Untitled Document

Online Manual
for the Black Cube phono stage

Valued customer,

Congratulations on buying the Lehmann audio Black Cube phono RIAA preamplifier. The Black Cube is manufactured in Germany using very high quality components and carefully constructed to give you many years of musical pleasure.

This unit is only for inserting between a turntable's passive cartridge output and any audioamplifier's high level input. The Black Cube will handle nearly any system cartridge from high-level to low-level MM or MC and is made to fulfill the demands of audiophiles who enjoy analog music reproduction. Please keep this manual nearby the Black Cube so that you can refer to it for further use.

Precautions:

Please read the following before operating your Black Cube phono preamplifier. Wherever applicable below, Black Cube includes also the external power supply and its cable. Installing the Black Cube

- Be careful to use an apropriate cable for the connection between your power outlet and the Black Cube external power supply. Make sure that you have the appropriate version for your mains voltage.

- Be careful to prevent the Black Cube from getting wet; do not allow water to enter the Black Cube, especially when raining or snowing, or near a body of water. Otherwise fire or electrical shock may result.

- Do not place heavy objects on the power cord. If the cord is damaged, fire or electrical shock may result. In particular, it is possible that one might accidantally place a heavy object on a carpet that covers the cord; avoid these situations!

- Do not install the Black Cube in a place where it might be exposed to oil, smoke or steam (for example, near a cooking table or humidifier). Otherwise, fire or electrical shock may result.

- Do not place the Black Cube on an unstable surface, such as an unstable bench or slanted surface. Otherwise, the device may fall or drop, resulting in an injury.

- Do not place the power cord near a heating device. Otherwise, the cord sheath may melt, resulting in fire or electrical shock.

- Do not locate the Black Cube in a place subject to excessive heat, such as inside a car with all the windows closed, or in direct sunlight. Otherwise, fire may result.

- Do not handle the power plug with wet hands. Otherwise you may receive an electrical shock.

- When you remove the power plug, be sure to hold the plug. Never pull on the cord. Otherwise, the power cord may become damaged, resulting in fire or electrical shock.

- The Black Cube offers superb sonic quality. To ensure best possible results, you should use the best quality connecting cables that you can afford. Regular maintenance involves keeping all connections clean using a quality contact cleaner.

Using the Black Cube

Do not touch the Black Cube under the following circumstances:

- If you hear thunder, remove the power plug from the AC outlet as soon as possible. If you fear a lightning hit and the Black Cube has been connected to an AC outlet, do not touch the power plug. Otherwise you may receive an electrical shock.

- Do not attempt to modify this equipment. Otherwise, fire or electrical shock may result. Warranty is void on modified devices. Exceptions: dip switch settings and fitting of custom input load when done carefully by a skilled person, (trained technician) normally this is your dealer.

- If you think the Black Cube needs to be checked for maintenance or repair, consult your dealer.

- Do not place a container of water or any small metal object on top of the Black Cube or the external power supply. If water is spilled or if the metal object gets inside, fire or electrical shock may result. This applies to vases, pottet plants, glasses, cosmetic bottles, medicine, etc. Do not change the setting of the dipswitches with any tools that consist of metal.

- Do not damage, process, bend, twist, stretch or heat the power cord. If the cord is damaged, fire or electrical shock may result.

- When you are connecting other audio devices to the Black Cube make sure that you first turn off the power to all devices to be connected. Refer to the user´s guide for each device and use the specific cable for connection.

- Set the volume levels of all devices to minimum before connecting the Black Cube to your actual setup and to the AC outlet. Otherwise, an extremely loud noise could damage your loudspeakers or even your hearing.

- If you plan not to use the Black Cube for a long period of time (such as when you are on vacation), remove the power plug from the AC outlet. Otherwise, a fire could possibly result. If any abnormality occurs while using the Black Cube, remove the plug from the AC outlet.

- If you notice any abnormality - such as smoke, smell, noise, etc. - remove the plug from the AC outlet. Confirm that the abnormality is no longer present, then consult your dealer for repair. If you continue using the Black Cube under abnormal conditions, fire or electrical shock may result.

- If a foreign object or water enters inside the equipment, remove the Plug from the AC outlet and consult your dealer for repair. If you continue using the Black Cube under this condition, fire or electrical shock may result.

- If the power cord is damaged (for example if it is cut or if the core wire is exposed), ask your dealer for a replacement. If you continue using the Black Cube under this conditions, fire or electrical shock may result.

- If the Black Cube or the external power supply is dropped, or if the case is damaged, remove the plug from the AC outlet and consult your dealer. If you continue using the Black Cube under abnormal conditions, fire or electrical shock may result.

Maintenance

- Before cleaning the Black Cube, remove the power plug from the AC outlet for safety. Otherwise, an electrical shock may result.

- Do not open the external power supply of the Black Cube. There are hazardous voltages inside that might result in an injury or an electrical shock.

Description

The passive filter network of the Black Cube is located between two passive amplifier stages. Phase errors that occur due to active filter designs are thereby eliminated. Low-loss, low-tolerance WIMA foil capacitors in the filter network are responsible for a very good localization and soundstage reproduction.

Sensitivity for 250mV/eff. output voltage: 0,21mV/2,2mV switchble on board (MC/MM).

Input capacity: 220pF default, input impedances: 47 kOhms/ 470 Ohms/100 Ohms switchble on board (Dip-switches with gold plated contacts), one slot for solder free installation of custom impedance on pcb. One custom impedance for the adaption of your favourite system will be supplied without extra cost when ordered with Black Cube. No need of expensive impedance plugs!

Input connectors can be desoldered to solder the system cables directly to the audio board. (No connector is as good as no connector)

Output impedance: <100 Ohms Gold plated RCA-connectors, massive ground connector

The external regulated power supply of the Black Cube can be placed up to 2m away from the audio section. The cable between power supply and audio section is shielded to keep rfi away from the nearly noiseless and highly stable supply voltages. This effect is even enhanced by additional supply voltage filtering on the double sided audio pcb.

Case of 1,5mm aluminum protects the audio electronics.

Please read this manual first before connecting the Black Cube to mains voltage!

Connectors: (simplified)

Input side:

1. Ground connection (GND) If your turntable has a separate ground cable you should connect it here. You can connect: 4mm plugs, open ends, cable shoes

2. Signal input conectors (IN) Please connect your tuntable´s output here. To minimize loss, placement of the Black Cube should be as near to the turntable´s output as possible. The left connector is to be connected with the left channel. Technically trained persons may solder the tonearm cables directly to the input connectors on the pcb. (No connector is as good as no connector) In this case you have to pay special attention to the correct phase! Of course you MUST disconnect the unit from mains before soldering!

Output side:

1. Signal output connectors (OUT) RIAA-filtered high-level output. Please connect your output cables here to the following line-level preamplifier, active loudspeakers with volume control or power amplifier with volume control. Take care for the correct channel connection. W a r n i n g: You must not connect the output cables to a following phono input because RIAA-filtering and amplification would be done twice! You could damage the following phono stage or your power amplifier and loud-speakers! The resulting noise could even damage your hearing!!!

2. Control (LED)

3. Input for the external power supply Matching of gain and input impedances You can change input impedance (loading) and gain by dipswitches on board the audio circuit board for each channel separately. This type of selection is high flexible and also offers an available opening (slot 3) for inserting a resistor to accommodate cartridges which require special loading.

Before you make any changes to the input impedance or gain please do the following:
• Disconnect the power from the Black Cube's power supply.
• Place the Black Cube on a clean smooth surface.
• Carefully remove the four screws of the audio board's case with a screwdriver
• After removing the top you can now move the dipswitches to the configuration for each channel. Do not use any tools that could damage the electronic circuit to maintain the desired settings.
• The dipswitches They are located on the inside of the unit near the input RCA connectors. Both channel must be configured identically.

Common configurations:

If all the switches are in the off-position the input sensitivity is 2.2mV and the input impedance 47kOhms. This is fairly standard for many MM phono cartridges. Dipswitch 1 controls the gain stage and can be moved to the "on" position to achieve higher amplification for a MC cartridge. Switching only this switches to the ‚on‘ position might be suitable for some low output MMs. You can also reconfigure the impedance switches to achieve MM/ 470 Ohms for some high output MC's. Impedance switches connect the resistors in parallel. Therefore if you turn switches 2 and 4 "on" you will get a resulting impedance of 82 Ohms. By adding a special resistor of your choosing in slot 3 the possibilities of system matching are virtually unlimited. If you have a cartridge that needs a special input impedance please contact your dealer to have it installed.

After changing the gain and/or impedance to the desired values, please replace the top cover making sure of the correct orientation (use the ground input as your guide). When you have secured all of the screws, the Black Cube can be reconnected to your music reproduction system and to mains.

W a r n i n g:

If any question occurs or if you are uncertain about the gain or impedance needed, please contact your local dealer.

Technical Data

Input sensitivity:
MM MC for output level of 250mV/-10dB 2,2mV/1 kHz 210µV/1kHz 755mV/ 0dB 7mV/1 kHz 680µV/1kHz 1,55V/ +6dB 14mV/1 kHz 1,35mV/1kHz Gain 1kHz 40dB 61dB Max. input level1kHz: 63mV 5,8mV

S/N-ratio:
unweighted referred to 0dBu 77dB 69dB
CCIR 468-2 referred to 0dBu 75dB 67dB

Channel deviation: typ. max. 0,5dB

Channel crosstalk: fx = 1 kHz > 86dB fx = 10 kHz > 85dB

Input impedances: 47kOhms/470 Ohms/100 Ohms switchable on board the audio pcb. One place for custom impedance on board the audio pcb

Input capacitance: 220pF

Output impedance: < 100 Ohms minimum imp. following stage: >10kOhm

Measures: wxhxd (case only) 114mm x 44mm x 108mm

Power consumption: app. 0,7VA external power supply (2x15V)