N72 Rev 3.1 Now Shipping!

[tpryan]

Revision 3.1 of the N72 is now shipping with "slow rise" phantom power switching. Be careful not to mix up the BC184C transistors with the MPSA06 and MPSA56 transistors in the phantom circuit! Updated BOM, schematic and assembly instructions are now on line.

Please post all questions regarding Rev 3.1 changes in this thread.

[KevinL]

I have an older (pre 3.0) N72. What does the "slow rise" phantom power switching fix? I'm curious because I had an AT4047 FET blow on me once using the N72. I don't know if it happened when phantom was applied or not.
Could a phantom power spike from the N72 cause this to happen?

[tpryan]

What does the "slow rise" phantom power switching fix?

It doesn't fix anything, it's a new feature that can reduce the pops and thumps heard when switching phantom without muting first. Switching phantom without muting is still bad practice, but the very slow rise and fall makes it less bad.

[DWM]

I recently built a ver 3.1 of N72. The only discrepency I found was C25 is listed in the BOM as 22uF/50V and on the schematic as 22uF/35V, but the kit came with a 47uF/50V capacitor (at least that is what was left over). I believe this is what the ver 3.0 used there (I built one of them too). Is it OK to use the 47uF, or should I get a 22? If not OK, would it be a good idea to change the one in the ver 3.0 board to 22?

[tpryan]

Either the 47uF or the 22uF will work fine. The larger value gives no measurable improvement, so there's no need to match them.

[j_gander]

I had the same discrepancy with C25 in my kit and one other small one as well. C15 on the BOM is listed as 470 uF/6.3 volts, but what I received was 470uF/10 volts. Is it safe the assume that this is a substitute?

Thanks for your help.

Jesse

[tpryan]

Is it safe the assume that this is a substitute?

Yes. The BOM will be updated as time permits.

[ghetto3jon]

no sonic differences, i assume. can version 3.0 be easily tweaked to get slow rise phantom?

p.s., i thought all the SCA kits already had slow rise phantom...is 3.1 just "slower"?

[tpryan]

no sonic differences, i assume.

No, the only changes were to the phantom circuit. These have been shipping for more than a year, BTW.

can version 3.0 be easily tweaked to get slow rise phantom?

Nope.

i thought all the SCA kits already had slow rise phantom...is 3.1 just "slower"?

The new active circuit is 33 times slower than the old passive circuit.

[Archmart]

Hey Hey!

It's been two and a half years since I last worked on my 5th of 8 kits (2 of each at the time). I'm about to resume and finish up one more J99 and two N72s.

The N72s are Rev. 3.0. I wonder if there's an upgrade path I should take before I put the work into these?

Please advise.

Thanks,
Archmart

[Randyman...]

Howdy,

The N72 PCB's I just received are rev 3.2, but the printed and online BOM and Schematic is still at 3.1. (Or was it PCB @ 3.3 and BOM @ 3.2? - I'm at work right now so I'm recalling from memory - but I know the documentation was 1 revision behind the PCB).

Any differences to be aware of? The last N72's I built were from 2008 or so...

FYI/PS - I was missing a 27 Ohm resistor and had a spare resistor of another value in one of the kits. No biggie - but I thought I'd let you know. I already purchased the replacement resistor. Should have them done tonight! 16 SCA's is a beautiful sight

Thanks

[tpryan]

Rev 3.1 to 3.2 introduces some silk screen improvements and adds pads for additional RF filter caps at the XLR connectors.

[Randyman...]

Nothing drastically different - I made it through both of them just fine

It looks like the 604 Jumper has been re-located and a few other things. No sweat! Both of my SCA chassis are FULL!!! I never thought I'd be able to say that

Now - onto the DIY Compressor craze for a few more months. You really should get into the DIY Compressor Market - Lots more money to be made! I know your complete kits would be a welcomed addition to the noobish DIY compressor audience. People like Hairball Audio and others make it somewhat easy to do an 1176 - but still not as easy as your SCA kits in "complete" form.


Happy new year