My house voltage is about 124 V most of the time. I have several vintage tube audio components that benefit from lower line voltage for the obvious reasons. I built a bucking transformer that brings the voltage down to ~110 V and it works very well. I most often use an integrated amplifier (Fisher, HH Scott) but also have tube mono blocks (Pilot, Dynaco, Heathkit) with a stereo tube preamp or sometimes 2 mono preamps. I feel I would need several bucking transformers to use the mono gear all at once (2 amps and 2 preamps). This would require building several more at > $50.00 each. I have a very large Variac that is rated at 20 amps. I want to use this to supply 110 V to all the mono equipment at the same time.
1. Are there any disadvantages to using the Variac in this way?
2. Is the bucking transformer route the better way to go and if so why?
3. What does everyone do to supply lower line voltage to your tube gear?
Would love to hear your thoughts on this, Thanks
I may be wrong here, but I am not sure if you need to do anything about the voltage and 124 volts would not cause any problems here.
My voltage can be that high and below 100 Volts at time.
Larry – N7LUF
I like the idea of the variac, in particular if you have converted an of your amps into SS rectifiers.
IMO bucking transformers are an inelegant solution for where you can’t use a transformer, like in a portable device that needs a few DC volts dropped.
Many 120-volt loads are rated at 115-volts. Connected loads should be able to withstand ±10% or 103.5 to 126.5. A Square D 250SV43B ($268.05 at Newark $130.00 at automation direct 250VA ACME) wired 10% (250SV46B for 6.6%) would provide 124-volt input would result in 112-volt output at 20-amp (2.4kVA). You could cord and plug the 10.5 lb. transformer or mount it next to the panel and have one circuit permanently connected and the audible hum may be remote. The load VA will not change the circuit volts and currents will fluctuate (higher voltage lower current, lower voltage higher current). The variac has to be fiddled (I like to fiddle with stuff) with, the buck/boost transformer it is fixed and requires no adjustment. Or you could get a constant voltage transformer SolaHD (Emerson) 23-22-112 $819.85 at Mouser and $990.13 at Digikey and would be fixed (for the most part) at 120-volt output. I have a Variac but generally only use it for testing, the Phico Radio (27-620) I got kinda working (2-AM station and some short wave stations, preachers mostly) rated at 115-volts, once I got it working it is plugged into a 120-volt (124-volt the highest I have seen) and have had not problems. The voltage at my house varies with the utility voltage in the morning and supper time is when the voltage will be less than 120-volt.
Latest Post: hi all im new Our newest member: The Tow Rat Recent Posts Unread Posts
