I have attached the schematic I am working on, it's a mix of the Altec 1566 and a tone buffer from anglefire. Ignore the power supply, this schematic has been modified since I printed it.
I have looked at many schematics and they almost all have caps on the cathodes. the one I am concerned about is C10 on V1B.
I would assume that it would be electrolytic due to it's size, and you stated the big ones are electrolytic.
Let me know what you think
I have looked at many schematics and they almost all have caps on the cathodes. the one I am concerned about is C10 on V1B.
I would assume that it would be electrolytic due to it's size, and you stated the big ones are electrolytic.
Let me know what you think
Yes, if present it needs to be 10's of uF so an electrolytic is needed.
Alternatively, you could try omitting it. As this stage provides the loop gain for a Baxandall active tone control you might get away with less. It is followed by a CF so the anode load resistance will be high enough. So, electrolytic or miss it out.
Alternatively, you could try omitting it. As this stage provides the loop gain for a Baxandall active tone control you might get away with less. It is followed by a CF so the anode load resistance will be high enough. So, electrolytic or miss it out.
Hello All,
If you are torn about using a cathode bypass capacitor or not try this thing that I sometimes do.
Place a 10 ohm resistor in series with and between the tube cathode and the capacitor, this will add to the ESR of the capacitor and will reduce the amount of bypass slightly. The resistor is the great equalizer among capacitors. The resistor swamps the variable ESR behavior among electrolytic capacitors.
Get fancy, adjust the value of the series resistor to adjust the gain and adjust the degree of feedback at the tube cathode.
Get technical, add Fast Fourier Transform to adjust the THD and the ratio of H2 to H3 harmonics.
DT
If you are torn about using a cathode bypass capacitor or not try this thing that I sometimes do.
Place a 10 ohm resistor in series with and between the tube cathode and the capacitor, this will add to the ESR of the capacitor and will reduce the amount of bypass slightly. The resistor is the great equalizer among capacitors. The resistor swamps the variable ESR behavior among electrolytic capacitors.
Get fancy, adjust the value of the series resistor to adjust the gain and adjust the degree of feedback at the tube cathode.
Get technical, add Fast Fourier Transform to adjust the THD and the ratio of H2 to H3 harmonics.
DT
I thought R28 should be closer to 360k because I want to bring the Plate/grid voltage down to about 90v
If you have a common cathode triode gain stage with a resistive load, you're inviting trouble by having cathode degeneration. No cap on cathode resistor will lead to a lot higher plate resistance, which will lead to a lot more distortion with an anode resistor.
If you have a gyrator or a CCS, then it's another thing.
If you have a gyrator or a CCS, then it's another thing.
Then you should use Ra = 220 k, Rk = 1k.
Draw a load line and see that now Ua = 90 V, Ia = 0,75 mA and Uk = 0,7 V.
Anyhow you can adjust the final values of Ra and Rk by experimenting.
Leaving out the cathode cap will lead to higher plate resistance, but if the load resistance is high like in this case, the distortion is essentially lower.
I have used unbypassed cathode resistor in many circuit and know how it is.
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