The best way to build input channel switcher?

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Same principle here ?

Very interested in this discussion, but for a slightly different application. I want to be able to A-B test source components. Let's say I have two DACs installed into a grounded enclosure. The raw signal comes from a digital file, say from a NAS or PC. Can I split the input to feed both DACs, then use a simple switch as described to move between DAC outputs?

I want this simple and with the best audio quality (without going overboard). Simple switch or relay, plus coupling caps and resistors, as in:
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DF96: ... Switching noise comes if the switch sees some DC. Coupling caps and ground leak resistors prevent that.

East: use relays and shunt to ground the source that is not selected . Via resistor of 600R if you like...

Jean-Paul: Switches or simple electronics (i.e. without a clock signal) driving quality relays with correct termination is the way to go...

DF96: That will still click, unless the relay is (unusually) make-before-break. ... You need to ensure that everything is at the same DC potential before, during and after any switch transition. That means coupling caps and ground leaks, as I said.
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So, in the example I gave, I could use a rotary make-before-break switch of the DAC signal out wires from both DACs, plus caps/resistors as described, and this would work (without damaging either DAC)?

Thanks for your thoughts.
 
Today I was looking in the service manual for my old JVC stereo amplifier, to see if I found something intresting, and yes, indeed, I did!

somewhere on one of the PCBs in there, I found the CD4066 (datasheet from TI) a digital IC switch. the datasheet says it can be used for analog signal switching, and thats exactly what I'm looking for!

have anyone tried this? Pros, cons?

EDIT:
this IC is prodeced my many manufactors, and is called CD4066/HEF4066/74HC4066
 
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CD4066 for audio ? Noooooooo ! You can't be serious. This is one of the worst solutions for input switching the audio industry ever invented. Any solution is better that this one. Throw that amp away or replace the input switching circuit and enjoy good sound.

http://www.time-step.com/distribution/4066.html

Relays are the way too go if one wants quality (for those who don't know what app that is please use google). Plain and simple. No Arduino, no CPU, just good relays with gold clad contacts or plain rotary switches with silver gold clad contacts (Elma etc) that will switch your precious analog signals. Don't follow in the pit of "clicking of relays" as that is the standard line manufacturers of digital switching stuff use a bit too often. A bit the same like "small footprint" and "low cost". I never used otherwise and hear no clicks with relays or good switches. Relays and rotary switches are unwished babies as they simply cost too much money. Just a simple resistor to GND will prevent clicking almost completely. And if it bothers you then pull down volume when switching inputs. Don't bother with make before break and such. If quality is of no importance just like audio manufacturers do then follow the digipot/digiswitching route for MP3 (garbage in/garbage out) and please add an Arduino/PIC/AVR and be busy coding for some time as that is the new electronics. Also an app should be written so you can adjust volume with a smartphone. For Gods sake: who forces us mortals to use mobile phones for everything we do in life ?

Check the DCB1 "Mezmerize". No one complains about clicking noises. Sounds excellent too. Any part in the signal chain affects sound quality so keep that amount to a minimum and use quality parts, good power supplies and good switching material. This is what analog is about.
 
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Oh, I'm sorry :p I thought it might be a good (and compact) idea, but I later read that 4066 add a lot of distortion to the signal. I guess asking about the 4066 on an audio forum is like asking a car enthusiast why he dives an expensive car if he just goes from A to B.

Yes, I've understood that quality relays is the way to go. But what are quality relays actually? I saw some someone recommend tiny reed relays for input audio, since they are cheap, and only draw a couple of milliamps. You see, I'm still going to use a microcontroller in my amp (sorry about that), so the it would be best to use 5v relays that didn't draw more than 30 mA of current. However, if thats impossible, I could easily add a transistor to add more voltage and current to the relay.

I'm going to have four input channels. That means I'll need to buy 2*4 = 8 relays. Do you know where I can get great relays that doesn't cost a fortune?
 
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Hi you need sealed, low power relays with bifurcated gold clad or plated contacts for audio switching. So I take you want them to be affordable. Not expensive and just good (but certainly not the best):

Takamisawa RY5W-K 5VDC

For example:

TAKAMISAWA RY5W K 5V DPDT Signal Relay x20 Pcs | eBay

Also just good, different footprint. As you can see they are discontinued like many good but more costly parts. Silicium is cheaper than copper wire and silver/gold ! Still they are easy to find:

http://www.mouser.com/ds/2/307/G6H_0609-17141.pdf

Quality SMD relays for sale here on the forum:

http://www.diyaudio.com/forums/swap...deal-500-units-499-attenuators-switching.html

I stock a large amount Finder 30.22SH low power 6 V DC relays in the same layout but the datasheet seems to have an error as it states a quite high minimum switching voltage and current (0.1 V 1 mA which normally is 10 mVDC 0.01 mA with telecom relays so maybe it got written down wrong as the difference is too much). They have gold clad contacts and I use them in audio with quite good results.

http://gfinder.findernet.com//assets/Series/32/S30EN.pdf

Always use a driving transistor and a diode across relay coil....
 
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Better ones (harder to find) NAIS/Panasonic DS2E-M-DC5V:

http://pewa.panasonic.com/assets/pcsd/catalog/ds-catalog.pdf

Real good ones cost serious money like the Teledyne relays:

http://www.farnell.com/datasheets/77219.pdf

BTW allow me to give some info/rule of thumb:

Gold contacts are used for voltage switching while silver contacts are used for current switching.

Just remember that, it will save you time when you want to repair a japanese amplifier with intermittently failing channels (so a failing output relay)...
Ask yourself why the relay fails in such amps...
 
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Thanks! I'll make sure I get se good quality relays that doesn't destroy the precious analog signal. Since you said that gold is used for voltage switching; does that mean gold relays should be used for the input switching, while silver relays should be used in speaker protection circuits where a lot of current passes through ?

But about the Japanese failing amps. Do they use silver or copper relays instead? Will silver fail because the surface is oxidizing and making a bad contact? That may happend to copper relays too if the copper isn't protected form the oxygen in some way.
 
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Does that mean gold relays should be used for the input switching, while silver relays should be used in speaker protection circuits where a lot of current passes through ?

Yes

But about the Japanese failing amps. Do they use silver or copper relays instead? Will silver fail because the surface is oxidizing and making a bad contact? That may happend to copper relays too if the copper isn't protected form the oxygen in some way.

They often use non sealed 2 A max. rated gold contact relays for switching outputs to speakers. For some reason this error continued for many years. Use sealed Schrack 8 or 10 A rated relays (silver contacts) with the same footprint and the amp won't fail anymore. They even use less power than the original ones.

* Silver oxide conducts current but we don't like oxides so..... use sealed relays to avoid oxides....
 
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Hi everybody, I want to add a few more questions to this excellent thread. This time I'll try to be more clear to explain my situation. Sorry from the OP :)

What I have is a 30 years old tube pre-amplifier and soon I'll have it serviced to change some old components and make a few modifications. It has a quite cheap rotary switch for line inputs without relays or so. At the modification process, I want to add a mechanical switch for two MM level phono inputs. It can either be a toggle or a rotary switch.

From this thread I understand that, relays must be used at switches. Should I use them even if I'm looking a mechanical switching action? When I want to change input, I'll take my a** to the system rack. Repeat that if I'm not happy with the volume level.

Regards

 
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Hi you can use a high quality rotary switch too. Why the use of relays ? They offer excellent performance at reasonable cost. A cheap rotary switch can drive relatively cheap but excellent performing relays. A very high quality rotary switch from let's say Elma costs a lot more. Just bought two of those today as a coincidence.

If you have some patience you can find Elma switches now and then for reasonable prices. Or Grayhill which are also very good.

It is the bad cheap switches that gave mechanical switches a bad name. The use of good switches with good cabling is nice but crosstalk might occur when wired the non optimal way. Relays offer better separation but again this is not always like that. It starts with good materials and then some craftsmanship. When using cheap materials all over even good craftsmanship can not help you :)

When using a rotary switch without relays it is best to place the switch as close as possible to the circuit. In a preamp it is best to place it right in the vicinity of the input RCA connectors and use an extension rod for the volume knob. All mechanical stuff and thus some (nice!) labour.

Digipots and digital input switches are only produced as they're cheap. There is really no alternative to classic metalwork if you are into quality. Just replace such a "digital" circuit once for quality (electro)mechanical stuff and you will know. Point is that switches are becoming more expensive and they're also harder to find. You will see the day that new ones are extinct !
 
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Generally shorting are using for stepped attenuators otherwise your volume control will be a horror experience. You can imagine why yourself I hope ! Hint: your speakers will be the victims.

I would use a larger high quality model for input switching (as you switch that one way quite often) and a small one for the MM stuff. Most of the switches can be changed to less positions by changing the "stop pin".

First determine how many positions (so how many input channels like Aux, DAC, Tuner etc) you need, then search. Don't dismiss suitable looking switches (but equipped with features you won't use) too fast. For instance a 2 deck 3 pole 4 position switch can be handy if you also want to switch indication LEDs with the otherwise unused third pole....

With Elma you have the gold flash versions and the 3 µm gold plated types. The latter are better but harder to find. Small difference though, the gold flash versions are also fine.
 
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Grounding what ? If you want to switch ALL grounds/GNDs of source you will need a switch with extra decks for GND switching. Beware that plops and clicks will be the case. You will need to turn volume down and live with the possible clicks. Better not switch the GNDs. Technically it might be better but you will need to live with the negative stuff too.
 
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Well, forgive my ignorance but to my understanding next best thing than using a single input system is switching both signals AND grounds. This switching action must occur before the chassis ground. And I don't know if there is such a switcher but if grounds should connect BEFORE the signals noise issue would be better. Maybe a half shorting-half nonshorting type switch? :)
 
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We are talking audio GND not PE ! PE is the one at the 120 V/230 V AC mains side that is connected for safety. Switching that one is not legal and plain stupid at the same time. When PE is used it should be connected directly without switches etc. to the metal case. Class I/II devices don't have PE connected, these devices are encased in plastic insulating cases. PE is used to prevent people from getting electrocuted !

Switching audio GND: think of the input RCA and then you switch not only the hot but also the cold/GND wire....In good audio audio GND is not connected straight to PE. What might be best for safety as seen in some puritanical areas is in fact worse for audio. This is a total different discussion. Normally one connects audio GND via a low ohmic resistor to PE to avoid ground loops. I prefer to have audio GND and PE separated. The metal case is connected straight to the PE pin. Audio GND is kept floating. It takes some practice to keep things non humming and it needs strict wiring and extra care at the 230 C AC side of the wiring like plastic insulation sheets etc. I can do this as I am the only one operating my equipment (I say this to silence the PE fundamentalists). There is a large difference when PE is connected directly to audio GND as PE is the "sewer" for electrical noise, switching noise/RF from PSUs etc. You don't want that in your audio chain do you ? I don't otherwise building good sounding equipment seems a waste of time.

Regarding switching audio GND: in theory you can't have noise etc. from unused inputs creeping in but in practice the drawbacks like clicks/DC potential differences etc are a nuisance.
 
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Hi, I didn't mean switching the earth, that's not topic of this thread. I mean to switch the ground of the input cables along with the signal.

Jean Paul, I'll ask a theoretical concept: Lets think we are switching the ground of the inputs but not with a 1 deck 4 pole switch but with a 2 deck 2 pole switch. Signals will be connected to upper deck and it will be non-shorting type; while grounds will be connected at bottom deck and it will be shorting type. With this technique, grounds will switch earlier than signals and prevent clicks. As I said, I don't know if this is applicable... Maybe a nonsense idea huh? Did I deserve a good punch? :)

Regards
 
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I have a dvd player and a laptop, both class II insulated, which give annoying shocks if they are not connected to earthed equipment

Either:

You have a cheap dvd player/laptop with switched PSU that leaks to the metal case. Small chance though that they're both not OK...

Or:

You have a large personal build up of static electricity yourself for example if you wear plastic/polyester based clothing and wear sneakers that isolate you from the ground...the leakage path is the device you are touching...and you discharge through them...

Or:

You have a device elsewhere in the chain that needs PE connected but it is used in a non-PE socket....and that particular device is connected to your laptop/dvd player...
 
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