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Post by marcello66 on Nov 15, 2015 11:08:26 GMT
Hi all.. I've found a great forum here and i hope someone can help me. (Sorry for my bad english) I've got LB P1 and think it sounds great for my budget. But i have a hum problem. I accidentally discovered that touching caps or metallic parts the hum disappears... So, ive connected with a wire the LB P1 ground to metallic part of my guitar amp that is earth grounded. Now the Little Bear sounds great without noises. What's the question? How i can earth grounding the little bear? Its come with a switching psu that dont have the heart ground connection.... Any suggestions? Thanks in advance
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Post by marcello66 on Nov 16, 2015 7:37:55 GMT
Nobody can help me?
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Post by Deleted on Nov 16, 2015 7:57:36 GMT
Nobody can help me? The problem is almost certainly due to the SMPS. Consumer grade SMPS plugpacks, and even in DVD players etc. have a small value high voltage capacitor between the mains side and the output side. This can cause a high voltage, low current mains voltage with HF noise riding on it , that is as high as half the AC mains voltage, between the output side of the SMPS and earth. This can also cause a tingling sensation when you rub your finger over the metal case of a SMPS powered device. Grounding the metal case of the device can often result in a marked reduction of hum.
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Post by marcello66 on Nov 16, 2015 11:07:18 GMT
Thank you for the response Sandyk Sorry if I ask again , i'm really a newbie...and need some help...just a little bit.. What is the best solution to shield the case and connect it with earth ground? I put the LB in a metal case, but how i connect the earth ground to the case ? Maybe i've found a low cost solution .. www.ebay.it/itm/Audiophile-Quality-DC-24V2A-switching-power-adapter-PSU-/250806526350Auction says "2/3 pin power jack ICE grounded".....you think will work ?
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Post by Deleted on Nov 16, 2015 19:58:49 GMT
Thank you for the response Sandyk Sorry if I ask again , i'm really a newbie...and need some help...just a little bit.. What is the best solution to shield the case and connect it with earth ground? I put the LB in a metal case, but how i connect the earth ground to the case ? Maybe i've found a low cost solution .. www.ebay.it/itm/Audiophile-Quality-DC-24V2A-switching-power-adapter-PSU-/250806526350Auction says "2/3 pin power jack ICE grounded".....you think will work ? I doubt that it will solve the problem. You would need to check with a Digital Meter that there is no A.C. voltage measured between it's output and mains earth. This design appears to be more about lower noise from it's output, possibly due to larger filter capacitors. If you have a mains plug from a hardware store etc. you could try connecting a single wire to the earth pin of the plug, and then connecting the other end of the wire to the metalwork of the device that the SMPS plugpack is powering. Carefully check a diagram of the plug before wiring it up as a mistake could be fatal!
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Post by marcello66 on Nov 17, 2015 11:58:36 GMT
I thank you very much Sandyk, i waiting for the smps i've ordered...after that i will try to do (carefully) my experiments with your suggestions.. After all...i will post my work (the LB reboxed and modded). Thanks again!
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Post by marcello66 on Nov 17, 2015 13:59:07 GMT
...Just last question.. Im the only owner of a Little Bear P1, (or Indeed G2) with this issue? I dont understand if my P1 is broken or is a problem of every P1 owner.. I did research on the internet but it seems i'm the only one with a humming boad...is possible? :/
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Post by tubehead on Nov 28, 2015 15:30:38 GMT
when i made my own 24v linear power supply the humms in both my little bear and bravo audio v1 went away. switching power supply's don't belong in audio IMO.
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Post by Deleted on Nov 28, 2015 20:15:00 GMT
when i made my own 24v linear power supply the humms in both my little bear and bravo audio v1 went away. switching power supply's don't belong in audio IMO.
The problem is not with switching supplies in general, but the cheap Consumer Grade versions. The Professional versions don't have a capacitor between the Primary and secondary sides, which is needed with consumer grade supplies to meet legislated RF/EMI specifications.
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Post by marcello66 on Feb 29, 2016 8:57:47 GMT
when i made my own 24v linear power supply the humms in both my little bear and bravo audio v1 went away. switching power supply's don't belong in audio IMO. I changed the power supply and now I have less noise ... but it's still perfectly audible. Could you suggest me the scheme / project that you used for your power supply? Thanks in advance
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Post by marcello66 on Mar 4, 2016 9:46:14 GMT
Dear friends, im sorry again... im a newbie and i know. Im searching infos for a 24V2A linear psu project... But is so difficult ... Anyone can share a link to a easy project or a link to web store when i can buy this psu? Tnx im advance
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Post by Deleted on Mar 4, 2016 10:21:45 GMT
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Post by marcello66 on Mar 4, 2016 12:31:32 GMT
Alex.... i thank you very very much
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Post by marcello66 on Mar 5, 2016 0:46:00 GMT
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Post by pointer11 on Feb 19, 2017 20:47:08 GMT
Just receive mine little bear p1, and it is very noisy. I tried to power it from battery power, and it did not change nothing. It is giving high frequency noise in background at constant level. If I move the amp around at some moments noise gets lower, at some points higher. If I put the board in metallic box, then it gets bit lower, but still hear the hiss noise.
Any ideas what could be faulty?
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Post by pointer11 on Feb 25, 2017 12:20:54 GMT
And seems that right channel is much more noisy that left channel...
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Post by PinkFloyd on Feb 25, 2017 13:40:02 GMT
Hi Pointer,
Sounds like radio frequency interference to me and or poor grounding. These open frame amps are susceptible to all sorts of nasties as they are not shielded and it can sometimes be quite difficult to remedy the interference. Switched mode power supplies can radiate quite a lot of noise so try turning off the rest of your equipment (one by one) and see if the noise stops. The imbalance in volume could be down to a poorly matched potentiometer or even a poorly biased tube (valve). My advice is to send it back, along with a list of the problems, and insist they supply you with one which is working properly.
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Post by fertom on Nov 8, 2017 19:04:03 GMT
Ye it is only ground problem it is not good enough
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