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Old 13th November 2008, 07:29 PM   #1
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Default HRII debug thread, post the problems you had here


I will try to help... also forum folks will try to help.

Gain or sensitivity:

The HRII had wrong gain resistances, not only Nordic by i was also using low level into the input.... the 390 ohms resistances in series represents 780 ohms, and this is too much sensitivity..you can reach full power with 400 milivolts RMS into the input...so.... normal CD players output level will saturate earlier..in place of dinamics you gonna have compression and distortion.

Also, Nordic has suggested 220 ohms (total of 440 ohms)... this made things worse.... this allows you to use those MP3 players, or MP4 players or some Ipods....but.... with this enormous sensitivity we gonna have more problems than audio.

I am trying some DVD and CD players i have here, and i found that 1K8 is a very good value, so you can inject 1 volts RMS without enter the clipping.... you can use also 1k plus 1K or 1K plus 820 ohms or other combination... the idea is to reach full power into the power amplifier when your pr amplifier volume will be around 75 percent of it's maximum.

This will give you "room" to increase volume to musical programs of low level and will accept peaks or normal program levels.

Hardly suggested to change those resistances as soon as possible.

Sorry, my mistake...i was fooled by some low level units i had and Nordic was fooled by his passive pr amplifier that was "eating" level...was loading his audio source.... the result is that he needed more sensitivity into the power amplifier.

Do not use the high frequency booster...was good to my old speakers, not more needed to me... i hope not needed to you..because if you have high level of high frequencies into your musical program you gonna have a big mess (distortions... saturations).... to use this you have to be very selective about how to use, when to use and why to use... better to keep this off!

regards,

Carlos
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Old 13th November 2008, 07:30 PM   #2
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Default Reduce to 100 ohms each one of them


I will return to comment in details a lot of things about this amplifier.

And will explain how and why.

regards,

Carlos
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File Type: gif reduce to 100 ohms each one.gif (36.7 KB, 187 views)
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Old 13th November 2008, 07:32 PM   #3
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Default This will be the schematic, because this one had boards made with those numbers


Despite i love the one posted at Greg web site, the part numbers does not match the part numbers you have into boards...and more than 100 boards were sold (without profit, group buy, Nordic group buy).

So... we will talk using that schematic, not so pretty, but more used.

regards,

Carlos
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File Type: pdf hrii schematic.pdf (36.1 KB, 47 views)
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Old 13th November 2008, 07:35 PM   #4
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Default 47pf or 56pf or even bigger ones will result more safe


In special if you decide to use faster transistors or to assemble into your own board.

Mine is operating with 47pf... and i think will be a little big dangerous to reduce.

I am using 100 Megahertz transistors.

regards,

Carlos
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Old 13th November 2008, 07:36 PM   #5
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Default Here is how to adjust stand by current


If needed i will comment this

attached,

regards,

Carlos
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File Type: gif dx amplifier adjustment.gif (11.4 KB, 173 views)
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Old 13th November 2008, 07:38 PM   #6
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Default Avoid to use the treble booster switch.


attached,

regards,

Carlos
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Old 13th November 2008, 07:39 PM   #7
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Default I am tweaking... one channel is operating with 300 mA


and other is operating with 60 mA... this is stand by current.

regards,

Carlos
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Old 13th November 2008, 07:42 PM   #8
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Default Here you have the small board used to adjust bias


This board was not provided, it is to be made by Diyers.... P2P, or small boards, or stripped board..well..the way you decide to make.

Here you have a suggestion.

Transistor is ANY, middle power, TO220 or something alike, NPN transistor, with gain from 50 to 150..... power there is very small...if plastic will be better, as you will not need insulator as this transistor goes attached to the heatsink.

The colector has a red wire that goes to positive mark into the board...... the emitter must have a blue wire that goes to the negative mark you have into the board.

This bias circuit is used into the Dx Standard too.

regards,

Carlos
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File Type: gif hrii bias circuit.gif (67.4 KB, 119 views)
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Old 13th November 2008, 07:44 PM   #9
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Default To allow you to have easier adjustment you can split the base to emitter


resistance into two parts...a fixed 500 ohms resistance, or 470 ohms fixed resistance and a 500 ohms trimpot.

regards,

Carlos
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Old 13th November 2008, 07:45 PM   #10
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Default Here you have some resistance adjustment and the


current you will have when using 35 plus 35 volts supply.... and using 16 plus 16 volts to the rail zeners.

regards,

Carlos
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File Type: gif hrii, bias trimpot adjustment.gif (5.5 KB, 99 views)
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