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I'm building my son his first amplifier and I'd be grateful for some advice

From the HackerNap manual
20 inches of 16AWG enamelled wire coiled round a quarter inch drill bit
 
Jon Dennis said:
Thanks Alan. That looks pretty straight forward, I think. The wire needs to be coated with some sort of insulator, I guess, is that a diy job or does it come ready coated ? Is it plastic coated or something else ?
Thanks,
Bo
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Its Magnet wire coated with enamel its used for transformers, inductors, electro magnets etc.
https://uk.rs-online.com/web/p/copper-wire/7790713/

You dont have to molest your Napa board to add this and the resistor to the output


Alan
 
booja30 said:
Then I'd wait for the Nelson Pass ACA (Amp Camp Amp) to be in stock again and build that: https://diyaudiostore.com/products/amp-camp-amp-kit?variant=7072933085218
They are estimating it will be available again in April.
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I've heard the Amp Camp Amp. It runs out of steam pretty quickly unless you're running it into horns. And when it runs out of steam, it sounds like a Fender Champ-Amp.

v1eeqoqrf9lmbsuyysdk.jpg
 
mega lord said:
Hi Jon,

No they go in series with the +ve. The naim board will have a 0R22 resistor on the output. That will need removing. The zobel network is what goes to ground (resistor and cap in series). The naim board will already have that (from memory).

If you want the coils i have then PM me your address ( i assume you are in the uk) and i will remove them from the Cambridge audio amp and send you them. If you want to make your own then no worries. There is a certain satisfaction gained from making such things yourself. Enjoy.
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Hi , thanks for the clarification :oops: and the extra info. And thanks again for the kind offer but there's no need to molest your Cambridge amp, I've just ordered a roll of suitable wire and am looking forward to making my first inductor.
Cheers,
Bo
 
Yank said:
I think something like this might be a good starting point:

https://www.lundahltransformers.com/old-fasioned-30w-push-pull-amplifier/

It's essentially the Mullard 5-20, which many hobbyists built in the 1950s.

Unless you need a phono stage, it probably doesn't need further preamplification with line-level sources. Put two channels in one chassis, hang a volume control and selector switch on the front, and call it a day.
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That's great, thanks, I'll have a good look at that.
Cheers,
Jon
 
They don't really fit the brief anyway, but as the ACAs only manage 10-12 Watts, I run a bridged pair. Twice the power with less distortion.

Since I needed the 'bedroom' amp downstairs, the ACAs took its place and I have to say the old Audiolab tuner and Micro Utopias have suddenly come alive.

I'd recommend them (with a couple of component upgrades) on that basis alone, but the absence of any mains voltage makes them an ideal first build, imo.
 
I'm sure I read that the way they're hooked up most of the harmonics cancel, but then not everything you see on t'internet is necessarily so...

Minimalist Class A still sounds good to me, either way.
 
I'm going to need a chassis for this amplifier... does anyone have any recommendations for suppliers of decent looking but not too expensive chassis ? It doesn't need to be massive or sporting banks of heatsinking fins, just a reasonably presentable metal box.

Also, in coming up with a layout for the various components of this amplifier are there any 'real no-no's that I should be aware of ? Any 'inadvisables' ? More positively, any 'real good idea's ?

Something that's on my mind is the wiring loom. I assume that I should be trying to keep the wires carrying DC away from the wires carrying AC as far as I can, and ditto the signal wires from the input sockets to the pre amp section. Are there any other considerations around this ?

Another thing that's on my mind is the earthing design. What I've picked up from various discussions is that there should be a single point of earthing in a pre amp and a single point of earthing in a power amp. What I'm not sure about is whether a single point of earthing holds true for an integrated amp, which is what I'm going to be building. I suspect that, in fact, there should be a single point of earthing in relation to the power supply and a separate one relating to the signal path. This is a guess, though, and I'd be grateful for some wise counsel.

Thanks for all the input so far, you've been a real help already.

Cheers,
Bo
 
One trick - buy an old style amp from ebay or wherever. Gut the innards and use the case, power input, switches, knobs and so on. All the cutting and drilling is done for you!
And it will look professional - you could always put a film or coating on the front ot disguise it if you must.

Much safer too... with things like fuse holders aready in place.
 
JensenHealey said:
One trick - buy an old style amp from ebay or wherever. Gut the innards and use the case, power input, switches, knobs and so on. All the cutting and drilling is done for you!
And it will look professional - you could always put a film or coating on the front ot disguise it if you must.

Much safer too... with things like fuse holders aready in place.
Click to expand...
Good idea, thanks. I'll have a shufti on EBay.
Cheers,
Bo
 
Hifisonix have a lot of information about earthing in a document about ground loops.
You might also have a look at Rod Elliott’s pages about audio by googling Elliott Sound Products.
Cheers Andy.
 
Yank said:
INSULATED solid core wire - magnet wire!
Click to expand...

If you're lazy you can use ordinary insulated signal wire. Find a cheap biro or similar, cut a length, wind the wire onto that. Then wrap with tape to keep it in place.

Alt: if the power levels aren't going to be high, wrap the wire around the resistor. Then solder the ends onto the resistor leads so the coil can't unwind or fall off. That should work fine provided the resistor doesn't get too hot an melt the insulation. (Note the resistors *shouldn't* get hot because the audio should all go though the wire! :) )
 
andrewsutton said:
Hifisonix have a lot of information about earthing in a document about ground loops.
You might also have a look at Rod Elliott’s pages about audio by googling Elliott Sound Products.
Cheers Andy.
Click to expand...
Thanks, Andy, I'll do that. There's some interesting papers on the MIT website on this too.
Cheers,
Bo
 
Jon Dennis said:
That would be very kind, thank you. Can I just check, I assume that these components would be connected between the output +ve and -ve lines ?
Thanks again.
Bo
Click to expand...

Just to be safe I'm going to assume the worst and proceed under the assumption that you mean +ve and -ve to be the +40V and -40V power rails (which is normally what +ve/-ve would refer to). Placing the inductor//resistor across those would effectively put a short across the power rails because the inductor//resistor has effectively zero impedance. Please don't do this! At best you'll blow a fuse, at worst...

The inductor//resistor combo should replace the existing 0R22 wirewound resistor between the output of the amplifier and the + speaker terminal, in line with the output signal. In other words, the amp drives the speaker through the inductor//resistor instead of through the 0R22. Installing it will probably be a bit of a hack on a Naim PCB because there's not much room for it. HackerNAPs and Avondale amps have space on the PCB for it, making the job quick, easy, tidy, and reliable.

The inductor//resistor combo is typically built by fitting the resistor inside the inductor coil. This page shows how I did it for the HackerNAP amp (which is a derivative/mash-up of the Naim power amp, Avondale power amps, and Acoustica modifications): https://www.pinkfishmedia.net/forum/threads/building-a-hackernap.124486/

Good luck!
 
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