Reed Switch Audio Attenuator - Page 4 - diyAudio
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Old 20th May 2013, 07:55 AM   #31
dheming is offline dheming  United States
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Quick update. The new reed switches arrived last week. These are definitely going to be much easier to experiment with than the previous ones:

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Here's the basic setup I'm going to use for testing:

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This weekend I ordered a variety of tiny magnets to play with. Once they're here a new arm will be built to accommodate them.
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Old 30th September 2013, 11:21 PM   #32
dheming is offline dheming  United States
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I did another round of testing using small neo cylinder magnets. In order to get a tighter spot of magnetic focus I tried a dual arm setup with a magnet on each side of the switch board. This worked much better at activating the dual stacked reed swtiches, but it was still inconsistent between adjacent positions.

I have no doubt that this would work for a single switch per position, series attenuator. However I think getting it to work 100% glitch free with a stacked pair of reed switches per position ladder attenuator will be a challenge. If someone still made a DPST reed switch it would be a different matter. Either way perhaps the biggest drawback to this whole approach is that it will be physically huge.

Now that the ELMA A47 is here I am shelving this reed switch attenuator project. For my passive monitor controller I am going to use a 10k quad A47 and just be done with it. Time to get my DAC and headphone amp projects done now.
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Old 1st October 2013, 04:17 PM   #33
mlloyd1 is offline mlloyd1  United States
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sounds like it was fun while it lasted.
thanks for sharing ...

mlloyd1
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Old 1st October 2013, 04:59 PM   #34
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+1.

I'm also a big reed fan, but physics wins out.

I thought of mounting the reeds "vertically" in a tight circle, with a bar magnet describing a smaller circle inside them. This would need some inter-reed screening since there is a lot of hysteresis in the reed.

A further thought-experiment would use a coil driven magnet whose flux could be reversed and varied to ensure adjacent reeds did not close.

But it never got beyond "just a thought!"
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Old 9th December 2013, 12:02 PM   #35
ASLHK is offline ASLHK  Hong Kong
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Quote:
Originally Posted by soldersplash View Post
FYI - You don't need 36 relays for a 36 position attenuator. It is possible to make 127 step using 7 relays. Arranged as 1/2dB per step gives a practical 0dB to -63dB attenuator. Think binary...

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I will start to programming on 64 steps Binary reed relay base attenuator soon but I worry about pop noise when switching. Who can tell me how to solve problem ? May be I will release some kits for DIY with reasonable price if I can solve problem on pop. I also had finished a 42 steps reed relay + VTC step attenuator with no pop but It cost too high. It need 24 reed relay per channel + multi-tap transformers. I try to developt a very high quality step attenuator with low cost to use in our integrated amplifiers.
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Old 9th December 2013, 12:10 PM   #36
AndrewT is offline AndrewT  Scotland
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for no pop:
no DC at the switches,
make before break.
as the least requirement.

Would a mute function that operates just before switching and releases just after switching be required?
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Old 10th December 2013, 02:57 AM   #37
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A mute function could work, but in general, relay switched attenuators are hard to completely de-click, since they operate relatively slowly, and not completely predictably. With CMOS switches, folks have implemented 'zero crossing switching', which can work to some degree, but it's not so simple. For example, in the case of having to switch two or more channels, the zero crossings won't happen at the same time, so the switching will be randomly skewed according to the peculiarities of the signal.

Most folks who do relay switched attenuators just live with the clicks, and if you're careful, you can arrange the clicks to be somewhat small compared to the signal itself, e.g. with make before break switching, or any of a number of schemes to try to minimize disturbances.
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Old 10th December 2013, 03:34 AM   #38
ASLHK is offline ASLHK  Hong Kong
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Quote:
Originally Posted by Monte McGuire View Post
A mute function could work, but in general, relay switched attenuators are hard to completely de-click, since they operate relatively slowly, and not completely predictably. With CMOS switches, folks have implemented 'zero crossing switching', which can work to some degree, but it's not so simple. For example, in the case of having to switch two or more channels, the zero crossings won't happen at the same time, so the switching will be randomly skewed according to the peculiarities of the signal.

Most folks who do relay switched attenuators just live with the clicks, and if you're careful, you can arrange the clicks to be somewhat small compared to the signal itself, e.g. with make before break switching, or any of a number of schemes to try to minimize disturbances.
Make before break is only workable in simple switching circuit but for Binary switch seem to be no way to do it. Due to it is not switch one switch to other. It is combination like binary digit. My design is not all reed relay. I use reed relay on signal path. Multiplexier for grounding. It take avantage of fast switching but higher resistor. I think it will not degrade sound quality but save much of space. I start to programming it today. I will start a new post when it sucessful.
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Old 10th December 2013, 08:07 AM   #39
BV is online now BV  Slovakia
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Quote:
A mute function could work, but in general, relay switched attenuators are hard to completely de-click, since they operate relatively slowly, and not completely predictably.
Proper relay "timing" (different for increasing/decreasing attenuation)can solve all audible problems..I am using Lpad relay attenuators, 8relay, 0,5dB step. The only audible "clicking" is mechanical sound of relays.

Last edited by BV; 10th December 2013 at 08:17 AM.
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Old 10th December 2013, 12:59 PM   #40
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"..since they operate relatively slowly, and not completely predictably..."

That is not true of miniature reed relays.

Switching time of about 1.5mS with very little variation. Software - or even hardware! - to do a mute, switch, open mute is pretty basic.
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