At your risk. Take all safety precautions. Including a suitable fuse in series with any battery for fire hazard protection in case of a short circuit.
ECC83 is nailing it.
Signal path:
Recording:
[Is it OK if I call you mine? - Paul McCrane, CD] - Sony CD Walkman - Pleiades V6 ECC83, Rag=10MΩ, Vb=48V, Cc=27nF, Vh=12V, Rh=10Ω - 1 track side A head coil of Tascam Porta 03, normal tape speed - TDK SAX 60 cassette
Reproduction:
TDK SAX - Sony TC-D5 Pro II - Sennheiser HD580
The heaters where powered by 12V in series with 10Ω.
An anode to grid resistor of 10MA was connected to ECC83 for reducing the self negative (from cathode electron emmision) bias and create an anode current of 360μA at only 48V at the anode.
The recording head was connected in place of an output transformer, ie to Vb and the other terminal of the head coil to anode.
So DC tape bias is 360μA.
How does it sound like?
Just one side of ECC83 was connected to left channel of recording head. So reproduction at headphones is only on the left channel.
Reproduction was surprisingly good. With no distortion. This time there was treble and no bass heaviness. This is due to the high anode internal resistance of ECC83. Modulation was up to 0VU. The hiss was thick broadband since DC bias is used.
An ECC82 was also connected. Vb=12V so that Ia is 500μA. It was bass heavy or lacking treble as in previous experiments. There was some distortion, possibly coming from the Pleiades V6 operated at less anode power dissipation, that is having less max power output.
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