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NAD 216 THX - Make it sound better?
NAD 216 THX - Make it sound better?
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Old 10th August 2013, 09:41 AM   #1
ron1999 is offline ron1999  Israel
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Default NAD 216 THX - Make it sound better?

Hi there,
I own a NAD216 amp, it's been playing in my stereo system for almost 13 years now.
about 5 years ago it start making some problems - taking it for service resulted in two things:
1. amp was fixed
2. service guy removed several components / changed several components - making the amp sound way better than stock

three months ago the amp went off again, this time it was due to electrical problem from the AC network.

took it again to service -
this time the service guy (a different one) used the amp original electrical schemes and just went over them and made sure all working properly.

now the situation is simple - i had an improved amp (i do not know exactly by what measuers), i sent it to service and now i got a stock amp again.

i need assistance in reviewing the amp electrical schemes and noting there what places can be "Improved" by manners of:
1. remove / bypass redundant / unnecessary protections
2. remove / bypass circuits that are in no use (bridge channels part / soft clipping)
3. remove filters applied in the amp which are not necessary

i found the schematics of the amp here:
Index of /~jga/nad216thx

link is taken from a thread located here:
Help with a noisy NAD 216

i could not locate and electrical schemes for any Silverline amps from NAD for comparison, so if any1 has some assistance about that as well, this may also help


would appreciate any kind of help

BR


Ron.
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Old 10th August 2013, 09:59 AM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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In "Stock" mode the response between 20 and 20kHZ is + or- 0.8DB worst case!
That is pretty flat so removing any filter/clipping/protection bits and pieces will make the amplifier non linear and possibly dangerous.
Can you be specific as to the difference in sound reproduction?
Any "Professional Engineer" that removes components or indeed changes the values without the authorisation by way of an official update from the manufacturer, requires re-training in my view.
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Old 10th August 2013, 10:20 AM   #3
ron1999 is offline ron1999  Israel
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Hi Jon,
regarding the sound -
after the modding, amp sound had improved dramatically on the lower end (very low to be specific) -
it sounded like a complete spectrum wad added to the amp the lower end, more of a feel rather than hear frequencies.
in addition, highs had become more sharp / crisp.
Somewhat like an expanded headroom was added to the amp original sound

regarding the note about removing / modifying components -
when designing a product for mass production you make a lot of compromises - for matters of manufactureability , regulatory, safety etc. this means that more often that one would like, he needs to move from its optimum design towards alternatives and other routes.
as an individual, i care less of those aspects and more about the sound of the product i want to tweak.
i practice my own words in the field of cars handling / engine tuning for motorsports, where im more experienced than in the world of audio electronics...
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Old 10th August 2013, 12:15 PM   #4
Vrystaat is offline Vrystaat  South Africa
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Some people say that removing the Dc protection relay makes an amp sound better. Well you can bypass it but should anything goes wrong you will have to buy new speakers, not worth trying that. Maybe you must just check if the main power supply caps is Ok. I have a Nad 214 which is basically the same, got a 240mv dc offset on one channel, turns out to be be a leaking cap. I have replaced all elcos and never had problems again, sound better than new.
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Old 10th August 2013, 02:30 PM   #5
ron1999 is offline ron1999  Israel
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thanks for the suggestion - after latest fix amp returned to me in new like-stock condition - all caps renewed (plus - the third couple of caps replaced from 4700uF/80v to pair of 15000uF/100v pair)

what about the signal path of the inputs?
is there any play in that direction?
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Old 10th August 2013, 05:27 PM   #6
crispycircuit is offline crispycircuit  United States
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Does that amp have Lab/direct input & normal input. The tech could have wired them differently for better low end...
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Old 10th August 2013, 05:53 PM   #7
ron1999 is offline ron1999  Israel
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Inputs of this amp are single pair of RCA plugs - they go through certain route -
via bridge / not bridged switch and via soft clipping circuits (you can see that in the attached file)
in addition - i want to make sure if there are any other filters along the way...



you can see the electric scheme of the amp in the link at the first post of this thread.
from a quick glance that i took - the amp has a single pair of inputs.
Attached Images
File Type: jpg nad-216-sch_cr.jpg (78.1 KB, 633 views)
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Old 10th August 2013, 09:58 PM   #8
crispycircuit is offline crispycircuit  United States
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C103&C104 are input DC blocking caps.They also set up the low frequency of the amp. I would doubt the value is wrong.
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Old 10th August 2013, 11:05 PM   #9
Vrystaat is offline Vrystaat  South Africa
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Check this, Sakis gave me some info, he has seen this all. This is a great amp. Fix it, you will be a happy chappy. Nad 214 DC on output
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Old 10th August 2013, 11:10 PM   #10
ron1999 is offline ron1999  Israel
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It is funny that you mention this -
after the tuning of the amplifier, i had a problem in my pre-amp, it was this exact thing - something went wrong inside it, and it sent out DC to the amp.
this resulted in fried up tweeter's of my B&W CDM1NT...

i never thought this could be it - but now it makes a perfect sense.

will i go over this again, taking this chance?
if this was the change that added so much headroom in the lower spectrum of the amp, think i would do it again...

Do you think i can recalculate the cap's value to cut the frequency at a lower stage, keeping the DC protection along with expanding the lower end headroom?
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