Magnetic Nanocrystalinne core used (Nanoperm): Magnetec 070
Primary 350 turns gave an inductance of 16H.
Secondary 35 turns grave an inductance of 140mH.
It will be tested on a Pleiades V6 breadboard prototype.
The transformer will be connected directly to the anode of a triode connected EF183.
Anode voltage will be less than 6V.
A few megohm resistor from anode to grid will neutralize the self assuming negative grid bias.
Heaters will be underheated (see othe euroelectron posts).
All above values will be optimized by experiment while a microphone with input transformer is coupled to grid through a capacitor. Or a CD player before a voltage divider is connected so that expected bass drop due to the output transformer can be measured with a test CD.
16H may be too low. But the transformer will be carrying direct current (less than 100uA). An Altec octal 15095 which has a very high inductance had been tried a few years ago. Sound was excellent. There was still some bass drop, perhaps due to the DC current saturating the Altec core.
If the first prototype of 16H (which may not be magnetized as it contains few turns, small H) proves to be too low it will find another great use.
The high output impedance of the valve driving the low inductance will make a nice current source. Same way as when we drive a tape recording head.
So we will have a slope increasing with frequency.
If we connect a secondary to another Pleiades amplifier we may de emphasize the pre emphasis. On the EMI BTR2 this is done by a capacitor in series with resistor from anode to grid.
So we may have a great tape recorder simulator without moving parts.
If the core is saturated at peaks we may have the nice tape instantaneous peak limiting. If saturation is difficult to obtain we may experiment with different cross sectional core area, other number of turns, other electron tube anode voltage etc.
The second integrating amplifier, (high cut filtering at 6dB per octave) will round off the waveform. Similar techniques are used on FM radio pre post emphasis (see Orban) or disc recording and playback (RIAA recording playback curve).
So we may be left with a high average signal to peak distribution as when we record on reel tape. So it may sound nice and warm and natural and big and loud and alive. (If not using such processing these peaks drive mad analog to digital converters and so we need to reduce the signal too much before it goes to the ADC.)
And then we can digitize if wanted.
Primary 350 turns gave an inductance of 16H.
Secondary 35 turns grave an inductance of 140mH.
It will be tested on a Pleiades V6 breadboard prototype.
The transformer will be connected directly to the anode of a triode connected EF183.
Anode voltage will be less than 6V.
A few megohm resistor from anode to grid will neutralize the self assuming negative grid bias.
Heaters will be underheated (see othe euroelectron posts).
All above values will be optimized by experiment while a microphone with input transformer is coupled to grid through a capacitor. Or a CD player before a voltage divider is connected so that expected bass drop due to the output transformer can be measured with a test CD.
16H may be too low. But the transformer will be carrying direct current (less than 100uA). An Altec octal 15095 which has a very high inductance had been tried a few years ago. Sound was excellent. There was still some bass drop, perhaps due to the DC current saturating the Altec core.
If the first prototype of 16H (which may not be magnetized as it contains few turns, small H) proves to be too low it will find another great use.
The high output impedance of the valve driving the low inductance will make a nice current source. Same way as when we drive a tape recording head.
So we will have a slope increasing with frequency.
If we connect a secondary to another Pleiades amplifier we may de emphasize the pre emphasis. On the EMI BTR2 this is done by a capacitor in series with resistor from anode to grid.
So we may have a great tape recorder simulator without moving parts.
If the core is saturated at peaks we may have the nice tape instantaneous peak limiting. If saturation is difficult to obtain we may experiment with different cross sectional core area, other number of turns, other electron tube anode voltage etc.
The second integrating amplifier, (high cut filtering at 6dB per octave) will round off the waveform. Similar techniques are used on FM radio pre post emphasis (see Orban) or disc recording and playback (RIAA recording playback curve).
So we may be left with a high average signal to peak distribution as when we record on reel tape. So it may sound nice and warm and natural and big and loud and alive. (If not using such processing these peaks drive mad analog to digital converters and so we need to reduce the signal too much before it goes to the ADC.)
And then we can digitize if wanted.
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