If you follow the thread on building a class A amplifier here:
Single gain stage transistor amplifier.
you may realize I am continuing to have fun dabbling with the 'single ended' transistor amplifier with some measure of success. Distortion levels vary, possibly due to bad connections, so I need to re-do the circuit again (solder-less of course). Sometimes I am able to listen without much distortion at all on the desktops, so the concept is workable.
As you can imagine, I am getting a little impatient, and tired of listening to the right channel only or left channel only on the large floor standing speakers or the smaller desktop speakers I have. Wouldn't it be nice to hear the sound from two speakers, albeit in mono? Is it possible to convert a stereo signal to mono? Happily there is a way to do this, and readers will probably know all about it. Some testing with the said class A amplifier and the ES 333 speakers in series provided a good level of sound, and relatively similar to the stereo music I have heard, although the amplifier needs to be improved greatly.. I am more comfortable listening to two speakers in mono rather than one speaker, there is more sound and it does not seem to come from a narrow corridor on one side of the room. To listen in stereo you have to be in the 'sweet spot' that varies by speaker, of course. There are other benefits, in depth and sound stage, although you can hear the stereo effect when seated to one side of the speakers, much of the time spent listening is in semi-mono. The 'stereo/mono' switch on FM tuners is another feature which readers will be familiar with, and it does not render the radio station unlistenable to.
Here is the proposed system: the simplicity of putting together a mono amplifier circuit, single channel, and listening to music from two speakers is a quick fix that is difficult to pass up. I can do all the listening tests and enjoy the music at the same time. One circuit, one power supply, one transformer, etc, at the cost of some input resistors and some wiring to add the L and R signals together.
I have not been able to find any threads on DIY audio that are related to this concept and I was wondering: is anyone listening in mono over two vintage speakers (Bluetooth speakers do it all the time).? Any advantages?
Single gain stage transistor amplifier.
you may realize I am continuing to have fun dabbling with the 'single ended' transistor amplifier with some measure of success. Distortion levels vary, possibly due to bad connections, so I need to re-do the circuit again (solder-less of course). Sometimes I am able to listen without much distortion at all on the desktops, so the concept is workable.
As you can imagine, I am getting a little impatient, and tired of listening to the right channel only or left channel only on the large floor standing speakers or the smaller desktop speakers I have. Wouldn't it be nice to hear the sound from two speakers, albeit in mono? Is it possible to convert a stereo signal to mono? Happily there is a way to do this, and readers will probably know all about it. Some testing with the said class A amplifier and the ES 333 speakers in series provided a good level of sound, and relatively similar to the stereo music I have heard, although the amplifier needs to be improved greatly.. I am more comfortable listening to two speakers in mono rather than one speaker, there is more sound and it does not seem to come from a narrow corridor on one side of the room. To listen in stereo you have to be in the 'sweet spot' that varies by speaker, of course. There are other benefits, in depth and sound stage, although you can hear the stereo effect when seated to one side of the speakers, much of the time spent listening is in semi-mono. The 'stereo/mono' switch on FM tuners is another feature which readers will be familiar with, and it does not render the radio station unlistenable to.
Here is the proposed system: the simplicity of putting together a mono amplifier circuit, single channel, and listening to music from two speakers is a quick fix that is difficult to pass up. I can do all the listening tests and enjoy the music at the same time. One circuit, one power supply, one transformer, etc, at the cost of some input resistors and some wiring to add the L and R signals together.
I have not been able to find any threads on DIY audio that are related to this concept and I was wondering: is anyone listening in mono over two vintage speakers (Bluetooth speakers do it all the time).? Any advantages?
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You can mix two stereo line level signals to mono with a couple of 10 k resistors to prevent the to channels to from being blown up. Then you follow with an amplifier stage to boost the level back up.
A commercial product that does this is a "mixer" You can start with a entry level product like a PV4 or Alesis 4 channel, but I've found it economic to bid on warehouse mixers like the Peavey MMA-875t or the crown 180m or 180ma. If you get the dual RCA input card, you have all that plus a 75 or 80 watt mono amp. I've gotten these for $35 working & $25 freight. If they don't work, they are not hard to fix. One pair output transistors and a output transformer tends to prevent wiring caused meltdowns. Crown Power Amp 180MA 80 Watt 4 Channel Power Amplifier Amp | eBay
There are oriental mixer amps for the warehouse announcement market, but I obviously don't know the brands. The US brands above have <.2% HD, which is fine IMHO for any speaker <$1000.
A commercial product that does this is a "mixer" You can start with a entry level product like a PV4 or Alesis 4 channel, but I've found it economic to bid on warehouse mixers like the Peavey MMA-875t or the crown 180m or 180ma. If you get the dual RCA input card, you have all that plus a 75 or 80 watt mono amp. I've gotten these for $35 working & $25 freight. If they don't work, they are not hard to fix. One pair output transistors and a output transformer tends to prevent wiring caused meltdowns. Crown Power Amp 180MA 80 Watt 4 Channel Power Amplifier Amp | eBay
There are oriental mixer amps for the warehouse announcement market, but I obviously don't know the brands. The US brands above have <.2% HD, which is fine IMHO for any speaker <$1000.
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As a mixer, you can use exactly the same simple small amplifier A. The difference is the larger resistance of the resistor in the collector (100-330 ohms). The source channels are connected to the input through 1-10 k resistors. The output is connected to the input of the next amplification stage.
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