A prevent jitter scheme of relay attenuator - diyAudio
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Old 5th January 2012, 05:48 AM   #1
Sinc is offline Sinc  China
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Join Date: Jan 2012
Default A prevent jitter scheme of relay attenuator

Pictures:
1.Schematic:
2.Step_keep:
3.Step_up:
4.Step_down:
5.Ro:
6.All:

Note:
1.Ra is zhe same as Rb for any relay attenuator(8421dB or others).
2.The time for every step must be enough.
Question:
1.Is it practicable?
2.Is it already exists?
The chinese may be more detailed:
(英语太烂,为了不产生误解,只好用中文作详细复述)
用继电器组成数控级进音量,其好处就不说了,最头疼的是其切换过程中的抖动问题(特别是采用8421级进法 )。
针对此,设计如下方案(因加入了缓冲,故称有源冗余法):
如图,采用AB两个镜像组,在原来级进音量后各加一级缓冲,切换时,通过Ja,Jb的配合,以达到消除抖动 的目的。
切换过程有些繁琐,每1整步分6小步,但用单片机控制,问题不大;

注意:
1.缓冲级音染要极小;
2.必须留给每个步骤足够的稳定时间;
3.RoA,RoB不能太大,亦不可太小。

因输出有缓冲,此法倒是适合那些音量电位器后置的方案。
曾在国内的论坛上贴过,但无人响应。
也许他们太忙,也许此法太拙,或者此法早已存在(据说,只有神才能创造,人所做的不过只是重复)。望各位前 辈高人指点一下!
Attached Images
File Type: png Schematic.png (14.5 KB, 78 views)
File Type: png Step_keep.png (4.3 KB, 71 views)
File Type: png Step_up.png (21.0 KB, 70 views)
File Type: png Step_down.png (21.0 KB, 69 views)
File Type: png Ro.png (3.7 KB, 65 views)
File Type: gif All.gif (40.3 KB, 26 views)
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Old 5th January 2012, 10:08 AM   #2
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Convert or add a Schmidt trigger to the opamp. The hysteresis prevents flipping back and forth.
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regards Andrew T.
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Old 5th January 2012, 12:24 PM   #3
Sinc is offline Sinc  China
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Join Date: Jan 2012
Thank you!
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