Switch on Transients for GainClone

dtm1962 · 17th July 2003, 09:40 PM

I have built a Gainclone using the LM3875 chips, using basically
Joe R. circuit (tubeless) using a 10K pot.

Has anyone experience Switch- On Transients to the point where
a 3 Amp FastBlow fuse (temporary as I will use 2A Slo-blos) will blow on Turn-on.

I seemed to have DC offset on turn on (as the woofers will move in/out on start up), but my steady state DC offset is 1.6mV
& 2.4 mV for each channel.

I am using a single 300W Plitron 20+20V dual secondaries for the
Xformer and a total of 8000 uF for PS Capacitance.

There is no cap/resistor across the Power Switch at this time.

Is there anything I could add to prevent transient thumps etc on Power Up.

Any help would be appreciated.

Thanks in advance

li_gangyi · 18th July 2003, 10:57 AM

that might be because on cap charges faster than another...leading to the offset and stuff...try no cap or a smaller cap...no cap for testing only~!

carlosfm · 18th July 2003, 11:23 AM

Toroids have big inrush currents at turn on.
Put a 10 Ohm 7~10 watts resistor in series with one of the primary wires.

li_gangyi · 18th July 2003, 11:30 AM

Or you could use a NTC termistor...

17th July 2003, 09:40 PM	#1
dtm1962 diyAudio Member Join Date: Apr 2003 Location: Sarnia, Ontario, Canada	Switch on Transients for GainClone I have built a Gainclone using the LM3875 chips, using basically Joe R. circuit (tubeless) using a 10K pot. Has anyone experience Switch- On Transients to the point where a 3 Amp FastBlow fuse (temporary as I will use 2A Slo-blos) will blow on Turn-on. I seemed to have DC offset on turn on (as the woofers will move in/out on start up), but my steady state DC offset is 1.6mV & 2.4 mV for each channel. I am using a single 300W Plitron 20+20V dual secondaries for the Xformer and a total of 8000 uF for PS Capacitance. There is no cap/resistor across the Power Switch at this time. Is there anything I could add to prevent transient thumps etc on Power Up. Any help would be appreciated. Thanks in advance __________________ Dan

18th July 2003, 10:57 AM	#2
li_gangyi diyAudio Member Join Date: Jun 2003 Location: Woodlands Circle	that might be because on cap charges faster than another...leading to the offset and stuff...try no cap or a smaller cap...no cap for testing only~! __________________ Kids in the back seat cause accidents...Accidents in the back seat cause kids...

18th July 2003, 11:30 AM	#4
li_gangyi diyAudio Member Join Date: Jun 2003 Location: Woodlands Circle	Or you could use a NTC termistor... __________________ Kids in the back seat cause accidents...Accidents in the back seat cause kids...

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
Transients and Crossover Components	discl	Multi-Way	1	2nd March 2008 01:43 PM
Turn on/off transients	Pierre	Class D	60	9th January 2007 03:47 AM
WTB: Pot/rotary switch + resistors for Gainclone, FR drivers, Madisound $$, more.	Spasticteapot	Swap Meet	1	7th May 2006 10:48 PM
turn-off transients with LM1875	Dennis Hui	Chip Amps	12	2nd July 2003 02:40 AM


	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

18th July 2003, 11:23 AM	#3
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	Toroids have big inrush currents at turn on. Put a 10 Ohm 7~10 watts resistor in series with one of the primary wires.

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