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hackernap advice thread

Did you go down the route of using higher input voltages ? out 40v-fe 45v
which would make for increased heat (..sinking requirements)
 
Lucaslucas said:
Did you go down the route of using higher input voltages ? out 40v-fe 45v
which would make for increased heat (..sinking requirements)
Click to expand...

Yes, I did, in fact my FE is at about 50v, and Output at about 55v. I have no problems at 'normal' listening levels, only when I wind it up. In fact, the sinks feel no higher than room temp, at normal levels.

I'm just glad that I erred on the safe side by fitting the sinks, rather than relying on the enclosure.
 
Paul3 said:
Yes, I did, in fact my FE is at about 50v, and Output at about 55v.
Click to expand...

Those are the wrong way around - you want your front end to have a higher voltage than the output stage.

50VDC for output and 55VDC for the front end are perfect as long as that's DC voltage across the amp's power inputs and not the raw AC from your transformers!

Edit: I use 35-0-35 for the output stage, which gives approximately 50VDC. For the front end I use 40-0-40, which gives a raw 56VDC, which is dropped to about 50 - 51VDC after the amp's on-board VBE.
 
My Canterbury Windings transformer for the stereo HackerNAP turned up yesterday. Cor! What a monster! I'm gonna need a bigger case...

Now the caps are imminent, I've got a few questions about the HackerCAP boards. i've got the two types of Q-speed diodes from the group buy which I've just looked at but they don't appear to be polarised. Is this correct please?

In my hurry to order all the bits and pieces I forgot to order the 10uH 8A ferrite core inductors from Digikey. Is there a substitute I can use for these please, and what resistors go in their place on the other two boards?
 
The diodes will be polarised.. Its what diodes do ;-)

Got a pic of the packaging of them?
 
(Message to self- engage brain before asking silly questions...) Thanks Sam, they're the ones - guess they go the other way round on the negative side?
 
The correct orientation is marked on the boards, each diodes space has a box around it with a thicker line on one of the long sides.. This is where the tab goes.

You should be able to make out in this pic of mine that all diodes are fitted with the same orientation.


HackerNAP Internals by http://www.samcatchesides.com/, on Flickr

Thanks,
Sam
 
Suffolk Tony said:
My Canterbury Windings transformer for the stereo HackerNAP turned up yesterday. Cor! What a monster! I'm gonna need a bigger case...
Click to expand...

Nice! Which one did you go for?

Suffolk Tony said:
In my hurry to order all the bits and pieces I forgot to order the 10uH 8A ferrite core inductors from Digikey. Is there a substitute I can use for these please, and what resistors go in their place on the other two boards?
Click to expand...

To be honest I'm not sure how much difference the inductors make for the HackerNAP's output stage PSU. I've been tempted to replace mine with wire links to see what happens. Using inductors is a trade-off:

Pro: slight reduction in the HF noise into the output stage
Con: slight increase in PSU impedance

A mitigating factor with the HackerNAP is that the heavy filtering of the front-end supply should make the output supply inductors pretty much redundant. I have long suspected (but never measured or done listening tests) that the lower impedance of a non-inductor output stage PSU could actually make a bigger difference to the amp's sound quality because the main thing we want for the output stage is low output impedance.

Anyone care to do some listening tests with a set of wire links vs inductors? Note: this applies to the output stage PSU only!

For the front-end supply, stick with chunky resistors rated to 5 or 6 watts (or more if you like; over-engineering is good!) Almost any resistance in the range 1Ohm - 47Ohms will be fine. More resistance = more noise filtering. I've used 4R7 in mine, but will probably use 47R in my next build.
 
Many thanks for the information Hacker; I'll use wire links in mine. The transformer's an HN5, the same as Cobo used in his HackerNAP.
 
Any body fancy letting me tag onto their component purchase? Since I posted all the boards out I've not found the time to get it done. Now the caps are on the way I really ought to get on with it :)
I had some caps, tranistors and wire for inductors kicking around so don't need everything.

I'm fairly handy at making inductors for the output so am happy to make some extra up for a willing participant.

Ta.

Stefan
 
On the note of inductors.... the wire links I proposed are for the 4 inductors on the output stage HackerCAP *only*. The ones that go between your Kendeils. There are 8 in total on a stereo amplifier.

Do NOT replace the hand-wound output inductor on the HackerNAP amplifier boards with a wire link (2 in total for a stereo amplifier). You run the risk of releasing the magic smoke.

Just want to clear that up ahead of time ;-)
 
OK, I think I need to rebuild my front end supplies. What's the given wisdom for the front end supply? Is it 1000uF / 100V -- 47R /5W -- 1000uF / 100V -- 47R /5W -- 1000uF / 100V? And should the resistors be inductive or non-inductive? Thanks.
 
Wont make any difference for the resistors at those values :) You could use 1/10 the R values and it will still be very quiet.

[And yes, you can safely replace the output inductor on the hackernap board with a link - if it is a 0r1 or 0r22 resistor ;) ]
 
flashgo said:
OK, I think I need to rebuild my front end supplies. What's the given wisdom for the front end supply? Is it 1000uF / 100V -- 47R /5W -- 1000uF / 100V -- 47R /5W -- 1000uF / 100V? And should the resistors be inductive or non-inductive? Thanks.
Click to expand...

Like Martin says, it really doesn't matter too much. I've used 1000uF / 100V caps with 4R7 in a RCRCRC combination using generic rectifier boards. Seeing as we're all using pretty low-power transformers, it's best to keep the capacitance low. But really, with such a stiff RCRCRC followed by FET VBE it just doesn't matter.

Where you might find benefit is to use film capacitors for C9/C11 instead of the currently specced electrolytics. Something like these 2.2uF/63V MMKs should work very well. You'll need a 5mm lead pitch. You could omit C10 and C12 (just don't fit them at all) and put the 2u2 MMKs in C9 and C11 instead of the Panasonic FC electrolytics.

Come to think of it, in addition to C9 and C11 you could actually replace C5, C6, C7, and C8 with the MMKs, too. If you did that you'd completely eliminate all of the electrolytics from the on-board front-end PSU.

The thinking behind this is that the currently-specced large electrolytics in C5,C6,C7,C8,C9,C11 are a hangover from the legacy designs in which front-end supplies are derived from the output stage supplies. In those amps the front-end needs a high degree of isolation from PSU rail disturbances caused by the output stage; the isolation is provided by RC filters using large (100uF or so) capacitors.

The HackerNAP's front-end, on the other hand, has a completely separate PSU and is therefore unaffected by the behaviour of the output stage. My thinking is that having done away with the source of the old problem we can also do away with the old solution! Instead of large electolytics, let's try smaller films.

Oh, I'd drop one of those MMKs into C25, too.

Hrm.... I think I might be whipping the soldering iron out in the coming weeks...

martin clark said:
[And yes, you can safely replace the output inductor on the hackernap board with a link - if it is a 0r1 or 0r22 resistor ;) ]
Click to expand...

Well yes, but then it's not really a wire link any more ;-) Truth be told, if you're using very high inductance speaker cable (why???) you could actually use a wire link!
 
In the belief there is no such thing as a "dumb question", why do the resistors in the front end PSU need to be such a high wattage? If the current draw is tens of milliamps then surely the wattage in a 10ohm resistor is the order of a few milliwatts? Or has my recollection of Ohm's law faded over time?
 
Thanks Joe. I thought it might be something to do with start-up rather than the steady state as it were. Always best to check!
 
Hacker - Very tempted to give those mods a go... My 2nd amp is soldered, casework done but no wiring yet so at the right stage to easily desolder a few components and give it a try.. Easily lets me do an A vs B as well (A being standard BOM build and B being with the above mods)...

Mighty tempted..

Sam
 
BowerHinton said:
In the belief there is no such thing as a "dumb question", why do the resistors in the front end PSU need to be such a high wattage? If the current draw is tens of milliamps then surely the wattage in a 10ohm resistor is the order of a few milliwatts? Or has my recollection of Ohm's law faded over time?
Click to expand...

There's Jo's point, and then there's my inclination to over-engineer. I think I may have 2W or 3W wirewounds in mine. I guess 5W is perhaps going a bit far ;-) Constant power consumption should be way down, even on 47R resistors. I reckon less than 100mW. Even 1W resistors is over-egging it a bit!
 
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