The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    Need some fancy calculations here

    Share

    wildiowa

    Posts : 173
    Join date : 2012-03-19

    Need some fancy calculations here

    Post by wildiowa on Sun Dec 31, 2017 11:56 am

    Let's see...the constant operation of four KT88's will increase my home temperature by....how much???? Even if I am not listening to music I may crank them up today. My kids in NYC are at the mercy of the building super running the boiler and leaky drafty windows...58 degrees in their apartment. I at least have my own thermostat. Only 15 below zero this morning...worse tomorrow....happy  new year!
    avatar
    Peter W.

    Posts : 577
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Need some fancy calculations here

    Post by Peter W. on Sun Dec 31, 2017 12:12 pm

    Easy enough, and hardly fancy:

    1.6A @ 6.3 V = 10.08 watts. This is the filament consumption of a KT88.

    10.08 x 3.41 = 34.39 BTU

    34.39 x 4 = 137.56 BTU in total, in one hour.

    Less than a single candle (157 BTU/Hour), as it happens.

    But, that is _only_ the KT88s.  

    Do the 'other- math:  If a typical ST120 draws ~3A as a constant, that comes to 360 watts. Given that it is a tube device, assume that it is <40% efficient. Meaning that 60% of the energy it consumes goes off in heat. So, 0.6 x 360 x 3.41 = actual BTUs per hour. Or 736 BTUH. About 4.7 candles - a bit better as a heater.
    avatar
    deepee99

    Posts : 1791
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Need some fancy calculations here

    Post by deepee99 on Sun Dec 31, 2017 5:48 pm

    Peter W. wrote:Easy enough, and hardly fancy:

    1.6A @ 6.3 V = 10.08 watts. This is the filament consumption of a KT88.

    10.08 x 3.41 = 34.39 BTU

    34.39 x 4 = 137.56 BTU in total, in one hour.

    Less than a single candle (157 BTU/Hour), as it happens.

    But, that is _only_ the KT88s.  

    Do the 'other- math:  If a typical ST120 draws ~3A as a constant, that comes to 360 watts. Given that it is a tube device, assume that it is <40% efficient. Meaning that 60% of the energy it consumes goes off in heat. So, 0.6 x 360 x 3.41 = actual BTUs per hour. Or 736 BTUH. About 4.7 candles - a bit better as a heater.
    Peter, thanks for the arithmetic.
    I realise that <40% includes a slop factor, but I was under the impression that a typical tube amp was actually about about 4 percent efficient from wall watts to speaker outputs, the remainder going to heat and light. Did I flunk math somewhere? Or was I just mis-informed about the calculus?
    avatar
    peterh

    Posts : 892
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Need some fancy calculations here

    Post by peterh on Sun Dec 31, 2017 6:15 pm

    deepee99 wrote:
    Peter W. wrote:Easy enough, and hardly fancy:

    1.6A @ 6.3 V = 10.08 watts. This is the filament consumption of a KT88.

    10.08 x 3.41 = 34.39 BTU

    34.39 x 4 = 137.56 BTU in total, in one hour.

    Less than a single candle (157 BTU/Hour), as it happens.

    But, that is _only_ the KT88s.  

    Do the 'other- math:  If a typical ST120 draws ~3A as a constant, that comes to 360 watts. Given that it is a tube device, assume that it is <40% efficient. Meaning that 60% of the energy it consumes goes off in heat. So, 0.6 x 360 x 3.41 = actual BTUs per hour. Or 736 BTUH. About 4.7 candles - a bit better as a heater.
    Peter, thanks for the arithmetic.
    I realise that <40% includes a slop factor, but I was under the impression that a typical tube amp was actually about about 4 percent efficient from wall watts to speaker outputs, the remainder going to heat and light. Did I flunk math somewhere? Or was I just mis-informed about the calculus?
    Efficiency is dependent on power level. At low level it's very low, at full power
    it may come close to 50%.
    But all power injected in the mains cable is converted to heat in either the amp or the
    speakers. A minuscule part is converted to sound, which in it's turn would be heat.
    ( some sound will reach outside but that should be fractional :-)

    Happy new Year and continue burning your amps in both ends !

    Dale Stevens

    Posts : 87
    Join date : 2014-07-06
    Age : 68
    Location : Loris, SC

    Re: Need some fancy calculations here

    Post by Dale Stevens on Sun Dec 31, 2017 7:15 pm

    i'm having a CC and Pepsi over this..... Happy New Year to all . Dale
    avatar
    Peter W.

    Posts : 577
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Need some fancy calculations here

    Post by Peter W. on Tue Jan 02, 2018 8:24 am

    Dale Stevens wrote:i'm having a CC and Pepsi over this.....   Happy New Year to all .   Dale

    De gustibus non est disputandum.
    avatar
    arledgsc

    Posts : 477
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Need some fancy calculations here

    Post by arledgsc on Tue Jan 02, 2018 8:55 am

    According to the Kill-a-Watt meter my ST120 consumes about 225W at idle and also at moderate volume levels (WZ68 employed and biased at 50mA). Enough heat to notice during the warmest summer months but not enough to fully heat a room during the winter. But if its all the heat you have it is better than nothing. (I picture you warming your hands to the glow of vacuum tubes!).

    My old plasma screen TV was a real room heater. When replaced with an LCD I noticed an immediate savings on my electric bill.

    Sponsored content

    Re: Need some fancy calculations here

    Post by Sponsored content

      Similar topics

      -

      Current date/time is Tue Jan 16, 2018 9:43 am