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KSA-5 inspired amplifier builds


AlexS

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  • 2 weeks later...

Pretty much on hold until the middle of February. The delivery for the case is delayed and I want to make sure that everything will fit before continuing with ordering the PSUs. The manufacturer has problems with their supply chain for the heatsinks...

I will post an update as soon as I receive the case!

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  • 2 months later...

Hello everyone,

it's been a while... busy life, covid, work, supply chains, mouser, jlcpcb, etc...

Anyway - the power supplies are finally done and tested: +21,04V and 21,01V. Transformer is a dual 22V/50VA.

The rectified and smoothed voltage to the 7812 and 7912 are at +/- 36V DC, that's a hair too much. Hopefully that will drop a little when the amplifiers are connected. That's the next step.

Cheerio!

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Hey Pars, these are Mill-Max p/n 4275-0-00-80-00-00-08-0. There are different sizes available. For bigger holes check Mill-Max p/n 4357-0-00-15-00-00-03-0, take a look at the catalog, there lots of options.

Something like this will cut you perfect right angles, cost around $20 or so. You can then make a wooden base for it (attach instead of the black plastic parts) and clamp it to a table to make it rock solid.

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Edited by audiostar
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For cutting small things I have this cute saw:

https://www.proxxon.com/en/micromot/27160.php

The soldering pins I source from a German distributor... similar things should be available everywhere:

https://www.reichelt.de/de/en/soldering-pins-1-mm-pack-of-100-rtm-1-100-p15321.html

The corresponding lugs are these here:

https://www.reichelt.de/de/en/solder-lugs-1-mm-tin-plated-pack-of-100-vt-rf-1-100-p231422.html

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First testdrive with amps and psus hacked together. Works fine! Input voltage for the 78/7912 dropped to 31V DC. That's great!

Did a few hours of listening - no flaws to be heard. Had some great fun there and quite forgot that I was testing a new amp!

A tiny bit of 50Hz mains voltage hum to be heard, but that's probably because of no shielding at the moment.

Next: integrate the headphone protection board...

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2 hours ago, AlexS said:

Next: integrate the headphone protection board...

Where would you put that, there is virtually no space left inside the box 🙂

Everything looks very nice so far, congratulations. 

Btw, I am using the same WAGO connectors, they very handy for quickly connecting multiple wires together during tests. Can even put 2mm test leads inside. 

Edited by audiostar
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spacer.pngAfter having double checked that the input voltages to the 78/7912 are within limits (max 35V)... measured 31V, I added the remaining 7812 and 7912 to generate the supply voltages for the protection circuit.

And modified my prototype so that it no longer needs a individual power supply.

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The audio 50Hz humm also went away after I no longer crossed the audio input lines with the 230V power cord!! :D

 

Edited by AlexS
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  • 2 weeks later...

Easter update... a friend of mine has a 3D-Printer:

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And this is what those parts are for:

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There will be an additional PCB mounted on top of the volume pot that will also serve as wiring distribution and protection circuit. I will only need tapped holes to the heatsinks, all PCBs are otherwise held in place by the plastic spacers.

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  • 5 months later...

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