In-rush Protection for NAKSA 70 - diyAudio
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Old 30th June 2011, 06:27 PM   #1
Hogg is offline Hogg  United States
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Default In-rush Protection for NAKSA 70

Is there current in-rush protection built into the NAKSA amps? If not is a soft start circuit recommended?

Hugh and I have a mutual friend who wanted to build my NAKSA 70 during my absence. The rectifiers blew when the amp was powered on. I had a similar problem at his home with a Greg Ball amp, GB150D, and solved it, after repairing the power supply, by adding a soft start circuit.

Jim
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Old 1st July 2011, 11:24 AM   #2
AKSA is offline AKSA  Australia
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Hi Jim,

No requirement for a soft start circuit on the NAKSA, the problem on Paul's is something quite different, relating I believe to LED voltage references. I'm replacing it routinely.

The switch on pulse on the NAKSA 70 is just less than 3V, quite trivial, the switch makes more noise.

Hope this is helpful,

Hugh
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Old 1st July 2011, 05:18 PM   #3
Hogg is offline Hogg  United States
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Hugh, thank you for the reply. Too bad, I was hoping to pin this on Paul


Jim
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Old 3rd July 2011, 11:30 AM   #4
AKSA is offline AKSA  Australia
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Ah, no Jim, Paul has been blameless, the fault is likely mine!!

My apologies for delay..... I'm presently in another city visiting my Mom in hospital and this has played havoc with my timetable.

Hugh
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Old 5th July 2011, 12:43 AM   #5
Hogg is offline Hogg  United States
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Hugh,

No reason to apologize; you have your priorities correct. Hoping your mother improves quickly. Take care.

Jim
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Old 20th August 2011, 04:36 PM   #6
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Jim,

Your amp is up and running. it is a lovely amp. I reconfigured your on-off switch. I'd originally configured the switch as a AC phase reversal switch [the fuse is always on the 'hot'], that would allow tweaking to minimize leakage currents on the safety grounded chassis.
The switch, with center off, is now configured with one 'on' labeled as 'start' which put a 10 Ohm in series with' hot' to minimize turn on surge. The other 'on' position is labeled 'run' and bypasses the resistor.

Not a fancy soft start, but adequate, if needed.

-Paul
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Old 22nd August 2011, 07:21 AM   #7
AKSA is offline AKSA  Australia
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Thanks Paul, great news, both that the amp got through OK - that pond is mighty big - and that all is well and Jim can have his amp quam celerime.....

Have you noticed the intense quiet of this amp, Paul, and the wonderful imaging?

Cheers,

Hugh
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Old 22nd August 2011, 12:31 PM   #8
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Hugh,

When I put the Naksa70 in my system, I pulled it out to check that hardwired power cord I put in, connected safety ground to chassis and circuit ground..... not the slightest hum or noise with my ear pressed against the speakers. Its the quietest (by that metric) amp I've ever had in my system.
As to imaging, the Naksa70 accurately portrays height information (when in the recording and with speakers capable). Width (including placement outside the speakers positions), and to a lesser extent, depth, are generally easy for a power amp to convey, but accurate height portrayal is far rarer. The Naksa70 gets all 3 coordinates right!

FWIW,
Paul
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Old 23rd August 2011, 12:44 AM   #9
AKSA is offline AKSA  Australia
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Wow, Paul!!

Now, how do we measure imaging? There's a tough call......

Many thanks for careful work,

Cheers,

Hugh
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