The Pleiadss V6 amplifier schematic is used:
Cc is 22nF.
Input transformer is Altec Peerless 4722.
The 2DV4 Nuvistor.
A 1.9MΩ Pleiades bias (pull up) resistor.
An AA Alkaline 1.5V battery. Always a suitable fuse in series with a battery must be used for safety.
The Sennheiser MD441 U3 sounds very natural at 3in. The low anode current, typically 6-7μA compensates for bass heaviness from proximity effect, Fletcher-Munson, voice effort effects.
Changing to MD21 HN the sound is much louder and the mic can also be used at 1-2in as there is no proximity effect. Very impressive sound. Much less hiss. Some clicks heard sometime. If these are attracts from the internal HN transformer picking up signals or a bad ground connector connection? The MD21 should he more suitable. Treble by the pressure doubling effect and the excellent design of the mic may be too much so the mic can be used at 45 degrees etc. The loud ticking clock at 30ft distance from mic can be very clearly heard through the headphones.
The Shure Unidyne III sounds very nice too. With its usual edge, its usual upper KHz boost.
On this setup the MD441 U3 sounds more bass full and natural but at lower level so there is some hiss.
Signal path, setup:
Male singing voice - moving coil mic - Pleiades V6 2DV4 - Sony TC-D5 Pro at mic in, in mono mode - Sennheiser HD580
How is the sound without the Pleiades V6, ie by directly connecting to Sony TC-D5 pro?
Low level, so more hiss as rec level must be increased, bass heavy and treble heavy. Connecting inbetween mic and Sony the Pleiades V6 the sound becomes, loud, big, lower noise, with superb midrange, ie presence.
So all the other world class components shine in all their glory.
With the simple Pleiades V6 all 3 top class mics sound ready to be used for top quality vocals without need of further EQ.
It's perhaps time to start connecting the V6 to the brilliant Uher 4200 report reel to reel analog 7.5ips recorder.
Is a worlds class vocal quality possible with a top mic, a top recorder and a booster amplifier compensating for flat frequency response from producer's brain to listeners brain?
Further reading:
(Flat frequency response from Bain to brain), Sound picture recording and reproducing characteristics - D. P. Lowe, K. F. Morgan - JSMPE
The Pleiades Bias - euroelectron
Operating Features of the Audion - E. H. Armstrong
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