Simple 100W power amp - Page 2

Tekko · 28th April 2012, 03:28 PM

What is that board from ? Kinda looks like a board to some old kit.

sakis · 28th April 2012, 06:13 PM

very very important : the cable you use from pcb to transistors you need to split it having a flat cable including B C E connections is a very bad thing to do...twisting is even worst .

You need to at least remove the base cable from the pack

Aniket · 10th May 2012, 08:02 AM

Thanks friends.
I did some changes. Increased the +ve FB resistor to 3.3K from 2.2K.
Increased 3.3K resistor to 5.6K keeping the zener in place. The amp stays cool at idle, but the output trans. get a bit hot while playing music. Sound is really good with crisp treble and clear vocals. Bass is good too.
@Stormrider- KSA3503 are really hard to find, i looked out for MJ15003/4 but they turned out to be fake ON semi's.
@AndrewT- Input trans. are BC556B, please advice if BD139/40 are not good Vas devices. Mention any substitutes.

Regards,
Aniket

AndrewT · 10th May 2012, 10:50 AM

Look up Greg's data for devices. He has a table of suggested VAS devices with a few oddballs thrown in for comparison.

djk · 10th May 2012, 11:02 AM

Add a second pair of output transistors before attemting >50 watts output into 4 ohms. "

A Crown D150 only uses one pair and can drive 140W/4Ω, the D150AII was rated at 155W/4Ω.

http://www.crownaudio.com/pdf/legacy...spec-sheet.pdf

The original DC300 would do 340W/4Ω at clip with two pair of 2N3773.

Aniket · 10th May 2012, 02:51 PM

Please send me Greg's link

Tekko · 10th May 2012, 03:10 PM

What is the rail voltages of that crown amp ? Looking at the 2N3773 datasheet, at 50V Vce, you can pull about 3A through a single 2N3773, so up to 50V rails seem to be safe with a 4 ohm load.

Aniket · 15th May 2012, 05:07 AM

Should i add more output trans. ??
will this increase performance/ power?? by how much?

djk · 15th May 2012, 07:25 AM

"What is the rail voltages of that crown amp ?"

If I remember correctly, about ±50V.

"Should i add more output trans. ??
will this increase performance/ power?? by how much? "

If you like.

If you have a good heatsink and adequate thermal grease and good insulators it is probably OK with one pair.

A second pair would just allow it to handle low impedance loads better, it would probably not put out any more power.

Tekko · 15th May 2012, 08:10 AM

Moar OP devices does lower THD alittle though, atleast in ltspice it does.

28th April 2012, 03:28 PM	#11
Tekko diyAudio Member Join Date: Jan 2005	What is that board from ? Kinda looks like a board to some old kit. __________________ The point of life is to build atleast one audio amplifier before you die.

28th April 2012, 06:13 PM	#12
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	very very important : the cable you use from pcb to transistors you need to split it having a flat cable including B C E connections is a very bad thing to do...twisting is even worst . You need to at least remove the base cable from the pack __________________ SERVICE ΕΝΙΣΧΥΤΩΝ ΚΑΙ ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

10th May 2012, 11:02 AM	#15
djk diyAudio Member Join Date: Feb 2001 Location: USA	Add a second pair of output transistors before attemting >50 watts output into 4 ohms. " A Crown D150 only uses one pair and can drive 140W/4Ω, the D150AII was rated at 155W/4Ω. http://www.crownaudio.com/pdf/legacy...spec-sheet.pdf The original DC300 would do 340W/4Ω at clip with two pair of 2N3773. __________________ Candidates for the Darwin Award should not read this author.

10th May 2012, 03:10 PM	#17
Tekko diyAudio Member Join Date: Jan 2005	What is the rail voltages of that crown amp ? Looking at the 2N3773 datasheet, at 50V Vce, you can pull about 3A through a single 2N3773, so up to 50V rails seem to be safe with a 4 ohm load. __________________ The point of life is to build atleast one audio amplifier before you die.

15th May 2012, 07:25 AM	#19
djk diyAudio Member Join Date: Feb 2001 Location: USA	"What is the rail voltages of that crown amp ?" If I remember correctly, about ±50V. "Should i add more output trans. ?? will this increase performance/ power?? by how much? " If you like. If you have a good heatsink and adequate thermal grease and good insulators it is probably OK with one pair. A second pair would just allow it to handle low impedance loads better, it would probably not put out any more power. __________________ Candidates for the Darwin Award should not read this author.


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10th May 2012, 08:02 AM	#13
Aniket diyAudio Member Join Date: Apr 2012 Location: Delhi, India	Thanks friends. I did some changes. Increased the +ve FB resistor to 3.3K from 2.2K. Increased 3.3K resistor to 5.6K keeping the zener in place. The amp stays cool at idle, but the output trans. get a bit hot while playing music. Sound is really good with crisp treble and clear vocals. Bass is good too. @Stormrider- KSA3503 are really hard to find, i looked out for MJ15003/4 but they turned out to be fake ON semi's. @AndrewT- Input trans. are BC556B, please advice if BD139/40 are not good Vas devices. Mention any substitutes. Regards, Aniket

10th May 2012, 10:50 AM	#14
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Look up Greg's data for devices. He has a table of suggested VAS devices with a few oddballs thrown in for comparison.

10th May 2012, 02:51 PM	#16
Aniket diyAudio Member Join Date: Apr 2012 Location: Delhi, India	Please send me Greg's link

15th May 2012, 05:07 AM	#18
Aniket diyAudio Member Join Date: Apr 2012 Location: Delhi, India	Should i add more output trans. ?? will this increase performance/ power?? by how much?

15th May 2012, 08:10 AM	#20
Tekko diyAudio Member Join Date: Jan 2005	Moar OP devices does lower THD alittle though, atleast in ltspice it does. __________________ The point of life is to build atleast one audio amplifier before you die.

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