High End Line Driver
I visit a local car audio install shop every weekend as I'm friends with the owners and most of the customers. They cater to high end installs mostly in sound quality.
One day, they asked me if I could design for them a line driver as they couldn't find one that fits their requirements mainly: High end components, Minimum parts in the signal path, clipping LED's, independent gain controls/output and minimum alteration of the signal.
I said, No problem. just give me funding and I'll do the rest. And they did.
A month later, I finalized the circuit, sent it to be made with real professional quality PCB's. Three weeks later, I had the boards. A first prototype was made to verify operation and sound quality.
Here is the prototype. That is the complete case I was using for 9 months before the actual prototype enclosure was made.
When the case arrived, it was time to assemble and see if everything fits... The actual RCA connectors for the production has not arrived so I used temporary ones which were ok but not good enough to be called "high end".
Yes, that's a glass top cover.
Top cover is anodized aluminum. We also tried black anodized and even copper plated!
Phoenix pluggable power terminal blocks
Here are some internal shots with the temporary parts:
My prototype unit used Elna Silmic II input caps. and solid core PCOCC teflon insulated wires
Custom wound toroid
Here is where we can separate the PS from the signal boards. Jumpers transfer +/-15V and ground from the PS to the preamp boards
And then the parts arrived! Burr Brown OPA2604 Op amps and the correct RCA connectors...
My 4ch unit updated, op amps changed to AD823 and input caps to Nichicon Muse.
The board can be separated from the SMPS section and joined to another as a host.
That allows the boards to be daisy chained for the 8 channel model.
Burr Brown Op Amps
Nichicon Fine Gold input caps
Panasonic FM powersupply caps
Independent Bourns Cermet Gain control per channel
Clipping LED indicator per channel pair
Balanced output capability
Bare Essentials - Minimum parts in the signal path
Heavy duty RCA connectors
Heavy gauge steel/aluminum/glass enclosure
Each one is hand built!!!!
Voltage input: 0.88v - 9.16V
gain adj range: 0.32dB to 20.68dB
Voltage output: 9.49V RMS before clipping led lights up
Signal to noise ratio: 112.84dB
Channel Separation: 110.14dB (measured between adjacent channels)
THD+N (JIS-A filter): 0.0025%
Input impedance: 22kOhm
Supply range: 10V-15V
Supply current: ~150mA (4ch) ~250mA (8ch)
(Specifications above were measured on a bare PCB, no case, so production unit should be better!)
Page created and copyright R.Quan © 23 Jan 2011.