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    Attenuator and Tube lifetime

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    Stimpy

    Posts : 2
    Join date : 2015-12-22

    Attenuator and Tube lifetime

    Post by Stimpy on Sat Nov 12, 2016 3:50 am

    Is the use of an attenuator more damaging to tubes, giving them a shorter lifespan?

    Would I be better to pass through the attenuator on my ST70 and lower the levels on my source (DAC)... if it is going to be kinder on the tubes.

    peterh

    Posts : 718
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Attenuator and Tube lifetime

    Post by peterh on Sat Nov 12, 2016 4:28 am

    Stimpy wrote:Is the use of an attenuator more damaging to tubes, giving them a shorter lifespan?

    Would I be better to pass through the attenuator on my ST70 and lower the levels on my source (DAC)... if it is going to be kinder on the tubes.
    If you are talking about a resistive network connected to the output of an amp that
    reduces the signal delivered to the speakers .. yes it will increase the load of the
    amp and is of no general value outside guitar amps.

    Bob Latino
    Admin

    Posts : 2437
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Attenuator and Tube lifetime

    Post by Bob Latino on Sat Nov 12, 2016 11:02 am

    Stimpy wrote:Is the use of an attenuator more damaging to tubes, giving them a shorter lifespan?

    Would I be better to pass through the attenuator on my ST70 and lower the levels on my source (DAC)... if it is going to be kinder on the tubes.

    The VTA stepped attenuator is not a resistive load that is connected to the OUTPUT of the amp. The VTA stepped attenuator connects to the INPUT of the amp. The VTA stepped attenuator will not shorten the life of your tubes. You can "bypass" the attenuator if you want by simply turning the attenuator all the way to the right. If you do that, there will be a straight path from the input jacks to the driver board input eyelet. If you measure the resistance from the input center pin to the "IN" eyelet on the driver board with the attenuator turned all the way to the right, you will get 0.0 ohms. This is a straight path to the "IN" eyelet on the driver board with just one extra solder connection in the way. If your DAC has a variable output, you could adjust the output of the DAC rather than turn the knob on the attenuator if that is the way you want to adjust volume ?

    The VTA stepped attenutor is a good option to have IF all you have is a single high level signal source. This would include a CD player, output from a DAC, Ipod, MP3 player or a line level output from a computer connected to your VTA ST-70 or ST-120. If you have the need for multiple inputs or your signal sources is a turntable (without a built in phono preamp) then you will need a preamp. The attenuator may also be used WITH A PREAMP as a master gain control for a preamp that has too much gain. Some preamps give virtually all their volume from the 7 o'clock position to the 11 o'clock position. You can fix that by running your preamp into a VTA ST-70/ST-120 with an attenuator set at about the 2 or 3 o'clock.  By doing this, you will now have greater "range" on your preamp's volume control to attain higher volume levels.

    Bob

    Stimpy

    Posts : 2
    Join date : 2015-12-22

    Re: Attenuator and Tube lifetime

    Post by Stimpy on Sun Nov 13, 2016 10:56 pm

    Thanks Bob

    The first paragraph answers my question. That's exactly how I use the attenuator, just love the feel of the dial for volume control

    peterh

    Posts : 718
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Attenuator and Tube lifetime

    Post by peterh on Mon Nov 14, 2016 4:46 pm

    Stimpy wrote:Thanks Bob

    The first paragraph answers my question. That's exactly how I use the attenuator, just love the feel of the dial for volume control
    Nice to hear. I was thinking of a device used in guitar amp world thats also
    called "attenuator" but this is connected between output and speakers. The use
    is to allow the amp to clip at full power while delivering only a fraction
    to the speakers. This saves the ears while still sounding like jimi hindrix.
    Glad to hear that you did not used this type :-)

    Peter W.

    Posts : 204
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Attenuator and Tube lifetime

    Post by Peter W. on Mon Nov 14, 2016 5:19 pm

    Stimpy wrote:Thanks Bob

    The first paragraph answers my question. That's exactly how I use the attenuator, just love the feel of the dial for volume control

    It is also useful to understand the difference between an AUDIO taper and LINEAR tape Volume Control/Attenuator.

    http://www.resistorguide.com/potentiometer-taper/

    In the configuration as suggested by Bob L., either would do, but one may behave more like what you expect (audio taper) than the other.

    Technically, an Attenuator that goes between the amp and the speakers is called an L-Pad and is rated at much higher wattages than a volume control - with the associated expense. They keep the load on the amplifier constant, but vary the energy delivered to the speaker. As previously mentioned, L-Pads have specific applications, volume control being only one of them.

    http://www.parts-express.com/parts-express-speaker-l-pad-attenuator-100w-stereo-1-shaft-8-ohm--260-264

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