Not Your Mommy's GC
My 1st real DIY project, well my first project of any kind in 15 years. Its bold, but not as bold as my BOSOZ, in progress.
This is a differential input (buffered) inverting GC with a ultra low noise power supply for the INA134 used as a buffer.
Its an old Kyocera CD 301 cd player, got 2 (one of which was working) on ebay for $30.
faceplate was redone and interior was gutted.
Here is the interior:
Top board in the middle is the power supply and buffer.
Bottom board on the right is for controlling the voltages across every LED. Believe it or not the blue ones are set below spec and still light up.
Amp module is around the heat sinks. Two LM3886TF chips.
PCB, I don't need no stinking PCB for my module!
More details on my web site here:
Close up of LM3886 Module
I can't see any picture attached...
Am I the only one? :confused:
Underside of Amp Module
I used parts (black gate caps and holco/riken resistors) from Peter Daniel's inverting configuration posted here a long time ago, back when inverting was the rage. Now noninverting is the rage, but looks like buffering is acceptable too. Whew.
Kimber speaker wire and pure silver wire used in the signal path. Power supply caps are Panasonic FC.
You can see from the inside pic (above) that I added 4 filter capacitors to the diode bridge, the DC just had too much ripple using the 1,000 uF caps per rail (4 rails). Had to do it, now bass is much better and HF is clear and articulate.
All diodes are high speed soft recovery, MUR1520 in the main supply (8 heatsinked unnecessarily) and MUR820 in the low noise supply.
These sinks in operation get only slightly warm. If cranking max output into a 5 ohm resistor they get much to hot to touch. If cranking max output into speakers, they get very hot, but you can still touch them. So they seem adaquate, but I am going to drill some vents into the top cover to let them cool via convection easier (holes are already in the bottom of the case for this purpose).
Here is the back panel.
One switch selects RCA or XLR inputs, it grounds the positive terminal of the differential input should RCA be selected. That way the balanced input passes through no switches.
The other switch turns off the Aux (low noise) power supply so that external batteries (another project in the works) can be used. You see the miniplug under the speaker binding posts for this input.
Low Noise Power Supply
Here is bottom of the low noise power supply board. It uses Linear Technologies LT1964 and LT1962 surface mount ultra low noise voltage regulators mounted on bottom of board. You see that they are small, but they seem to be working well. I get some hash on the highest setting on my scope, backgrounds are silent, things are good!
Here is a close up of the differential receivers on the low noise PS board. This is to be used with my BOSOZ so I wanted differential inputs.
2 more LEDs indicate power is applied.
Another view of the LN supply
Another view of the low noise board.
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