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MINI AMP
Linestage Module |
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The MINI AMP, originally designed by Erno Borbely, is a very high quality discrete
operational amplifier (op-amp). Why design a discrete op-amp? While state of the art op-amps are very good quality and many boast great specifications,
they still possess both technical and sonic limitations due to their monolithic nature. A discrete op-amp allows the designer to hand pick each and
every component for both performance and sonic enhancements. Transistors can be selected for low noise, low capacitance and quick response time. High
quality film caps can be applied as well as super low noise resistors. Higher voltage rails can be incorporated allowing for greater voltage swings and
beefier output devices, able to withstand heat, can be selected to operate in full class-A mode providing both excellent linearity and high current
drive.
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| The Mini Amp with Dale
metal film resistors and onboard voltage regulators. |
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The MINI AMP has very good open-loop linearity at high frequencies, is extremely stable and boasts some very impressive specs like; an input noise
voltage below 1uV, a slew rate greater than 100V/usec and a THD figure that’s so low most test equipment can’t measure it! S/N ratio greater than 110dB
and a frequency response of 5Hz to 110khz +/-0.5dB. But most importantly, this is the BEST op-amp you’ll ever hear, with loads of low level detail,
impressive bass, a nice neutral but warm midrange and rounded out with a very smooth and extended top end.
Did we say this is an op-amp? Yes, we did.... and therefore you can use the MINI AMP like you would any other audio op-amp. For
example; it can be configured for inverted or non-inverted outputs; balanced or single-ended operation; balanced to singled-ended converter; it can be
set up for unity gain, gain of 10, 20, etc. The MINI AMP can be used as a simple but great sounding linestage, a buffer amp, an I/V converter in your
DAC, a summing amplifier for a mixer and in active crossover filters. It's even quiet enough that you could drop an RIAA filter in between a pair
of these amps and create great sounding phonostage.
Our MINI AMP features a JFET input circuit incorporating matched devices and a bipolar output stage operating in full class-A mode.
Its input impedance is approximately 1 Mohm and its output impedance is less than 100 ohms. It requires a power supply capable of providing + 24 and -
24 volts DC @ 0.5 amperes.
We have packaged the MINI AMP as a mono amplifier, i.e. two boards are required for stereo operation and four boards are required for
balanced stereo operation. The MINI AMP is packaged on a silkscreened 4-layer printed circuit board measuring a very petit 3"(76mm) by 3"(76(mm). This
4-layer board features a dual ground-plane design providing a very low impedance return path and superior shielding for added immunity from noise. Each
unit also includes on-board voltage regulation circuitry. These regulators can be bypassed if using a power supply with a more elaborate regulation
scheme. The kit includes all components necessary for proper operation and all components are individually packaged in plastic bags and marked with
their reference designators.
As usual, with all Welborne Labs kits, we offer several options including: with or without the on-board voltage regulators, kit or
assembled, and upgrade options featuring the ELNA Cerafine capacitors and the low noise Linear Technology voltage regulators. We suggest you mate a
couple of the MINI AMPs with our PS5
dual-mono power supply kit, throw in a volume control, selector switch and RCA jacks and you will end up with a killer linestage that’ll enhance ANY
system.... tube or solidstate!
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| The Mini Amp without
onboard voltage regulators and stuffed with Caddock resistors |
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The assembly manual includes step-by-step instructions for assembling and testing each
amp along with connection diagrams for configuring these amps for the different applications listed above. We will try to post more application
info on our website soon.
Click
here for an example connection diagram for a 5 input linestage
using the MINI AMP and our PS5 power supply. |
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Ordering Instructions |
| Be sure to order two amps for single ended stereo operation. For
balanced operation order four amps. |
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Basic Version includes Dale metal film resistors, Nichicon low impedance
electrolytic capacitors, Wima film capacitors and National Semiconductor voltage regulators. |
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Ultimate Version includes ELNA Cerafine electrolytic capacitors, Wima film
capacitors and the Linear Technology voltage regulators.
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MINIB |
Basic MiniAmp with Voltage Regulators |
$80.00 |
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MINIBX |
Basic MiniAmp without Voltage Regulators |
$71.00 |
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MINIU |
Ultimate MiniAmp with Voltage Regulators |
$99.00 |
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MINIUX |
Ultimate MiniAmp without Voltage Regulators |
$76.00 |
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MINIA |
Assembly/Test Fee for each Amp |
$30.00 |
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