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Old 9th December 2012, 07:21 AM   #191
LeonvB is offline LeonvB  Netherlands
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No, you can't turn off the on-board firmware. You need to remove it from the socket. See the paragraph "Using external I2C controllers".
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Old 11th December 2012, 08:44 PM   #192
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I have connected the volume control pot (supplied10k) and it's working ok,
but I would like to be able to use a bigger part of the turn. As it's now I'm
bearly using a quarter turn. Full volume is really loud and half turn almost silent.
Any ideas, maybe a 5k pot ? Is there 10k two turn pot's ?

It's for the B III se
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Old 11th December 2012, 09:49 PM   #193
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The value of the pot won't make any difference.

The pot just forms a voltage reference which is read by an ADC. It is the DAC itself that does the attenuation digitally.

The attenuation is a linear progession (as the pot is linear) from 0db to -63.5db - but note that decibels are a logarithmic scale.

To change the range would require custom firmware, or an external way to manipulate the reference voltage.

You could also perhaps use an anti-log pot and/or adjust the output level of the output stage.
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Last edited by Russ White; 11th December 2012 at 09:51 PM.
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Old 11th December 2012, 10:32 PM   #194
RollE2k is offline RollE2k  Sweden
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How's it going with the 4:1 mux, any ETA? :-)
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Old 11th December 2012, 10:55 PM   #195
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Quote:
Originally Posted by Russ White View Post
The value of the pot won't make any difference.

The pot just forms a voltage reference which is read by an ADC. It is the DAC itself that does the attenuation digitally.

The attenuation is a linear progession (as the pot is linear) from 0db to -63.5db - but note that decibels are a logarithmic scale.

To change the range would require custom firmware, or an external way to manipulate the reference voltage.

You could also perhaps use an anti-log pot and/or adjust the output level of the output stage.
Thanks, maybe I will go for some (sort of) gearbox solution.
A multiturn linear 10k pot would work right ?

This one maybe http://se.farnell.com/eti-systems/mw...m-0/dp/1307124

Last edited by dahlberg; 11th December 2012 at 11:02 PM.
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Old 14th December 2012, 04:51 PM   #196
lhquam is offline lhquam  United States
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I finally finished by Buffalo-IIISE. The enclosure is really too small (11.6" x 9.5" x 2.5" inside dims) for good separation between the analog boards and the power supplies, but the hum levels are far below audibility. Good enough.
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Old 14th December 2012, 10:16 PM   #197
Davey is offline Davey  United States
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Quote:
Originally Posted by dahlberg View Post
Thanks, maybe I will go for some (sort of) gearbox solution.
A multiturn linear 10k pot would work right ?

This one maybe MW22B-3-10K - ETI SYSTEMS - POTENTIOMETER, 3 TURN 10K OHM | Farnell Sverige
Reverse-log pots are not common, but you could use a (normal) log taper pot and hook it up backwards. Just remember that CCW increases volume.

Alternatively, you could add an external resistor in series with the ground end of your existing linear-taper pot. This prevents from turning the volume all the way down, but that might not be a problem. If you use a 10k resistor with your 10k pot then your volume at max CCW will be what it is now at 50%.

Cheers,

Dave.
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Old 15th December 2012, 12:44 AM   #198
lhquam is offline lhquam  United States
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Another alternative is a resistor in parallel between the wiper and one end of a linear pot as shown in this article: Potentiometers (Beginners' Guide to Pots)

Quote:
Originally Posted by Davey View Post
Reverse-log pots are not common, but you could use a (normal) log taper pot and hook it up backwards. Just remember that CCW increases volume.

Alternatively, you could add an external resistor in series with the ground end of your existing linear-taper pot. This prevents from turning the volume all the way down, but that might not be a problem. If you use a 10k resistor with your 10k pot then your volume at max CCW will be what it is now at 50%.

Cheers,

Dave.
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Old 15th December 2012, 02:50 AM   #199
Davey is offline Davey  United States
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Oops, yes you are correct. A law-faking resistor would need to be attached from +3.3VDC to the wiper in this case to yield the correction dahlberg is looking for.

Sorry about that.

Cheers,

Dave.
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Old 15th December 2012, 09:06 PM   #200
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Quote:
Originally Posted by lhquam View Post
I finally finished by Buffalo-IIISE. .
Looks good. Enjoy!
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