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    M-125 and SP-12/PH-12 Build Pictures

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    turbotoy

    Posts : 47
    Join date : 2012-04-15

    M-125 and SP-12/PH-12 Build Pictures

    Post by turbotoy on Sun Apr 15, 2012 10:38 am

    Hello all, first time post here, though I've browsed the forum for a while. I've been conversing with Roy and Bob for a while, and Bob asked me to post some pictures and thoughts here on the forum. About 5 months ago I built a SP-12/PH-12 combo and was thrilled with the quality of the kit and the help I got from Roy. I just recently decided to take the plunge and built a pair of M-125s.

    I should state that I jumped from a very mid-fi setup to my current system all in one shot, so I can't really give a meaningful subjective review. I also haven't heard many systems at this level, so I don't have much to go off of for benchmarks. However, I'll try to give my perspective.

    Note that in the photos the equipment stands are extremely temporary, I'm playing with layout before building a "final" stand design. You can also tell from the lack of baseboard what my work priorities are!

    Both the preamp and M-125s were a real pleasure to build. You can tell the level of detail that went into each and every aspects of the kits. For working on the M-125s I made up a little stand out of plywood, some pictures of it are below. I HIGHLY recommend doing this when building these amps. The thought of anything touching the day old paint on the transformers was not pleasant to me, and I wanted a nice stable platform to work off of. There are probably lots of other ways to do it, but the design shown was very stable and would also fit with the tubes installed. Well worth the 15 minutes it took to make.

    So, the SP-12/PH-12 and M-125s are driving a just completed pair of Zaph Audio ZRT 2.5 speakers in 65 liter ported enclosures. These speakers use the Scanspeak Revelator series of drivers. The cabinets, which are truly works of art, were built by Lee Taylor. I was going to build them myself until I discovered that Lee offered them, and it turns out he's only about 1.5 hours from me. I'm a decent carpenter, but these cabinets are the result of 50+ years of his cabinet building experience and available tooling; I would have never come close to this sort of quality.

    On the analog side, I have a Sony PS-X70 TT with a Denon DL-103R cartridge run through a K&K step up transformer before heading into the PH-12. The last piece I really need to complete this system is a good CD player. I'm currently using an old Yamaha changer, and it's finally one of the last weak links in the system. Would love opinions on good options for CD players these days if anyone has any!

    So, in all honesty, the Zaph ZRTs are such a radical change from what I had before (Paradigm Monitor 3s), that it's hard to know exactly what the amps are and aren't doing. I *can* tell you that the system sounds absolutely spectacular!! The level of detail that comes through is just incredible, and it's completely non-fatiguing. I've never heard a system with this level of clarity that didn't sound somewhat harsh and metallic at the same time. There have been a handful of tracks where I have been able to clearly discern lyrics that have never been comprehensible before; I think that speaks volumes by itself! Low end extension seems impossibly low and clear for 7" drivers. The room these are in is about 36' x 28' with some halls and stairwells, so it's not your normal listening environment. I didn't want to have to use a subwoofer and its accompanying challenges in my system, and it turns out that I really don't need one. The other interesting thing is that the Zaphs are VERY efficient relative to what I was used to. I'm running 4-5 steps down on the main attenuator to reach about the same level as before. In hindsight, 125 watts is likely overkill, but better to error that way I figure. I'm still letting everything break in, but I have little doubt that the M-125s could reach extremely high SPL with these speakers.

    I had some friends over yesterday, and everyone, including some folks that have never really heard even decent gear, concluded that vinyl sounded better given my current CD player. To me, I think that just means my CD player is in need of improvement; I think both formats should sound spectacular. However, I think it also speaks volumes to the quality of the PH-12, and in all honesty, the 103R cartridge too.

    In any case, some pictures are below. I look forward to learning more from all the great individuals at this forum!











    Bob Latino
    Admin

    Posts : 2413
    Join date : 2008-11-26
    Location : Massachusetts

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by Bob Latino on Sun Apr 15, 2012 12:04 pm

    Hi Turbotoy,

    Your amp building stand is an excellent idea. You can move the amp around as you build it without the two transformers rubbing on the surface below. Your wiring on both the preamp and amp would serve as a good model of how electronic gear should be wired. Nice job !

    Bob

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by costerdock on Sun Apr 15, 2012 2:41 pm

    Great work - looks fantastic and I bet it sounds awesome. I'd probably get rid of the tube depot stickers to have it look even cleaner. The stand is a great idea - I used a very soft towel - the stand would have been a better idea since on the towel they rocked a bit - didn't affect the paint though.

    danf

    Posts : 58
    Join date : 2009-01-19

    Gorgeous work!

    Post by danf on Sun Apr 15, 2012 4:59 pm

    It is a pleasure to see such a careful wiring job and high level of craftsmanship! As Bob said: your amp stands are clever and effective.

    I hope that you don't wince if I make a safety suggestion. With your skill it should be easy to make some covers for the circuit boards. If you have curious visitors someone might touch the exposed HV and get a shock. I guess that these amps don't come with a ventilated cover - that would also work but would trap heat from all of those output tubes.

    One approach is to mount standoffs at the circuit mounting holes and put a piece of stiff perforated metal on top. You would have to drill or punch holes for the tubes.

    turbotoy

    Posts : 47
    Join date : 2012-04-15

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by turbotoy on Sun Apr 15, 2012 7:34 pm

    Thank you for the kind words. Bob's extremely detailed instructions made it easy to get the wiring nice and neat right from the start. I studied all sorts of pictures and configurations from Roy on the preamp before deciding how to mount everything. Admittedly, the M-125 wiring picture is of the second amp I built, but the first was just a little less perfect.

    danf - I don't cringe at all when folks bring up safety issues. I work in the nuclear industry as a ME and as-is it's very hard to justify that the design is sufficient from a hazard prevention perspective. I'll note, I consider this 100% on me, the builder, not the kit designer. I'm 32 and single, and there are never really kids in my house. That said, when I had a bunch of adults pocking around the amp the other day, I ran over from across the room to give them the "don't touch" warning. You just can't predict what humans (or dogs) will do.

    Bob or others, what have the other M-125 owners done in this regard? When I was assembling the kit I almost ran studs or standoffs up through for the very reason you mentioned, but was at the "want to hear it" point.

    I'm thinking the most elegant thing to do would be to make a "box" from brushed SST sheet that is about 3/8" high. Through the top would be penetrations for the caps, tubes and bias pots. I could tig weld the corners of the box to make it all the more unique/finished looking. I'm really wondering what other M-125 owners have done though.




    tubes4hifi
    Admin

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    Join date : 2008-11-30

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by tubes4hifi on Mon Apr 16, 2012 1:04 am

    your have a fantastic system that probably cost 1/3 to 1/4 of what an equivilent system would have cost in a hi-fi store. Also, fantastic choice of speaker system, I haven't actually heard them but for several years those were on my wish list, and I had actually considered offering them to my customers on my website, because I know the design and the components of those speakers are top notch. Just curious what the cabinents cost, as I'm sure they cost as much or more than the speaker components, wood working is NOT something I'm good at.

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by plexus on Mon Apr 16, 2012 1:18 am

    Forgive me if I am wrong but its not a good idea to parallel wires that are carrying any AC. granted I am sure the cross talk would be small, maybe. it looks nice but i think the best practice is to cross AC lines 90 degrees and twist those complimentary pairs (which you've done). i know one can argue that the audible difference might be small to insignificant however its a cheap easy thing to change to ensure the best quality, sacrificing the clean look for sure. but who see that after you take and post the pic?

    Bob Latino
    Admin

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    Join date : 2008-11-26
    Location : Massachusetts

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by Bob Latino on Mon Apr 16, 2012 5:52 am

    plexus wrote:Forgive me if I am wrong but its not a good idea to parallel wires that are carrying any AC. granted I am sure the cross talk would be small, maybe. it looks nice but i think the best practice is to cross AC lines 90 degrees and twist those complimentary pairs (which you've done). i know one can argue that the audible difference might be small to insignificant however its a cheap easy thing to change to ensure the best quality, sacrificing the clean look for sure. but who see that after you take and post the pic?

    What turbotoy has done in his M-125 build is parallel wires carrying AC with wires carrying DC. I have never known or seen any induced interaction between AC and DC wires that were paralleled on any Dynaco type amp. Even if you were to parallel two pairs of wires that carry AC, as long as you twist both sets of wires carefully I have never noticed any induced interaction between the two sets of wires. When you twist two wires of a pair carrying AC, both wires remain at right angles to each other and the fields will cancel. During the design of the M-125's careful attention was paired to wire routing. The end result is that the M-125 amps are about 5 dB quieter than the VTA ST-70 or the VTA ST-120.

    Re: Covering the driver board on the M-125. Unless you have young children or pets that may have access to your amp, IMHO, it isn't really necessary. If you do have pets or young children that could touch your amp, then keep the amp on a shelf or some place where they can't get at it

    Bob

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by plexus on Mon Apr 16, 2012 10:08 am

    Just ti beat a dead dog a little... I see wires that carry AC audio signal paralleled all over that amp. those wires coming off the phase splitter into the power tubes will likely crosstalk. sure looks nice though. id want to scope the end points of all those paralleled signal wires to be sure. its not art class, its high end audio. Smile

    TMadden

    Posts : 99
    Join date : 2011-12-22

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by TMadden on Mon Apr 16, 2012 11:26 am

    Wow, very nice system and beautiful workmanship. Thanks for sharing!
    People like you, Roy, Bob and Zaph help make DIY audio an incredible hobby!

    wedg714

    Posts : 74
    Join date : 2011-11-23

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by wedg714 on Mon Apr 16, 2012 4:31 pm

    i think your wiring job is very nice. i see absolutely nothing wrong there. but i guess that old saying about pleasing all of the people all of the time is proven once more!!

    plexus

    Posts : 94
    Join date : 2012-02-18
    Location : Toronto, Canada

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by plexus on Mon Apr 16, 2012 4:39 pm

    wedg714 wrote:i think your wiring job is very nice. i see absolutely nothing wrong there. but i guess that old saying about pleasing all of the people all of the time is proven once more!!

    I agree, it looks very nice. but its electrically problematic. depends what you are going for I guess.

    wedg714

    Posts : 74
    Join date : 2011-11-23

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by wedg714 on Mon Apr 16, 2012 4:52 pm

    yeah, right

    Captain Coconut

    Posts : 213
    Join date : 2009-10-13
    Age : 64
    Location : Great White North

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by Captain Coconut on Mon Apr 16, 2012 5:04 pm

    plexus wrote:I agree, it looks very nice. but its electrically problematic. depends what you are going for I guess.

    Boy, I could swear you're Erik from CAM. Obsessive/compulsive like him! Wink

    Bob Latino
    Admin

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    Join date : 2008-11-26
    Location : Massachusetts

    Re: M-125 and SP-12/PH-12 Build Pictures

    Post by Bob Latino on Mon Apr 16, 2012 5:13 pm

    plexus wrote:
    wedg714 wrote:i think your wiring job is very nice. i see absolutely nothing wrong there. but i guess that old saying about pleasing all of the people all of the time is proven once more!!

    I agree, it looks very nice. but its electrically problematic. depends what you are going for I guess.

    Plexus > You do have your right here to express your opinion here. The problem is unless you have ...

    1. Heard the M-125 amp (as I have)
    2. Put the M-125 on a scope (as I have)
    3. Had the M-125 run through a IM distortion analyzer (done by a friend of mine who has the gear)
    4. Had the M-125 run through a THD distortion analyzer (done by a friend of mine who has the gear)
    5. Had the M-125 run through a spectrum analyzer (done by a friend of mine who has the gear)

    You shouldn't really comment on what you "think" might be wrong because of what you think might be a wiring issue. Every M-125 builder is given a wiring diagram showing roughly where the wires should be layed out, which wires should be twisted and approximately where the wires should be run. If done correctly there is minimal (if any?) interaction and the amps are dead quiet. (-95 dB signal to noise ratio)

    Bob

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