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    Ultravalve for $2000

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    j beede

    Posts : 317
    Join date : 2011-02-07
    Location : California

    Ultravalve for $2000

    Post by j beede on Thu Mar 31, 2011 3:32 pm

    I looked over and listened to the AVA Ultravalve at last year's NorCal audio show in Emeryville and was not particularly impressed. What about that amplifier makes it a bargain at $2000? Maybe Bob should offer an anodized faceplate option for his stereo amps! Can you educate me on this?
    ...j

    Captain Coconut

    Posts : 209
    Join date : 2009-10-13
    Age : 64
    Location : Great White North

    Re: Ultravalve for $2000

    Post by Captain Coconut on Thu Mar 31, 2011 4:03 pm

    I had one of AVA's preamps about 8-10 years ago and couldn't unload it fast enough. Noisy as hell, no bass, no depth and an abysmal headphone section were just a few of its shortcomings. The company has a loyal and rabid following however. Rolling Eyes

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Ultravalve for $2000

    Post by Bob Latino on Thu Mar 31, 2011 7:18 pm

    I am not surprised that both of the above posters found the "AVA Ultravalve" amp somewhat "lacking" in musical value. The "Ultravalve ST-70" (an oxymoron?) still uses two older design 6GH8A driver tubes. Personally, I don't care how you jerk the circuit around, a 6GH8A pentode/triode tube, as used on the Ultravalve ST-70, is not a good driver tube. It is not linear at all drive levels and rolls off the top and bottom end of the audio spectrum. Coventional wisdom is to use an all triode drive system. The ultravalve also (AFAIK) still uses a bandwidth limiting circuit although I have heard that the bandwidth limiting on the newer untravalve ST-70's is less than it used to be. On the AVA web site they call it > "getting the bandwidths of the power supply, audio circuits, and input acceptance into the right set of ratios so that no input signal short of output clipping could drive the unit into gross distortion at any frequency." I guess this is a rant here but my thought is > "don't use bandwidth limiting for God sakes, just design a friggin circuit that is FLAT and linear at all drive levels and also sounds clean WITH tube warmth thrown in." Now > charge $2000 for this amp ? Huh ? I'll build you TWO VTA ST-70's for that price.

    Personally. I don't thing AVA sells many "Ultravalve" ST-70's ...

    Bob

    j beede

    Posts : 317
    Join date : 2011-02-07
    Location : California

    Re: Ultravalve for $2000

    Post by j beede on Thu Mar 31, 2011 9:26 pm

    The only experience I have with AVA was with the "double Dyna 400" of "100 years ago". It drove the Magneplanar Tympani 1-U very well and was a desireable amplifier in those days. I think the van Alstine theory has always been to filter the input stage so that the power supply can better service the audible spectrum. I suppose the challenge is adding a filter that is abrupt enough to benefit the power supply without impinjing on the audible range in terms of roll off or phase error, etc.

    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: Ultravalve for $2000

    Post by Luddite on Thu Mar 31, 2011 10:37 pm

    Bob Latino wrote: I guess this is a rant here but my thought is > "don't use bandwidth limiting for God sakes, just design a friggin circuit that is FLAT and linear at all drive levels and also sounds clean WITH tube warmth thrown in." Now > charge $2000 for this amp ? Huh ? I'll build you TWO VTA ST-70's for that price.

    Personally. I don't thing AVA sells many "Ultravalve" ST-70's ...

    Bob

    Bob,

    I realize there may be a mutual "history" factor involved here, then maybe I'm drawing an erroneous conclusion. Never-the-less, perhaps a wee bit more objectivity could be mustered...IMHO, that is.

    Best Regards,
    Charlie

    RockyAM

    Posts : 26
    Join date : 2008-12-14

    Re: Ultravalve for $2000

    Post by RockyAM on Fri Apr 01, 2011 6:20 pm

    I'm with Bob on this one. Why not design a driver circuit that doesn't need bandwith limiting instead of using a driver circuit that does need bandwith limiting. This seems to me something like this. Lets say you have an automobile design whose steering mechanism vibrates or shimmys at 80 miles an hour. OK, so lets put a governor on the engine so that you can't go above 75 and you will never notice or have to deal with the problem at all. What you should do is design a better steering mechanisn on your automobile that won't shimmy at 80. RockyM

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