simple latfet hpa

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ed
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#1 simple latfet hpa

Post by ed »

It lives!

I’ve mentioned this in a couple of different threads. Not sure whether it should be in solid state instead, but does it matter.

As mentioned before it’s a latfet(Exicon), source follower, active loaded with a v.reg. Super basic. I wanted it because the Topping doesn’t have a headphone out, and thought it might be a good excuse to use it for my first attempt at PCBs. A bit of a gamble as I didn’t breadboard it but just trusted the spice results. In reality it tests ok with the scope and sig gen.
hpa front1.jpg
hpa lhs1.jpg
The heat sinks are a complete overkill, but I had them in the box, and they were only a fiver for the pair so no more extravagant than a couple of board mounted sinks. The ali panels I cut out of a 400mm x 300mm sheet which was also £5 from ebay. So all in all it's the usual cheapskate project from me. Fingers crossed that it sounds ok, and as good as the testing suggests.
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pre65
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#2 Re: simple latfet hpa

Post by pre65 »

Well done Ed, nice to see a DIY project.
Life is what happens to you while you're busy making other plans. John Lennon

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#3 Re: simple latfet hpa

Post by Nick »

a good excuse to use it for my first attempt at PCB
Finding out how easy it is was a real breakthrough for me. Its so simple now once you get your head around the toolchain.
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#4 Re: simple latfet hpa

Post by ed »

I have to admit it's far more fun than drilling holes in paxolin and bending T&E wire for tracks. I'm creeping up on some TSSOP and 32 pin pdip now. The muses/DA6116 remote preamp now looks a bit more inviting.
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#5 Re: simple latfet hpa

Post by Nick »

Yep, I did have a stencil (for applying solder paste) made for one thing I build, but not tried using it yet.
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#6 Re: simple latfet hpa

Post by ed »

just had the first long listen after getting the wiring done...and chasing a faulty lm317..very frustrating....One channel worked with a faulty lm317 but the exicon got very hot, very quickly...quite an education tracking that down in such a simple circuit.

It's extremely musical, maybe a tad bright, but I can deffo hear things I've never heard before. It's early days for sure but every indication is that it's a keeper, and I can honestly say that it reveals lyrics like I've never heard before.

There is a bit of negative material on the interweb, saying that v.regs are not the best active load in an audio circuit...The technicalities are over my head but the reality for me is...I love it!....I may try a bigger version for a main power amp with LM350 and some Hitachi 1058s that I've found in the bit box.
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#7 Re: simple latfet hpa

Post by ed »

I've just managed to get Arta to run under wine with the trusty Behringer dac/interface.
I'm not sure just how accurate these are because I used the internal generator instead of the normal sig gen, but they do look pretty good so far.
hpa-fr.jpg
and
hpa-thd.jpg
a better fr plot
hpa-fr1.jpg
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#8 Re: simple latfet hpa

Post by IslandPink »

Nice work Ed . Anything that gives you more on vocals is likely to be a winner.
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#9 Re: simple latfet hpa

Post by nic »

Look into the Mitsubishi RD16HHF1 . It's an RF lateral TO220 device , very low capacitance so more fragile and lower dissipation than the Exicons , needs a much higher value of gate stopper (470R-1k) and requires around +5V on the gate to bias to 1A . Availability is the main caveat and Ebay is full of fakes but it's a decent sounding device and doesn't need a low impedence source to get the best out f it

cheers

Nic
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