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Old 7th October 2011, 06:53 AM   #631
Vladco is offline Vladco  United States
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Quote:
Originally Posted by linuxworks View Post
the one I designed does have all that: The LCDuino-1 Display I/O Processor (also search the delta1 and delta2 for the attenuator and input selector). all open source and with a huge amount of functionality.
What's the address for open source site?
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Old 7th October 2011, 12:26 PM   #632
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follow the links on amb.org for lcduino and firmware or download (link on left hand side of menu area). a zipfile is created and a link is mailed to you.
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Old 8th October 2011, 10:38 PM   #633
Jos v E is offline Jos v E  Netherlands
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Lightbulb Online calculator for logarithmic relay-attenuators

Hi,
I have made relay-based attenuators for many years now, with logarithmnic behavior. That means: each step provides an extra attenuation with a fixed number of dBs, like 1dB.
That is unlike 'R2R' attenuators that provide a linear voltage scale, which is undesired for audio.

During these years I have received many questions on dimensioning the resistors in such attenuators. Sorry that I waited until now to create an online calculator to do so...
The calculator includes rounding of ideal resistor values to E-series values, and computing the undesired effect of attenuator inaccuracies due to such rounding. See:
Logarithmic Attenuator Calculator
Hope this helps our community!

Quote:
Originally Posted by danzup View Post
Yes , that is the problem and defect !
About the other question :
Resistor-Switch Attenuator Networks for Audio Volume Control
read there all about !
It is like a bible of attenuators in audio and Hi End audio.
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Old 9th October 2011, 08:13 AM   #634
tvicol is offline tvicol  Romania
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Quote:
Originally Posted by Jos v E View Post
...
The calculator includes rounding of ideal resistor values to E-series values, and computing the undesired effect of attenuator inaccuracies due to such rounding. See:
Logarithmic Attenuator Calculator
Hope this helps our community!
Many thanks, Jos !
Your project was the source of inspiration (the Bible ) for our project presented here by Danzup.

Regards,
Tibi
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Old 9th October 2011, 02:44 PM   #635
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I am looking this thread a long time and very interested in Jos work for a long time.

I just remember REVOX B285 that uses Analog Device AD7528 and AD7118 AD convert to control audio volume with 0,1dB of resolution.
This was an aplication of R-2R attenuator where the audio signal is applied in AD voltage reference pin. Of course the log beharvior is done by software.

regards
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Old 9th October 2011, 04:38 PM   #636
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fwiw, I have not found the need for 'log behavior' when the steps *are* already logarithmic (ie, they are spaced by db).

one of my attenuators was relay based at .1db spacing and I used that as a 'trimmer' box (for subwoofer level matching, in one install). .1 is too fine for everyday use, though.

half db is just about right. no matter where I am on the range, half a db is a nice little bump up or down. to find the sweet spot while listening, half db gets you there and each step is noticeable but not too much.

to move fast, I have 2 sizes of steps: large steps and native steps. native steps are what the engine, itself, does (half db in most cases). large steps are what the user can define and when you map alternate arrow keys to those functions you move quickly and without delay. I usually set my bigsteps to be 3.5db; that seems about right to speed thru a fast vol-change sequence but not over-run or under-run too much. once I'm near where I want to go, I then use the main arrows and go by half a db at a time.

and so, with that scheme, I never found the need to have 'non uniform' db spacing. the key is to have enough steps. 64 steps is not enough and you have to play games. but modern controls often will go 96 to 0 (and above) and in half db or better steps. with that granualarity, you can totally forget about so-called log mappings. not needed anymore.
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Old 13th October 2011, 12:50 PM   #637
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Default R/2R Nixie/LCD Versions

Hi
Volume Controller Nixie version was finished in april. It was successfully tested.
Two LCD versions are also finished, there is one small difference as an option.

Options:
- volume control R/2R -127dB...0dB
- passive board control, bass&treble, 4 steps in 5dB from 0dB to +20dB
- Nixie PWM (brightness)
- IN-13 VU PWM (brightness)
- Nixie underleds PWM (brightness)
- RC5 learning and control + encoder control
- Fade-out on Mute, fade-in on UnMute
- UnderNixie leds fade-in & fade-out in Mute.
- 6 Inputs selection
- old-school option "-20dB" in one go
- variable volume control speed

First LCD version backlight goes down automatically if no RC5 button pressed and if encoder do not use.
Second LCD version has backlight brightness control via RC5.
Now the case is underway.

More info here
Tube preamp_Nixie version
in russian language

Links to video - how it works
IN-13.mp4 - YouTube
All Options.avi - YouTube
LEDs up_down manual.avi - YouTube
Mute_UnMute.avi - YouTube


Great THANKS to Kim (FarmTech) for help me to implement this idea - the volume R/2R controller with Nixie...
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Old 13th October 2011, 03:50 PM   #638
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I see your lcd display uses the same exact bargraph style as mine. interesting...
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Old 13th October 2011, 04:15 PM   #639
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linuxworks, bargraph style can be change without any prob. I used some other stiles for tests, but yours bargraph style I like more...
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Old 13th October 2011, 06:59 PM   #640
Leon08 is offline Leon08  Germany
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Nice work!
But I don't know why so many people use atmel microprocessors.What's good on them or better said what's better then by other?
I use only Microchip PIC's and i'am happy with them.I tried also atmel, but it was much more complicated then PIC's, for me at least.

Last edited by Leon08; 13th October 2011 at 07:06 PM.
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