Fredenstein MAGIC PRE User manual

MAGIC PRE
Rev. A
Operating Manual

Fredenstein Magic Microphone Preamplifier
The MAGIC PRE microphone preamplifier's most obvious feature is the green glowing “magic
e e” vintage vacuum tube for output level indication. The “Magic E e” tube is perhaps the most
attention grabbing visual feature of this preamp and something ever bod notices in an rack.
Besides being just fun and another wa to impress clients, this visual treat complements the rich
vintage character of the preamp. The “e e” closes near optimal ouput levels.
The preamp follows what ma be thought of as a ver traditional topolog that uses both an input
transformer and an output transformer. Both are high qualit American made transformers. The
steel-core output transformer in particular is a ver important sound shaping component which
helps produce a smooth vintage sound without being dark or just “mid-rang ” or mush .
A single discrete amplifier is used for the active gain element and there are no chip based amplifiers
in the signal path. To achieve an unusual high level of performance the circuit is based on our OPA2
discrete audio operational amplifier. As in all Fredenstein products, the OPA2 is not a cop of an
older design, but is a completel new design manufactured in SMT technolog with matched and
integrated dual input transistors to guarantee vastl improved specifications compared to older
designs. The OPA2, in the tradition of similar modules, is socketed and can be exchanged without
tools. The industr standard pin-out makes it compatible with man other amplifier modules.
A 2 MOhms high impedance direct input is located on the front-panel, it accepts unbalanced
signals, the rear microphone input is automaticall disconnected when a plug is inserted in the DI
connector.
The features include a maximum gain of 70 dB, a 20 dB Pad, and Phantom-Power support, plus a
new feature simpl labeled “Color”. The “Color” switch is intended to produce some tube-like
harmonic content that, while not calling attention to itself, can bring some sounds to life and bring
them forward in the mix and seem to make them sound more detailed and dimensional. While the
color circuit does increase distortion, the audible effect is subtle enough that few people would ever
describe the effect as “distorted”.
As all Fredenstein products, the Artistic Pre is designed b a German-American team and
manufactured in Taiwan.
Installation:
Please power down our rack or box first before inserting the Artistic Pre. The power requirements
are fairl demanding at a maximum of +100mA,-160mA and Artistic Pre ma need to be mounted
in racks capable of suppl ing sufficient power, such as the Fredenstein Bento series.
Fredenstein Magic Pre Rev. A Manual V1.0 August 23, 2016 Page 1

Fredenstein Magic Microphone Preamplifier
Overvie :
Rotary Control:
GAIN : Gain Control, minimum +15 dB
(with PAD), maximum +70 dB
Magic Eye Level Indicator: -15 dBu to +15 dBu
S itches:
COLOR : when lit green, adds harmonics
PAD : -20 dB Input Attenuator when lit
amber
P48 : +48 Volt Phantom Power when lit
red
DI : High Impedance unbalanced
Input
Fredenstein Magic Pre Rev. A Manual V1.0 August 23, 2016 Page 2

Fredenstein Magic Microphone Preamplifier
Gain Control:
Microphone Preamplifier Gain Control, minimum +35 dB, maximum +70 dB without PAD
engaged, minimum +15 dB, maximum +50 dB with PAD.
Magic Eye Level Indicator:
This is a vintage 6E5C vacuum tube that is designed to displa optimum signal conditions. In this
case, we use it to show the mic preamp output level. The “e e” is wide open (about 90 degrees unlit
and 270 degrees softl glowing green) when there is no signal and and begins moving 30 dB below
DFS or clipping (-15 dBu output). The “e e” closes as the signal level increases and the two edges
graduall approach each other until the overlap slightl . Where the don't quite overlap or where
the “e e” closes completel represents +15 dBu t picall and is analogous to a bar graph meter
going into the ellow. This ma be considered a near optimum level. When there is noticeable
overlap, consider it similar to going into the red and ma be levels ma too hot. Keep in mind, that
this indicator is not precise and for true precision ou should rel on the meters of our A to D
converter, and the Magic E e indicator is a visual tool and for optimal audio performance one might
be advised to alwa s use one's magic ears. With a few minutes of practice, ou should find the
Magic E e tube to be about as useful as most meters and more fun than most.
Color:
When lit (green), introduces a careful blend of added harmonic content into the signal path. This is
somewhat intended to simulate the behavior of choice vacuum tube circuits. In this case, the
balance of harmonics has been carefull tailored, be ond what tends to happen with tubes or valves.
The overall amount of harmonics does depend on level (via the Gain Control knob) and the Magic
E e tube can be used to help dial in the amount that ou tend to prefer. Of course, when ou can,
dis-engage the Color switch to compare and check b ear. It is like cooking with spice, somewhere
between too little and too much is just the right amount, so use the Gain Control accordingl .
PAD – Input Attenuator:
Setting the PAD switch (orange light) activates a 20dB attenuator at the input allowing higher level
signals to pass through the preamplifier (note: Pad is affecting the DI input as well). Man modern
condenser mics have ver hot output levels and the PAD can help prevent clipping. The minimum
gain changes from +35 dB to +15 dB
P48 Phantom Po er:
Most FET condenser microphones as well as some other microphones with built-in amplifiers
require +48V Phantom Power. Setting the P48 switch (red light) enables +48V through the balanced
microphone line. Please check our microphone documentation if ou are not 100% sure. Enabling
P48 on microphones not designed for P48 might cause severe damage to the microphone. The DI
input is not supplied with Phantom Power.
DI – Direct Input:
The most common use for the DI input is to connect instruments like guitars directl to the Magic
Pre. The input impedance is greater than 2 MOhms to insure compatibilit with most instrument
pickups. After inserting an unbalanced (Tip-Sleeve) plug, the balanced microphone input through
the box or rack is automaticall disabled.
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Fredenstein Magic Microphone Preamplifier
Technical Data:
Frequenc Response : 20 Hz – 40,000 Hz, +/- 1 dB
Distortion 1kHz : < 0.03% at +4 dBu output level
< 0.015% at +20 dBu output level
< 0.04% at +26 dBu output level (clips at +28 dBu)
50Hz : < 0.08% at +4 dBu output level
< 0.08% at +20 dBu output level
10kHz : < 0.02% at +4 dBu output level
< 0.05% at +20 dBu output level
Input Noise : < -127 dB
Input Impedance : > 1600 Ohms
DI Impedance : > 2 MOhms
Max. Input Level : + 10 dBu, Pad activated
Max Input Level DI : + 18 dBu unbalanced
Output Impedance : 600 Ohms
Max. Output Level : + 26 dBu
Input Attenuator : - 20 dB (switchable)
Maximum Gain (XLR) : 70 dB
Minimum Gain : 35 dB
Minimum Gain 20 dB PAD engaged : 15 dB
Maximum Gain (DI) : 42 dB
Minimum Gain : 8 dB
Minimum Gain 20 dB PAD engaged : -12 dB
Current draw : +100mA, -160mA
Color Engaged Distortion : approximatel 0.1% at -10 dBu output level
approximatel 1% at -5 dBu output level
approximatel 3% at 0 dBu output level
approximatel 4.5% at +24 dBu output level
Frequenc Response : : 20 Hz – 20,000 Hz, +/- 1 dB
Fredenstein Magic Pre Rev. A Manual V1.0 August 23, 2016 Page 4

Contact Info:
Fredenstein Professional Audio
b Orion Communication
7F-1, No. 582, Ruei Guang Rd.
Neihu District
Taipei 114
Taiwan
Phone : + 886-2-2657-2618
Email : [email protected]
Web : www.fredenstein.com