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hackernap advice thread

Lucaslucas

just a brand new second hand
Couple of questions to start this off.
As always, appreciate the help - it is certainly not taken for granted.

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I have some 10uH inductors that are rated to 5a, but my transformer has secondaries of (<) 5a. I already have 1mm insulated wire if diy inductors are the best option.

Also, with the inductor at L1/R25, from BM 1.2: "It should
measure as a dead short: zero Ohms
" - well mine are reading 1.1 & 0.9 ohms.
 
Hi Lucas,

I've got what calls itself BOM 1.6 and this has L1 as 20 inches of 16AWG enamelled wire coiled round a quarter inch drill bit. This should be near enough to zero resistance. Did you use enamelled wire and if so did you remove the enamel at each end when terminating until you got shiny copper?

That said it is likely that your meter is struggling to measure low resistances, both of mine do. Some meters use a constant current source of milliamps and drive this across the resistor under test, measuring and converting the resulting voltage to give a resistance reading. If your meter is using a 1mA current and the true resistance is 0.1 ohm say, it will be trying to measure a developed voltage of 0.0001 volts. That's difficult for a meter to measure.

If you have any other perhaps thinner wire of about the same length lying around try measuring that and see what you get. I'm willing to bet the meter measuring range bottoms out at just under a volt for any low resistance you measure. The variation you are getting between the two of 0.2 ohms might just be the tarnishing and contact resistance of the probes.

The other comforting thing is that you are not getting a value of 15 ohms, which would obviously indicate a duff connection to the inductor wire at one end of the composite component.

It is much harder to check and diagnose things like this after you have built the whole unit up so keep up the double checking as you go!
 
I'm using 12uH 4a inductors in my recent build and it's been running without problems for a few weeks now. I believe the current rating on the transformer is the maximum safe current it can supply if required. In practice it's unlikely the hackernap will draw a full 5a. Your inductors should be fine.

I agree with John on the L1/R25.

Col.
 
I guess the requirement for 20 inches of wire may be where the issue lies, as I have used 16 inches as per the build manual. Didn't notice the difference on the BOM but I did feel the wire was a little short. Plenty of wire left, so I will try it with one and see if it makes a change and report back.

And also, my multimeter is just a bog standard one so probably does suffer from the issue you describe. Interesting to consider the limitations of the test equipment in these things.
 
Its good to hear that, especially because I noticed your build thread a few weeks ago and am kind of following in a similar vein, which includes using the HN9 transformer from Canterbury Windings.

I'm using 12uH 4a inductors in my recent build and it's been running without problems for a few weeks now. I believe the current rating on the transformer is the maximum safe current it can supply if required. In practice it's unlikely the hackernap will draw a full 5a. Your inductors should be fine.

I agree with John on the L1/R25.

Col.
 
Well done for starting this thread Mr Lucas. I suspect it'll be a long one!
 
At the risk of redundancy, the most up-to-date "official" documentation can always be found here: http://www.box.net/shared/jnasoijb2gg7mopasbuo

With regard to the L1 inductor, the BOM (v1.6) does indeed say 20 inches of enameled wire wrapped 16 times around a 1/4" cylinder such as a drill bit. 15 wraps or 17 wraps ain't gonna kill it!

If your hand-wound L1 inductor reads as anything other than a dead short (or perhaps a tiny resistance in milli-ohms if you've got a super-accurate DVM) then there's something very wrong. Of course you should be measuring the inductor out of circuit on its own.

For the PSU inductors (output stage) you'll want as low a DCR as you can find. The 10uH inductors in the BOM have a very low resistance and are ideal.

For the PSU resistors (front-end) you'll probably want larger values than those in the v1.6 BOM. Instead of 4R7 go for 10R or even 47R. It's just a little icing on the top is all, no sweat if you already have 4R7. It just adds a bit more filtering.

Cheers,
Carl
 
I would like to post another question about DC offset.

Currently there is the first of four hackernap modules running on a testbench into the recommended crappy old speaker.
The DC offset startet at about 21 mV and is now, after after a few hours of music at 27 mV. So, it doesnt get better. I guess, it should be fine for now, but I am a little bit concerned about the long term stability of the module.
What can one do to reduce the DC offset to a lower value if, for example, the offset is above 50 mV, or to just get the lowest value possible?
 
You can adjust the DC offset by changing R15, the emitter resistor for TR3. I just did this with success on a NAPA board where the recommended range for the equivalent of R15 is between 560 & 680. The desired offset is less than 40mV.
 
Of course you should be measuring the inductor out of circuit on its own.

Ah, well I didn't do this. I followed instructions in the build manual which say solder, then the inductor and resistor should both measure 0 across (p8). Is that incorrect then or am I misunderstanding?


..................
Quick update, I think as John suggested the answer is that, after testing it on various things (at 0.5 ohms, including itself), my multimeter is crap.
 
Ah yes well, if you go around believing everything I wrote in the build manual you're gonna get yourself in trouble! :D

Perhaps I should ammend the manual... There's a thought: please let me know of any suggestions for build manual improvements. I'll incorporate everything I can and keep the most recent edition available on the web page.

Cheers,
Carl
 
Perhaps I should ammend the manual... There's a thought: please let me know of any suggestions for build manual improvements. I'll incorporate everything I can and keep the most recent edition available on the web page.

Cheers,
Carl

Hi Carl
Could I send you a copy of the BOM which I have amended in a few places, and included some part numbers, which can be uploaded to Mouser making ordering easy.

BTW, I have a Mono HackerNAP fresh in my system, driving a Brik and staying nice and cool. I now need to box up his brother.
Many thanks for this design.
Paul

6293059098_e5f5cac704.jpg
[/url]
IMG_0388 by paul31154, on Flickr[/img]
 
I like the R Cores Paul. How do they sound??
John
Hi John
I need to get the 2nd boxed up to have a proper listen, and compare with my NC200s with AST transformer.

How are your HNAPs coming along?

Thanks again for your help setting up the VBE s
 
A few of us (well me at least) found tr4 and tr6 / ztx's a bit confusing as they have the writing on the opposite side to most transistors. Looking back at a previous thread here, cobo did a useful little combination graphic to show which way they go round. May be good to include, if its available.


Perhaps I should ammend the manual...
 
Loving those monoblocks Paul. Very nice!

The image for tr4/tr6 is still in my flickr page. Anyone who wants to use it is more than welcome.

Here it is.



If I can help anyone out with pics of sections of the boards just let me know and I'll do my best while the top's still of my case.

Col.
 
I was unsure what heat sink to fit to my Mono HackerNAPs, if any, as many seem to rely on the enclosure for cooling, a la Naim.

In the end I bolted the output transistors to the rear panel, and 1 C/w heat sink on the outside.

It seems I made the right move, as while listening at increasingly high volumes, 11 - 12 o'clock on my B4, the heat sinks became very hot to the touch. I'll repeat this and measure the temps, after I've retested the bias etc.

They do sound nice, especially when turned up. Very clear bass, extending much longer and deeper than I've heard before. More space around instruments and vocals, helped by the very quiet background.

System - MacMini, SSD, Amarra, Young, B4, 2x HackerNAPs, Isobariks

Thanks again Hacker
 
Hi, Paul

Its best to bolt your transistors directly to the heatsink, unless your heatsink is in very good contact, which is difficult to do, the transistors will be a lot hotter than the heat sink.
Mine are bolted to a thick L shaped extrusion which I laped flat and bolted with heatsink compound to the heatsink.

Pete
 
Hi Pete
I'll get them warmed up again and check the relative temps with the infrared thermometer I've just borrowed.
 


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