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Specifications and benchmarks

Measurements were done on Mini³ high performance edition and Mini³ extended runtime edition
amplifiers with a default gain of 5. The parts selection are as specified in t section.

The tests were conducted using the following equipment:

1.  Wavetek 188 4MHz sweep function generator
2.  Tektronix TDS2014B 100MHz quad trace digital storage oscilloscope
3.  Protek 6510 100MHz analog dual trace oscilloscope
4.  Fluke 95 50MHz digital dual trace ScopeMeter
5.  Fluke 187 digital multimeter
6.  Toshiba Satellite A65 laptop computer with Celeron 2.8GHz CPU and 768MB RAM
7.

Firewire Audiophile mobile interface

8.

Audio Analyzer 5.5 software

9.

dummy loads 330Ω/33Ω/none

10. other custom test jigs, cables and software

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Summary of Contents for Mini3

Page 1: ...sion 1 was never released Version 2 is the current offering featuring a smaller sturdier and more attractive aluminum case The technical difficulties with version 1 were solved in version 2 and the battery run time has been greatly increased See the History section for details Unless otherwise noted all information in these pages pertain to Mini version 2 There are two variants of Mini the high pe...

Page 2: ...engraved panel set Why not offer a full kit AMB is not prepared to stock all the needed parts and offer them as a full kit This amplifier is AMB s contribution to the DIY community rather than a for profit product AMB cannot assume the commercial support role that might be implicit with a full kit However to make sourcing parts easier AMB includes the PCB mount battery contacts and the ferrite bea...

Page 3: ...r supply with positive ground and negative outputs which in the Mini would require two batteries and resulting in a larger less portable case a single 9V battery is employed and a virtual signal ground is synthesized by using a TLE2426 precision rail splitter chip This simplifies the power supply yet provide the advantage of a dual tracking split supply without associated complexity The result is ...

Page 4: ...uts anywhere between 15V DC to 24V DC actual voltage with a minimum current rating of 300mA for battery charging and for running the amplifier Onboard voltage regulation allows a low cost unregulated linear AC to DC adapter to be used while protecting the opamps from being damaged by over voltage The charging circuit utilizing a LM317L voltage regulator wired as a constant current source safely ch...

Page 5: ...opper islands beneath the SOIC 8 opamps allows improved heat dissipation when a small amount of heatsink compound is applied especially for the AD8397ARDZ opamp which has a thermal E pad at the bottom A strip of the ground plane is exposed along each bottom side allowing the amplifier s signal ground to be electrically connected to the case via the board slots without the need to add any wires The...

Page 6: ...Schematic diagram The following is the schematic diagram of the Mini amplifier See the Parts list section for more details Here is the same schematic diagram in PDF format 34KB ...

Page 7: ...tput channel The V and V supply rails are connected to U3 the precision rail splitter chip It derives a virtual ground IG which is centered halfway between V and V it ensures maximum possible output voltage swing and symmetrical clipping when the amplifier is driven into overload In effect the rail splitter offers the characteristics of a tracking dual rail power supply from a single battery at a ...

Page 8: ...rd The Mini circuit board is made of high quality FR 4 glass epoxy double layer with plated through holes as well as silkscreen and solder mask It is intended to slide into the bottom slot of a Hammond 1455C801 or 1455C802 extruded aluminum case The board dimensions are 1 9875 x 3 1375 50 48mm x 79 69mm and is 0 062 1 58mm thick Photos of the top and bottom side of the circuit board are shown belo...

Page 9: ...The following is a view of the silkscreen layer You may also view the following ...

Page 10: ... panel set from AMB then you may skip this section and read the Notes below The information here is relevant if you will be drilling your own panels Since all Mini panel components DC power jack input output jacks LED indicators and volume control potentiometer are board mounted it is important that the holes on the front and rear panels be drilled accurately to match The following diagrams and ta...

Page 11: ...ard the plastic bezels provided and mount the panel directly to the case The bezel pads the panel about 0 065 1 65mm away from the edge of the circuit board causing the front 3 5mm stereo mini jacks to become recessed possibly preventing the plugs from seating properly The plastic bezel also creates an unsightly gap around the rear DC power jack and possibly preventing the DC power plug from makin...

Page 12: ...meter panel nut Some knobs would rub against the nut unless mounted with a large gap to the panel The potentiometer is securely attached to the board via eight solder joints and does not need additional reinforcement Similarly if you have a plastic front panel and are using non isolated 3 5mm stereo jacks with a threaded collar you may omit the panel nuts The indicator LEDs should be mounted with ...

Page 13: ...eries Farnell o other similar Notes about all resistors The Mini circuit board is designed for miniature through hole axial lead 1 8W or 1 4W resistors with a body length no longer than 4mm the recommended Xicon Panasonic and Multicomp resistors are 3 5mm or 3 2mm and no wider than 1 9mm Do not use oversized resistors in particular do not mount resistors vertically tombstone style The extra lead l...

Page 14: ...er for extended periods of time even when the battery is fully charged The drawback is longer time to charge the battery from a totally drained state back to full charge Depending on the capacity of the battery it may take 15 hours or more You could decrease the value of this resistor to increase the charge current The formula is I 1 25V R where I is the charge current in Amperes and R is the valu...

Page 15: ...ther similar C5 C5 aluminum electrolytic capacitor 100µF 25V low ESR high reliability Lead spacing 0 100 2 5mm radial diameter 0 250 6 3mm maximum height 0 59 15mm o Panasonic FC Digi Key o Panasonic FM Digi Key Farnell o Nichicon HE Mouser o Nichicon PW Mouser Notes about C4 and C6 If you prefer you may use 10µF 16V solid dipped tantalum capacitors 0 100 lead spacing radial in these locations Ple...

Page 16: ...There is no substitute part for this Opamps The recommended opamps for Mini high performance edition is as follows U4 Texas Instruments Burr Brown OPA690ID SOIC 8 AMB audio shop Mouser Digi Key Farnell U5 Analog Devices AD8397ARDZ SOIC 8 AMB audio shop The recommended opamps for Mini extended runtime edition is as follows U4 National Semiconductor LMH6642MA SOIC 8 AMB audio shop Digi Key Farnell U...

Page 17: ...d panels Mouser Digi Key Newark Farnell A precision drilled engraved aluminum front and rear panel set is available from AMB audio shop Use these for ease of build upgraded appearance and to assure a perfect fit The Mini s shown in the Overview section are equipped with these panels Volume knob The Alps volume control used in the Mini has a 6mm 0 236 D shaft so the volume knob should be made for t...

Page 18: ...s are available from various sources including Thomas Distributing and zbattery com in the US You can try another brand of 9V NiMH battery but you ll have to check the fitment AC DC adapter Due to Mini s onboard voltage regulation the AC DC adapter requirement is not very stringent It should be a linear adapter not switching to avoid high frequency noise but does not need to be regulated It must o...

Page 19: ...moisture While you look at the board layout please also take the time to look at the schematic diagram and associate each part with their location in the circuit While this is not normally required to build a working amplifier one of the opportunities of DIY is to learn about how the circuit works Try to determine what each part does and why the particular part or value is chosen There are many we...

Page 20: ...e the thermal compound does not ooze out the sides and the pin orientation is correct The side of the opamp with pin 1 is beveled and usually has a dot denoting pin 1 Viewing the board with the Mini logo proper side up the pin 1 pad of both U4 and U5 are at the bottom left side Press the tweezer tip on the top of the opamp to keep it from shifting while soldering Apply only a tiny amount of solder...

Page 21: ...p When you are done with the opamps use a Q tip and isopropyl alcohol or specialized electronics flux remover to clean off the flux Now mount and solder the rest of the parts starting with the lowest profile parts and work up in the following order see details below Resistors Diodes Multilayer ceramic capacitors Voltage Regulators U1 U2 Rail splitter chip U3 Ferrite beads L1L L1R L1G Tantalum capa...

Page 22: ...rom the board surface allowing at least 1 8 3 2mm clearance as shown in the following picture The U2 voltage regulator should have its pins bent 90 downward for insertion into the board You must check that the mounting hole is aligned properly while the pins are bent to fit their pads Apply a small amount of heatsink compound to the bottom of the regulator to help it transfer heat to the board No ...

Page 23: ...f the battery is too thick the whole assembly may not fit into the case In that event you can file away a portion of the bottom of the battery contacts to eliminate the gap and obtain additional clearance See the following diagram When soldering the battery contacts it will help to first secure the battery and contacts to the board by wrapping several turns of rubberband around the whole assembly ...

Page 24: ...e pulling on the ribbon will pop the battery out easily after the rear panel is removed If you have a black anodized Hammond case you should grind away some of the anodizing from the board slot in order for the exposed ground plane strips on the bottom of the board to make contact with the case This provides RFI shielding You do not need to do this with the clear anodized version The board will go...

Page 25: ...Wavetek 188 4MHz sweep function generator 2 Tektronix TDS2014B 100MHz quad trace digital storage oscilloscope 3 Protek 6510 100MHz analog dual trace oscilloscope 4 Fluke 95 50MHz digital dual trace ScopeMeter 5 Fluke 187 digital multimeter 6 Toshiba Satellite A65 laptop computer with Celeron 2 8GHz CPU and 768MB RAM 7 M Audio Firewire Audiophile mobile interface 8 RightMark Audio Analyzer 5 5 soft...

Page 26: ... power 11Vp p 3 9Vrms with external power Power output 300mWrms into 33Ω 30mWrms into 330Ω 180mWrms into 33Ω 30mWrms into 330Ω Frequency response at 0dBV output 0Hz 4MHz 0 3dB limited by function generator Rise time 100KHz square wave at maximum output 10 to 90 166nS 54nS Slew rate 100KHz square wave at maximum output 52V µS 162V µS Quiescent current battery current draw while power on 25mA 10mA N...

Page 27: ... load Mini high performance edition 330Ω load vs 33Ω load Mini extended runtime edition 330Ω load vs 33Ω load Comments on the RMAA test results The measured performance with 300Ω load is excellent for both Mini editions exhibiting extremely low THD and IMD distortion low noise floor and low stereo crosstalk through the entire audio frequency range There is virtually no degradation of performance o...

Page 28: ...roduced by a Wavetek 188 4MHz sweep function generator The following are the 100KHz square wave rising edge response of the Mini high performance and extended runtime editions as tested with a Tektronix TDS2014B 100MHz digital storage oscilloscope The rise time as well as the peak to peak output amplitude is shown on the right hand side of the display As could be seen the extended runtime edition ...

Page 29: ...are wave 10KHz square wave 100KHz square wave 100KHz sine wave 100KHz triangle wave 100KHz Lissajous Mini extended runtime edition 1KHz square wave 10KHz square wave 100KHz square wave 100KHz sine wave 100KHz triangle wave 100KHz Lissajous ...

Page 30: ...xtended runtime edition LMH6643MA dual operational amplifier SOIC 8 D1 D2 D3 3 1N4001 1A rectifier DO 41 512 1N4001 1N4001FSCT ND Farnell 9564993 D4 1 BZX55C12 12V 500mW zener diode DO 35 LED1 1 T 1 3mm super bright LED red for charge indicator your choice your choice your choice LED2 1 T 1 3mm super bright LED blue for power on indicator your choice your choice your choice J1 1 DC power jack 2 5m...

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