H-Amp™ Using & Applications


Complete details on using the H-Amp can be found in the manual (PDF download).

The Radial H-Amp is a unique device that can take the high power output from an amplifier and convert it for use with headphones. The amplifiers output can be a routed directly to one or more H-AMPs (fig.1) or 'tapped' off a full-range loudspeaker (fig.2). The intent is simple: to provide an easy to use interface for situations where headphones are needed.

Because the source signal is the mono output from a single amplifier the H-Amp also operates in mono. There are two headphone outputs, each with a separate level control to allow two musicians to share the same H-Amp. This makes it great for situations where a large orchestra may need separate headphones for all of the musicians. A special EQ has also been added in the case that two different types of headphones are being used or maybe one player wants to tailor their EQ for a specific need.

The H-Amp is completely passive. In other words, it does not require any form of powering. The H-Amp uses the output from the power amp to drive the circuit and inside, special high-temperature ceramic potentiometers are able to withstand the amp's high power output without concern.

Using the H-Amp

The Radial H-Amp can be connected directly to a solid state power amp or be connected in parallel with a loudspeaker. Connection to the H-Amp is made via a Neutrik Speakon 4 pole connector with two poles wired following common practice for full-range loudspeaker cabinets as shown here:

As with all electronic equipment, always turn down levels and turn off your audio system before making connections. This will protect sensitive equipment from damage due to turn on transients. Depending on power, we recommend using 12awg (2.0mm) or 14awg (1.6mm) gauge speaker wire for optimal signal transfer between the amp or loudspeaker and the H-Amp. The H-Amp is equipped with two Speakon connectors wired in parallel for input and throughput connections. The "THRU" jack allows multiple H-Amps to be connected in parallel to create a larger network of headphone for application such as orchestras, conferencing and so on.

Connecting Headphones

Connecting the headphones is simply a matter of plugging in and adjusting levels. Always make sure the H-amp's level controls are turned down (fully counterclockwise) before connecting your headphones. This will ensure that excessively loud systems will not erroneously damage your headphones. Once connected, simply increase the level controls until a comfortable listening level has been achieved.

Note that the H-Amp is capable of producing extreme sound pressure levels that can damage your hearing. Using the H-Amp at high levels is not recommended and subjecting yourself to high levels may in fact be harmful to your well being. Please familiarize yourself with local health and safety regulations and carefully follow these guidelines.

You will notice that the H-Amp produces a mono output for your headphones. This makes sense as the usual source for the H-Amp will be a loudspeaker or wedge monitor fed by a mono auxiliary send from the console. The individual level controls for each headphone output allows each musician to set the volume that is comfortable for their own use.

Using the Tone Shaping EQ Filter

The H-Amp is equipped with a simple Tone Shaping filter that can be set to tailor the sound of the mix going to the headphones. The Tone Shaping filter section is located on the H-Amp's side panel and uses three recessed switches to prevent accidentally changing the setting. A fourth recessed switch allows Headphone-1 to bypass the filter section in cases where only the Headphone-2 outputs needs to be tailored.

There are two primary uses for the Tone Shaping filter. The first is when the H-Amp is connected in parallel with a loudspeaker. In this case the filter is designed to compensate for the tonal discrepancies between the loudspeaker and the various headphones that are on the market. For instance, if the wedge monitor has added boost in the bass region, you can decrease the bass in the headphones by depressing the low-cut filter

The second application for the Tone Shaping filter can be applied when two headphone users are plugged into one H-Amp. The filter can be assigned to only affect one of the headphone outputs by depressing the PHONE 1 BYPASS recessed switch. This way, you can account for discrepancies between two brands of headphones or maybe tailor the sound for one user to increase the click sound of a tempo track should this be needed

Calculating The Load: H-Amp In Parallel With A Loudspeaker

The H-Amp has an 80-Ohm characteristic impedance that will increase based on how the headphone level control is set. Although this high impedance will have very little effect on the amplifier load, we recommend that no more than two (2) H-Amps be connected in parallel with a loudspeaker.

Calculating The Load: Dedicated Amplifier (No Loudspeaker) When the H-Amp is used with a dedicated power amplifier such as in a studio or orchestral environment, you merely check the minimum impedance of the amp to calculate the number of H-Amps you can use. The following are typical examples:

Start with the H-Amp's characteristic impedance of 80-Ohms and divide by the amp's minimum load rating to determine the number of H-amps the amp can safely drive. For instance, an amplifier with a minimum load of 4-Ohms could have 20 H-Amps connected to it. Because each H-Amp is able to power two headphones, you can connect 20 headphones to each side of a stereo 8 Ohm amp for a total of 40 headphones!