Hi all,
I'm looking for help on a DIY Amp selector to switch between AVR and stereo amp for one set of speakers.
I know this has been covered a lot but I'm struggling with finding the correct rated (4PDT or 4x3 rotary or similar) break before make switch.
***
Background
I have the current setup - an AVR amp with pre out to a stereo amp to drive front speakers. Everything stereo related is connected to the stereo amp and everything TV related to the AVR.
Now as the stereo amp is older it has no AV bypass therefore I have to set the volume to a specific position on amp each time I go between stereo and AVR as well as turning on another amp every time I use the AVR... anyway I want to get away from this by selecting the amp to use with a simple switch in line on the speaker cable.
The speaker cable is two twists of 14awg per terminal (total ~11awg) chunky but sounds great and I will use the same within the switch box with screw/banana type terminals
***
Calculation for switch rating
Stereo Amp power - 110Watt per channel
Speakers - 8 ohm
Thus using R=V/I and R=V²/P
DC Voltage - 29.66V
DC Amps - 3.71A
***
Options I have found.
Option 1.
I would like a rotary switch and people have suggested ones such as these in previous searches which I like the look of and could be just right...
Elma - 2A @ 42V
https://uk.farnell.com/elma/01-1433/switch-4-pole-3-pos/dp/1876080
Greyhill - 5A @ 28V
https://www.mouser.co.uk/ProductDetail/Grayhill/44UA45-01-4-02N/?qs=ls7QRyWmRk4KuC7xeL0ZtA==
Lorlin - 1A @ 24V ac/dc -
https://www.mouser.co.uk/ProductDetail/Lorlin/CK1457/?qs=VJkHNLJxjTeoQOv%2BImgcpg==
These seem to be suggested a fair amount however the rating is lower than I have calculated for above and I'm concerned the contact size maybe a bottleneck for the speaker cable. Am I missing something here?
Option 2.
Multiple stacks of these switches to get the additional amp rating up and splitting the inputs/outputs between the two layers (ie an 8x3 switch rather than a 4x3) . However more posts have warned against this method as one contact could in theory be made before the other thus taking the full load rather than half and overloading the switch. Is this really a likely scenario to happen?
Should I actually be worried about that and surely this would only happen if switching to an amp already playing at significant volume?
Fidelity-Audio
Option 3.
I have seen other posts with the following type of switches but not really a fan of the look and they seem pretty low quality (not gold contacts etc) I want to get away from this but it may be the only option...
https://cpc.farnell.com/multicomp/m...gle-4pdt-on-on-sq/dp/SW05736?st=4pdt switches
https://www.ebay.co.uk/itm/Heavy-Du...-/272304082452?_trksid=p2349624.m46890.l49292
Option 4.
Then there is a large jump to the industrial style switch... But this seems overkill and again not great contact quality?
https://uk.rs-online.com/web/p/rotary-cam-switches/0758642/
https://uk.farnell.com/schneider-electric/k2h014uch/rotary-switch-4pole-14-6a-230v/dp/3108369
Option 5.
Supply separate power and use relays to switch between. To be honest passive would be my preference rather than overcomplicating this but if I can't find a rated switch this might have to do.
***
Any help would be appreciated in either reassuring option 1 or 2 or suggesting another option that I have yet to find in the hours of trawling the internet! Opinions welcome 🙂
Many thanks in advance.
Sam.
I'm looking for help on a DIY Amp selector to switch between AVR and stereo amp for one set of speakers.
I know this has been covered a lot but I'm struggling with finding the correct rated (4PDT or 4x3 rotary or similar) break before make switch.
***
Background
I have the current setup - an AVR amp with pre out to a stereo amp to drive front speakers. Everything stereo related is connected to the stereo amp and everything TV related to the AVR.
Now as the stereo amp is older it has no AV bypass therefore I have to set the volume to a specific position on amp each time I go between stereo and AVR as well as turning on another amp every time I use the AVR... anyway I want to get away from this by selecting the amp to use with a simple switch in line on the speaker cable.
The speaker cable is two twists of 14awg per terminal (total ~11awg) chunky but sounds great and I will use the same within the switch box with screw/banana type terminals
***
Calculation for switch rating
Stereo Amp power - 110Watt per channel
Speakers - 8 ohm
Thus using R=V/I and R=V²/P
DC Voltage - 29.66V
DC Amps - 3.71A
***
Options I have found.
Option 1.
I would like a rotary switch and people have suggested ones such as these in previous searches which I like the look of and could be just right...
Elma - 2A @ 42V
https://uk.farnell.com/elma/01-1433/switch-4-pole-3-pos/dp/1876080
Greyhill - 5A @ 28V
https://www.mouser.co.uk/ProductDetail/Grayhill/44UA45-01-4-02N/?qs=ls7QRyWmRk4KuC7xeL0ZtA==
Lorlin - 1A @ 24V ac/dc -
https://www.mouser.co.uk/ProductDetail/Lorlin/CK1457/?qs=VJkHNLJxjTeoQOv%2BImgcpg==
These seem to be suggested a fair amount however the rating is lower than I have calculated for above and I'm concerned the contact size maybe a bottleneck for the speaker cable. Am I missing something here?
Option 2.
Multiple stacks of these switches to get the additional amp rating up and splitting the inputs/outputs between the two layers (ie an 8x3 switch rather than a 4x3) . However more posts have warned against this method as one contact could in theory be made before the other thus taking the full load rather than half and overloading the switch. Is this really a likely scenario to happen?
Should I actually be worried about that and surely this would only happen if switching to an amp already playing at significant volume?
Fidelity-Audio
Option 3.
I have seen other posts with the following type of switches but not really a fan of the look and they seem pretty low quality (not gold contacts etc) I want to get away from this but it may be the only option...
https://cpc.farnell.com/multicomp/m...gle-4pdt-on-on-sq/dp/SW05736?st=4pdt switches
https://www.ebay.co.uk/itm/Heavy-Du...-/272304082452?_trksid=p2349624.m46890.l49292
Option 4.
Then there is a large jump to the industrial style switch... But this seems overkill and again not great contact quality?
https://uk.rs-online.com/web/p/rotary-cam-switches/0758642/
https://uk.farnell.com/schneider-electric/k2h014uch/rotary-switch-4pole-14-6a-230v/dp/3108369
Option 5.
Supply separate power and use relays to switch between. To be honest passive would be my preference rather than overcomplicating this but if I can't find a rated switch this might have to do.
***
Any help would be appreciated in either reassuring option 1 or 2 or suggesting another option that I have yet to find in the hours of trawling the internet! Opinions welcome 🙂
Many thanks in advance.
Sam.
Hello Sam
Did you consider the difference between music-signal and a static frequency (at full power)?
Depending on what music you’re listening, the peaks and the average signal differ a lot.
(Look for the „crest-factor“)...
So even if you often listen at full volume (I‘d doubt you do), the signal will close to never be at 30V ~4A...
More of this in a different context: Taming the LM3886 Chip Amplifier: Thermal Design – Neurochrome
Did you consider the difference between music-signal and a static frequency (at full power)?
Depending on what music you’re listening, the peaks and the average signal differ a lot.
(Look for the „crest-factor“)...
So even if you often listen at full volume (I‘d doubt you do), the signal will close to never be at 30V ~4A...
More of this in a different context: Taming the LM3886 Chip Amplifier: Thermal Design – Neurochrome
Any of these:
https://uk.farnell.com/webapp/wcs/s...39898,65336589,65158817,65331705&pageType=PLP
4PDT toggle switches (so it´s CLEAR which amp you selected), all rated 5 to 6A, all with way more than adequate voltage rating.
Robust Industrial type switches, not "audiophile rated", thanks God.
Between 5 and 7 GBP, a sensible price.
EDIT:
Those are no nonsense INDUSTRIAL switches.
50 milli Ohm contact resistance (way less than cable resistance).
Gold is useless at speaker level signals, coating is a few atoms thin and evaporates after 3 or 4 operations at any sensible current.
https://uk.farnell.com/webapp/wcs/s...39898,65336589,65158817,65331705&pageType=PLP
4PDT toggle switches (so it´s CLEAR which amp you selected), all rated 5 to 6A, all with way more than adequate voltage rating.
Robust Industrial type switches, not "audiophile rated", thanks God.
Between 5 and 7 GBP, a sensible price.
EDIT:
LOW QUALITY?
Those are no nonsense INDUSTRIAL switches.
50 milli Ohm contact resistance (way less than cable resistance).
Gold is useless at speaker level signals, coating is a few atoms thin and evaporates after 3 or 4 operations at any sensible current.
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Hi both,
Thanks for the replies 🙂.
@myleftear - you make a good point and that is some interesting reading. I had only considered the peak values as I assumed the switch would need to be able to handle up to this load regardless of time period at that load? But you are correct I have never listened (and probably will never) at full volume or even much above the half way mark!
@JMFahey - thanks for taking the time to put those together, I had looked and sort of overlooked those as I was being a bit picky about finding a rotary style. I agree price wise these are far more the area I am intending.
Audiophile rating certainly isn't needed but a calculated sensible option is very much appreciated 🙂
RE:
Thanks again,
Sam.
Thanks for the replies 🙂.
@myleftear - you make a good point and that is some interesting reading. I had only considered the peak values as I assumed the switch would need to be able to handle up to this load regardless of time period at that load? But you are correct I have never listened (and probably will never) at full volume or even much above the half way mark!
@JMFahey - thanks for taking the time to put those together, I had looked and sort of overlooked those as I was being a bit picky about finding a rotary style. I agree price wise these are far more the area I am intending.
Audiophile rating certainly isn't needed but a calculated sensible option is very much appreciated 🙂
RE:
I was under the impression that the gold was there for protecting the contacts from corrosion more than anything? Meaning repeatability on making a good contact every time. The Elma switches and alike seem to be rated to 25000 cycles, I would be surprised if the gold plating disappears after 3 or 4?
Thanks again,
Sam.
There should be no DC here!! You want the AC ratings.
The AC current rating would be important in test-bench work, but can be cheated in PA work, and grossly exceeded in domestic work.
Do you always have 110 Watts of audio flowing when you flip the switch? It is wise, and less ear-breaking, to turn sound down to "zero", switch, and turn up. And done like that, the AC voltage rating is unimportant. (None of these switches will arc-over at these voltages, though repeated switching above rated voltage will zap the contacts.)
The Lorlin sure is not rated 1 Amp, I read 0.15A.
The Greyhill is an industrial job and will serve you well. The price is a bit gaspy.
Yes, switches above a few milliAmps will not be Gold. Coin-Silver alloy has been used but there are many other alloys with better value.
Hmmm ok, so am I missing the point entirly on the ratings of switches, or have I started off in the wrong place?
Please excuse me on this, I have mechanical design engineering knowledge but the logic of electrical still seems to allude me sometimes.
You are correct I would always turn down the volume when switching and It certainly wouldn't be anywhere near full volume when switching, but I can't guarantee that others in the household would be so cautious as to turn down the volume down to zero before switching 🙂 hence my thinking to make sure the switch would be able to cover the extreme scenario.
I agree the prices are extreme on some of the quoted switches but I gave up on price limits just to try and understand the type of rated rotary switch that might be acceptable.
Please excuse me on this, I have mechanical design engineering knowledge but the logic of electrical still seems to allude me sometimes.
I think I might be getting a bit too confused already here. what quoted AC current rating would be acceptable for this type of switch then?
You are correct I would always turn down the volume when switching and It certainly wouldn't be anywhere near full volume when switching, but I can't guarantee that others in the household would be so cautious as to turn down the volume down to zero before switching 🙂 hence my thinking to make sure the switch would be able to cover the extreme scenario.
The datasheet shows 1A @ 28V AC/DC but since checking elsewhere it seems more in the range of 150mA, thanks.
I agree the prices are extreme on some of the quoted switches but I gave up on price limits just to try and understand the type of rated rotary switch that might be acceptable.
Just a quick update,
I had a look this morning into the grayhill switches and in their data sheet for a 250mA switching capacity stated 4A continuous load and similar another 200mA will do the same for 6A continuous with a 20°C temperature rise.
https://www.mouser.co.uk/datasheet/2/626/Rotary_08_09-335035.pdf
https://www.mouser.co.uk/datasheet/2/626/Rotary_50_51-335052.pdf
So this leads me to believe the switching capacity called out in the specs is only the limit you should operate the switch under but the switch in static position itself is capable of far more continuous load. Hence why I keep reading that a lower rated switch will be fine for the application - this coupled with the info from @myleftear means most of these switches will be fine.
I feel like the penny has dropped and I'm finally on the right track here.
Sam
I had a look this morning into the grayhill switches and in their data sheet for a 250mA switching capacity stated 4A continuous load and similar another 200mA will do the same for 6A continuous with a 20°C temperature rise.
https://www.mouser.co.uk/datasheet/2/626/Rotary_08_09-335035.pdf
https://www.mouser.co.uk/datasheet/2/626/Rotary_50_51-335052.pdf
So this leads me to believe the switching capacity called out in the specs is only the limit you should operate the switch under but the switch in static position itself is capable of far more continuous load. Hence why I keep reading that a lower rated switch will be fine for the application - this coupled with the info from @myleftear means most of these switches will be fine.
I feel like the penny has dropped and I'm finally on the right track here.
Sam
Hi Sam
While surfing around out of boredom, I just saw the "Dynoavox AMP-S" which seems to do MOL exactly what you are looking for, except for the DIY of course... (But it may confirm your idea you already had)
While surfing around out of boredom, I just saw the "Dynoavox AMP-S" which seems to do MOL exactly what you are looking for, except for the DIY of course... (But it may confirm your idea you already had)
I did see that in my searching too! It does look like exactly what I was aiming for but lacking a bit in the DIY, and it would be nice to know the spec of the parts within.
Also it seemed a little pricey before I started looking at the price of some of the switches!
Also it seemed a little pricey before I started looking at the price of some of the switches!
I'm planning to build the same thing, amp switch box and I ordered this switch: https://nl.mouser.com/ProductDetail...LeFHW4ufKVg==&countrycode=DE¤cycode=EUR
5A, 125V rating and not to expensive, 13€
I also looked at the dynavox box but besides wanting to DIY it, I also want some 'safety' load resistors so my (tube) amp always sees a load when the other amp is selected. I plan on never switching amps while they're powered on, but I want some backup insurance just in case.
5A, 125V rating and not to expensive, 13€
I also looked at the dynavox box but besides wanting to DIY it, I also want some 'safety' load resistors so my (tube) amp always sees a load when the other amp is selected. I plan on never switching amps while they're powered on, but I want some backup insurance just in case.
Thanks guys, So I ended up going for a NOS Grayhill switch from eBay for £18, should be arriving soon.
A bit more expensive than others but it won me over in the end.
So now just on the search for a decent case to house it all and some binding posts.
Hopefully I'll get some images in here once I've started to build it but that might not be for a while yet.
Sam
A bit more expensive than others but it won me over in the end.
So now just on the search for a decent case to house it all and some binding posts.
Hopefully I'll get some images in here once I've started to build it but that might not be for a while yet.
Sam
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