RE: Another Baby O amp created

MagneQuest/Peerless Forum

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In Reply to: RE: Another Baby O amp created posted by mqracing on December 19, 2011 at 13:01:18:

Mike and I had a chat about this; here are some thoughts I had:
The Baby O circuit (separate from power supply and audio output transformers ...) could probably use a 300B with little or no modification. It would have close to the original voltages and currents, so it would produce the same power as a 2A3.
For the listed voltages, it draws about 50mA (50v across the 1000 ohm cathode resistor), and a 300B at that point would have 250v plate to cathode. (This would be more like a 320v power supply, not the 350v shown on the circuit.) The 1950 WE data sheet shows the average current at full power to be 20% higher, so I would not want to increase the voltage and current beyond the Baby-O design. WE also says you will get 4.4 watts - that may be a bit optimistic.
Beyond that there are two choices:
1) You can increase the voltage without increasing the current (by increasing the bias resistor), which will give more power but with a higher distortion. This change would cause a big departure from the Baby-O sonics so I would not recommend it - it will become a whole different amp.
2) You can ask Mike to make some DS-025s that are gapped for more current. You will lose some inductance and hence some deep bass, but otherwise it would retain the Baby-O basic character. Gapped for 70mA and operated at 300v at 60mA, which is a well documented 300B operating point, with very nearly the same cathode resistor - less than 2% different. You might get 7 watts. Full power DC current is 74mA, so DC overload will be similar to the Baby-O.

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Follow Ups Full Thread

Topic - Another Baby O amp created - mqracing 08:38:15 12/17/11 (8)

Baby O schematic - mqracing 20:30:09 12/19/11 (1)

RE: Baby O schematic - triode3 04:06:20 12/20/11 (0)

Hi Mike! - Colonel Sanders 03:02:27 12/19/11 (1)

RE: Hi Mike! - mqracing 09:41:40 12/19/11 (0)

RE: Another Baby O amp created - Mossback 02:40:39 12/19/11 (3)

RE: Another Baby O amp created - mqracing 13:01:18 12/19/11 (2)

RE: Another Baby O amp created - Paul Joppa 12/19/1122:03:06 12/19/11 (1)

Thank you Paul - Mossback 08:34:27 12/20/11 (0)

Follow Ups

RE: Another Baby O amp created - Paul Joppa 12/19/1122:03:06 12/19/11 (1)

Thank you Paul - Mossback 08:34:27 12/20/11 (0)

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