p3a dc offset

ambed · 27th December 2009, 01:35 PM

I have build p3a amp and i measured 16-17mv(20 mv when not warm up) dc offset,does its ok?

Stormrider · 27th December 2009, 03:17 PM

Anything under 100mVdc is usually considered OK. Under 50mVdc is better; so your 20mV is perfectly fine.

sakis · 27th December 2009, 04:36 PM

-----use beter quality of material (resistors capacitors )
-----match your ltp stage
-----use proper rail voltage

at this circuit and under these rules ofset can be a nice round total zero ....
and yes .... anything that is lower than 100mv ( i would say 50 is better ) is absolutelly not importand

nigelwright7557 · 27th December 2009, 08:15 PM

16mV isnt going to move the speaker much or generate much heat in it.

destroyer X · 09:15 PM

32 microwatts of power (0.000032W)...really you should not worry about.... till 100 milivolts is bureaucratically considered fine.... usually factories suggest you to produce some adjustment when the off set is bigger than 25 milivolts.

regards,

Carlos

ambed · 14th January 2010, 05:07 PM

can yo tell your opinion about this pcb layout??maybe there are some mistakes or somthening that .....

nigelwright7557 · 14th January 2010, 05:10 PM

Quote:

Originally Posted by ambed

can yo tell your opinion about this pcb layout??maybe there are some mistakes or somthening that .....

I might have added a ground plane if your pcb software allows it.
Failing that just thicken up tracks as much as possible.

Bone · 14th January 2010, 05:41 PM

Ambed, Q9 the transistor which determines the bias current, needs to be mounted in contact with either Q5 or Q6 as these transistors determine thermal drift not the output pair. It should not be mounted on the main heatsink.

Stormrider · 14th January 2010, 06:24 PM

Rod Elliot doesn't say so in his project outline.

richie00boy · 14th January 2010, 06:26 PM

Bone is right. Rod probably doesn't mention it as his PCB is laid out correctly already.

27th December 2009, 01:35 PM	#1
ambed diyAudio Member Join Date: Jun 2009	p3a dc offset I have build p3a amp and i measured 16-17mv(20 mv when not warm up) dc offset,does its ok?

27th December 2009, 03:17 PM	#2
Stormrider diyAudio Member Join Date: Apr 2006 Location: Connecticut	Anything under 100mVdc is usually considered OK. Under 50mVdc is better; so your 20mV is perfectly fine. __________________ AJ

27th December 2009, 04:36 PM	#3
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	-----use beter quality of material (resistors capacitors ) -----match your ltp stage -----use proper rail voltage at this circuit and under these rules ofset can be a nice round total zero .... and yes .... anything that is lower than 100mv ( i would say 50 is better ) is absolutelly not importand __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

27th December 2009, 08:15 PM	#4
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	16mV isnt going to move the speaker much or generate much heat in it. __________________ http://www.murtonpikesystems.co.uk PCBCAD40 pcb design software.

27th December 2009, 09:12 PM	#5
destroyer X diyAudio Member Join Date: Feb 2004 Location: Recife - Brasil Northeast	16 mv is almost nothing. 32 microwatts of power (0.000032W)...really you should not worry about.... till 100 milivolts is bureaucratically considered fine.... usually factories suggest you to produce some adjustment when the off set is bigger than 25 milivolts. regards, Carlos __________________ Try to build an amplifier folks ... it is pure adrenaline!.. when not work first time, then becomes a nice challenge...and we usually overcome the trouble... and we feel very well to be mastering the machine. Last edited by destroyer X; 27th December 2009 at 09:15 PM.


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14th January 2010, 05:41 PM	#8
Bone diyAudio Member Join Date: Jun 2004 Location: Dorset, UK	Ambed, Q9 the transistor which determines the bias current, needs to be mounted in contact with either Q5 or Q6 as these transistors determine thermal drift not the output pair. It should not be mounted on the main heatsink.

14th January 2010, 06:24 PM	#9
Stormrider diyAudio Member Join Date: Apr 2006 Location: Connecticut	Rod Elliot doesn't say so in his project outline. __________________ AJ

14th January 2010, 06:26 PM	#10
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	Bone is right. Rod probably doesn't mention it as his PCB is laid out correctly already. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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