Hi! I'm finishing up my amplifier project, and I'm going to add four AUX inputs at the back. 
I know that you will get some noise if you just have a switch, and don't turn down the volume, so I'm going to add a digital potentiometer that's controlled by an Arduino MCU. When I'm changing the channel (by using a remote control or pressing a soft switch) the volume is turned down to 0, the input source is changed, and then restored to the main volume.
The question is what is the most efficient way to do this? of course you can use eight relays, but I've heard something about MUX and deMUX. I'm not familiar with these, and I don't know if these will affect the sound in any way.
I want something that is (cheap), reliable, and high quality that doesn't destroy the pure gainclone sound.
What you you guys use to change the input channel?
I know that you will get some noise if you just have a switch, and don't turn down the volume, so I'm going to add a digital potentiometer that's controlled by an Arduino MCU. When I'm changing the channel (by using a remote control or pressing a soft switch) the volume is turned down to 0, the input source is changed, and then restored to the main volume.
The question is what is the most efficient way to do this? of course you can use eight relays, but I've heard something about MUX and deMUX. I'm not familiar with these, and I don't know if these will affect the sound in any way.
I want something that is (cheap), reliable, and high quality that doesn't destroy the pure gainclone sound.
What you you guys use to change the input channel?
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Hi,
Do you mean to use caps and leak resistors specifically for switch? I'm also looking for a switch solution for two MM level inputs.
Regards
The best and only way to have clean inputs and noise free is to use relays and farther more shunt to ground the source that is not selected . Via resistor of 600R if you like ( done mine directly shorting the sources with no probs so far ( 5 years running 24/7 )
Now days i designed a toggle switch or a push button to control a 4017 and every time you push 4017 jumps to the next source .
I am planing an integrated amplifier that only features one knob in the front :
Click CW to power on , increase volume CW ,and push the same button to cyclic select a source .
Neat ha ?
Now days i designed a toggle switch or a push button to control a 4017 and every time you push 4017 jumps to the next source .
I am planing an integrated amplifier that only features one knob in the front :
Click CW to power on , increase volume CW ,and push the same button to cyclic select a source .
Neat ha ?
If they are not already present then yes. Note that relays don't actually change anything - you still have contacts to make and break. Making a contact between two things at different potentials will cause a click.
Unselected sources can be shunted to ground via resistors - just like the selected source! 1M may do the trick, but a smaller value may be needed if electrolytic caps are used.
I actually have a relay module with eight separate relays that will give me 4 input sources. Do you mean that the resistor should be connected to the other terminal on the relay, like this fancy illustration?
Here is correct link: https://picasaweb.google.com/115453...hkey=Gv1sRgCL7LrsLfpY3EaA#5953307913638363714
Switches or simple electronics (i.e. without a clock signal) driving quality relays with correct termination is the way to go. If you like noise from switched PSUs and clock signals from an MCU you could use an Arduino. Features, features and more features but less sound quality. Even the best digital potentiometer can not compete with LDR based volume control or stepped attenuators of known quality. You know the cheap Ebay stepped attenuators ? Really very good for a low price.
Keep it analog if it needs to be good or excellent. Make it digital if you want a pc or Ipad to control the amp and sound quality is not important. Don't forget to implement a very bright shining blue LED to light the room in that case
Check the Rudi Ratlos VCPre design here ! Best of both worlds...
Keep it analog if it needs to be good or excellent. Make it digital if you want a pc or Ipad to control the amp and sound quality is not important. Don't forget to implement a very bright shining blue LED to light the room in that case
Check the Rudi Ratlos VCPre design here ! Best of both worlds...
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My plan was to have a separate (linear) transformer that supplied the voltage for all the digital electronics. If I'm running the input signal through the relays, why and how will the digital relay driver affect the sound? the relays are either on or off.
but will I potentially get some noise if I hook the gound rail of the Arduino to the ground rail of the amplifier? Maybe it's possible to add an inductor to filter some HF noise?
Ofcource I'll need a big, bright, blue LED so that will get ANY teenager to love me!
but will I potentially get some noise if I hook the gound rail of the Arduino to the ground rail of the amplifier? Maybe it's possible to add an inductor to filter some HF noise?
Ofcource I'll need a big, bright, blue LED so that will get ANY teenager to love me!
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Hi, I'm a newbie here, so always nervous while asking questions (they may be silly).
Is this applicable on a Seiden rotary switch? Any schematics available for this? I'll be using it inside a tube pre-amplifier (not a separate switcher chassis)
Regards
I'm going to use a digital potmeter that will adjust the volume down before changing the channel. then It will restore the original volume.
this is a great application for ldr's. muting 'relays', so to speak.
I don't think ldr's are that great for audio as vol control elements, but they are ideal for muting. you could then leave the digipot alone, mute the ldr and then unmute it. less 'changes' to the digipot would be best (from experience).
So you say that I should probably use the digital potmeter for muting only, right? My idea was to control the volume with a remote control and a rotary encoder. what can I use instead of a digital potmeter, that a microcontroller can control?
no, I meant using an ldr as a muting device (after the digital pot).
the digipot would still be your main vol control but you would not have to change its value just to mute 'between' changes. you'd use one element for vol control and the other (ldr) just for muting.
I personally love the cs3318 atten chip. its noise-free (I can't see or hear noise), its very high-end (for solid state devices) and you have plenty of channels in case you want to go 5.1 or active crossover (which is how I use mine).
I gave up on the PGA chips for various reasons; but the cirrus 3318 is an amazing digital vol control chip. its not cheap and its a little hard to solder to (use a chip carrier) but its my favorite digital pot for audio use.
the digipot would still be your main vol control but you would not have to change its value just to mute 'between' changes. you'd use one element for vol control and the other (ldr) just for muting.
I personally love the cs3318 atten chip. its noise-free (I can't see or hear noise), its very high-end (for solid state devices) and you have plenty of channels in case you want to go 5.1 or active crossover (which is how I use mine).
I gave up on the PGA chips for various reasons; but the cirrus 3318 is an amazing digital vol control chip. its not cheap and its a little hard to solder to (use a chip carrier) but its my favorite digital pot for audio use.
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