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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Why Would a Negative Supply Be Necessary? posted by FlaCharlie on August 2, 2007 at 18:31:42:
Your math is correct but, unfotunately, there is an additional requirement. Since the coupling between the stages is via the cathode, the resistor in the cathode is a 'load'. The term 'long tail' reflects the requirement that this resistor (the 'tail' of the differential amplifier) be 'long', i.e., have a high value. In fact, the lower the value of the cathode resistor, the poorer the signal balance between halves. This is because the circuit relies on the cathode resistor being a 'constant current' source. The higher the resistance, the closer to a 'constant current source it becomes.
The article below shows an alternative approach that does not require a negative voltage supply. By the way, the 6SL7 will provide plenty of gain for your application. For an even better tube (the 6SL7 is an excellent sounding tube), try the 6188.
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Follow Ups
- RE: Why Would a Negative Supply Be Necessary? - mikeyb 08/3/0705:45:02 08/3/07 (0)
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