Ok...my gainclone works BEAUTIFULLY...but I have this tiny hum in it. Sounds like the television hum. I know these things are supposed to be silent. I tried a resistor from input ground to ground...doesn't help. I can UNPLUG the input ground to ground and there is NO CHANGE in hum or fuction...weird huh? Everything is fairly simplistic....Peter Daniels schema etc. Its not a 60 hz hum...but sounds like a harmonic...like 120 hz or 240 or something. I have an IEC receptical which has a "filter" in it for the power input. I have star ground...two chassis...star ground in the amp chassis. Any ideas?
-Matthew K. Olson
ps...the hum goes away basically if I unplug the source...discman or regular cd player makes same amount of hum
pps...I have a 50k to ground resistor instead of a pot...its after the caps 2.1uF but before my 10k resistor on the input ...hope that helps
-Matthew K. Olson
ps...the hum goes away basically if I unplug the source...discman or regular cd player makes same amount of hum
pps...I have a 50k to ground resistor instead of a pot...its after the caps 2.1uF but before my 10k resistor on the input ...hope that helps
Ok...I've been fighting this stupid hum all day long. Its more like a buzz...sounds exactly like a flourescent light, and exactly as loud. I removed my 50k input resistors to ground....no difference. W/ or w/o input ground attached doesn' t seem to matter. This is too weird. I've got power ground attached to power grounds, speaker ground and input ground...all mounted to the chassis...I've tried different configs....still no change...it only gets worse. The buzz does NOT go up and down w/ volume change. ...and worse...now my toroid is humming. Plitron 18-0-18 225va. Please help!
-Matthew K. Olson
-Matthew K. Olson
Shooting the hum
Can you try two 12v batteries in series, as a +/-12v supply, and see what happens?
Can you get two big capacitors, at least 10000uF each, switch everything on, and then see if the hum goes away when you turn the AC off?
Is the gainclone inside a metal box which is also grounded?
Have you tried disconnecting the amp ground from the wall ground?
Carlos
Can you try two 12v batteries in series, as a +/-12v supply, and see what happens?
Can you get two big capacitors, at least 10000uF each, switch everything on, and then see if the hum goes away when you turn the AC off?
Is the gainclone inside a metal box which is also grounded?
Have you tried disconnecting the amp ground from the wall ground?
Carlos
Ok...I don't have car batteries...but that is an idea.
I have almost 15kuf on the rails of capacitance right now. yes, the hum goes away when I turn the ac off. again, the hum though is not being amplified...I can turn up my discman to whatever level...actually I can't...gets too loud! :-D but anyway, the hum isn't amplified...the ps case is not grounded, and the wall ground is not attached. I tried messing w/ that...no difference. Yeah, the ps case is not grounded...but I think I've tried w/ a jumper wire to ground it...gets worse I think.
Also...when I jumper the inputs to ground...ie...so there is for sure no signal...I still get hum. BUT...if I have nothing plugged into the inputs...no hum. Wish it was like that when I plugged stuff in! doesn't matter what I plug in though...whether its a test RCA that shorts input to ground or my discman or a regular cdplayer or a preamp...120hz hum...audible in a quiet room.
-Matthew K. Olson
I have almost 15kuf on the rails of capacitance right now. yes, the hum goes away when I turn the ac off. again, the hum though is not being amplified...I can turn up my discman to whatever level...actually I can't...gets too loud! :-D but anyway, the hum isn't amplified...the ps case is not grounded, and the wall ground is not attached. I tried messing w/ that...no difference. Yeah, the ps case is not grounded...but I think I've tried w/ a jumper wire to ground it...gets worse I think.
Also...when I jumper the inputs to ground...ie...so there is for sure no signal...I still get hum. BUT...if I have nothing plugged into the inputs...no hum. Wish it was like that when I plugged stuff in! doesn't matter what I plug in though...whether its a test RCA that shorts input to ground or my discman or a regular cdplayer or a preamp...120hz hum...audible in a quiet room.
-Matthew K. Olson
Whether the RCA ground is connected or not the hum is there...weird huh? RCA grounds are connected w/ everything else at star ground. I kind have this sinking feeling that when I cranked down the RCA's there was a shard of aluminum that went through the teflon and is grounding the RCA to the case ...ie...away from star ground. But ....I'd have to have done that at both spots. Lemme get some pics and post em. Hang on
-Matthew K. Olson
-Matthew K. Olson
Mattyo5 said:
Hi,
Disconnect internal wires from RCA, check with instrument isolation beetwen RCA cold pin and chasis. RCA must be isolate, then cold pin from RCAs connect to input ground on IC or ground point on ELCOs on IC. Star ground must be on ELCOs. Speaker ground connect also on ELCOs ground. In first moment leave enclosure ungrounded. Try buzzing. If is OK, connect enclosure thru 10E or so on star ground on ELCOs. 3 caps on inputs can not be problem.
About trafo humming; what happen when power cable to amps is disconnected and power supply is on, is still same level of buzzing? I have some sugestion, but now is 1.50 AM for me, I go sleep now, sorry.
until tomorrow
regards
Whats ELCO's?
One of the RCA's was not isolated. Fixed that problem...but no improvement. The other RCA is fine. What a pain...I've been at this ALL DAY LONG and I'm no better than when I started!
-Matthew K. Olson
I'll see what I can do about attaching a 10 ohm resistor in various places. Thanks
One of the RCA's was not isolated. Fixed that problem...but no improvement. The other RCA is fine. What a pain...I've been at this ALL DAY LONG and I'm no better than when I started!
-Matthew K. Olson
I'll see what I can do about attaching a 10 ohm resistor in various places. Thanks
ELCO is electrolytic. I know from experience that isolating or not input RCA doesn't make much difference. Try to run the grounds as simple as possible. Do you have 2 ground wire or one from PS? You should ground the chassis.
I eliminated some interference in my amps by connecting both channels binding posts (ground) together. Otherwise the circuits were always very quiet.
I eliminated some interference in my amps by connecting both channels binding posts (ground) together. Otherwise the circuits were always very quiet.
I have used a jumper to ground the power supply chassis...from cap to chassis...and get quite a bit of hum. Icky. I have one ground wire coming from the power supply. Why...do I need two...why? Would that make a difference?
Everything...all grounds come together at star ground, or at the connectors which are at star ground. Jeez this is driving me crazy.
-Matthew K. Olson
Everything...all grounds come together at star ground, or at the connectors which are at star ground. Jeez this is driving me crazy.
-Matthew K. Olson
Ok...my toroid is buzzing. I put my ear up to the toroid and I can hear audible buzzing...what gives???? Like something is moving back and forth in there. Could that ALSO give rise to a 120hz hum coming out of the speakers? how do I stop a PLITRON toroid from buzzing?
-Matthew K. Olson
FRUSTRATED
-Matthew K. Olson
FRUSTRATED
Matt,
If your hum stops when you disconnect your input interconnects you might have a ground loop though your source if it is grounded as well. Does it have an IEC power cable? Try opening your source (ie CDP) and disconnect the ground at the case socket and see if the hum goes away. Or try a source with a two-wire cord. You might try some different interconnects too.
If your hum stops when you disconnect your input interconnects you might have a ground loop though your source if it is grounded as well. Does it have an IEC power cable? Try opening your source (ie CDP) and disconnect the ground at the case socket and see if the hum goes away. Or try a source with a two-wire cord. You might try some different interconnects too.
The fact that the hum disappears when you disconnect the source is indicative of the fact that is indeed a ground loop.
By the way, have you used shielded wire for the input connections?
Tie Input, Output, PSU ground and 0volts of transformer to one point and isolate all of these from chassis earth. Use braided earthing strap to electrically connect RCA ground to chassis earth. This should solve your hum problem.
If the torroidal transformer is buzzing, either the windings are loose (should be re-wound) or the mains voltage is slightly higher than what the primary was designed to handle. Check out which is true.
All the best!!
By the way, have you used shielded wire for the input connections?
Tie Input, Output, PSU ground and 0volts of transformer to one point and isolate all of these from chassis earth. Use braided earthing strap to electrically connect RCA ground to chassis earth. This should solve your hum problem.
If the torroidal transformer is buzzing, either the windings are loose (should be re-wound) or the mains voltage is slightly higher than what the primary was designed to handle. Check out which is true.
All the best!!
Mattyo5 said:
Hi,
On pic 1 is your wiring diagram. When small AC ripple current on DC power rail flow from wire A thru CAP1, wire B and C make Vripple (dashed line). This is your problem. When you shortening input RCA, this V appear on input of your amp. Solution is to rearrange ground star according pic 2. IMHO
regards
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.