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Old 20th February 2012, 06:00 PM   #1011
BMW850 is offline BMW850  Netherlands
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Nothing about voltage drop ...
I thought the proper operation you need to have a stable power supply

currentflow,
Thanks for the explanation, I definitely try 470uF C1 and C2

Regards,
Rudy
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Last edited by BMW850; 20th February 2012 at 06:14 PM.
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Old 20th February 2012, 08:21 PM   #1012
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Originally Posted by BMW850 View Post
Nothing about voltage drop ...
I thought the proper operation you need to have a stable power supply

currentflow,
Thanks for the explanation, I definitely try 470uF C1 and C2

Regards,
Rudy
Hi Rudy,

Since you'll be using these modules to protect your speakers, it's worth spending a little time to ensure they operate reliably.

Your measured voltage of 15.1V before the regulator when the relays are on is now greater than the minimum required value of 14.5V, which is good news. As we don't know how much ripple is present before the regulator, the changes to C1 and C2 would definitely be beneficial although their values are not critical. You could use 330uF or 470uF with a minimum working voltage of 25V to improve on the results. Select the largest of these values which will comfortably fit on the PCB. Another possibility would be to fit a single 1000uf/25V instead of two capacitors, if there is room.
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Old 21st February 2012, 03:46 PM   #1013
BMW850 is offline BMW850  Netherlands
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Hello currentflow,

Thanks for your help, I now have a 1000uF capacitor soldered in there, and the speaker protection module is now stable.

Thanks vintage audio lab for a "good and stable speaker protection module you send me"
We on this forum do the research to make this a good and stable working speaker protection module

Regards,
Rudy
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Old 21st February 2012, 04:47 PM   #1014
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Originally Posted by BMW850 View Post
Hello currentflow,

Thanks for your help, I now have a 1000uF capacitor soldered in there, and the speaker protection module is now stable.

Thanks vintage audio lab for a "good and stable speaker protection module you send me"
We on this forum do the research to make this a good and stable working speaker protection module

Regards,
Rudy
One of the pleasures of DIY is in improving others' designs... Out of curiosity, what is the voltage before the regulator now that you've changed the capacitors, with the relays on? Over 16V?

Steve
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Old 21st February 2012, 08:08 PM   #1015
BMW850 is offline BMW850  Netherlands
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One of the pleasures of DIY is in improving others' designs... Out of curiosity, what is the voltage before the regulator now that you've changed the capacitors, with the relays on? Over 16V?

Steve
Hi Steve,

Everything is now connected and the speaker protection module works.
Input voltage 7812 regulator with the relay on, is now 16, 67v

Regards,
Rudy
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Old 21st February 2012, 08:20 PM   #1016
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Hi Steve,

Everything is now connected and the speaker protection module works.
Input voltage 7812 regulator with the relay on, is now 16, 67v

Regards,
Rudy
Looks good to me. Now enjoy your Hx!
Steve
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Old 22nd February 2012, 05:29 PM   #1017
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Default Question on gain

Hi everyone, quick question here...

The gain of the Hx amp seems very high compared to "consumer" power amps. Basically, a consumer amp rated at 200W RMS into 8 Ohms will show a gain averaging at around 28x.
Now when I look back at the schematics of the Hx, the gain seems to be around 120x. Am I missing something?

I think Carlos determined that 390Ohm resistor for direct connection to portable devices, hence the huge gain ratio.

Picture showing the two resistors used for calculating the gain:
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Old 22nd February 2012, 05:34 PM   #1018
a.wayne is offline a.wayne  United States
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Can you or has anyone measured the signal to noise ratio .... ?
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Old 22nd February 2012, 05:43 PM   #1019
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I had similar question in the past and Carlos answered me that I can change the value of the 390R resistor to adjust the gain of the amp.
Also I think that gain is determent by the two resistors in the NFB and not by this in the input to the GND. In this case you are right because they have the same value but keep it in mind.

Regards!
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Old 22nd February 2012, 06:09 PM   #1020
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You are correct Gain =r2+r3\r2===121.5 Evette
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