! preliminary information ! market introduction shortly ahead
Audiospecials - Monophonic
Mono-Preamplifier featuring adjustable equalizing for LPs which were not cut after the RIAA standard.
After the sucessful introduction of the Phonolab audiospecials asked me to design a successor of their Monophonic. In its original design the Monophonic could no longer be offered and the experiences gained from the Phonolab-project showed that there was room left for technical as well as sonic improvement. Also they wanted a optical design closer to the Phonolab. The supply should be either through a own external supply or from the PSU22 of the Phonolab.
Mono - Stereo - where are the differences?
Besides the major difference, that Mono is a single-channel and stereo a dual-channel recording system, some less familiar still though important differences exist.
For one is the way the groove is cut into the vinyl, either in ´Microgroove´ style or in ´Stereo groove´ technique. Stereo pickups can be used for both groove styles without issues.
Many mono-pickups are just modified stereo-pickups in a way that the two channels are connected together and the needle is of round or soft elliptical shape.
For second there existed quite a row of EQ-curves with partly drastically differing shapes before RIAA became the standard in 1964.
As the attached graphic shows especially 78rpm LPs cut with ´Norm-groove´ differ clearly from the RIAA, while the later 33 and 45rpm ´Microgrooves´ are much closer following the RIAA. A old EMI 78 cut after ´European 78´ shows a mild Bass cut and a pronounced Treble lift. Reproduced via a RIAA-amplifier it will sound too thin and treble emphazised.
In order to replay all the different EQ-curves optimally the amplifier needs to have switchable or adjustable EQ circuitry. This of course means an increased effort, that surpasses that for a second stereo channel. Due to this -and the expectable lower number of produced devices- the price will probably be higher than for a qualitatively comparable stereo amplifier.
The circuitry of the Monophonic is based on the proven concept of the Phonolab, supplemented by two continously adjustable controls which allow to dial in on almost every EQ curve with excellent accuracy.
The user is supplied with a table listing the optimal settings values for the different EQ-curves.
The RIAA for example is chosen by setting the left control knob to 3.6 and the right one to 4.4. The user is of course free to chose whatever setting suits his taste.
On the backside panel one also finds clear similarities to the Phonolab. Input- and output connectors for left and right, in asymmetrical RCA/Cinch as well as symmetrical XLR and Lemosa/Fischer style, to be able to use the Monophonic in any stereo setup.
Internally the signal treatment is single-channel Mono though.
The gain and impedance settings are switchable over a large range through a rotary and a DIP-switch.
Did you recognize the second power connector?
The left connector is the same style as featured in the Phonolab/PSU22, the right one is a typical 2.1mm hollow connector for a wall power supply. The Monophonic can as such be powered from a single supply voltage of a 12Vtyp. wall power supply as well as from the dual voltages supplied by the PSU22.
Additionally there is a push-button power switch to switch the Monophonic On and Off.
Lucky You when You already own a Phonlab and PSU22. You can expand Your vinyl setup by a very capable Mono preamplifier with the same appearance and with the same sonic signature.