Hello fellow diyaudio members, today I was playing one of my vintage tube guitar amps, in particular my 1950's Danelectro Montgomery Wards Airline 8511 amp, it is a simple radio style amp with series strung filaments and line operated B+ supply, and I noticed that the amp sounded more compressed and distorted on this particular day, compared to other days. I have some idea that the only thing that changed was the ambient temperature in the room. As many of you may know, the east coast of the US was hit with some of the coldest weather it has seen in several decades, and therefore my bedroom, where I keep the amp, was particularly cold compared to the average day, probably in the low 60's. I was wondering, I know humidity can affect carbon comp resistors and fiber boards, but can temperature significantly change the values of components or how tube amps may operate? Is it possible to have a noticeable change in sound with a 10-20 degree Fahrenheit change? Why does this occur? I am pretty sure there are no failing components, and the tubes have been fine the day before, so I guess it is the temperature or humidity affecting the tone? Thanks for your input.
My first suspect would be dried up 50 year old electrolytic capacitors. These are aluminum cans filled with slime water and sealed with cheap rubber. They are highly non-linear when it comes to temperature, once they are dried up. I test them with a calender. Audio sounds funny, weak, odd frequency response, calender says the e-caps are over 20 years old, out they all go. the USA ones had a date, YYWW where year is 19YY. If they are oriental, probably were produced after 1980. See this thread about the cheap way to replace them: http://www.diyaudio.com/forums/tubes-valves/201265-vintage-magnavox-tube-amp-3.html
My 1st suspect would be changing contact integrity from the cold or condensation. I'm in NJ and there is a green spot on a rug in the basement from where condensation has dripped off a large copper drain pipe in the past. It has never dripped in the 7 years I’ve been in the house but the rug and pipe have had the green on them since I moved in. It dripped the other day for the 1st time and I blame the weather. No, the plumbing is not at risk of freezing.
If I transport my boss compressor pedal in my trunk in the winter, it temporarily becomes a distortion pedal when 1st used. As the moisture dissipates it turns back into a compression pedal.
Of course the issue could be something else.
If I transport my boss compressor pedal in my trunk in the winter, it temporarily becomes a distortion pedal when 1st used. As the moisture dissipates it turns back into a compression pedal.
Of course the issue could be something else.
The electrolytics were replaced about a year and a half ago with Blue Sprague Atoms, which I highly doubt are the problem. The amp has since returned mostly to normal as the temperature went back up. I believe it may have to do with component drift or contact integrity as jjman said, but I am not sure, and the amp works fine, and I actually like the new tone... haha, but anyways I forgot to check my line voltage the other day so if it gets cold again I will. Normally the line voltage is at 120 volts here exactly, but that also depends on usage. Right now it is at 122 according to my old fluke tester. I feel that it does vary enough that it could make a difference in tone from 117 in the heat of august to 125 sometimes in winter. Who knows, thus is the nature of the beast that we call a tube amp.
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