Quote:
Originally Posted by amb /img/forum/go_quote.gif
Be careful with the AD8066. Even though it's nowhere as finicky as the AD8397, it is still a very fast, wideband opamp and could become unstable if used in a circuit that has inadequate rail decoupling or poor PCB layout. I don't know about the XM4, just thought I'd throw this caution out.
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Thanks for the help, The specs are here.
http://www.practicaldevices.com
and here
Practical Devices Corporation
XM4 Portable Headphone Amplifier
Product Details
XM4 Headphone Amplifier
* Uses 0.1% tolerance mil-spec resistors in the analog feedback circuit.
* Uses TLE2426 rail splitter, with noise reduction, to create a stable and low-noise analog ground.
* Uses OPA2134 ultra-low distortion (.00008%) low-noise high performance audio amplifier.
* Audio power supply bypassing uses both high-value Electrolytic and Tantalum capacitors to create an ultra-stable low-noise low-impedance power supply.
* Polished Aluminum volume knob.
* Proper dual-layer impedance-controlled Printed Circuit Board.
* Optional Lithium-Ion FastCharge® System is available.
Block Diagram of XM4 Headphone Amplifier
Audio Performance and Quality
The XM4 is constructed using only high-quality audio components:
Amplifier Stage:
* Burr-Brown OPA2134 ultra-low-distortion low-noise high-performance Audio Amplifier: The heart of the amplifier stage uses the well-respected Burr-Brown OPA2134 ultra-low-distortion (.00008%) low-noise high-performance audio amplifier.
* Mil-spec 0.1% metal film feedback resistors: The feedback stage around the amplifier uses Military-spec (MIL-R-10509) 0.1% metal film resistors, chosen for their very low noise and excellent high-frequency characteristics (Vishay-Dale RN55 series).
Audio Power Supply Stage:
* Texas Instruments TLE2426 Precision Virtual Ground: Powering the audio stage is the split-rail power supply, which is created by the Texas Instruments TLE2426 "Rail Splitter" Precision Virtual Ground. To further reduce noise and improve ripple rejection, the TLE2426's noise reduction pin is used
* Tantalum and high-value Electrolytic Capacitors: To further improve the stability of the power rails, a combination of both Tantalum and high-value Electrolytic capacitors are used. Electrolytic capacitors provide bulk decoupling of the power rails, but due to electrolytics' relatively-high ESR (Equivalent Series Resistance - a small unavoidable parasitic resistance in series with the capacitor), electrolytics do not have good high-frequency performance. Therefore, Tantalum capacitors, with their excellent ultra-low ESR performance, are used to fill in the spectrum where the electrolytics left off. The result is an exceptionally stable low-noise power supply for the audio stage.
PCB Layout:
* Professional Printed Circuit Board. The XM4 uses a proper professionally-built FR-4 impedance-controlled PCB. Care was taken during the design of the PCB to ensure audio signals have ground shielding and a low-impedance return path, which is not possible with any hand-wired board.
T
I am not being lazy , I just don't know anything!!
