optocoupling power stage - hiss with 6N137 - Page 3

ionutgaga · 8th February 2008, 01:09 PM

out after notch
0.5v/div, 2us

ionutgaga · 8th February 2008, 01:10 PM

out before notch
1v/div, 1us

ionutgaga · 8th February 2008, 01:12 PM

out before lc filter
20v/div, 1us, positive

ionutgaga · 8th February 2008, 01:13 PM

out before lc filter
20v/div, 1us, negative

ionutgaga · 8th February 2008, 01:14 PM

Same white noise....

ionutgaga · 11th February 2008, 05:28 AM

Even if i replace floating smps with 2 x 9v bat, still noisy.
Even if i remove inductor from pcb (at about 20cm), noise is still the same...
Even if i put a more decoupling caps for vcc (ceramic, mkt, etc) ...
Even if i put rc snubbers; scottky antiparalel diodes, adjusting deadtime, etc... still the SAME noise...
6N137? ... i don't know...

Eva · 11th February 2008, 06:28 AM

Try adding more capacitance to the outputs of the L7805...

ionutgaga · 11th February 2008, 06:40 AM

... tryied...

Eva · 11th February 2008, 08:23 AM

Try increasing and decreasing the value of 6N137 load resistors and also try changing 6N137 LED drive current.

lumanauw · 11th February 2008, 08:49 AM

Are you using TO247 mosfets? It will have significant capacitance between Drain/flange with ground (if the heatsink is grounded).
You can try putting aluminum oxide insulator (1-1.5mm thick) to lower this capacitance.

11th February 2008, 06:28 AM	#27
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	Try adding more capacitance to the outputs of the L7805... __________________ I use to feel like the small child in The Emperor's New Clothes tale

11th February 2008, 08:23 AM	#29
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	Try increasing and decreasing the value of 6N137 load resistors and also try changing 6N137 LED drive current. __________________ I use to feel like the small child in The Emperor's New Clothes tale

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
EL34 Power Stage	AmpBuilder225	Tubes / Valves	6	16th February 2009 04:39 PM
phono stage hiss	woodturner-fran	Tubes / Valves	6	15th April 2008 08:59 PM
2 stage power amp	Leolabs	Solid State	3	29th March 2006 01:48 AM
Single Stage power amp.	lumanauw	Solid State	10	2nd April 2004 09:03 AM
power output stage	Jennice	Pass Labs	22	19th June 2003 11:59 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

8th February 2008, 01:14 PM	#25
ionutgaga diyAudio Member Join Date: Jul 2006	Same white noise....

11th February 2008, 05:28 AM	#26
ionutgaga diyAudio Member Join Date: Jul 2006	Even if i replace floating smps with 2 x 9v bat, still noisy. Even if i remove inductor from pcb (at about 20cm), noise is still the same... Even if i put a more decoupling caps for vcc (ceramic, mkt, etc) ... Even if i put rc snubbers; scottky antiparalel diodes, adjusting deadtime, etc... still the SAME noise... 6N137? ... i don't know...

11th February 2008, 06:40 AM	#28
ionutgaga diyAudio Member Join Date: Jul 2006	... tryied...

11th February 2008, 08:49 AM	#30
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	Are you using TO247 mosfets? It will have significant capacitance between Drain/flange with ground (if the heatsink is grounded). You can try putting aluminum oxide insulator (1-1.5mm thick) to lower this capacitance.