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Golden Age Premier PRE-73 preamp
Golden Age Premier PRE-73 is a 1073 Style Microphone Preamp. It is a one-channel vintage style microphone-, line- and instrument preamplifier. The signal path uses only discrete components like resistors, capacitors and transistors. The in- and output is transformer balanced, using two different transformers, each one optimized for its purpose. This is the way audio components were built before integrated circuits became available.
The circuit used in the PRE-73 PREMIER is similar to the preamp section in the classical 1073 module (see history of the 1073)with a corresponding sound character that is warm, punchy, sweet and musical. These classic characteristics have been heard on countless recordings through the years and it is a versatile sound that works very well on most sound sources and in most genres.
Image: Golden Age Premier PRE-73 preamp
Features
- Vintage Style electronics. No integrated circuits in the signal path.
- Maximum gain in mic mode is 80 dB, enough to handle passive ribbon mics with quiet sound sources.
- Classic 23-position Gain/Line switch with 5 dB steps and a gain range of 20 to 80 dB for mic and -10 to +20 dB for line.
- A two band LF (+/-15 dB) and HF (+/-20 dB) shelving equalizer with two selectable frequencies for each band.
- Inductor based +/- 15 dB midrange equalizer section with three selectable frequencies. The lowest one is selectable between 350 and 700 Hz.
- Switchable impedance in mic mode, 1200 or 300 (low-Z) Ohm, will change the tone of most mics. The input impedance in line mode is 100 kOhm.
- Switchable phantom power and absolute phase.
- A high-impedance instrument input (DI) for any sound module, electric guitar or bass.
- A simple but effective 4-step LED output level meter. The red clip light which comes on at +25dBu, about 2dB before the output stage clips.
- The output level control makes it possible to make fine gain adjustments and also to overload the main gain stage(s) for more character.
- Separate combo XLR/TRS jack for the MIC and LINE input and separate output XLR and TRS jacks for flexible connections.
- Selectable 600 Ohm output termination (jumper switch).
- Classic style knobs and buttons.
- Connector free internal wiring, all connections except the ones to the gain switch –are soldered for the purest signal and most longterm stable signal path.
- UK made Carnhill microphone input and line output transformers.
- The pcb is prepared for the Carnhill 9046M line input transformer.
- Polystyrene capacitors in the amplifier circuits.
- Tantalum capacitors in the signal path.
- Beefed up power supply.
- Sturdy toggle switches with gold plated contacts.
- External power supply to avoid interaction with the audio circuits and transformers.
Some notes from the Sound on Sound review:
- The low-Z mode usually alters the tonal characteristics of (passive) dynamics (and some transformer-coupled capacitor mics) which can be musically useful.
- The minimum mic input level for a +4dBu output is -77 dBu, and the maximum is around +13dBu (with output fader set at about 9 o’clock to avoid overloading the output stage).
- Unity gain for line sources is achieved with the gain switch set to 30dB and the output fader fully clockwise
- The DI input impedance is stated as 100kΩ which is lower than most active DIs and may well affect the tonality of electric guitars.
- The grey output fader has no panel calibrations at all, but introduces 16dB of attenuation at the 12 o’clock position, and fades down to fully off (-76dB) at the counter-clockwise end. This control actually adjusts the signal level from the input gain-stage going into the output driver stage, and so allows the input stage to be deliberately overdriven without clipping the outputs. However, a toggle switch next to the output level knob inserts a 14dB pad after the output transformer, specifically to allow the output stage and its transformer to be intentionally overdriven as well.
- The Air EQ options are +3 or +6 dB shelving boost at 30kHz.
- An unbalanced TRS insert point is also included on the rear panel of the Pre-73 Premier (wired conventionally with tip=send and ring=return). This insert point is intended for use with Golden Age’s own EQ73 or EQ81 equalizers.
- The output transformer used in the PRE-73 PREMIER is made for having an ideal load of about 600 Ohm. The input impedance of
most modern units is 10 kOhm or more. The PRE-73 PREMIER therefore has a 600 Ohm output termination resistor that is engaged by the jumper (JP1) located just behind the XLR output jack. The termination resistor will lower the output level slightly and also affect the upper frequency range, Remove the jumper if the PRE-73 PREMIER feed a unit with a 600 Ohm input impedance.
One note of warning: the phantom power remains available on the ‘combi’ XLR when the DI or line modes are selected, which introduces the risk of causing damage to connected line-level sources should phantom be left on or activated inadvertently. Having said that, the line input pad will reduce the voltage seen by any connected equipment, reducing this risk, and on the plus side this arrangement allows the line input mode to be used when working with extremely loud sources and very high-output active mics!
Image: frequency response. The curves represent the two different high-pass filter options and two Air EQ boost settings, as well as the flat mode. A chirp is a signal in which the frequency increases (up-chirp) or decreases (down-chirp) with time; basically a sweep signal. The voltage decibel (dBV) is a unit of measurement of the ratio of an amount of voltage V to V0 = 1 volt given by 20 log10(V/ V0) = 20 log10(V). dBu (unloaded) = dBV + 2.21845. Professional audio equipment operates at +4dBu = 1.8dBV.
Using the PRE-73
- Switching between mic and line input is done by setting the LINE/MIC switch to one of the line or mic gain positions.
- If you want the smallest amount of coloration, always set the OUTPUT level potentiometer at or close to maximum and adjust the output level with the stepped LINE/MIC gain switch.
- If you want more character, turn the OUTPUT level potentiometer counterclockwise and increase the gain with the LINE/MIC switch. This will drive the input gain and the equalizer stages harder and provoke more character from them. For even more character, you can also overdrive the output stage and the output transformer but then used the 14dB pad to reduce the output.
- Instruments can be connected to the TS input jack on the front panel. It has an input impedance of about 100 kOhms. Engage the DI switch to select this input.
- Engage the 48 V phantom power for any mic that needs it. It´s a good procedure to always disengage the phantom power and wait for about 10 seconds before unplugging the mic.
- When the LOW-Z switch is engaged, the input impedance of the input in MIC mode drops from 1200 Ohms to 300 Ohms. This will change the tone of most mics and will give you one more sound-shaping option. It will also increase the signal level.
- There is an internal jumper just behind the MF frequency switch that can be set to 350 or 700 Hz, the default from factory is 350 Hz.
History of the 1073
See the [AMS Neve] website for an extended version.
Rupert Neve’s (and here) early pro audio career began by creating valve-based consoles in the early 1960s. Rupert Neve experimented with audio transistors and found that the BC182 and BC184 transistors had an even better performance than their predecessors.
Photo: Rupert Neve
These transistors were used to create a new preamp/EQ module… the 1073. Neve Electronics had gone from strength to strength, building consoles for facilities worldwide using Neve Electronics’ new solid-state designs. In 1970, Wessex Studios in London commissioned Rupert Neve and his team to create a console for music recording; it needed excellent signal isolation, powerful preamps, and an EQ section that complimented the musicality of any signal source. This console would become known as the Wessex A88…
The Wessex A88 used a 45-series module size for its input stage, this modular build allowed for easy maintenance as the complex input sections could be removed and swapped with ease. Earlier modules such as the 1066 module used this format also, but rather than use existing module designs; the Wessex A88 was the first to employ the new module – the Neve 1073.
Image: The Neve A88 Console (Wessex Studios, 1970)
The 1073 Preamp
The unique gain staging employed in the 1073 module uses two distinct transistor-based gain stages on the input stage, layered on top of each other; these amplifiers do the heavy lifting, bringing the level up to -15dBu. The final transformer-coupled output amplifier then brings the signal level up to line level. This unique layout helped produce the high gain level required for music recording. In the 1960s & 70s, class A amplification design was still the best way to amplify an audio signal, with one amplifier handling 360° of the waveform. By having multiple class-A gain stages working together, the 1073 was more efficient than its predecessors. Additionally, this design allowed the 1073 preamp to handle low and high sensitivity microphone sources while maintaining a low noise floor.
Image: The iconic 1073 red gain switch
Video
Setup in Skippy Studio
References
Manual
Note: this is the manual of the PreQ-73 (with the three-band equalizer)
Dear skippyweb.eu admin, Your posts are always interesting.
Dear skippystudio.nl owner, Your posts are always interesting.