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    Newbie here - starting my Bob Latino M 125 Monoblock build

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    costerdock

    Posts : 33
    Join date : 2011-07-27

    Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Sat Jul 30, 2011 9:32 pm

    My first post - hello from the East Bay (CA) - just started my M125 build this weekend with pop.

    We finished the two driver boards:





    Hopefully the images turn out ok - first time doing this. I need to trim the leads a bit - my dad's wire cutter wasn't the best tool for trimming -I'm going to pick up something smaller. Hopefully the solder looks good - he's built a bunch of Heathkits (up to the big color TV) so I should be in good hands.

    Transformers being painted:

    Prepped:



    Painted:



    Not bad for day 1.

    Thanks,

    Chris


    Last edited by costerdock on Sun Jul 31, 2011 12:01 pm; edited 1 time in total

    Bob Latino
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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Bob Latino on Sun Jul 31, 2011 9:11 am

    Hi Chris,

    Thanks for the photos ... Your build is looking good ...

    The only thing I can see is that on each driver board the 10K AC balance control should have been put on the BOTTOM of the driver board. This is the small blue pot that is between the two black caps (120 uF and 47 uF) that are on the top of the board. The reason this pot should be placed on the bottom is that, once set, it shouldn't be REadjusted. Having this control on the bottom, it is "out of sight" and cannot easily be adjusted unless you take the bottom cover off. Just remember not to turn this control. Just use the other two pots (DC balance) to adjust the bias.

    Another thing is that when you do get to the point of wiring the amps up - do one amp at a time and get that one amp up and running before you start the second amp. If you try and do both amps at once you can get confused going back and forth between each amp. You also need a much larger work space to do two amps at once.

    Bob

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Sun Jul 31, 2011 12:00 pm

    Thanks very much Bob - I will definitely complete the first amp for the next section before starting the second one. Your point about the balance pot makes complete sense - I'll look into moving it to the bottom of the board.

    Thanks,

    Chris

    Bob Latino
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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Bob Latino on Sun Jul 31, 2011 12:34 pm

    Chris,

    I would just leave that pot there in place. Because it has 3 solder points, that AC balance control is sometimes difficult to remove and you also run the risk of breaking the pot trying to remove it. What I would do is place a small piece of tape over the screwdriver slot of the control to remind yourself that this pot is not to be adjusted..

    Bob


    Last edited by Bob Latino on Sun Jul 31, 2011 6:19 pm; edited 1 time in total

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Sun Jul 31, 2011 6:15 pm

    Agreed - I'll figure a way of signifying not to touch it - should be very simple.

    Kit is coming along nicely - instructions are excellent. Done for the day - all components installed on one chassis - next week the chassis wiring begins. Hopefully by next weekend the first amp will come to life.

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Sun Aug 07, 2011 7:19 pm

    First amp is finished - I'm still waiting on the Weber Rectifiers that I ordered last week Saturday (I wish I ordered them sooner - didn't know they would take soo long) - hopefully they will come in soon. I did the preliminary test of installing the two driver tubes - and powered the amp on - both tubes lit up and stayed lit - so far so good. I would est 1 day for the driver board and two days for the chassis moving carefully. And by day I mean - @4 hour days.


    Bob Latino
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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Bob Latino on Sun Aug 07, 2011 7:32 pm

    Hi Chris,

    Although the Weber WZ68 works best in that amp, you can try the amp out with a GZ34 tube rectifier. Most "guitar stores" carry GZ34 tube rectifiers. If you have a local guitar store close by, you could pick up a GZ34 and see if the first amp plays OK ..

    Bob

    mantha3

    Posts : 298
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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by mantha3 on Mon Aug 08, 2011 7:28 pm

    Get a pair of GZ33... An old Mullard rock solid tube!!!.

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Mon Aug 08, 2011 8:46 pm

    Thanks guys - today I ordered a set of Sovtek GZ 34s - fairly cheap and the guy is very near by - should have them in a couple of days.

    Those Mullards look pretty nice - I'll have to save up for those though. I see mixed opinions regarding the Sovteks (for rectifier tubes) - reliability being the concern. It will be nice at least in the beginning to try tubes vs. the webbers (very fitting as I had some dual webber carbs on my old car) - see if there is much difference - my speakers (Cornwalls) are efficient and from what I've read on this forum seems to nod more towards the Mullards for high efficient speakers.

    mantha3

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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by mantha3 on Tue Aug 09, 2011 6:59 pm

    With the Cornwalls you probably won't turn the amps up that much at all.. You may just want a spare GZ34 on hand. Prices are going up on the Mullard NOS GZ33.. Not too much of em left around. Nice amp/speaker combo! That must be a loud combo when cranked!

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Tue Aug 09, 2011 9:35 pm

    Proud to note that the first amp is done - received the weber rectifier today - tested two output tubes - both lit - both biased at .6 volts - slight hum through speaker (expected) that went to dead silence after I short out the interconnect cable.  With four tubes at 1.2 volts same thing - absolute DEAD silence!

    I'm tempted to listen to it through my preamp - but thinking I should wait.  We will see.

    Thanks!

    Chris

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Tue Aug 09, 2011 10:01 pm

    Ok after 5 minutes - I hooked it up - sounds awesome. I do notice a very slight noise when I switch to triode mode and back - still plays and still sounds fine so I assume this is completely normal.




    Bob Latino
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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Bob Latino on Wed Aug 10, 2011 5:55 am

    Hi Chris,

    Turn the volume down when you make the switch from triode to pentode/ultralinear. It mentions that in the manual. Yes .. There may be a slight noise when you make the switch from one mode to the other ..

    Bob

    costerdock

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    Join date : 2011-07-27

    Life is good....

    Post by costerdock on Sat Aug 13, 2011 8:07 pm

    Both amps finished - now I just need to kick back and listen to them.



    So far they sound absolutely incredible!

    Bob Latino
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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Bob Latino on Sun Aug 14, 2011 7:24 pm

    Hi Chris,

    That's a nice setup that you have there ... What kind of a speaker is that ? Looks pretty big ...

    Bob

    Captain Coconut

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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Captain Coconut on Sun Aug 14, 2011 8:04 pm

    With the Cornwalls that close to the turntable, do you have trouble keeping the needle in the groove? Shocked

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by mantha3 on Tue Aug 16, 2011 6:34 pm

    is it bad to have one amp right under the other... The other getting too hot?

    Looks great! Nice amps! I'd love to hear em. Have fun! Get some NOS preamp tubes and do some tube rolling!!!

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Tue Aug 16, 2011 9:05 pm

    Bob Latino wrote:Hi Chris,

    That's a nice setup that you have there ... What kind of a speaker is that ? Looks pretty big ...

    Bob

    Thanks Bob - speakers are 77 Klipsch Cornwall decorators.


    Captain Coconut wrote:With the Cornwalls that close to the turntable, do you have trouble keeping the needle in the groove? Shocked

    Seems like I should but the turntable is fine - it is actually to the right of the speaker - not directly in front of it. I need a bigger room!


    mantha3 wrote:is it bad to have one amp right under the other... The other getting too hot?

    Looks great! Nice amps! I'd love to hear em. Have fun! Get some NOS preamp tubes and do some tube rolling!!!

    Thanks - so far the heat isn't too bad - there is 4 inches of clearance from the top of the tube to each self above both amps - the back of the cabinet is removed so it should get enough air. I definitely need a new audio rack though. The shelf bottom over the tubes does get warm - but doesn't burn your hand - and the other side of the self gets only warm - this after 3 hours of rockin out. I'm glad I have the weber rectifiers (one less heat source) - I may go with just two output tubes since I do not need that much power for the cornwalls - but all in all seems just fine.

    Bob Latino
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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Bob Latino on Sat Aug 27, 2011 10:35 am

    Hi Chris,

    I saw this photo on the other forum. I see that you now have a better arrangement for your M-125's. IMHO your newer placement on the top of each speaker is better than the earlier arrangement with the two amps inside the cabinet. Your amp's should run cooler with the arrangement as you have in the photo below.

    Bob



    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Sat Aug 27, 2011 1:17 pm

    Thanks a bunch Bob. Eventually I will want them in a rack but until we move - I'll have to keep it this way - I do really like it this was as in the dark listening to music it is really cool/surreal.

    So in the picture they are sitting on some new black placements with a thick rubber mat directly under that (more so to protect the speaker - these amps are heavy!) - the speakers sit on four rubber cups - so they are solid to the floor - no rocking(well there is some rockin out).

    Here is the continuation of this at the other forum:
    http://www.audiokarma.org/forums/showthread.php?t=389183

    Thanks!

    Chris

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Fri Sep 09, 2011 9:41 pm

    Several weeks of listening. All I can say is that these amps sound wonderful - very clean, very quiet background, lots of detail - wonderful highs and lots of punch. Listening to Dave Mathews on vinyl - simply incredible symbols, vocals, guitar lots of dimension.

    I swapped out the weber rectifiers for a couple of weeks with Sovteks GZ34s - those lasted 2 weeks then went piff - both at around the same time while turning the amps on - gone - arc then no bias - webers back in and in to stay. I couldn't tell any difference with the Sovteks. Perhaps someday I'll try the old Mullards - but my concern would be cost - I wouldn't want those to fail (I hear they last forever.)

    I did have a ground loop hum that was due to the interconnects connecting to the preamp - I lifted the ground on the amps and the hum went away - I've since picked up a couple HumX devices to safely lift the ground. My house is old(built in 30's) with combo 2 prong and 3 prong outlets all over the place.

    I made the right decision building and choosing these great amps.

    Thanks,


    Jhoman

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    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by Jhoman on Sat Sep 10, 2011 6:54 am

    Very nice build!

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Fri Sep 16, 2011 7:55 pm

    Jhoman wrote:Very nice build!

    Thanks very much Jhoman!


    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Sat Nov 19, 2011 3:32 pm

    Update time.

    Ok - I had some very faint noise issues - a ringing microphonics that was very subtle (I would have to put my ear up to the CW squawker and wait patiently for it to come and go)  - it was driving me nuts.  The amps are dead silent otherwise with this occasional slight ringing sound.  I swapped the driver tube with the rear phase splitter tube on the one amp that the sound seem to be mostly coming from and it became worse.

    I contacted Jim McShane and from his advice I placed an order for a matched pair of quiet NOS GE 12BH7As - It has been over a week - the amps are now dead silent with these as the driver tubes - I'm extremely happy.  I love these amps - but the slight ringing was like water torture - I could not stop focusing on it.

    I'm now running the GEs up front - the most quiet of the 4 EH 12BH7As in the rear and 4 Sovtek KT88s.

    Thanks,

    Chris

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Newbie here - starting my Bob Latino M 125 Monoblock build

    Post by costerdock on Fri Sep 12, 2014 4:26 pm

    Three years later - these amps still going strong - I couldn't recommend them highly enough. Thanks again Bob!


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