TO-3 SYMASYM - Page 62

AndrewT · 03:54 PM

Quote:

Originally Posted by jprco

.................... When I assemble the amp as per the guide and do the bias adjustment with only 1 MJE4281 and 4302, I set it to 24m between MP!/MP2 no problem. But when I insert the second pair of MJE's, the value measured jumps to about 48mV - do I need to readjust the pot back to read 24 mV or leave it at aROUND 48 mV.
The other question was if it easier to adjust the bias measuring the voltage across say a 100R resistor instead of the fuses (after everything with the board as checked out okay) as was done with the DX type amps................

MJEs, not for output devices.
If you havean output bias that changes from 24mVre to 48mVre by adding and extra pair of output then you have a broken amplifier.

Revert to single output pair and check what you post and edit the data if necessary.

DO NOT set and measure the amplifier quiescent current by measuring across 100r resistors in the fuse location. This is very bad practice. DX has been told this repeatedly but he refuses to listen and keeps posting the same wrong information.

Junie · 29th December 2012, 09:48 AM

Finished Amp.

Junie

Rudi_Ratlos · 29th December 2012, 09:59 AM

Junie: your build looks absolutey nice and attests you great craftsmanship!

I hope that you like the sound of the SYMASYM as well.

Best regards - Rudi

Junie · 29th December 2012, 10:07 AM

Thank you Rudi,

The sound is fantastic, though I made a bias conservatively due to small heatsink. I'm happy that katie melua voice is really good on this amp :-)

evette · 29th December 2012, 06:05 PM

Hey Mr. Junie Can I have 1 For christmas past Pleaseeeeeeeeeeeee. Evette

Junie · 30th December 2012, 08:44 AM

Hi Joe,

How I wish Canada is only a kilometer away from my place so i can bring my amp and try in your speakers then we can have a tea and listen to your favorite tunes. HAPPY NEW YEAR

!!

With warm regards,
Junie

atupi · 30th December 2012, 05:19 PM

@Junie congratulations for your build. I love your case, and how you organized everything inside.
Regards,
Adrian

brianco · 30th December 2012, 06:06 PM

Being new to this business of DIY solid state power amps I have little idea of heatsink requirements. [Juni's remarks that his heatsinks are small has reminded me of this fact.]

I have a pair of sinks which are 200mm long, with 40mm fins [including 10mm backplate] and fins on 8mm centres, and 160mm high. Are these adequate for this amp? Or can I reduce the heigth to a more ideal size [as I suspect that too much radiating surface can be detrimental]?

The rest of the case will be made from 7.5mm alloy plate. I intend plenty of ventilation and to place the heatsinks on the external sides. Having plenty of alloy I am considering building the heavy end of a dual mono PS in a seperate chassis.

Lastly, what size transformers will adequately cover the needs for such a supply?

Thank you for any advice you may be able to offer.

evette · 31st December 2012, 01:55 AM

Junie You,ll always be able to visit me with the most warm welcome You always have a great pleastant thing to say Thank You MY FRiend. Joe

Rudi_Ratlos · 31st December 2012, 07:25 AM

Brian, your heatsinks are more than adequate. Any 1 C/W heatsink will do it.
Concerning the transformer: if you plan to build a dual-mono design (like Junie did) I recommend you to use 2 x 25 VAC / 160W.
Else take 1 transformer, 2 x 25 VAC / 250W - 300W. This is what I am using myself.

Best regards - Rudi_Ratlos

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29th December 2012, 09:48 AM	#612
Junie diyAudio Member Join Date: Sep 2010 Location: Dubai, UAE	Finished Amp. Junie

29th December 2012, 09:59 AM	#613
Rudi_Ratlos diyAudio Member Join Date: Jun 2009 Location: Hamburg / Germany	Junie: your build looks absolutey nice and attests you great craftsmanship! I hope that you like the sound of the SYMASYM as well. Best regards - Rudi

29th December 2012, 10:07 AM	#614
Junie diyAudio Member Join Date: Sep 2010 Location: Dubai, UAE	Thank you Rudi, The sound is fantastic, though I made a bias conservatively due to small heatsink. I'm happy that katie melua voice is really good on this amp :-)

29th December 2012, 06:05 PM	#615
evette diyAudio Member Join Date: Jun 2006	Hey Mr. Junie Can I have 1 For christmas past Pleaseeeeeeeeeeeee. Evette

30th December 2012, 08:44 AM	#616
Junie diyAudio Member Join Date: Sep 2010 Location: Dubai, UAE	Hi Joe, How I wish Canada is only a kilometer away from my place so i can bring my amp and try in your speakers then we can have a tea and listen to your favorite tunes. HAPPY NEW YEAR !! With warm regards, Junie

30th December 2012, 05:19 PM	#617
atupi diyAudio Member Join Date: Oct 2010 Location: Bucharest	@Junie congratulations for your build. I love your case, and how you organized everything inside. Regards, Adrian

30th December 2012, 06:06 PM	#618
brianco diyAudio Member Join Date: Aug 2005 Location: Scottish Borders - Kelso; on the famous Tweed River!	Being new to this business of DIY solid state power amps I have little idea of heatsink requirements. [Juni's remarks that his heatsinks are small has reminded me of this fact.] I have a pair of sinks which are 200mm long, with 40mm fins [including 10mm backplate] and fins on 8mm centres, and 160mm high. Are these adequate for this amp? Or can I reduce the heigth to a more ideal size [as I suspect that too much radiating surface can be detrimental]? The rest of the case will be made from 7.5mm alloy plate. I intend plenty of ventilation and to place the heatsinks on the external sides. Having plenty of alloy I am considering building the heavy end of a dual mono PS in a seperate chassis. Lastly, what size transformers will adequately cover the needs for such a supply? Thank you for any advice you may be able to offer.

31st December 2012, 01:55 AM	#619
evette diyAudio Member Join Date: Jun 2006	Junie You,ll always be able to visit me with the most warm welcome You always have a great pleastant thing to say Thank You MY FRiend. Joe

31st December 2012, 07:25 AM	#620
Rudi_Ratlos diyAudio Member Join Date: Jun 2009 Location: Hamburg / Germany	Brian, your heatsinks are more than adequate. Any 1 C/W heatsink will do it. Concerning the transformer: if you plan to build a dual-mono design (like Junie did) I recommend you to use 2 x 25 VAC / 160W. Else take 1 transformer, 2 x 25 VAC / 250W - 300W. This is what I am using myself. Best regards - Rudi_Ratlos