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Old 2nd July 2007, 06:46 PM   #2081
microp is offline microp  Latvia
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Default HI!

Sorry for no pics ... still can't find my camera's charger.


I assembled my first DX!!!!!!!!!!!!!

I am using 25-0-25 power supply for start (+-38 later)

What a great feeling... i turned power on.... NO SMOKE around.

It's a progress for me.

For +-25V supply (with 10ohms 5W resistors) it shows me 310 (positive) and 280 (negative) mV... Is it OK???? In Greg's web there is 1100 and 800mV... but as I am using lower PS I think it's ok!?


Other pics later (just one pic of my dead camera)

regards,

microp
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Old 2nd July 2007, 06:51 PM   #2082
microp is offline microp  Latvia
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Default Sry...

Little regulations and it shows 1040mV and 1020mV... think now its ok!?
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Old 2nd July 2007, 06:53 PM   #2083
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Hi Microp,

That is fine to start with.

Next measure the voltage at the output terminal.

Those currents are likely to change when a load is connected, so keep a eye on them as you do so.


Cheers ........ Graham.
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Old 2nd July 2007, 07:04 PM   #2084
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Hi usernamex,

Followed your links and found contact for Stefano Monteferri.
This name rings a bell with me for radio work about 20yrs ago.

Fancy feet on that amplifier; must cost a few Euro !

Cheers ........ Graham.
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Old 2nd July 2007, 07:23 PM   #2085
microp is offline microp  Latvia
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Default Output is set to 1,5mV....

...removing resistors....???!!!
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Old 2nd July 2007, 07:24 PM   #2086
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Default Microp..... from 0.600 to 1100 will be fine.


It is fine...this current will work fine....but.....not absolutelly needed to be so high this way.

Not needed to go to 1100 or up..the equipment will be more hot than the needed temperature.... this value was a "guarantee that will work sugestion of current"...the unit will work fine using lower currents too.

The idea is to mark the potentiometer adjustment and listen the amplifier into very low volume..... than decide the one your amplifier will sound better when volume is very low..... that volume you will need to put your ears touching the speaker.

Or try a headphone for testings.

The 1100 suggestion is a guarantee that the amplifier will not be underbiased...just that....for safety reasons.... your amplifier will sound fine, reading from 600 milivolts (0.6V) to 1100 milivolts (1.1V)..... you decide the better one.

If you do not want to decide.... adjust to 700 milivolts the positive rail and let this way.

When you replace your supply, you will need to readjust.

regards,

Carlos
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Old 2nd July 2007, 07:27 PM   #2087
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Default Thank you all the information Usernames and Charlie-fd


Also the images you sent....i have observed all them.

Thanks by the TNT magazine testings.....Molto Buonno!...grazie!

Also the link with the PDF..... good too.

Graham is my teacher...older and more experienced.... i love when he enter to help,he belongs to the Dx crew..as Greg, Klaas, Nordic and all folks that have some experience and had constructed Dx units.

Now he is trying to tell you that 800 miliamps will be a problem.

Well...you may know that...but...if you wanna try...good luck!

regards,

Carlos
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Old 2nd July 2007, 07:43 PM   #2088
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I belive there has been some misunderstanding:

1. 800mV on the resistors / 80mA bias not 800 miliamps

2. the pot in question was not a volume pot: usernamex was talking about using a smaller pot + resistor vor VR1 and/or VR3 in order to better set bias and DC
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Old 2nd July 2007, 07:56 PM   #2089
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Default Yes.... was a misunderstanding...good to produce a fine adjustment the way you are


doing...this will make adjustment easier Usernamex and Charlie_fd

I was thinking about that some days ago...but fast i gave up..because a lot of guys will decide different transistors and different supplies, also different selection of bootstrap current..... tweaking the Voltage amplifier current..than...the adjustment splited in such way will be more problem to me than solution.

To avoid complains i will keep the way it is.... but for sure your technical decision was appreciated.

Not so hard to adjust.... i had not problems here with standard trimpots...those old ones.

But i understood...smooth the adjustment...turn it easier..having more room to turn more degrees the trimpot.

I will not include it in Dx amplifier, as this will depends that people will obbey all the schematic parts, voltages and currents...and this do not happens always, as people loves to introduce their own ideas...

To introduce into Dx,amplifier, this better method to adjust bias, i would have to modify schematic, boards and a lot of details....i will keep them the way it is...but i like the idea..very good!

regards,

Carlos
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Old 2nd July 2007, 08:07 PM   #2090
microp is offline microp  Latvia
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Default Haaaaaaaaaaaaa

It's alive!!! Sound perfect. Now just regulations and enjoy great music!!!

Thanks to all helped me create this artwork
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