output hum

Retsim_X · 18th September 2005, 07:09 AM

hey people i have just finished a 200wrms x 2 solidstate amp

we have alternate power at home and run off a modified sine wave inverter.

the problem is i need a way to (when the volume is right down) to eliminate the horrible hum

like i mean you cant even use headphones the hum iss so bad and loud

plz i need help

ps the hum is comming from the speakers @ 50 hz

Retsim_X · 18th September 2005, 10:10 AM

actualy is it easiest just to rewind the trnsformer agian so it has +/- 80 v in the caps and regulate it at +/- 60 v ?

sry we run a modified SQUARE wave inverter

Fritzell · 18th September 2005, 10:53 AM

How have you grounded it? Stargrounded? Is the inputs shielded?

Regulated PSU isn't a very good alternative

Retsim_X · 18th September 2005, 11:55 AM

absolutly it was one of the first things i did and checked

Fritzell · 18th September 2005, 03:49 PM

If you have grounded everything in a perfect way like a star then the hum might go right into the main pcb. Take it and put it far away from the transformer and see if it helps.

I assume you have rectified the AC and youre using significant big reservoir capacitors

Retsim_X · 19th September 2005, 06:22 AM

+/- 50v power

8000uF caps

200wrms x2 amp

the amp board is on the opposite end of the 17" box

thank u

ChocoHolic · 19th September 2005, 08:08 PM

Except some very particular designs...
Normally heavy hum is not caused by the ripple on the DC rail.
Ripple on the DC rail usually causes just some hum, but not heavy hum. And typically this hum would be 100Hz, not 50Hz.

Do you have the hum also, if the amp is not connected to any
signal source? No computer, no TV, no radio etc....
Most often you get such heavy hum, when you connect two parts of equipment that both are grounded. ... grounded at different points and causing a ground loop between two (or more) parts of the equipment. So most suspect are computers (PSU always grounded), TV (antenna grounded), radio (antenna).

Good luck
Markus

andjur78 · 19th September 2005, 08:47 PM

Sometimes you will need to seperate the Audio and PSU grounds to elliminate ground loops within your amplifier system.
Does the amplifier hum get worse when you connect a source to it's input terminals?
For a start seperate the input audio grounds and see if it goes away(attenuates is probably a better word)
Comman practice is to lift this ground away with a 47 ohm (or thereabouts) resistor.

18th September 2005, 07:09 AM	#1
Retsim_X diyAudio Member Join Date: Sep 2005	output hum hey people i have just finished a 200wrms x 2 solidstate amp we have alternate power at home and run off a modified sine wave inverter. the problem is i need a way to (when the volume is right down) to eliminate the horrible hum like i mean you cant even use headphones the hum iss so bad and loud plz i need help ps the hum is comming from the speakers @ 50 hz

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
Difference between SE output transformer and push-pull output transformers	hilbert_mostert	Tubes / Valves	12	8th March 2009 05:10 PM
3C24 in a SE output stage - output transformer impedance recommendation !!!	aldovan	Tubes / Valves	15	6th September 2008 10:18 AM
Adding secondary of output transformer into cathodes of output stage ? Eico ST-70	freddymac406	Tubes / Valves	3	21st April 2007 06:15 PM
Can An Output Transformer Change A Voltage Amp's Output Impedance From 0.1 To 47 Ohms	kelticwizard	Everything Else	11	25th March 2007 05:17 AM
I2S digital output in Marantz CD4000 and four TDA1541A with balance analog output	iklari14	Digital Source	30	18th July 2003 12:57 PM

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

18th September 2005, 10:10 AM	#2
Retsim_X diyAudio Member Join Date: Sep 2005	actualy is it easiest just to rewind the trnsformer agian so it has +/- 80 v in the caps and regulate it at +/- 60 v ? sry we run a modified SQUARE wave inverter

18th September 2005, 10:53 AM	#3
Fritzell diyAudio Member Join Date: Jul 2004 Location: Sweden	How have you grounded it? Stargrounded? Is the inputs shielded? Regulated PSU isn't a very good alternative

18th September 2005, 11:55 AM	#4
Retsim_X diyAudio Member Join Date: Sep 2005	absolutly it was one of the first things i did and checked

18th September 2005, 03:49 PM	#5
Fritzell diyAudio Member Join Date: Jul 2004 Location: Sweden	If you have grounded everything in a perfect way like a star then the hum might go right into the main pcb. Take it and put it far away from the transformer and see if it helps. I assume you have rectified the AC and youre using significant big reservoir capacitors

19th September 2005, 06:22 AM	#6
Retsim_X diyAudio Member Join Date: Sep 2005	+/- 50v power 8000uF caps 200wrms x2 amp the amp board is on the opposite end of the 17" box thank u

19th September 2005, 08:08 PM	#7
ChocoHolic diyAudio Member Join Date: Dec 2003 Location: Munich	Except some very particular designs... Normally heavy hum is not caused by the ripple on the DC rail. Ripple on the DC rail usually causes just some hum, but not heavy hum. And typically this hum would be 100Hz, not 50Hz. Do you have the hum also, if the amp is not connected to any signal source? No computer, no TV, no radio etc.... Most often you get such heavy hum, when you connect two parts of equipment that both are grounded. ... grounded at different points and causing a ground loop between two (or more) parts of the equipment. So most suspect are computers (PSU always grounded), TV (antenna grounded), radio (antenna). Good luck Markus

19th September 2005, 08:47 PM	#8
andjur78 diyAudio Member Join Date: Mar 2005 Location: Aussie	Sometimes you will need to seperate the Audio and PSU grounds to elliminate ground loops within your amplifier system. Does the amplifier hum get worse when you connect a source to it's input terminals? For a start seperate the input audio grounds and see if it goes away(attenuates is probably a better word) Comman practice is to lift this ground away with a 47 ohm (or thereabouts) resistor.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)