Hi,
I am currently building a Tube amp based on the Audio Note EL84. The main amp is functioning well. I have also constructed a Audio Note L3 phono pre amp. Also functioning well.
To complete my project I am now designing a PCB with which I can switch between different audio sources like CD player, Record player, Streaming device and Aux. The CD player, Streaming device and Aux use a simple NE5532 pre amp like https://xtronic.org/circuit/preamplifier-circuit-diagram-op-amp-12v/. Instead of the fixed resistors I use digital resistors on an arduino microcontroller to set the gain for each source. Also works fine. The sources are separated with 4 relays three relays connect directly to the NE5532 one relay get input from
But now the challenge/question. I have wired the two pre amps directly to the input of the EL84 main amp. This means when I use the Phono tube amp this input signal will be on the output of the NE5532. The other way around is not applicable as the relay of the Phono source is closed in that condition.
Will placing an input of the NE5532 output when I am not using it ham the pre amp? I tried to place two diodes on the output of the pre amp but found out that that is not working. Is there another method to make the input one way instead of diodes?
Please see the schematic attached if my description is not clear.
I am currently building a Tube amp based on the Audio Note EL84. The main amp is functioning well. I have also constructed a Audio Note L3 phono pre amp. Also functioning well.
To complete my project I am now designing a PCB with which I can switch between different audio sources like CD player, Record player, Streaming device and Aux. The CD player, Streaming device and Aux use a simple NE5532 pre amp like https://xtronic.org/circuit/preamplifier-circuit-diagram-op-amp-12v/. Instead of the fixed resistors I use digital resistors on an arduino microcontroller to set the gain for each source. Also works fine. The sources are separated with 4 relays three relays connect directly to the NE5532 one relay get input from
But now the challenge/question. I have wired the two pre amps directly to the input of the EL84 main amp. This means when I use the Phono tube amp this input signal will be on the output of the NE5532. The other way around is not applicable as the relay of the Phono source is closed in that condition.
Will placing an input of the NE5532 output when I am not using it ham the pre amp? I tried to place two diodes on the output of the pre amp but found out that that is not working. Is there another method to make the input one way instead of diodes?
Please see the schematic attached if my description is not clear.
Can't do that, and certainly not with diodes. You must have a passive or active mixer circuit.
Or add another input to the 5532 preamp for the tube preamp.
Or add another input to the 5532 preamp for the tube preamp.
Passive mixing with 1k resistors might work, but if you want to switch inputs, why not use switch(es)?
I have added an extra breaking relay switching with the phono relay. The relay breaks the input of the 5532 amp when the phono is on. This should work. Thank you for your thoughts!