AEA Preamps - FAQ
How do I set the level and gain on my AEA preamp?
Microphone Input Mode
The Mic Gain control provides from about +13dB to +62dB of gain for the preamp input stage. The Output Level control adds another +19dB of output gain, following the CurveShaper™ circuitry, for a total of +81dB of gain. The Output Level control can apply up to +19dB of gain in the full clockwise position, or it can attenuate the signal as much as -60dB just like a fader on a console. Though the optimum position of the Output Level control is unity at 0dB, the Output Level control may be used to fine tune the overall output level.
Start with the Output Level control pointing at the 0dB indicator and the Mic Gain control fully counterclockwise. Then, with the microphone in position increase the Mic Gain control until you are happy with the input level in your DAW, console, or tape machine. On the RPQ2, if the red LED is illuminated too often or too long, reduce the Mic Gain control one step at a time until it illuminates only briefly at the loudest peaks. The red LED is only triggered when the input level is 4dB or less away from clipping the preamp’s output. If the red LED occasionally flashes while recording, it does not necessarily mean that the preamp is clipping. Note, however, that if you subsequently apply the CurveShaper’s™ HF boost, you may need to reduce the Mic Gain control correspondingly to avoid system overload.
Line and Direct Input Mode
When using Line or Direct Input mode, the Mic Gain control is bypassed. The Output Level control allows you to control the overall level of the Line and DI sources. The Output Level control can apply up to +19dB of gain in the full clockwise position or can attenuate the signal as much as -60dB just like a fader on a console.
The RPQ500's Mic Gain control provides +13dB to +62dB of gain for the preamplifier input stage. The Output Level control adds another +19dB of output gain, following the optional CurveShaper™ circuitry, for a total of +81dB of gain.
Start with the Mic Gain control fully counterclockwise and the Output Level control pointing one tick below the +6dB indicator. This is the unity position on the Output Level control. Then, with the microphone in position, increase the Mic Gain control until you are happy with the input level in your DAW, console, or tape machine. On the RPQ500, if the red LED is illuminated too often or too long, reduce the Mic Gain control one step at a time until it illuminates only briefly at the loudest peaks. The red LED is only triggered when the input level is 4dB or less away from clipping the preamp’s output. If the red LED occasionally flashes while recording, it does not necessarily mean that the preamp is clipping.
For the TRP, center Level control and raise the Gain control.
How does the HF CurveShaper™ EQ work?
The RPQ2 and RPQ500 feature a unique high-frequency CurveShaper™ circuit that enables you to add a little extra “presence” or “air” to compensate for high-frequency losses that are inherent to most ribbon microphones, the result of distant mic placement, or to restore presence in a “dry” acoustical environment.
The circuit functions similarly to a conventional parametric shelving boost but with a significant difference: the slope and bandwidth vary as both the Curve Frequency and Curve Gain controls are adjusted. From a technical standpoint, it is evident the EQ shape of the CurveShaper™ is a bell. At its lowest setting, the peak frequency of the CurveShaper™ is 30kHz while at its highest setting, the peak frequency is 120kHz. In many instances, a bell with a peak at 120kHz is not very practical since it is above the human frequency threshold of hearing. But the CurveShaper™ has a very wide bandwidth that allows the left side of the bell to essentially act as a high-frequency shelf.
To activate the CurveShaper™ EQ section, depress the HF switch. Start by adjusting the continuously variable Curve Frequency control. The frequency markings on the Curve Frequency dial indicate the +3dB break-frequency when the Curve Gain is at max. Select the desired frequency with the Curve Frequency knob, and then dial-in the amount of boost you desire with the Curve Gain control. The two controls are interactive. Use your ears to determine what frequency and gain setting sounds best.
In Line Input Mode, the CurveShaper™ becomes a versatile EQ to add presence or air to any line level signal on a mix or in mastering.
Be careful when you add Curve Gain because this also affects the overall gain structure of the preamplifier and could introduce overload distortion. After you make this adjustment, you may need to reduce the Gain control to compensate for the CurveShaper’s™ signal boost.
What preamps do you recommend for ribbons?
Passive ribbon microphones generally have low output level and require preamps that supply a high level of gain. If the preamp you use doesn’t have enough gain, the signal might seem too soft or noisy. It is generally recommended to use a preamp that is at least 4 times the input impedance of the microphone’s output impedance. The average preamp has an input impedance sitting around 1200 Ohms. Passive ribbon microphones and numerous dynamic microphones are very particular about how they interact with preamps and their respective impedances play an important part in this. Since passive ribbon microphones and some dynamic microphones generally have a very high impedance, they are sensitive to what is referred to as “loading.” The lower impedance a mic must drive, the harder it has to work. If the input impedance of a preamp is too close to the impedance of the microphone, it may exhibit increased distortion, decreased headroom, poor transient response, and less overall frequency response. There are no negative consequences of using high input impedance preamps.
Our active ribbon microphones need a standard 48V phantom power source to operate. They perform well with a wide range of preamps ranging from vintage high-end models to USB or Firewire audio interfaces in home studio setups. IEC specifies P48 power which should be able to deliver 10 milliamps per input. The phantom current draw for active AEA ribbon mics is 7 milliamps. Please check the current values available on your unit to ensure the best performance.
Are the circuits in the TRP and RPQ2 the same?
The overall topology is very similar, but there are some minor differences. The TRP uses Toshiba LSK170s on the front end of the mic pre where as the RPQ2 uses Linear Systems LSK389s. The output circuitry between the two are slightly different the TRP has a more discrete balanced line driver where as the RPQ2 uses a THAT Corp line driver.
How do I power an AEA TRP Preamp in countries with 220-240 V mains?
TRP preamps for countries with 100 - 120 V mains power come with a standard voltage, UL approved 120V AC power supply. This transformer power supply is rated as a 120 V, 60 Hz device. However, since the AEA TRP is a light load, users report that it also will power a TRP from 50 Hz 120 V AC mains. These users use external 240 to 120 V AC transformers to operate their US 120 V units. The power rating of the 50 Hz 240 to 120 V transformer has to be adequate to power the load. We recommend you consult with a qualified local technician before you buy or use such transformers.
How do I neatly power multiple AEA TRP Preamps?
AEA builds a special Heavy Duty 110/220 V TRP power supply which can run up to three TRP preamps. It is for TRP users who live in or travel to 220-240 V countries and/or use multiple TRP preamps. Weighting 2.4 pounds, it is a 5.3 inch square, 1.7 inch tall gray steel package. It houses a toroidal transformer and connects to the TRP via a supplied male to male DIN cable. AC mains power is supplied by a standard removable IEC power cord as used by most desktop computers. As there are many different mains power connectors around the world, we do not include a power cable with the TRP HD Power Supply. Your local AEA dealer can supply the appropriate cable for market cost.
How do I neatly rack mount my AEA TRP Preamp(s) and power supply?
The TRP HD power supply can fit onto most third party one rack unit equipment shelves. The two threaded holes on the bottom will allow it to be firmly secured to most shelves. A TRP can be secured next to the HD power supply it in a similar manner so both can fit in one rack space.