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    Dynaco ST70 mono question.

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    poconoman

    Posts : 106
    Join date : 2013-01-17

    Dynaco ST70 mono question.

    Post by poconoman on Thu Oct 02, 2014 1:16 pm

    Ok, it doesn't have the M/S switch up front. It was replaced by Bob's attenuator. Can I still use the amp in mono and if yes, what's the best way to set it up for mono? Speaker jack connections for mono?

    Thank you

    GP49

    Posts : 735
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Dynaco ST70 mono question.

    Post by GP49 on Thu Oct 02, 2014 2:01 pm

    Do not use it in mono in the way Dynaco provided, by paralleling the channels. Distortion will go up because the distortion-reducing feedback, which is different between the two channels, gets combined when you do that. Also the power supply will not support full power with both channels driven at the same time by the identical signal (a stereo signal usually has SOME out-of-phase content that eases up the demand on the power supply).

    We have discussed this before. A Stereo 70 really does sound better as two separate amplifiers than as one combined, parallel one; the reduction in sound quality outweighs the rather limited power increase. If you need more power, buy a more powerful amplifier. If you must, you can BRIDGE the Stereo 70 (run the two channels out of phase and connect the loudspeaker between HOT output taps) but that requires an active phase inverter stage that is at least as good as the amplifier, and also makes the setup unusable with any kind of common ground speaker switching or output-driven headphone box.

    Guest
    Guest

    Re: Dynaco ST70 mono question.

    Post by Guest on Thu Oct 02, 2014 2:10 pm

    beat me to it...ditto on the above, its just not worth the hassle to try and run it in mono.

    poconoman

    Posts : 106
    Join date : 2013-01-17

    Re: Dynaco ST70 mono question.

    Post by poconoman on Fri Oct 03, 2014 9:08 am

    Thanks for the replies! I'll use it the way it is. Very Happy

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