Direct drive from anode to tape recording head part 8

At your risk. Take all safety precautions. A suitable fuse should always be used in series with a battery for thermal injury protection as well as fire hazard protection.


Summary: E88CC RC coupled and then a series resistor was tried today.
ECC83 direct to anode still sounds best. It seems worth carrying on with direct to anode experiments. With direct to anode there is sense of high class sound quality although so far there is distortion at high levels and s problems.


A brief description of today's E88CC head drive experiments:


Resistors were connected to anodes. Capacitor coupling. Series resistor to head. The usual stuff.


Values used:
Ra=4.7KΩ
Rs (series R to head)=17KΩ or 330Ω or 2.2KΩ.
Cc (coupling to head)=1μF, other channel 820nF
Rag=10MΩ
Vb=36V to 12V
Rb(DC tape bias resistor from 12V to head)=33KΩ for 400μA bias current


Almost all combinations sounded horrible.


With 17KΩ tape modulation is too low.


With 330Ω extremely high and with 2.2KΩ very high.


Almost unlistenable sound. ECC83 direct to anode sounds like paradise compared to this.


Other values of Rs need to be tried.


Treble was too low.


And treble does not increase when cathode temperature drops. This is possibly because the tube drives its load resistor and not an inductive load.


When an inductive load is driven and cathode temperature falls the increase in internal anode impedance creates a higher and higher high pass or low cut turnover frequency. This gives very sparkling acoustic guitar sounds.


ECC83 gave much more treble at normal cathode temperature.


Perhaps something else to be tried is ECC83 RC coupled with a higher load resistance and series resitor than E88CC and higher Vb.


There is also possibility of distortion at the grid circuit of the electron tube since the Sony CD player Walkman line out is directly connected to grids through coupling capacitors.


Something else needed to be tried is driving 2 tracks simultaneously from each triode ie 2 head coils in parallel. So that anode current can be 800μA which is a sensible current for ECC83. If this works it will immoderately make 2 track cassette (using almost full width of cassette tape) stereo from the Tascam Porta 03 head.


Something else that needs to be tried is forgetting cassettes and trying ECC83 anode to head on 1/4in tape running at 7.5ips.


Thinking about it, how can the Uher 4200 report have such great sound with just a small transistor operating at say 5V and low current? There is an inductive load at the collector instead of a load resitor. The designer must be a genius. An inductive load has also to be tried with ECC83 to save half Vb voltage and have bright and loud sound at the same time. Impedance coupling time? And a series resistor with of without series Cc to recording head? Or Cc with or without Rs?