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    Valves To Change Tonality in VTA ST-120

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    EddieGnz1

    Posts : 23
    Join date : 2013-10-16

    Valves To Change Tonality in VTA ST-120

    Post by EddieGnz1 on Tue Mar 18, 2014 8:41 pm

    so far I love my VTA ST-120. It does sound like a $4,000 amp. I just wanted to get various recommendations on tubes for the driver stage that will change the tonality just a touch but a noticable amount;

    The issue is that I added a Behringer electronic crossover and the crossover has made it a little too bright and possibly a tinge harsh on the highs.

    I read where someone changes out ONLY the center valve on the driver stage board because he feels that is where you can make the most noticable differences.

    My goal is to keep the frequency response at the original full bandwith of
    Frequency response . . . . 10 Hz to 30 KHz +/- .1 dB at 1 watt

    Power bandwidth . . . . … 17 Hz to 30 KHz +/- .3 dB at 60 watts

    Is there a tube you can recommend that will make the amp sound as if the Behringer active crossover was not there. I love the way it sounds without the active crossover but i need the active crossover for my configuration.

    Kind thanks,
    Eddie

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Valves To Change Tonality in VTA ST-120

    Post by sKiZo on Tue Mar 18, 2014 11:16 pm

    Twere me, I'd try a set of 12BH7's in the SIDE channels. Those tend to be less bright than most any 12AU7 I've tried.

    PS ... be helpful to know what you're using now?



    skriefal

    Posts : 116
    Join date : 2011-09-20
    Location : Utah, USA

    Re: Valves To Change Tonality in VTA ST-120

    Post by skriefal on Wed Mar 19, 2014 12:52 am

    You could also try a Mullard CV4003 or 12AU7 in the center position, or perhaps a 1950s RCA black-plate 12AU7.

    mazeeff

    Posts : 116
    Join date : 2014-01-06
    Age : 61
    Location : Grand Rapids, Michigan, USA

    Re: Valves To Change Tonality in VTA ST-120

    Post by mazeeff on Wed Mar 19, 2014 6:54 am

    Just out of curiosity, what is the source of your music? I play primarily Flac based music, and sKiZo got me hooked on using a DSP to adjust room EQ and tone. My ST-70 was far too bright, and using a HiFi Rolloff in the DSP made a big difference. Like yourself, I started out trying to fix my problem by changing tubes. I was never able to get the right sound until using the DSP. Only been using it for two days, but it is seems to work fine.

    Mike

    mijohn

    Posts : 33
    Join date : 2013-06-19

    Re: Valves To Change Tonality in VTA ST-120

    Post by mijohn on Wed Mar 19, 2014 10:10 am

    EddieGnz1 wrote:The issue is that I added a Behringer electronic crossover and the crossover has made it a little too bright and possibly a tinge harsh on the highs.
    How about removing the Behringer crossover and going back to what you had before!  Laughing

    Could be the new crossover just needs more time to 'burn in' before it sounds its best.

    corndog71

    Posts : 444
    Join date : 2013-03-19
    Location : It can get windy here

    Re: Valves To Change Tonality in VTA ST-120

    Post by corndog71 on Wed Mar 19, 2014 11:56 am

    The active crossover could also throw off the balance of the drivers that the passive crossover compensated for. A better solution would be to upgrade the parts of the passive crossover.

    ramon68

    Posts : 83
    Join date : 2009-04-12
    Age : 75
    Location : naples fl

    Re: Valves To Change Tonality in VTA ST-120

    Post by ramon68 on Wed Mar 19, 2014 1:40 pm

    I was thinking of getting an electronic crossover from Marchand Electronics for my mtm speakers. I have a transfer function plot
    provided by the speaker's designer and Phil Marchand showed me where the electronic crossover manual covers the issue of
    adding baffle step with a little arithmetic and a few resister changes.

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Valves To Change Tonality in VTA ST-120

    Post by sKiZo on Wed Mar 19, 2014 1:57 pm

    REAL crossovers are passive!  pirat 

    I'll probably be going thru some of that here in a bit. Just ordered a bunch of ERSE film caps to rebuild the crossovers on my McIntosh XR16's. Bet good money they wouldn't have set me back $100+ back 30 years ago when the speakers were built.

    (grumble mumble)

    I expect there will be some break in time involved, but I also expect to see immediate improvement with the new tech replacements. Then again, might be a downgrade depending on whatever unique process they used to match the caps to the board in the first place ...



    Wish me luck, eh ...

    mazeeff wrote:sKiZo got me hooked on using a DSP to adjust room EQ and tone. My ST-70 was far too bright, and using a HiFi Rolloff in the DSP made a big difference. Like yourself, I started out trying to fix my problem by changing tubes. I was never able to get the right sound until using the DSP. Only been using it for two days, but it is seems to work fine.

    Mike

    Takes the work right out of it, don't it? What you got for free would have cost some serious bucks back in the day ... techs in white suits taking over the house for hours with frequency generators, scopes, mikes hanging in shock cradles, slide rules and plots and graphs oh my ...

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