dual zone amp
Over the years I collected boxes full of surplus components, left-overs from projects, which just beg to be used. Now, in the lab and in my kitchen I listen mainly to streaming radio from the internet. The quality of the average stream resembles more AM radio then anything else so there is absolutely no need for hifi equipment. In fact I listen in mono to an open baffle full range speaker which requires very little power but needs some bass lift. The kitchen speaker doesn't need the bass lift so I decided to build a dual zone amp.
I have a number of nice alu boxes which are very well suited for little projects. I also have plenty of potmeters, switches and connectors.
That leaves us with some constraints but that is where the fun comes in.
I could have chosen the 'discrete' route and build an amp with transistors but that would probably not fit in the box and also I am a lazy sod so I shopped the rs catalogue for a suitable IC. As it happens there are a couple of 'no brainer' devices available. I settled for the TDA2616, a 9 pin package with standard 'veroboard' pin spacing.
The salvaged 15V toshiba laptop supply being just within specs.
Basicly only input and output capacitors are needed.
At first I thought of 'designing' a stereo box with mono switch like this:
But then I realized that it would not be possible to apply different EQ on the 2 channels.without adding a buffer somewhere.
Plan B goes mono all the way:
All of this is a huge compromise since passive mixing down to mono and filtering comes at an insertion loss cost. Fortunately the amp has 30dB gain and I only consider line level inputs, a total gain of 20dB should be enough. To be sure I 'spiced' the whole thing (remember I am a lazy sod).
Below a curve with CF=22nF.
With no filtering the attenuation is just 9dB with both input channels driven (left and right input tied together), in line with my design goal. The filtering is somewhat affected by the potmeter setting since the input impecance of the TDA is only 20K but that's no big deal, it's not a lab instrument we are building.
The TDA2616 is mounted on the bottom of the alu box for cooling, I took care to make a star grounding.
The filter capacitor is mounted in a socket for easy experimentation.
The finished result:
I have a number of nice alu boxes which are very well suited for little projects. I also have plenty of potmeters, switches and connectors.
That leaves us with some constraints but that is where the fun comes in.
I could have chosen the 'discrete' route and build an amp with transistors but that would probably not fit in the box and also I am a lazy sod so I shopped the rs catalogue for a suitable IC. As it happens there are a couple of 'no brainer' devices available. I settled for the TDA2616, a 9 pin package with standard 'veroboard' pin spacing.
The salvaged 15V toshiba laptop supply being just within specs.
Basicly only input and output capacitors are needed.
At first I thought of 'designing' a stereo box with mono switch like this:
Plan B goes mono all the way:
All of this is a huge compromise since passive mixing down to mono and filtering comes at an insertion loss cost. Fortunately the amp has 30dB gain and I only consider line level inputs, a total gain of 20dB should be enough. To be sure I 'spiced' the whole thing (remember I am a lazy sod).
Below a curve with CF=22nF.
The TDA2616 is mounted on the bottom of the alu box for cooling, I took care to make a star grounding.
The filter capacitor is mounted in a socket for easy experimentation.
The finished result:
Comments
Post a Comment