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    What other driver tubes is everyone using in M-125 amps?

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    Sutton

    Posts : 12
    Join date : 2011-04-30

    What other driver tubes is everyone using in M-125 amps?

    Post by Sutton on Tue Jun 28, 2011 10:52 am

    I have been looking and trying to determine if there are other tubes which might be used in the driver board of the VTA M-125 mono blocks? I have tried the 12AU7 and the 12BH7, but want to wander and roll some other things in, if possible. Will a 6414 tube work in either or both positions? How about an ECC99?

    Are there any old Russian tubes which would work? I have looked over the net and most places say to check with your maps manufacturer..so that is what I am trying to do. I love to listen to different types of tubes in different positions, and know the small signal tubes probably make the most difference, so I love to experiment. Just don't want to create a problem and hurt my babies. The ECC99 and 6414 both seem to have potential, but I want to check before doing any damage. I know there are many variants of the 12AU7 tube, and wonder if any of them will work well and handle the current swings in a better fashion than the AU? the 5814? 5963? 6189?
    6n6p Russian ECC99?

    Just interested in any thoughts and observations. These amps are so wonderful, I want to try every possible tube to find the ones which are "just right" and although the 12BH7 (I'm using RCA black plates now) sounds good, I just feel there have to be other possibilities out there.

    Thanks for any thoughts and observations..

    Sutton

    Westy56

    Posts : 58
    Join date : 2011-05-09
    Location : Albuquerque

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by Westy56 on Tue Jun 28, 2011 11:33 am

    Sutton wrote:I know there are many variants of the 12AU7 tube, and wonder if any of them will work well and handle the current swings in a better fashion than the AU? the 5814? 5963? 6189?
    Thanks for any thoughts and observations..

    Sutton

    All should work, but are rated differently. Same pin out.


    Steve

    Bob Latino
    Admin

    Posts : 2415
    Join date : 2008-11-26
    Location : Massachusetts

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by Bob Latino on Tue Jun 28, 2011 12:03 pm

    Hi Sutton,

    I have now in my own M-125 monoblocks a Mullard CV4003 (12AU7 equivalent) as the front voltage amplifier tube and a GE 12BH7A tube in the rear phase splitter/inverter position. The FRONT tube (whatever you use) has more influence on the sound of the amp than the rear tube. The ElectroHarmonix 12BH7A tubes (IMHO) are every bit as good as the GE or RCA 12BH7A's. The Mullard CV4003 is the best tube so far that I have used in the front position.

    M-125 driver board with Mullard CV4003 voltage amplifier and GE 12BH7A phase splitter/inverter tube



    Bob

    Sutton

    Posts : 12
    Join date : 2011-04-30

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by Sutton on Tue Jun 28, 2011 2:04 pm

    Excellent, as I just lucked into a stash of Mullard CV4003 tubes and they are awesome in another preamp I am using. I also had Roy build a SP9 with a PH12 phono section and I am just getting around to rolling 12AX7 and 6922, 6DJ8, Russian 6N23P-EV tubes. I have been having a ball. I hope I have four closely matched Telefunken 12AX7's as those are the ones where I now have some 1999 production Electro Harmonics 12AX7LPS tubes (wich have an excellent reputation for that year of procuction, anyway). Roy is also trying some 6N23P-EV's, so I'm anxious to compare notes.

    All wonderful stuff. I just want more gain from the monoblock M-125 amps. Compared to some other amps I have, I am having to turn the volume on the SP9 almost all the way up to equal the gain I am getting from another 100 watt tube amp at half the volume set on the preamp. I'm just looking to crank up the gain from the driver stage. Maybe the extra headhoom is inherent to the design, but I'd love to get some more spl from these beauties.

    Any ideas? Maybe I need to do a customized Driver board to get me where I want to be....

    What are some other folks doing?

    This is a great hobby isn't it?

    Sutton


    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by baddog1946 on Tue Jun 28, 2011 3:37 pm

    Hey Bob:
    What about a high(er) gain version of the board for these amps? I tried both hi and lo versions of the VTA boards in my ST-120's and I prefer the high gain version.

    Bob Latino
    Admin

    Posts : 2415
    Join date : 2008-11-26
    Location : Massachusetts

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by Bob Latino on Tue Jun 28, 2011 3:48 pm

    The M-125's have average gain for a tube amp and need about 1.1 volts in for 125 watts out. This is actually slightly more gain than a stock ST-70 which needed about 1.3 volts in for 35 watts out. IMHO a higher wattage tube amp should have slightly lower gain. The higher the gain the higher the residual noise level of the amp. The higher the gain combined with a higher wattage level would make the M-125's less usable with higher efficiency speakers.

    Bob


    Last edited by Bob Latino on Thu Jul 07, 2011 2:59 pm; edited 1 time in total

    baddog1946

    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by baddog1946 on Wed Jun 29, 2011 8:30 am

    Point well taken but its interesting that both my ST-120's are dead silent with either board in them and I am using a pair of Decware NFX full range speakers that are very sensitve SPL (100dB) even at high listening levels they are dead silent and maintain their fidelity. It is a testament to the excellent design topology of these amps.

    Sutton

    Posts : 12
    Join date : 2011-04-30

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by Sutton on Mon Jul 04, 2011 7:13 pm

    I have now tried an Amperex E80CC PQ with gold pins in each position, and prefer it in the second (phase splitter/ inverter) position, but think I still like the 12BH7A better in the second position, and the 6189W or the CV4003 the first position. The E80CC does give the amp more "slam" and at the same time makes it brighter...but everything is so subjective...and these amps so good that it is really hard to make a firm call wither way. Everthing sounds good in it. I think a Mullard GZ33 makes the most improvement however, but again...it could all just be in my mind. I just love rolling tubes and being on the "hunt" for something new and different. Anyone else?

    Sutton

    Posts : 12
    Join date : 2011-04-30

    Re: What other driver tubes is everyone using in M-125 amps?

    Post by Sutton on Thu Jul 07, 2011 2:54 pm

    I have now tried the RCA 12BH7A in the first position and the Amperex E80CC in the second position on the driver board of the M-125 amps. It seems that the 12BH7A adds warmth and tames the E80cc a little, while still allowing it to add the sparkle and air which seems overpowering when using a 12AU7 in the driver baords' first position.

    I have ordered some Tungstram E80CC tubes which are described as another excellent tube but with a slightly different sound than the Amperex, but equally good, to try them in the inverter/ phase splitter slot. I am beginning to realize that any difference is ever so slight and could be a purely subjective psychoacoustic thing. These amps are so good, I think they woulld sound great with two Chinese 12AU7 tubes in them. I am finally beginning to agree with Bob. They probably sound just as good with EH 12BH7A tubes in both positions, as anything else. Tube rolling is a lot of fun, but I don't know that it is getting me anywhere. Perhaps my ears are made of tin, and are not as good as I would like to think.

    I do know these are fabulous amps, and this is a lot of fun. Thanks to Bob and Roy for some really GREAT products to play with....are there not any other tube nuts out there playing around with different tubes?

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