Royer Labs SF-24 - Manual (Page 10)

Amplification Considerations
Almost any stereo microphone preamplifier (or pair of mono preamplifiers) with nominal gain
characteristics and built in 48-volt phantom power sources will give excellent results with your
SF-24 active ribbon microphone. Unlike standard ribbon microphones, which depend on a proper
impedance match to deliver optimal performance, the input impedance of your preamplifiers will
have minimal affect on the SF-24’s performance because the ribbon elements are loaded
perfectly via the microphones’ internal electronics.
Careful consideration should be given to the quality of the microphone preamplifier. Studio grade
preamplifiers usually sound much better than cheaper ones. Headroom, noise floor, transparency
and coloration are all factors to consider in determining which preamplifier is suitable for your
studio or live applications. Other features are usually secondary and fall into the category of
conveniences or interface capabilities (such as digital or optical outputs).
A good preamplifier should sound natural, with no sign of edginess or excessive noise. Vacuum
tube preamplifiers sound warm, yet wonderfully airy and transparent. Do not expect a vacuum
tube preamplifier to be as quiet as a solid-state preamp, as electron emissions from tubes tend to
convey more “thermal” noise than transistors. Tube preamplifier noise is far less of an issue with
the SF-24 than with conventional ribbon microphones because the SF-24’s high output will
override the noise. Transformer coupled designs tend to sound punchy and fullbodied and offer
the added benefit of true electronic isolation. This greatly enhances their ability to interface with
other equipment with minimal noise or hum. There are many excellent preamplifiers on the
market today. Choose one that fits your budget and offers good performance, but remember that
you get what you pay for. If you have the opportunity to audition one or more preamplifiers
before you buy one, do so. Microphones and preamplifiers work together as a team and some are
just better matches than others.
The SF-24 is capable of substantial output signal, especially when used for high SPL applications
like drum overheads. It will not overload or produce distortion up to its SPL handling capacity of
130 dB SPL. In actuality, the SF-24’s ribbons would stretch well before its electronics would
reach an overload condition. Due to the high output potential of the SF-24, it is recommended
that the microphone preamplifier you pair it with have a switchable pad to prevent the possibility
of overloading the preamplifier’s input stage electronics. Some preamplifiers are more
thoughtfully designed than others, with a suitable pad that is placed before the preamp’s active
electronics, not incorporated into a “feedback loop” as is sometimes found. The latter design
could still produce distortion due to overloading even if the pad were used. Although this is
rarely an issue, we felt that it was important to cover the subject.
In conclusion, preamplifier coloration is optional and a matter of personal taste. Some people
love the effect of coloration while others strive for absolute transparency.
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