Pioneer SA-9900 Amplifier Review
An unusual feature of the Pioneer SA-9900 amplifier is that it has two separate sets of treble and bass tone controls which have different turnover frequencies, all controls being of the multiposition switch type. Seven position switches are used for the extreme controls which have turnover frequencies at 50Hz and 20kHz, whilst the remaining tone control at 100Hz and 10kHz use eleven position switches, thus providing a very versatile system with adequately small increments.
In addition to a tone control defeat toggle switch, there are two toggle switches which insert a choice of two high pass and two low pass filters. All these filters have a 12dB per octave rate of attenuation which is particularly desirable at low frequencies, and the turnover frequencies are well chosen. Furthermore, the manufacturer has had the sense to omit a loudness control.
The volume control which is a step attenuator covering the range of 60dB in 2dB increments works in conjunction with a three position attenuator switch which offers 15 or 30dB extra attenuation, thus providing a more than adequate range for headphone or loudspeaker listening. However, the basic amplifier noise was found to be far too high when using headphones, in addition to which there was a constant hum at any volume
With the exception of the balance control which had an unusually good characteristic, the other amplifier controls did not have any significant effect upon balance.
On the input end there is provision for two auxiliary inputs, a tuner and two phono inputs for magnetic cartridges with the option of using a microphone in lieu of one of the phone inputs. This is simply achieved by inserting a plug into the microphone jack socket. In addition, there are connections for two tape recorders; all inputs being via phono plugs as there is no DIN connection.
Both tape monitoring and tape dubbing is either direction are catered for by two switches, and it is found that the crosstalk associated with either tape monitoring on between the inputs was minimal.
Further phono connectors allow entry into the amplifier between the pre-amplifier and the power amplifier, the two being able to be separated by a small slide switch.
The physical layout of the Pioneer SA-9900 is unusual because all connections are arranged at the sides of the amplifier, the right hand side housing ail inputs together with a phono input impedance selector switch and a phono input attenuator giving a 12dB range in gain. The right hand side has the two sets of loudspeaker outputs which are switched from the front panel, and also the power/preamplifier breakpoint and its switch.
Both the external finish and the internal layout and tidiness of the amplifier was excellent, with good quality boards and widespread use of wire wrapping.
The measured amplifier performance showed that it was quite happy to work into 4 ohm loads and that the power bandwidth was quite adequate, but there is concern about the high frequency intermodulation distortion which would be indicative of transient intermodulation problems.
The noise performance of the high level inputs was good, but that of the phono input was not to the very best standards and neither was the maximum available dynamic range.
So far as the overload performance was concerned, severe bass overload produced very unpleasant effects and high frequency overload gave a nasty splitting sound, but this shouldn’t be a problem in domestic use.