hypex ncore

[tiki]

Hello Bruno,
of course, I'll do that when my son will be back in his rehearsal room.
Thanks!
Cheers, Timo

[mr_push_pull]

some people go to lengths to minimize vibrations and my guess is that at a woofer's magnet those aren't quite negligible...

[StigErik]

Currently I'm using a 15 dB L-pad at the input of the Ncore module. Is it possible to lower the gain in the same way as with the UcD modules ? If so - how?

[Bruno Putzeys]

Originally Posted by StigErik

Currently I'm using a 15 dB L-pad at the input of the Ncore module. Is it possible to lower the gain in the same way as with the UcD modules ? If so - how?

Not much has changed since http://www.hypex.nl/docs/appnotes/gain_appnote.pdf

Gain is 4.17*(1+2*Rf/Rg). Rg=1.2k, Rf=2.2k. Rg, as noted in the bugs section of the data sheet is not marked (will be in the future), but it's called R141 and it's the one furthest to the left of the input connector. The maximum gain reduction you can get is 13.4dB, which is when you remove R141 altogether.

[roscoeiii]

Assuming of course that there is enough gain to adequately drive one's speakers is there any advantage to higher or lower gain for the ncore modules? For example, would anything sonically be sacrificed by lowering the gain to get a more fine grained volume control?

[Bruno Putzeys]

The amp certainly isn't going to get worse if you decrease gain (other than SNR it's not going to get better either).

[StigErik]

SNR is largely determined by the source I would guess.... thats one of the reasons I use that L-pad.

Ok, then I will remove R141 and end up with 25.8 - 13.4 = 12.4 dB gain. Nice.

[StigErik]

Ok, R141 removed with success, although SMD is difficult for us who have a solder iron the size of a sledgehammer.... how about let R141 be a regular through-hole resistor to make a bit more user-friendly?

[Bruno Putzeys]

I've got 2 reasons not to.
1) Have you ever removed a leaded resistor from a 4-layer board? Are you sure it's easier than SMD?
2) It wreaks havoc with the magnetic sensitivity (or lack of it). Because of the fairly enormous currents running close by the whole layout is done differentially with minimal loop area. A leaded resistor would introduce almost as much loop area as all the rest. The change in distortion would be clearly measurable.

It's not that hard anyway. I usually have a 3mm wide tip on my soldering iron unless I need to do a lot of smd. Put a dollop of solder on either end of the part you want to remove. Then either heat both ends at the same time by holding the tip along the part and touching both solder droplets at once or alternately heat the ends until the part comes off. It'll stick to the iron so wipe it off straight away so you can keep it. Then clean off the excess solder with wick (strong preference for the "chemtronics soder wick" brand, the rest is rubbish) and finally remove the flux with a tissue and acetone. It'll look like the part has never been there.

[StigErik]

1) I have, its fairly easy using a solder pump. The solder points are usually bigger as well, easier to hit with a big solder iron and my somewhat shaky hands... but there is always a risk of damaging the PCB.

2) Whow...


Thanks for your tip on how to remove SMD parts. I'll try that next time!