I think some level of faint hum is acceptable. I found the answer in a Naim forum.
NAP 200 Humming | Naim Audio Forums
Are you talking about hum from the amplifier box or hum from the speaker? Hum from the speaker may not be a big problem but it really shouldn't be there. What is the amp that is humming...presumably a clone of a Naim as you are asking in this thread?
A few things (not everything) that can cause speaker hum are:
- bad grounding arrangements
- inputs/input cables too close to the transformer
- an unstable or pseudo-stable circuit
- machinery or other equipment near the amp thats emitting loads of electrical noise.
- the device plugged in to the inputs (so disconnect it)
- a circuit with poor PSRR
- something wrong with your dc power supply(ies)
A few things (not everything) that can cause speaker hum are:
- bad grounding arrangements
- inputs/input cables too close to the transformer
- an unstable or pseudo-stable circuit
- machinery or other equipment near the amp thats emitting loads of electrical noise.
- the device plugged in to the inputs (so disconnect it)
- a circuit with poor PSRR
- something wrong with your dc power supply(ies)
Member
Joined 2009
Paid Member
"Naim (and other high-end hi-fi manufacturers) do not use near silent transformers because they produce inferior sound.
I am accurate in what I state.
Engelbert"
😱
Gareth, you really shouldn't go in to the Naim forum. Not on your own. It is not safe.
Last edited:
if you can hear hum through normal sensitivity speaker/s then you have too much hum.
Measure it using a DMM set to 199.9mVac and also meausre output offset using 199.9mVdc
If you get 0.0mVac and 0.0mVdc then effectively you have no hum + noise and no offset.
If you get 0.1mVac to 0.3mVac then you are at the lower end of what is acceptable with normal speakers. High sensitivity speakers need a lower level.
Offset can probably be <10mVdc to cause no concern. Some suggest that <100mVdc is acceptable, but I don't agree.
gents as i point my clones do hum 8mv when first on and you can hear it however 1 hr down the road just 0.1mv may be right at the bottom of my fluke 177 and have never found why Naim seem to be bad for picking up hum hand held radios as well vhf uhf not cells to hi
The reason is not too hard to see when you compare the basic 1970 NAP design to more recent ones with features like better input filtering, supply decoupling, output coil etc.
Most simple designs have similar problems because they don't have adequate filtering for today either. In a quiet environment, away from the mess of switchmode power supplies and wireless interlinks, they can all sound just fine but remember that's not the world most of us now live in and our expectations will be higher than is possible with most old equipment.
Since RFI and EMI are massive issues than that scarcely existed in homes of 40 years ago, it's not surprising that Naim's newer series designs have better PSRR and RFI filtering than the NAP series. In reality, the NAP series is now quaint history, not state of the art design and you need to get used to what you are dealing with. It would be nice to think that we can fix the old designs by just adding on noise filtering features but that generally degrades sound quality and takes us away from our goal of simplicity and wonderful sound quality. Don't think that many haven't already tried to do this though 😉
after week or so messing around, to start with bog std h140 kit tested all the parts and tested well all the R with in 1 % caps the same as well the only thing that was not std drivers not tip but MJE in put pair bc550 hfe 600 off set 50mv, 27k to 24k base to ground input 48mv, next changed in put pair tr1 hfe 600 and tr2 hfe 550 bit better 40mv, comment not very stable bais did not want to be satble set 36ma turn back on 12 hrs later 28ma re adjust never the same off set 40 mv, next change c2705-a1145 for ztx753-653 my my thats beter off set 0-3 mv bais now very stable and the same each time turn on, note note the wind got up during the day and the off set did wander around some what mmm coverd the amp with a box and back stable once more now i understand full enclosed enclosure, note the amp likes an enclosure temp 35 deg time to listen speaker JBL control1 and laptop, one point after an hour wound up a bit off set still 0-2 mv however bais up to 65mv mmm not good let it stand and it did come back down, coments please no hum at all mind uesing r core transformer all my pre amps x overs now use r core transformers and sounds so much better, mains filters for get
messing around with caps input was 10uf bp, tested with mmk 3.3 and 10uf not bad however 10uf bc128 is the best so far, feed back 47uf mmk 47uf cs-con and 68uf taint and the 68uf taint for me gave the best so far, vbe baising mmk 47uf 68uf taint and 47uf os-con gave the best to date. one point i noticed v drop over the 330ohm that feed the first two stages is not not the same for +- lines - 4.09 + 3.58 bit strange not sure why. i note avonedale use 220 ohm and naim do not at all over the next few days will have a play to what works
Perhaps you are getting confused. MMK refers to metallized polyester film caps, similar to MKT and these are only available up to a few microfarads before they get large and expensive.
Last edited:
Ian evox mmk yes you are right big and expensive, the input you can just get on the board however the rest are on flying leads not allways the best, just changed out 330 ohm for 220 ohm and the amp is a lot more stable both off set ( 0mv well +- 0.3 mv) and bais is stable after 30 mins rather an hour plus
So, my Naim ))
TaoBao tweaks:
now I think what to make the case
TaoBao tweaks:
now I think what to make the case
Attachments
Last edited by a moderator:
nice vovans, please keep everything original😀
How is the preamp sounding ? Can you listen to it via headphones ?
How is the preamp sounding ? Can you listen to it via headphones ?
Last edited:
please explain your phrase "please keep everything original". I'm sorry, I do not know much English.
No headphones are not listening. I wanted to try, but I forgot. All together sounds great, I really like! Without preamplifier not tried
Last edited:
He means keep everything original by using the same kind of capacitors and resistors, the same values, etc etc. This is because Naim amps are already designed with the kind of components to get that specific Naim sound. If we choose different kinds of components or values to "upgrade" it, it will not be original Naim sound (or close to) anymore.
BTW, you mentioned Taobao. I always go there to look for chassis. I don't know how to speak/write chinese so I write 'chassis' and 'aluminum' in Google translate but Taobao always shows everything else. Ha ha.
Can you help me with words to search for a chassis to build amps in Taobao?
Thank you very much!
penmarker
Thats right... just keep as it was engineered by group of professionals and dedicated ppl with knowledge and most right equipment.
I myself, preparing a new speaker set:
http://www.eminence.com/pdf/Beta_10CX.pdf
http://www.eminence.com/pdf/ASD1001S.pdf
Case is 60-70L, filter schmetic avaible but still considering the components...
I have listened to eminence kappa 15a on a karlson type case... lol... it needs only 0.1W power to get to everyday music listening experience... now imagine how we felt when we pushed PA amp to its limits XD
https://www.thomann.de/pics/bdb/125630/10830666_800.jpg
It will look like full range, but actually with two elements, tweeters screwed to the magnet of a bass-mid range speaker.
Thats right... just keep as it was engineered by group of professionals and dedicated ppl with knowledge and most right equipment.
I myself, preparing a new speaker set:
http://www.eminence.com/pdf/Beta_10CX.pdf
http://www.eminence.com/pdf/ASD1001S.pdf
Case is 60-70L, filter schmetic avaible but still considering the components...
I have listened to eminence kappa 15a on a karlson type case... lol... it needs only 0.1W power to get to everyday music listening experience... now imagine how we felt when we pushed PA amp to its limits XD
https://www.thomann.de/pics/bdb/125630/10830666_800.jpg
It will look like full range, but actually with two elements, tweeters screwed to the magnet of a bass-mid range speaker.
Last edited:
10uF tantalum are usually less than 15V
100uF is probably somewhere around 5V.
Anything higher will be specials.
100uF is probably somewhere around 5V.
Anything higher will be specials.