is to get a chip that is still easily available that has the same controllability but can also be made into a BLT so I can have 5W minimum at 12VDC and see if I can get any further. At the moment the 555 timer is a fixed speed and fairly slow at that. The timer in the schematic is the one I will have to setup with this and see if the audible mute becomes less prominent at high speed. I am also looking at a passive 2 band shelving equalizer to help reduce high frequency's that cause feedback.

If it can be made to work well all well and good. But I may end up with the same component count in the end. I attach a schematic of the voice mod I currently do.

regards

Fenris
 

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bertus

Joined Apr 5, 2008
20,061
Hello,

Are you realy using the 4066 in your schematic?
You can use an other swich of the 4066 for the muting.
You could put the switch between the output of U1B and C16.
If the 4066 is activated the resistance will be round 150 Ohms.
When deactivated it wil be in the range of meg Ohms.

Greetings,
Bertus
 
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Thread Starter

Fenris

Joined Oct 21, 2007
288
Hi Bertus

Yep I new I could have used the 4066 but the idea was to move in a different direction. Only one switch would be/is used so it is a large chip to have on board considering. So a more efficient use and ability to shrink the circuit down with out recourse to SMT is the main approach.

It may well come to nothing but it is another method I can give the guys at the dalek forum for creating 'the voice'.

regards

Fenris
 

Thread Starter

Fenris

Joined Oct 21, 2007
288
Hi Guys

Currently the component count stands at 17 items :D And I think I just blew my PSU :( It is/was at the right frequency to :D just a bit noisy due to the mute function being driven in such an oddball way.

regards

Fenris
 
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