First 3886 Build (multiple questions)

[!]

^ The "qualities" you want in wire aren't necessarily name brand or silver, just able to handle the current and low enough gauge, large enough diameter to be well mated to your PCB output terminals. Since the length is small I don't see a current problem but the terminal looks like it needs a larger wire for a good/long-term grip.

I noticed the electrical connection between the diode pins has no mechanical strength except for the solder itself. It is often recommended that you're not "supposed" to rely on solder alone for that, instead the connecting wire should wrap around the leads or another way is take a small piece of bare wire, like magnet wire, and lash it around them both is if it were rope tying two sticks together... if not a crimp connector.

On the other hand I see it as just a bench testing configuration, if it were a finished amp I'd also worry about the short mains leads to the transformer being not so well inserted into the terminal block strip.

[panson_hk]

yes, short circuit.

Will you use the same wire for connecting supply? What is the current handling capability of the wire?

[CanAm Man]

One comment, probably minor. Typically, it's not good practice to route your mains wires (even twisted ones.....) close to your audio. Do you really need to run your mains "twisted pair" to the same terminal strip you're using for your audio out/in?

[lost eden]

Originally Posted by panson_hk

yes, short circuit.

Right, I shall remove & insulate them.

Originally Posted by panson_hk

Will you use the same wire for connecting supply? What is the current handling capability of the wire?

Probably not. I don't know what the actual current handling is.

One comment, probably minor. Typically, it's not good practice to route your mains wires (even twisted ones.....) close to your audio. Do you really need to run your mains "twisted pair" to the same terminal strip you're using for your audio out/in?

If there is audible interference I could probably just run mains to the 'second' terminal strip. Thanks for the observation.

[panson_hk]

You must do so to avoid short circuit.

You can get hum noise if the AC mains/secondary is too close to the audio, particularly the small signal (input) section. It is also very dangerous that the mains is right next to the speaker output.

[CorySCline]

What software did you use for the 3d rendering?

[lost eden]

I've now got some strip board which I'll put the diodes & filter capacitors on & mount with spacers onto the aluminium. Can anybody tell me from experience whether the MUR860 will need small heatsinks on them for the sort of currents I will be putting through them? I've seen plenty of gainclone builds where they are left without heatsinks, so I presume this is safe?

Originally Posted by CorySCline

What software did you use for the 3d rendering?

It's just Google SketchUp. It's not particularly powerful, but for simple quick stuff like this it's ideal.

[!]

The diodes will not need heatsinks.

[AndrewT]

a To220 diode in a rectifier passing 1Aac on 50% duty cycle will only dissipate @300mW.
2Aac for ~600mW.
Rth s-a of ~5C/W gives Tc ~ Ta+3Cdegrees, when the rectifier is passing 2Aac continuously.

[lost eden]

Finally got around to buying some protoboard/stripboard to mount the diodes & filter capacitors on & got one into an operational state today. Sorry for the bad cellphone photo.



It's hard to do a good comparison with my the class-D TC2000/TK2050 amp, which I've been using for the past few years, until I build the second monoblock, but it certainly sounds quite nice so far from 1 speaker. In particular, there is virtually no hiss whatsoever, even with my ear right up against the speaker's tweeter. Not sure if that's inherent to the LM3886 or just that there is less junk in the signal path than with my class-D amp!