chip amp with distortion pin (?)

netrino · 7th January 2007, 07:55 AM

Hi! i'm new here...

recently i've made this simple amplifier

http://www.nxp.com/acrobat/datashee...1557Q_CNV_2.pdf

somewhere in the PDF says that if we connect pin 12 (Vref) with two diodes to the ground then the distortion is reduced...

can someone tell me what kind of diodes do i need and how i connect them? (i have some BA159 spare...)

P.S i have already posted it on another topic but problably nobody reads it there because of the topic title...

AndrewT · 7th January 2007, 08:10 AM

Hi,
did you test your link?
It took me to NXP and said "page requested is not found".

netrino · 7th January 2007, 04:50 PM

i believe it's ok now...

http://www.nxp.com/acrobat/datasheet...557Q_CNV_2.pdf

check page 4

AndrewT · 7th January 2007, 05:24 PM

Hi,
the spec does not call up the diode voltage, so I guess they are not zeners.
Assuming they are standard signal diode then two in series gives about 1.4V. But, this does not look right, the single supply amps probably need half supply voltage on the input pins.
I note a reference to DC voltages of 6V and 6.9V but I don't understand those either.

It should be safe to try a pair of 1n4148 , until someone else jumps in with a tried/tested solution.

netrino · 7th January 2007, 09:59 PM

i have tried the BA159 in series and nothing happend.....
i tried them to the opposite direction and the power supply
started to shaking!

netrino · 8th January 2007, 07:51 PM

Ηι...

nobody knows if it worths to do something with the pin 12?
and how am i going to do it?

Netlist · 8th January 2007, 08:32 PM

Quote:

Originally posted by netrino
i have tried the BA159 in series and nothing happend.....

But you didn’t measure harmonic distortion at low frequencies, did you?

I'd like to know as well, searched and found nothing but if the amp plays fine, who cares?

/Hugo

netrino · 8th January 2007, 09:55 PM

Quote:

Originally posted by Netlist
But you didn’t measure harmonic distortion at low frequencies, did you?
I'd like to know as well, searched and found nothing but if the amp plays fine, who cares?

/Hugo

no i haven't measured anything...but neither my ear heard any difference...as i said before it's a simple amp and it doesn't worth to
spend much time with it, i just want to tune it as much as i can and then leave it for future use...maybe for self powered speakers or something...

i appreciate any help with this mysterious pin 12!

7th January 2007, 07:55 AM	#1
netrino diyAudio Member Join Date: Jan 2007	chip amp with distortion pin (?) Hi! i'm new here... recently i've made this simple amplifier http://www.nxp.com/acrobat/datashee...1557Q_CNV_2.pdf somewhere in the PDF says that if we connect pin 12 (Vref) with two diodes to the ground then the distortion is reduced... can someone tell me what kind of diodes do i need and how i connect them? (i have some BA159 spare...) P.S i have already posted it on another topic but problably nobody reads it there because of the topic title...

7th January 2007, 08:10 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, did you test your link? It took me to NXP and said "page requested is not found". __________________ regards Andrew T.

7th January 2007, 05:24 PM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the spec does not call up the diode voltage, so I guess they are not zeners. Assuming they are standard signal diode then two in series gives about 1.4V. But, this does not look right, the single supply amps probably need half supply voltage on the input pins. I note a reference to DC voltages of 6V and 6.9V but I don't understand those either. It should be safe to try a pair of 1n4148 , until someone else jumps in with a tried/tested solution. __________________ regards Andrew T.

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7th January 2007, 04:50 PM	#3
netrino diyAudio Member Join Date: Jan 2007	i believe it's ok now... http://www.nxp.com/acrobat/datasheet...557Q_CNV_2.pdf check page 4

7th January 2007, 09:59 PM	#5
netrino diyAudio Member Join Date: Jan 2007	i have tried the BA159 in series and nothing happend..... i tried them to the opposite direction and the power supply started to shaking!

8th January 2007, 07:51 PM	#6
netrino diyAudio Member Join Date: Jan 2007	Ηι... nobody knows if it worths to do something with the pin 12? and how am i going to do it?

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