Prototype 125 watt monoblock tube amplifier KIT

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!

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

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?

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 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 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.

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 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.

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

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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!!

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

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.

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.

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

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

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

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.