Deleted
Deleted Member
Posts: 0
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Post by Deleted on Jul 17, 2014 19:28:31 GMT
could someone please remind me what the noise issue sounded like? have not used my panda since my Ember arrived and was wondering if i could now hear the problem. cheers
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dicky
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Post by dicky on Jul 17, 2014 19:32:23 GMT
It's a very low level mains hum. I had it on 2 Pandas but only on the right channel.
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Rabbit
Administrator
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Post by Rabbit on Jul 17, 2014 19:41:24 GMT
I also only got the hum on one side. It was way more obvious with a Senn hd650. AKG headphones didn't pick it out so easily. It's very low level but once you know it's there, you can't help but focus on it.
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juke
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Post by juke on Jul 17, 2014 21:57:53 GMT
for 50k 2.2uF or 3.3uF coupling caps will be O.K. in case someone needs them. Good to know Frans, thanks. Syd
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juke
very active
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Post by juke on Jul 17, 2014 22:01:58 GMT
It's a very low level mains hum. I had it on 2 Pandas but only on the right channel. I can't recall which channel I got it on but the tiny hum I'm getting now is near full volume on the left channel. It would never become apparent unless you were listening for it. When it was originally present it was down the other end back then and I heard it right away. I'd use the Panda happily now. Syd
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Post by imstimpy on Sept 22, 2014 21:55:11 GMT
Aside from a bit of scratching on the volpot, the only garbage I have seems to come from my toroid. This noise isn't audible until deep into the volpot- far past usable volumes.
I have a shielded toroid from Primrose but it is definitely putting some EMI into the input lines. It is really unfortunate that the input runs right past the toroid in this design. Lifting the toroid from the chassis seems to dramatically change noise on the line. Perhaps dicky was onto something when he built a separate chassis for his dual power supplies.
My Panda has a few optimizations, so it isn't exactly an apples to apples comparison.
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oldson
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Post by oldson on Sept 27, 2014 18:13:49 GMT
i wish someone could try my panda , cos i hear diddly squat!
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Rabbit
Administrator
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Post by Rabbit on Sept 27, 2014 18:18:24 GMT
I noticed it much more with Senn hd650. AKG K701 barely picked it up. So I think it's also dependent on which headphone you use. It's very low level and the house needs to be quiet to hear it. The easiest way is to listen and switch off. You become aware that a noise has gone, but it is extremely low level. Once you know it's there, your mind kind of focuses on it!!
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oldson
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Post by oldson on Sept 27, 2014 18:37:23 GMT
I noticed it much more with Senn hd650. AKG K701 barely picked it up. So I think it's also dependent on which headphone you use. It's very low level and the house needs to be quiet to hear it. The easiest way is to listen and switch off. You become aware that a noise has gone, but it is extremely low level. Once you know it's there, your mind kind of focuses on it!! maybe the lcd2 is not sensitive enough? (or my lugs ) i have been listening for a fair while now and hear absolutely nothing. i have noticed the mids seem really recessed compared to Ember, which i have just switched back to. the Ember just sounds so much better.
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solderdude
Administrator
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Post by solderdude on Sept 27, 2014 18:42:45 GMT
The LCD-2 isn't very efficient so a very faint hum that may be audible with some headphones may not be audible at all on the LCD2 and stays buried below your hearing threshold.
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Rabbit
Administrator
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Post by Rabbit on Sept 27, 2014 18:55:28 GMT
I noticed it much more with Senn hd650. AKG K701 barely picked it up. So I think it's also dependent on which headphone you use. It's very low level and the house needs to be quiet to hear it. The easiest way is to listen and switch off. You become aware that a noise has gone, but it is extremely low level. Once you know it's there, your mind kind of focuses on it!! maybe the lcd2 is not sensitive enough? (or my lugs ) i have been listening for a fair while now and hear absolutely nothing. i have noticed the mids seem really recessed compared to Ember, which i have just switched back to. the Ember just sounds so much better. I much prefer the Ember too. It has more authority and a real 'meaty' sound!! It may well be to do with the sensitivity of the lcd2. I am very sensitive to low level noises though and almost old about it though.
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oldson
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Post by oldson on Sept 27, 2014 20:07:52 GMT
i guess comparing Ember v Panda is a little unfair, chalk and cheese. we should all buy a Polaris for comparison with the panda.
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Post by blackeyeliner on Jun 21, 2015 18:11:39 GMT
Hello everyone! Just spent a LOT of time hunting the source of this bug. Do ALL pandas hum like this? I just ordered a new one because I was thinking I damaged it. Worth cancelling the order?
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Rabbit
Administrator
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Post by Rabbit on Jun 21, 2015 18:46:32 GMT
Hi Blackeyeliner. I'm afraid that there is some kind of problem with many of them that does seem to cause a very low level hum. Mine did it, although it was much more noticeable on the Senn hd650 than the K701. Knowing that the Senn has a hump in the top of the bass area, that's likely where it is. In the end, I gave up with mine and it went for something quieter.
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solderdude
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Post by solderdude on Jun 21, 2015 19:02:26 GMT
If you really want to keep using the Panda then you could try feeding it with a DC input voltage. It seems more Pandas have this, so another PCB may not be a solution. I suspect that there is some incorrect trace routing on the PCB where AC voltages creep where they should not. IF you have an external power supply at your disposal you could feed it with that and see if the problem is gone. I had a PCB for repairs a while back and as there was only a PCB I used a lab supply to feed it. Not seen any hum (but didn't really check for it either) A disadvantage of using a DC power supply is that the input protection circuit doesn't switch off when the power switch is flipped. Possibly there is a solution for that, certainly when you make an extarnal power supply yourself (trafo + bridge rect + smoothing caps). No guarantees though that feeding is from a DC source will eleminate the hum... it's just an (educated) hunch.
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