Tube DIY Asylum

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Excess Line Voltage vs Amplifier Sound

Posted by sayntjack on January 8, 2017 at 17:57:25:
Recently I have been spending some time with a couple of my amplifiers which use power transformers built in the late 50s and mid 60s when line voltages were typically 110-115 Volts vs my house voltage which runs between 118 & 124. At times I have noticed that my 1957 Heathkit W5-M's sound a little edgy on the mids & highs. A check on voltage at these times typically finds 123 / 124. Reducing this voltage to 118 using a tapped autotransformer eliminates the problem. Last night after about 3 hours of listening to a 6B4G triode version of a Dynaco ST70 I began to notice a significant lacking in bass weight. On a hunch I checked the voltage and noted it to be 124. With a quick reconnection to an auto transformer, not only was the bass restored it seemed to have a little more weight than was usual at my lower line voltage of 118. The output voltage of the autotransformer - 110!

The bottom line here seems to be that if you want your vintage tube equipment to sound right (and likely last longer) then you should ensure that its supply voltage is kept around 115. Most commonly this can be achieved by either an external device such as a variac or an auto transformer or by a replacement power transformer with a primary winding rated for nominal 120 volts such as those offered for Dynaco's by Bob Latino.