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


    Prototype 125 watt monoblock tube amplifier KIT

    Share

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by deepee99 on Sat Jun 09, 2012 7:23 pm

    Bob, as usual, thank-you for the quick info. It's a joy to meet you folks and this community.
    -d-

    RockyAM

    Posts : 26
    Join date : 2008-12-14

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by RockyAM on Tue Jun 12, 2012 4:31 pm

    Hey Bob, I had a friend listen to my M-125 monoblocks and he is interested in building a pair. He wanted to see what the inside wiring looked like. I lost your Email address so the only way I could contact you is through the forum here. Any way you could post a photo of the inside wiring? I guess I could have pulled the bottom cover off one of my amps but they were hot and he had to leave anyways. Thanks. RockyAM

    Bob Latino
    Admin

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

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Tue Jun 12, 2012 6:05 pm

    Sure - Below is a photo of the inside wiring of one M-125 monoblock.

    Bob



    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    More dumb M-125 questions . . .

    Post by deepee99 on Tue Jun 12, 2012 7:37 pm

    That is one beautiful build. My compliments to the assembler, whose handle I cannot recall from another thread. Also, to die for were those two custom wood-framed mirror amps that fellow built in Texas or wherever. JT something or other . . . egads! stark beauty. I would not attempt the same at home.
    Thank-you for the referral to Jim McShane for tubes. What a nice guy! He has some NOS GE 12BH7s for the front-end of the M-125s; I grabbed two sets but presume he has more if anybody's interested.
    Last I could tell, you still lean toward the Tung-Sol K-120s. But you doubt you and the folks around here have rolled a lot of tubes through the M-125s since then. Jim likes the Genalex KT-88s in your amp.
    Am in no rush for an answer as the kits won't get here till Monday and in my aulde age I'll probably be the summer putting them together, but are you still enamoured with the KT-120s? This question is informed with my desire to let the output tubes loaf a little bit rather than maxing them out.
    Selah.

    p.s. Your other recommendation, that I purchase new speaker wire from Blue Jeans Cable, also paid out. Got the roll of Canare wire almost before I ordered it. Good guys.
    Last question I would toss up. Back in my good old days, you kept your coax short and your speaker ledes long. Now, it appears the opposite is true. Could someone enlighten?

    Cheerio, and thank-you for bothering with these seemingly amateurish questions.

    turbotoy

    Posts : 47
    Join date : 2012-04-15

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by turbotoy on Tue Jun 12, 2012 8:46 pm

    The one above is mine, thanks! I'm running the KT-120s with NOS Sylvania 12BH7a tubes on the driver boards. I have nothing to compare them to, but I also have no burning desire to try anything else at the moment, I'm just enjoying listening!

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by deepee99 on Tue Jun 12, 2012 9:34 pm

    turbotoy wrote:The one above is mine, thanks! I'm running the KT-120s with NOS Sylvania 12BH7a tubes on the driver boards. I have nothing to compare them to, but I also have no burning desire to try anything else at the moment, I'm just enjoying listening!
    Works for me! Thanks
    d

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by deepee99 on Tue Jun 12, 2012 9:36 pm

    turbotoy wrote:The one above is mine, thanks! I'm running the KT-120s with NOS Sylvania 12BH7a tubes on the driver boards. I have nothing to compare them to, but I also have no burning desire to try anything else at the moment, I'm just enjoying listening!
    BTW, thought about selling those assembly stands, or at least renting them?

    turbotoy

    Posts : 47
    Join date : 2012-04-15

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by turbotoy on Wed Jun 13, 2012 8:54 pm

    deepee99 wrote:BTW, thought about selling those assembly stands, or at least renting them?

    Naah, it's just a small piece of plywood with 3 uprights. Anything remotely similar would work. It would cost more to ship than to find locally from some scrap. That said, I've been building my house for the last 6 years, so there's plenty of scrap lumber around and the saws are always setup. I probably wouldn't have used trim grade American cherry for the uprights if I hadn't been able to pull pieces that were almost the perfect size right out of the scrap bin!

    It's kind of analogous (albeit much more trivially) to me reading through Morgan Jones' book and longing to have piles of ex-BBC output transformers, attenuators, tuning caps, etc. lying around to execute some of the procedures that he describes, with the implication that everyone has such parts lying around the house.

    Bob Latino
    Admin

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

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Fri Jun 29, 2012 11:02 am

    Here is a better photo of the inside wiring of a VTA M-125 monoblock with the newer revised Supplementary Cap Module (SCM). This amp was built by VTA amp technician Sal Brisindi ... If you need upgrading or repairs done to your Dynaco tube amp or preamp get in touch with Sal at > Salb203(at)aol(dot)com

    Bob




    Last edited by Bob Latino on Sun Jun 22, 2014 6:53 am; edited 2 times in total

    costerdock

    Posts : 33
    Join date : 2011-07-27

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by costerdock on Fri Jun 29, 2012 2:39 pm

    Bob Latino wrote:Here is a better photo of the inside wiring of a VTA M-125 monoblock with the newer revised Supplementary Cap Module (SCM).

    Looks nice Bob - and that reference to newer/revised SCM - is that revised from the original M125's SCM? Or is that the standard SCM provided with the M125. If it is revised - could you comment on that/reasoning?

    Thanks!

    Chris
    PS - Love my M125s - however they are packed away in Flagstaff as I'm in the process of moving - so I haven't been able to hear them for a couple of months - can't wait to have them back.

    Bob Latino
    Admin

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

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Fri Jun 29, 2012 2:51 pm

    Hi Chris,

    The new SCM is electrically identical to the older SCM arrangement in your two M-125 amps. On your amps the SCM is on a FOUR lug terminal strip. The new SCM is on a FIVE lug terminal strip and now the two caps are spaced a little further away from each other. The VTA ST-120 also has the same new SCM arrangement because on the old arrangement with the ST-120, one of the SCM caps was situated almost directly over one of the right channels output transformer mounting screws. Getting the nut over the end of that screw was a real hassle with the older SCM arrangement. Right output transformer installation on the VTA ST-120 is now much easier with the newer SCM.

    Bob

    Sal

    Posts : 221
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Sal on Tue Jul 10, 2012 11:57 am

    Bob Latino wrote:Here is a better photo of the inside wiring of a VTA M-125 monoblock with the newer revised Supplementary Cap Module (SCM). This amp was built by VTA amp technician Sal Brisindi ... If you need upgrading or repairs done to your Dynaco tube amp or preamp get in touch with Sal at > Salb203(at)aol(dot)com

    Bob



    Hey,
    That amp looks familiar... :-)

    Thanks for the plug... although I have one preamp on my bench that is getting the better of me. Once I finish the ST-120 I am building, I'll tackle it once and for all.

    Sal.

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Filament envy

    Post by deepee99 on Sat Sep 22, 2012 12:15 pm

    Bob,
    I see Audio Research has a monoblock amplifier out now with 14 KT-120 tubes in it. Can we expect to see a kit version soon?
    Just curious; I'm happy with the M-125s but an M-30,000 would be cool (that's MSRP per monoblock, in dollars).
    Cheerio
    David

    Bob Latino
    Admin

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

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Sat Sep 22, 2012 5:15 pm

    Hi David,

    I heard that those Audio Research Reference 750's are about $45,000 EACH. Not too many folks will be able to afford them.

    Photo below of ONE monoblock.

    Bob




    denny9167

    Posts : 152
    Join date : 2011-05-09
    Age : 49
    Location : Texas

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by denny9167 on Sat Sep 22, 2012 9:53 pm

    Bob Latino wrote:Hi David,

    I heard that those Audio Research Reference 750's are about $45,000 EACH. Not too many folks will be able to afford them.

    Photo below of ONE monoblock.

    Bob




    The owner won't have need for a Dearborn,or a fireplace with those things. Seriously ARC makes some awesome products, you can't beat a D-125 and a pair of Maggie's.

    denny9167

    Posts : 152
    Join date : 2011-05-09
    Age : 49
    Location : Texas

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by denny9167 on Sat Sep 22, 2012 9:55 pm

    Sal wrote:
    Bob Latino wrote:Here is a better photo of the inside wiring of a VTA M-125 monoblock with the newer revised Supplementary Cap Module (SCM). This amp was built by VTA amp technician Sal Brisindi ... If you need upgrading or repairs done to your Dynaco tube amp or preamp get in touch with Sal at > Salb203(at)aol(dot)com

    Bob


    " />

    Hey,
    That amp looks familiar... :-)

    Thanks for the plug... although I have one preamp on my bench that is getting the better of me. Once I finish the ST-120 I am building, I'll tackle it once and for all.

    Sal.

    Sweet!!

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Those big ARs

    Post by deepee99 on Sat Sep 22, 2012 11:10 pm

    Well, I heard $30k each. Maybe for $45K they hook up a dedicated transformer on your light pole outside.

    WntrMute2

    Posts : 101
    Join date : 2010-11-21

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by WntrMute2 on Tue Sep 25, 2012 6:18 am

    Bob Latino wrote:Hi David,

    I heard that those Audio Research Reference 750's are about $45,000 EACH. Not too many folks will be able to afford them.

    Photo below of ONE monoblock.

    Bob




    I'm betting it won't sound much better than Bob's amps. Maybe louder, not better.

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    M-125 lessons learned

    Post by deepee99 on Wed Sep 26, 2012 6:18 pm

    Firstly, what I have learned from the experience of building Bob's
    M-125s is that there is one heck of a good support community out there
    in the VTA crowd, and that there are guys like Troy Madden who can fix
    stuff I break.
    Second, a crummy soldering iron can booger any well-intentioned kit
    project. Spend the money on a good one.
    Third, re-think your need for auxiliary gadgets. As these M-125s with
    KT-120 tubes burn in, they have obviated the need for a Bob Carver
    phase-coupled actuator and a powered Vandy subwoofer, which were
    needed in my transistor stack. I just simply don't need them anymore.
    Fourth, and most important (I am a recent student of this) is pay
    attention to your line voltage. Your local electric utility, under US
    Regs, is required to supply 120 volts, PLUS or MINUS 10%. This means
    they can swing 12 volts VAC either way, leaving you with a range from
    108 VAC to 132 VAC. I've learned the hard way that even 123 VAC is too
    much for the rectifiers in these amps. By all means, take control of
    your power source with a Variac or other conditioner. The tubes don't
    mind the lower voltages and if the volts drop by too much the current
    required would fry a fuse, which is a lot cheaper than a rectifier.

    And oh, BTW, enjoy the sound of a vaccuum.

    awise1961

    Posts : 7
    Join date : 2011-12-15
    Age : 55
    Location : New Hampshire

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by awise1961 on Thu Sep 27, 2012 6:00 pm

    Bob, thank you for the hospitality today when I visited to pick up my pair of M125 kits.
    For those of you that have never had the fortune to meet Bob in person, he's every bit the great guy you hear on this forum and then some.
    He graciously allowed me into his home to listen to his pair of amps while I was there to pick up my own kits.
    I'm excited to begin this next project of mine.
    My work bench has felt lonely over the Summer and it is happy to be holding the boxes of parts that I brought home from Bob's today.
    I promise to post photos as the project progresses.
    Thanks again Bob.

    Best Regards, Al. Wise


    Last edited by awise1961 on Thu Sep 27, 2012 6:01 pm; edited 1 time in total (Reason for editing : spelling)

    Bob Latino
    Admin

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

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Bob Latino on Thu Oct 18, 2012 12:33 pm

    Below are Al's photos of his M-125 build. Al, maybe you can tell us how you got the "M125" on the front face of the amp? The amps do not come with any lettering on the front. Also, those four BIG chassis supports on each amp are not stock. You did mention to me where you got them but I have forgotten?

    Bob









    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by deepee99 on Thu Oct 18, 2012 12:54 pm

    That is indeed a pretty build. I'm using Sorbothane feet on my M-125s and SP but don't have the cool decal.

    awise1961

    Posts : 7
    Join date : 2011-12-15
    Age : 55
    Location : New Hampshire

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by awise1961 on Fri Oct 19, 2012 7:21 am

    Bob Latino wrote:Below are Al's photos of his M-125 build. Al, maybe you can tell us how you got the "M125" on the front face of the amp? The amps do not come with any lettering on the front. Also, those four BIG chassis supports on each amp are not stock. You did mention to me where you got them but I have forgotten?

    Bob



    Hello Bob,

    Thank you so much for posting some of my photos. The amps are working fabulously. I've listened to them every day since I completed them and they have been burning in nicely.
    With regards your questions:
    1- The lettering was sourced from a local Michael's store and is merely adhesive backed vinyl. They have many different styles, fonts, and colors. It was easy to apply. I first placed a piece of tape on each amp to use as an alignment template.
    I want to add smaller lettering for the On/Off switch and "L", "R", and "Bias". Michael's only had the smaller lettering imbedded in a clear backer/frame. That will not do , so I will source these on line soon.

    2- The feet I used come from Cary Auido on line. The are called "Cary Soft Shoes" and are the isolation feet they use on their amps,preamps, and such. The cost $8.00 each, and although they come with mounting hardware, I found it to be inadequate for the M125 application and purchased longer machine screws, washers, and nuts from my local hardware store. These are the same "Shoes" that are on my AES Superamp MKii and AES AE-3 MKii that flank each M125.

    3- One modification not shown in the photos is my addition of a SPDT toggle switch on the back of each amp to allow easier switching between 4 ohm and 8 ohm speakers. I have a reasonably large collection of speakers of both impedence values. I'm fortunate to have access to a nice machine shop and exceellent machinist where I work, and he placed the hole in the exact same location on each amp. The switches were sourced from Radioshack.

    These are great amps. I wanted more tube power and by gosh I got it in spades.
    Just yesterday I added a pair of the venerable JBL 250Ti speakers. These speakers are beasts and the M125's drive them with amazing authority. I am hearing new detail in some familiar recordings that I have never heard before with other amps.

    Although I first fired up the amps with the Weber WZ68 SS rectifiers, a few days later I sourced a pair of NOS Mullard GZ33's from Kevin Deal at Upscale Audio. Upscale has a good commection of these tubes and they are priced at $99.98 each with free shipping. That's better than some of the questionable pedigree ones I saw for sale on that auction site. I've purchased from Upscale Audio previously and they are very trustworthy. I feel that the GZ33's offer slightly better, more defined bass extension than the WZ68's. I'll add the standard disclaimer: Your results may vary.

    Thanks for everything Bob!
    I'm sure that I made the right choice in building these amps. I'm considering building a second pair identically to this pair so that I can bi-amp some speakers. What a fun hobby!

    Best Regards, Al.Wise

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by deepee99 on Mon Oct 29, 2012 10:22 am

    awise1961 wrote:
    Bob Latino wrote:Below are Al's photos of his M-125 build. Al, maybe you can tell us how you got the "M125" on the front face of the amp? The amps do not come with any lettering on the front. Also, those four BIG chassis supports on each amp are not stock. You did mention to me where you got them but I have forgotten?

    Bob



    Hello Bob,

    Thank you so much for posting some of my photos. The amps are working fabulously. I've listened to them every day since I completed them and they have been burning in nicely.
    With regards your questions:
    1- The lettering was sourced from a local Michael's store and is merely adhesive backed vinyl. They have many different styles, fonts, and colors. It was easy to apply. I first placed a piece of tape on each amp to use as an alignment template.
    I want to add smaller lettering for the On/Off switch and "L", "R", and "Bias". Michael's only had the smaller lettering imbedded in a clear backer/frame. That will not do , so I will source these on line soon.

    2- The feet I used come from Cary Auido on line. The are called "Cary Soft Shoes" and are the isolation feet they use on their amps,preamps, and such. The cost $8.00 each, and although they come with mounting hardware, I found it to be inadequate for the M125 application and purchased longer machine screws, washers, and nuts from my local hardware store. These are the same "Shoes" that are on my AES Superamp MKii and AES AE-3 MKii that flank each M125.

    3- One modification not shown in the photos is my addition of a SPDT toggle switch on the back of each amp to allow easier switching between 4 ohm and 8 ohm speakers. I have a reasonably large collection of speakers of both impedence values. I'm fortunate to have access to a nice machine shop and exceellent machinist where I work, and he placed the hole in the exact same location on each amp. The switches were sourced from Radioshack.

    These are great amps. I wanted more tube power and by gosh I got it in spades.
    Just yesterday I added a pair of the venerable JBL 250Ti speakers. These speakers are beasts and the M125's drive them with amazing authority. I am hearing new detail in some familiar recordings that I have never heard before with other amps.

    Although I first fired up the amps with the Weber WZ68 SS rectifiers, a few days later I sourced a pair of NOS Mullard GZ33's from Kevin Deal at Upscale Audio. Upscale has a good commection of these tubes and they are priced at $99.98 each with free shipping. That's better than some of the questionable pedigree ones I saw for sale on that auction site. I've purchased from Upscale Audio previously and they are very trustworthy. I feel that the GZ33's offer slightly better, more defined bass extension than the WZ68's. I'll add the standard disclaimer: Your results may vary.

    Thanks for everything Bob!
    I'm sure that I made the right choice in building these amps. I'm considering building a second pair identically to this pair so that I can bi-amp some speakers. What a fun hobby!

    Best Regards, Al.Wise

    Al, thanks for the additional info. I will investigate.  BTW, I would second any kudos for Kevin Deal at Upscale Audio. I purchased me Ah Tjoeb CD player from him and when the transport went south a year ago he quite patiently walked me through the fixes, then replaced the xport at his cost. He's the sort of guy I'll go back to.

    Hope you're still enjoying your Bob Latino tunes. I sure am. I took a big plunge and ordered a pair of Richard Vandersteen's 5A Carbon speaks, which should be arriving in a few weeks. My experience with the M-125s drove me to acquire Roy Mottram's line- and phono-level preamps. These made a step-level improvement to what I was listening to. Highly, highly recommend.

    Sponsored content

    Re: Prototype 125 watt monoblock tube amplifier KIT

    Post by Sponsored content Today at 2:29 pm


      Current date/time is Sat Dec 10, 2016 2:29 pm