I am one lucky son of a gun. I have a friend who recently lent me a Vanderveen Ultra Lineair 40-S amplifier which was hand-built and gifted to him by Menno Vanderveen himself.
The line voltage in my listening room is always high - from 125V to as much as 130V. I thought it best to reach out to Menno and confirm my doubts about running this lovely old tube amp on such high voltages. He replied and let me know that 115V 60Hz would be the optimal supply for the amp.
I have read some things about bucking transformers in the past and I did a lot more reading to gain a good understanding. As is often the case, Rod Elliott's website was especially informative. His article on bucking transformers and some threads here and on vintage radio and guitar amp sites led me to come up with the attached design.
The DPDT switches and the Hammond 185D20 transformer are on order and I will report the results when I have them. I'm thinking that using a transformer with 2 x 120V primaries and 2 x 10V secondaries should give me the ability to reduce the line voltage by roughly 4.2%, 8.3% or 16.7% depending on how each switch is set.
The 10V output voltage rating for the secondary windings is at full load so I expect the voltage will be greater when the current flowing through the windings is lower than the 2.2A rating. On the other hand, Rod Elliott's article says that wiring the bucking transformer autotransformer-style reduces the theoretical voltage drop from 10V to 9.25V. We will see the end results when the project is completed and connected.
Diagrams and some calculations are attached and special thanks to Rod Elliott for sharing his wisdom so generously.
The line voltage in my listening room is always high - from 125V to as much as 130V. I thought it best to reach out to Menno and confirm my doubts about running this lovely old tube amp on such high voltages. He replied and let me know that 115V 60Hz would be the optimal supply for the amp.
I have read some things about bucking transformers in the past and I did a lot more reading to gain a good understanding. As is often the case, Rod Elliott's website was especially informative. His article on bucking transformers and some threads here and on vintage radio and guitar amp sites led me to come up with the attached design.
The DPDT switches and the Hammond 185D20 transformer are on order and I will report the results when I have them. I'm thinking that using a transformer with 2 x 120V primaries and 2 x 10V secondaries should give me the ability to reduce the line voltage by roughly 4.2%, 8.3% or 16.7% depending on how each switch is set.
The 10V output voltage rating for the secondary windings is at full load so I expect the voltage will be greater when the current flowing through the windings is lower than the 2.2A rating. On the other hand, Rod Elliott's article says that wiring the bucking transformer autotransformer-style reduces the theoretical voltage drop from 10V to 9.25V. We will see the end results when the project is completed and connected.
Diagrams and some calculations are attached and special thanks to Rod Elliott for sharing his wisdom so generously.
Attachments
This might cost more but has an "ease of use" to it which is nice...
Tripp Lite LC1200 Line Conditioner 1200W AVR Surge 120V 10A 60Hz 4 Outlet 7-Feet Cord: Amazon.ca: Electronics
Tripp Lite LC1200 Line Conditioner 1200W AVR Surge 120V 10A 60Hz 4 Outlet 7-Feet Cord: Amazon.ca: Electronics