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Old 24th February 2012, 11:40 PM   #721
Jempie is offline Jempie  Indonesia
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Still don't get it right
the gain of my preamp is to high so when the volume is 0 there is still a lot of sound
i have the regular board of vicol with 6 relais

want to make the steps bigger to reduce the volume

I have try the calculator of JvE Logarithmic Attenuator Calculator

1.5 dB steps
10k 10k 6.8k 4.7k 3.3k 1.5k
39R 680R 3.3k 10k 27k 56k 10k


2.0 dB steps
10k 10k 8.2k 5.6k 3.9k 2.2k
6.8R 270R 1.8k 6.8k 18k 39k 10k

what do i wrong
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Old 25th February 2012, 11:44 AM   #722
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Which one is the correct value for R31 ? In first release (ver 1.0) R31 for R2R 82K and shunt 16K. Now in rev 1.1 R31 for R2R 10K and shunt 82K.

Didiet
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Old 25th February 2012, 01:50 PM   #723
Jempie is offline Jempie  Indonesia
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Is there and calculation sheet to calculate the resistor value
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Old 25th February 2012, 05:51 PM   #724
tvicol is offline tvicol  Romania
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Quote:
Originally Posted by didiet78 View Post
Which one is the correct value for R31 ? In first release (ver 1.0) R31 for R2R 82K and shunt 16K. Now in rev 1.1 R31 for R2R 10K and shunt 82K.

Didiet
Didiet,

The correct value for R31 R-2R operation is 82K.
There is a mistake in rev 1.1 drawing which I'll correct.

Regards,
Tibi

Last edited by tvicol; 25th February 2012 at 06:08 PM.
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Old 25th February 2012, 05:53 PM   #725
tvicol is offline tvicol  Romania
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Quote:
Originally Posted by Jempie View Post
Is there and calculation sheet to calculate the resistor value
Jempie,

Use Jos calculator Logarithmic Attenuator Calculator

Regards,
Tibi
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Old 25th February 2012, 06:31 PM   #726
Jempie is offline Jempie  Indonesia
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tvicol

if I use the Jos calculator, your board is 10K use 6 relais 1 db attenuation
then the resistor value are;

10k 8.2k 5.6k 3.9k 2.2k 1k
270R 1.8k 6.8k 18k 39k 82k 10k

if i compare it to your value it's totally different
could you please explane

which steps must i do to get it work right on your board

thanks
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Old 25th February 2012, 07:10 PM   #727
tvicol is offline tvicol  Romania
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Quote:
Originally Posted by Jempie View Post
tvicol

if I use the Jos calculator, your board is 10K use 6 relais 1 db attenuation
then the resistor value are;

10k 8.2k 5.6k 3.9k 2.2k 1k
270R 1.8k 6.8k 18k 39k 82k 10k

if i compare it to your value it's totally different
could you please explane

which steps must i do to get it work right on your board

thanks
The values are pretty the same, depends only the reference in/out which is reversed.
For 1dB step attenuation and 63dB total attenuation, you must have:
R30 - 1K
R31 - 82K
R32 - 2K5
R33 - 47K
R34 - 5K8
R35 - 27K
R36 - 15K
R37 - 16K
R38 - 53K
R39 - 11K
R40 - 390K
R41 - 10K


For 1,5dB step attenuation and 95dB total attenuation, you must have:
R30 - 1K8
R31 - 68K
R32 - 3K9
R33 - 33K
R34 - 10K
R35 - 22K
R36 - 33K
R37 - 15K
R38 - 150K
R39 - 10K
R40 - 2M7
R41 - 10K

However I suggest you to go for something in between and choose 1,2dB step attenuation for a total of 76dB, which I believe will be more than OK.
R30 - 1K5
R31 - 82K
R32 - 3K3
R33 - 39K
R34 - 6K8
R35 - 22K
R36 - 22K
R37 - 15K
R38 - 82K
R39 - 12K
R40 - 820K
R41 - 10K

Regards,
Tibi
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Old 27th February 2012, 01:23 AM   #728
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Quote:
Originally Posted by tvicol View Post
Didiet,

The correct value for R31 R-2R operation is 82K.
There is a mistake in rev 1.1 drawing which I'll correct.

Regards,
Tibi
Thanks for clarification. Howto calculate value R-Shunt, so i can expand to 64 step for R-Shunt?
Didiet
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Old 5th March 2012, 08:33 AM   #729
longpcb is offline longpcb  Viet Nam
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Delete!

Last edited by longpcb; 5th March 2012 at 08:47 AM.
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Old 5th March 2012, 11:04 AM   #730
tvicol is offline tvicol  Romania
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Quote:
Originally Posted by didiet78 View Post
Thanks for clarification. Howto calculate value R-Shunt, so i can expand to 64 step for R-Shunt?
Didiet
Sorry for late replay, but I do not get mail notifications from this thread ... :-(

Our volume-controller can operate in shunt up to 32 steps.
A shunt calculator you may find on this page:
50-Step Shunt Attenuator Resistor Calculator - Neville Roberts

Regards,
Tibi
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