[sachu]

Excellent work..i love the poly carbonate...giving me quite a few ideas for future builds. Look forward to seeing the EHHA take shape.

Be careful when setting up the EHHA boards. I have lost not just the EHHA output mosfets, but sadly the S22 mosfets as well when something goes wrong. The costs can add up real quick. A steady hand and triple checking the boards go a long way in avoiding disaster here.

 

[jjazzyj]

Quote:

Originally Posted by sachu /img/forum/go_quote.gif Excellent work..i love the poly carbonate...giving me quite a few ideas for future builds. Look forward to seeing the EHHA take shape. Be careful when setting up the EHHA boards. I have lost not just the EHHA output mosfets, but sadly the S22 mosfets as well when something goes wrong. The costs can add up real quick. A steady hand and triple checking the boards go a long way in avoiding disaster here.

I've read your misadventures, that's why when I ordered my mosfets I ordered twice as many as I'd need.

 

[jjazzyj]

So I just finished up my S22/12V power supply. Everything tests good, looks like I did a good job. However the LED does not light. Now I ordered a kit from Glass Jar and it came with 2 10kohm resistors for the LED's but according to my calcs that value is too high, it should be 2 1.5kohm resistors. What LED resistors did anyone here use?

 

[johnwmclean]

Quote:

Originally Posted by jjazzyj /img/forum/go_quote.gif So I just finished up my S22/12V power supply.

12V what for? Is the LED orientation right?

 

[jjazzyj]

The 12V is the heater supply for the EHHA. The funny part is my LED tester lights up the LED on the board when I connect it with the same orientation that is on the board. I used an online LED resistor calculator to come up with the 2 1.5kohm value.

 

[johnwmclean]

A σ22 for the heater supply? OMG that’s overkill on steroids

, are you sure you didn’t mean the σ11?

 

[jjazzyj]

You misunderstood me the power supply for the EHHA is the S22 and in the same power supply chassis I also have a 12V power supply. So it is a S22/12V power supply.

 

[johnwmclean]

Good gratuitous, thank goodness for that. hehe.

There’s also a LED calculation on the AMB site, under the σ22 parts list, maybe check that out and see if the both calculations match.
I’ve used 10KΩ resistors for all my σ22 builds all parts were from GJA.

 

[jjazzyj]

I used that calculator just to make sure and it told me for a source voltage of 60V (as the LED sees both voltages and AMB sites says to do so) to use a 2900ohm resistor, hence the 1.5kohm resistor for each rail comment earlier.

 

[sachu]

Agreed, 10k is a bit too much to get the LED to glow well enough on the amp boards..1.5k should be plenty good here.

 

[Horio]

So I am in the process of finalizing my BOM for my MOSFET EHHA build. Question about the R32/R33 2Watt resistors. I am having a hard time finding metal film resistors to fit the bill. As an alternative I thinking of using a 2.2ohm 5% metal oxide resistor, or a 2.0ohm metal film 5% resistor. What would be the affect of using a 2.0ohm resistor anyway? Higher output?

Thanks

 

[sachu]

panasonic Metal oxide 2.2ohm resistors are fine. You could also try going for non-inductive wire wound type from Mills here.
As to using 2 ohm resistors, i think you may have to bias the quiescent current a tad higher to make sure the Mosfets are conducting and operating optimally. If I am missing something else here am sure someone else will chime in.

 

[Horio]

Thanks Sachu!

Another question, on the Cavalli website it shows C8 as polypropylene/polyester film capacitor with a lead spacing of 2.5mm. Was this a typo by any chance? I'm not seeing any 2.5mm L.S. polyester caps and looking at the 3D rendering on the boards page, it looks more like a multilayer ceramic capacitor.

 

[sachu]

Am sure you could make do with just a MLCC cap..I used a 5mm pitch polypropylene box cap on my builds.

 

[jjazzyj]

Well here are some photos of the finished EHHA power supply. It contains a 360VA SUMR custom transformer with 30-0-30 and 12-0 secondary windings each rated @ 5A. The 'glowy' concept of the chassis design was for the most part a success. The fit and finish of the final chassis, well I'd say about 75% I could get it to 90% but I'm being lazy for now. If I could have gotten the acrylic panels cut on a table saw with a plastic blade I'd have been happier then scoring and snapping which didn't turn out as nice as I'd hoped. Maybe later I'll redo the panels as the entire chassis design is modular. Now to build chassis #2 for the balanced EHHA preamp/headphone amp. I apologize for the bad pictures as my camera and skills for dark photos are extremely bad. Actually my photo taking skills are just bad in general.