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Old 9th February 2009, 04:06 PM   #991
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by RCruz
I measured with the DMM set for mA,
that's your mistake.

add a 1r0 or 10r 1% resistor in series with your load. Now measure the voltage drop across the test resistor.
What current is flowing?

Measure the voltage across your hot load resistors.
What resistance are they when hot? Store that change in resistance knowledge for next time it's needed.
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Old 9th February 2009, 04:35 PM   #992
Salas is online now Salas  Greece
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What Andrew said. That way you will know better.
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Old 9th February 2009, 07:14 PM   #993
RCruz is offline RCruz  Switzerland
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Thank you for your comments Gentlemen !

Ok.. I know resistance is variable with temp rise but the differences I read are too uge. With a 560r and 28v I read 78mA... that should mean the resistor droped to 360r...

So I decided to make the same setup with my old analog MM and.... bingo... I get 50mA.

The issue is in the DMM (I bought it for 9€ in a supermarket that sells china stuff )

I am glad this happened before I started using the DMM for more serious matters.

Now back to business:
About the resistors in the Riaa... can i use 1/2w for R1 and R3 ?

Ricardo
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Old 9th February 2009, 07:29 PM   #994
Salas is online now Salas  Greece
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Off course you can use 1/2W. Those cheap DMMs are normally OK for Voltage measurements and Ohmic measurements. In series I have heard they are not that reliable, but I think that the situation has gone way across the acceptability line with the particular one you mention.
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Old 9th February 2009, 07:42 PM   #995
RCruz is offline RCruz  Switzerland
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Yes it is really bad... I need a new reliable one... Already spoke with my Wife about it

I just bought all the resistors and the zener so I can start building.
I must put some resistors upright because they are so big 1w and 2w carbons.
Would you point me the resistors that need to be high quality (those that might affect sound quality the most) ?

Ricardo
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Old 9th February 2009, 08:20 PM   #996
Salas is online now Salas  Greece
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RinputLoad, series riaa resistor. Then the load resistors that tie to B+, and lastly the resistors that tie to ground. Pretty much everything, but I put them in the subjectively most important order for you.
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Old 9th February 2009, 08:28 PM   #997
RCruz is offline RCruz  Switzerland
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Thank you so much.

I am now "matching" the resistors.

Hope this work pays because I plan to use a pot for both channels (lack of tim€) so I will not have a balance control.

Ricardo
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Old 10th February 2009, 01:46 PM   #998
iko is offline iko  Canada
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salas, I just want to congratulate you on your design. The shunt and phono stage together are a very good match; very special sound. Good job indeed! And thank you for sharing your work with us.
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Old 10th February 2009, 01:59 PM   #999
Salas is online now Salas  Greece
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Good is to be shared, selfishness is idiocy IMHO. Happy listening! Thanks.
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Old 10th February 2009, 03:25 PM   #1000
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