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Phonostages — Oehlbach Twin Amp Ultra
Description, images, technical data and specifications
Oehlbach Twin Amp Ultra
Image source — © Oehlbach
The Twin Amp Ultra is a phono preamplifier from Oehlbach, the German company based in Cologne and known since 1974 for its cables and accessories. It is a transistor design for MM and MC pickups, with a separate external power supply. It was launched at a suggested price of EUR 399.
Key specs that matter
Input impedance is 47 kohm for MM and 100 ohms for MC. Connections are RCA sockets with 24 carat gold plating, plus a screw-type ground terminal. The power supply is external, linear and uses a shielded analogue transformer, running from 230 V/50 Hz. A switch-on delay protects connected equipment. The case is all metal with a brushed stainless steel front panel.
Engineering and use context
Phono stages amplify signals of a few millivolts, or much less for MC cartridges, so noise and hum from the power supply are the main challenge. Placing the mains transformer and all mains-voltage components in a separate case keeps their magnetic fields and electrical noise away from the sensitive signal path. The linear supply avoids the high-frequency switching noise of the plug-top adapters used by many phono stages at this price. The two input settings suit the two cartridge types. MM cartridges get the standard high-impedance load, while low-output MC cartridges get a low load that damps their electrical resonance, plus more gain. Precise RIAA equalisation restores the balance of treble and bass that is altered when records are cut. The circuit is built around operational amplifiers. The metal case shields against electromagnetic interference, and the internal wiring is shielded. The switch-on delay keeps the output muted until the circuit has stabilised, preventing thumps that could reach the loudspeakers. The ground terminal connects the turntable's earth lead to suppress hum.
Pairing
The Twin Amp Ultra suits amplifiers without a phono input and turntables with MM or MC cartridges. Its fixed MC load works with most low-output MC designs.
Alternatives
Oehlbach's Phono PreAmp Ultra is the brand's more compact MM/MC phono stage with a plug-in power supply.
Key specs that matter
Input impedance is 47 kohm for MM and 100 ohms for MC. Connections are RCA sockets with 24 carat gold plating, plus a screw-type ground terminal. The power supply is external, linear and uses a shielded analogue transformer, running from 230 V/50 Hz. A switch-on delay protects connected equipment. The case is all metal with a brushed stainless steel front panel.
Engineering and use context
Phono stages amplify signals of a few millivolts, or much less for MC cartridges, so noise and hum from the power supply are the main challenge. Placing the mains transformer and all mains-voltage components in a separate case keeps their magnetic fields and electrical noise away from the sensitive signal path. The linear supply avoids the high-frequency switching noise of the plug-top adapters used by many phono stages at this price. The two input settings suit the two cartridge types. MM cartridges get the standard high-impedance load, while low-output MC cartridges get a low load that damps their electrical resonance, plus more gain. Precise RIAA equalisation restores the balance of treble and bass that is altered when records are cut. The circuit is built around operational amplifiers. The metal case shields against electromagnetic interference, and the internal wiring is shielded. The switch-on delay keeps the output muted until the circuit has stabilised, preventing thumps that could reach the loudspeakers. The ground terminal connects the turntable's earth lead to suppress hum.
Pairing
The Twin Amp Ultra suits amplifiers without a phono input and turntables with MM or MC cartridges. Its fixed MC load works with most low-output MC designs.
Alternatives
Oehlbach's Phono PreAmp Ultra is the brand's more compact MM/MC phono stage with a plug-in power supply.
Specifications
Model name
Twin Amp Ultra
Inputs (balanced)
N/A
Inputs (single-ended)
N/A
MC current-sensing input impedance (Ω)
N/A
MM/MC voltage input impedance (Ω)
N/A
Output impedance (Ω)
N/A
Gain (dB)
N/A
Playback EQ curves accuracy (dB)
N/A
Frequency response low +/- 3dB (Hz)
N/A
Frequency response high +/- 3dB (Hz)
N/A
Total Harmonic Distortion + Noise (%)
N/A
Dimensions (mm)
N/A
Weight (kg)
N/A
Official link