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  • Old valve PA amp


    Recently I was asking for advice on choice of amplifier for my Bose 802s.

    I am a solo perfomer (guitar and voice) playing songs from the 50s, 60s, and 70s (in pubs).

    I have just bought (from ebay, Germany) an old Dynacord "Gigant" 150 watt PA amp (made in the late 70s I believe). Right now it is on its way to me from Germany. (These amps, so I've read, were one of the the state-of-the-art PA amps of that era, with lots of big name users -- see the Dynacord site).

    I decided to give this amp a try because I have always liked the sound of valve amps, and it's kind-of fitting to use an amp of that era, given the material I play.

    150 watts may not sound a lot, but I believe (through various searches on the net) that, roughly speaking, the actual power/loudness of valve amps is at least twice that of solid state. So a 150 watt valve amp would be equivalent to a 300 watt solid state amp (give or take some).

    I have already tired out my 802s with a relatively puny domestic hi fi amp, and they sound pretty good! -- even without the controller. I'm hoping, then, that for my purposes, this "Gigant"
    (= German for "giant") amp will be enough for what I do.

    I do have a technical question, though, that I'd be grateful for advice on. Are then any hazards that an amp of this sort might present to my speakers? And, if so, what precautions should I take?



  • #2
    With valve amps ("tubes" for the Yanks) using speakers of the correct impedance is critical. If the amp states that it is intended for an 8 ohm output, then you cannot show it a 4 ohm load.
    Is that Dynacord big and heavy? Was it cheap? It might sound sweet in an audiophile sort of way, but then again, those nuances will probably be lost in a typical "pub."


    • #3

      "Is that Dynacord big and heavy? Was it cheap?"

      Yes to both!

      Thanks for your advice.



      • #4
        Most tube amps are more sensitive to too high an impedance (as compared to solid state amps, which really don't like too low impedance). Anyway, your amp should handle both 8 Ohm and 4 Ohm fine (it shouldn't be that picky).

        The 802 should have no trouble whatsoever. I vaguely remember a demo where someone plugged the thing straight into the wall and it survived. That was 110V in the US, so don't try that in Europe. On second thought, don't try that all. Period. (The thought of a cable with an AC plug on one end and bananas or 1/4" on the other gives me the shivers).

        The "tube amps are louder at the same wattage" myth is only partially founded. It has a certain validity if used as a guitar or bass amp. If you run a solid state amp beyond its rated power it will sound terrible, so nobody would do that. A tube amp, however, starts distorting gradually (and pleasant to many ears), so many tube amps are getting run at or even above the rated power, whereas a solid state amp always needs some "headroom" and rarely gets run close to rated power.
        With a tube amp you can run louder if you are willing to tolerate the resulting tube distortion. For guitar and bass, that can even be desirable, but for voice, keys & acoustic guitar it may not be.