The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    M-125 too much for efficient speakers?

    Share

    jdsackett

    Posts : 4
    Join date : 2011-07-10

    M-125 too much for efficient speakers?

    Post by jdsackett on Tue Jul 19, 2011 12:51 pm

    Hello all. thinking pretty serious about putting together a pair of these mono blocks. My speakers are pretty efficient at allegedly 102db@1watt/1meter. Klipsch RF7s. At one time I had a mc275 going into them and it was plenty of power, BUT everybody knows there's no such thing as too much, right?? Anyway, will these amps sound good at barely above an idle? which is probably where they will be most of the time. God knows, i will never be able to crank them without hurting myself, but i still think a lot of power i reserve is nice to have for peaks, etc. Anyway, What do ya'll think?? Overkill?? Sound crappy because I'm not in the sweet spot of the amp?? Be okay, just wear hearing protection?? Hope your neighbors don't have any young children, or animals?? Input greatly appreciated. Regards, J.D.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: M-125 too much for efficient speakers?

    Post by Bob Latino on Tue Jul 19, 2011 2:43 pm

    Hi JD,

    The sound of the M-125's is the same clear, clean, high quality sound at all sound levels. At 102 dB efficiency, your speakers need very little input for full output yet you are also correct in mentioning the fact that it is always nice to have some "reserve" for peaks. Instantaneous peaks sometimes require 5 to 10 times average power to adequately reproduce a given sound pressure level. You could also operate these amps in the triode mode (65 watts per amp) and still have plenty of reserve.

    Another thing that plagues efficient speakers is their "ability" to show an amp's residual noise level to a much greater degree than normal efficiency speakers. The M-125's have an extremely black background and are noticeably quieter (-95 dB) than most tube amps especially if used with selected low noise driver tubes.

    Bob

    jdsackett

    Posts : 4
    Join date : 2011-07-10

    Re: M-125 too much for efficient speakers?

    Post by jdsackett on Tue Jul 19, 2011 5:44 pm

    You could also operate these amps in the triode mode (65 watts per amp) and still have plenty of reserve.

    That is exactly my thoughts. I was thinking st120 but don't think 30 some watts would work for me in triode.


    The M-125's have an extremely black background and are noticeably quieter (-95 dB) than most tube amps especially if used with selected low noise driver tubes.

    What tubes would you recommend in the front end Bob?? Somewhere around here i have a quad some old Svetlana winged c kt88s, but only have 4 of them. What do you like for power tubes and what kind of tube life can i expect? Some amps are hot rods and sacrifice tubes for power. Thanks for the input Bob, really helps. Best regards, J.D.

    jjones3318

    Posts : 57
    Join date : 2011-04-05
    Location : Boulder, CO

    Re: M-125 too much for efficient speakers?

    Post by jjones3318 on Tue Jul 19, 2011 5:55 pm

    I can second Bob - I listen at several different levels depending on what I'm listening to and the time of the day - the level doesn't affect the sound signature of the amp.

    As well as cutting the power to 65w in triode mode, you can also do 65w in UL mode with one pair of tubes instead of two pair, or 35w with one pair in triode. Plenty of options, and if you really don't need 125w you can save money by using 4 output tubes instead of 8. Personally I like having an amp I can tailor so easily to the speakers I'm currently using.

    I may have to drag my 102dB horns out of the closet and give them a listen.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: M-125 too much for efficient speakers?

    Post by Bob Latino on Tue Jul 19, 2011 6:27 pm

    jdsackett wrote:You could also operate these amps in the triode mode (65 watts per amp) and still have plenty of reserve.

    That is exactly my thoughts. I was thinking st120 but don't think 30 some watts would work for me in triode.


    The M-125's have an extremely black background and are noticeably quieter (-95 dB) than most tube amps especially if used with selected low noise driver tubes.

    What tubes would you recommend in the front end Bob?? Somewhere around here i have a quad some old Svetlana winged c kt88s, but only have 4 of them. What do you like for power tubes and what kind of tube life can i expect? Some amps are hot rods and sacrifice tubes for power. Thanks for the input Bob, really helps. Best regards, J.D.

    Hi JD,

    You can use KT88, 6550 or Tung-Sol KT120 output tube in the M-125's. If you only have four KT88's you could just run two KT88's in each amp for 65 watts per monoblock. I like the KT-120's and presently have four in each one of my own M-125's. They work very well in these amps and give about 10 extra watts per monoblock.

    For driver tubes you can use either two 12AU7 or two 12BH7 driver tubes OR one 12AU7 and one 12BH7. If you mix them I recommend a 12AU7 in the front initial voltage amplifier tube and a 12BH7 in the rear phase splitter/inverter tube. 12BH7's have larger plates than 12AU7's and can swing more voltage and are better in the rear position. In the front position either tube works fine. Right now I have a Mullard CV4003 (12AU7) in the front position and a GE 12BH7 in the rear position. The Mullard's are not that expensive ($30 each) and will probably last longer than most 12AU7 tubes. The ElectroHarmonix 12BH7 is also a very good tube that I have used in these amps in both positions. The EH tubes are quiet and sound very good in the M-125's.

    Bob

    jdsackett

    Posts : 4
    Join date : 2011-07-10

    Re: M-125 too much for efficient speakers?

    Post by jdsackett on Tue Jul 19, 2011 7:02 pm

    Thanks JJones, thanks Bob. Couple more questions. Where do you bias this guy?? And, I see you won't offer a stepped attenuator for this amp. Will a passive pre (glorified volume pot) work okay. Input voltage in the spec sheet looks okay for it. About how much shipping to Las Vegas? My gosh Bob, you're on the other end of the world from me Very Happy . Thanks again fellas. Best regards, J.D.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: M-125 too much for efficient speakers?

    Post by Bob Latino on Tue Jul 19, 2011 8:27 pm

    JD,

    There are two bias pots - one for the two left output tubes and one for the two right output tube. The recommended bias setting is 1.20 volts for each pair of left or right output tubes. This bias setting gives an idle current of 60 milliamps for each output tube.

    A passive preamp will work just fine with the M-125's.

    The two M-125 amp kits are shipped together in one HEAVY 70-72 pound box. Shipping from me in Massachusetts to Las Vegas on the two amp kits is $85.

    If you have any other questions about the purchase of a pair of M-125 amp kits you should probably Email me directly at my normal Email address > Bob01605@aol.com rather than use this forum for any questions related directly to the purchase of an item.

    Bob

    jdsackett

    Posts : 4
    Join date : 2011-07-10

    Re: M-125 too much for efficient speakers?

    Post by jdsackett on Tue Jul 19, 2011 9:27 pm

    Thanks for all the help Bob. Will get back to ya. regards, j.d.

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: M-125 too much for efficient speakers?

    Post by mantha3 on Wed Jul 20, 2011 9:02 pm

    Passive Pre-AMps work great for these amps. I run a passive on my ST120 and these amps run similar Pre-amp stages if I'm not mistaken...

    Here is my rig.. buy the amps mah man
    http://dynacotubeaudio.forumotion.com/t846-passive-pre-amp

    bcinnamon

    Posts : 26
    Join date : 2011-05-07

    Passive Pre Amp with Remote -- Terrific Idea

    Post by bcinnamon on Thu Jul 21, 2011 12:44 pm

    I am absolutely delighted with both the M-125s (which I have on a pair of 8' Eleganza speakers) and the ST-120 (on Kef Q-7s). Both amps were easy to assemble, started up smoothly and sound clear as bell as loud as I want to go.

    Don't hesitate, buy the M-125s (be prepared to tip the UPS guy for his extra workout).

    I haven't looked around, but if there is a good little remote control pot (like on my Jolida 5T pre-amp or on a PC home theater system), that would be a great component to build into this passive pre-amp along with a rotary switch and a collection of gold-plated jacks on the back. To make it more living-room friendly, powder coating the chassis would be nice. I powder coating my ST-120 (cost $125) and painted the transformers; I bet the powder coat cost at the factory would be much, much less.

    Sponsored content

    Re: M-125 too much for efficient speakers?

    Post by Sponsored content Today at 11:55 am


      Current date/time is Tue Dec 06, 2016 11:55 am