~30 years I have waited to start my first real tube project.
I have placed and order for two M-125 monoblocks from Bob. I have no idea how long this project is going to take, what rabbit hole I am really headed down, let alone how they are going to turn out.
I have not ordered tubes yet - I figured I would get suggestions and weigh options before jumping off that bridge too, as I simply do not have the time or funds to audition multiple sets.
I will be using Bob's chassis, but also building some type of custom wooded base enclosures.
I don't really have a set of suitable speakers to drive yet.. that is another whole project and source of indecision.
I have experience, but mostly with microcontrollers and 120V control/automation projects. I have read and fully understand the requisite high voltage safety tips and concepts and worked around 480/575 AC and DC in the underground mining industry - so have plenty of respect in that arena.
Open to thoughts, tips or suggestions before I actually dust off the Weller soldering station and embark on this project.
I have placed and order for two M-125 monoblocks from Bob. I have no idea how long this project is going to take, what rabbit hole I am really headed down, let alone how they are going to turn out.
I have not ordered tubes yet - I figured I would get suggestions and weigh options before jumping off that bridge too, as I simply do not have the time or funds to audition multiple sets.
I will be using Bob's chassis, but also building some type of custom wooded base enclosures.
I don't really have a set of suitable speakers to drive yet.. that is another whole project and source of indecision.
I have experience, but mostly with microcontrollers and 120V control/automation projects. I have read and fully understand the requisite high voltage safety tips and concepts and worked around 480/575 AC and DC in the underground mining industry - so have plenty of respect in that arena.
Open to thoughts, tips or suggestions before I actually dust off the Weller soldering station and embark on this project.
Thus my indecision 😉
I started a thread for that in the multi-way forum.
Seeking new build advice - please offer your .02
I chose the fairly large output project for several reasons, but one of them being a much broader choice of speaker projects.
It's hard to build a really good speaker yourself, unless it's a complete pre-designed kit that leaves little to chance. You could borrow some friends' speakers to try out, or buy some inexpensive speakers to compare.
A budget will help limit the options to start.
A budget will help limit the options to start.
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I have been involved in the speaker building hobby for over 30 years. But, I have every intention of building a proven design. Like the amp project, I simply don't have the time or budget for trial and error or multiple projects to find the holly grail.
Feel free to offer suggestions in the speaker thread. There is some context there as to what I am looking for.
I use my M-125s with KT120 tubes, but other owners seem to like KT88s, and I think the amps seem to run cooler with those tubes.
My speakers are home-built MTM using Seas Elite drivers and separate subwoofers with Seas drivers. Sound is fantastic. I've also used the amps with my old AR91 speakers, and they sound great with the amps. I'm not sure speakers that dip very low or require gobs of current are the best choice, but I've read comments by Maggie owners who say their VT120s drive the speakers well, and the M-125s have even more grunt.
Do read up on tube amp building first; there is much to learn not only about safety, but avoiding problems with your build. The kits have pretty good instructions, and mostly very good components. You will have fun, so why not build them?
My speakers are home-built MTM using Seas Elite drivers and separate subwoofers with Seas drivers. Sound is fantastic. I've also used the amps with my old AR91 speakers, and they sound great with the amps. I'm not sure speakers that dip very low or require gobs of current are the best choice, but I've read comments by Maggie owners who say their VT120s drive the speakers well, and the M-125s have even more grunt.
Do read up on tube amp building first; there is much to learn not only about safety, but avoiding problems with your build. The kits have pretty good instructions, and mostly very good components. You will have fun, so why not build them?
It should be fun. I've built one of Bob's ST-70's. His instructions are very good. Just take your time, follow the instructions and double check your work.
Good on you mate. You won't regret building them.
I got a pair off Bob 7 years ago and they have been everything I hoped for. Great sound.
The instructions are pretty comprehensive, almost impossible to stuff up if you follow them correctly.
They are very big amps. I run mine in triode mode with only a pair of tubes instead of a quad. This works out at about 45W before clipping and I can assure you they are huge Watts.
I got a pair off Bob 7 years ago and they have been everything I hoped for. Great sound.
The instructions are pretty comprehensive, almost impossible to stuff up if you follow them correctly.
They are very big amps. I run mine in triode mode with only a pair of tubes instead of a quad. This works out at about 45W before clipping and I can assure you they are huge Watts.
Sadface; you most likely know this already, but for others who may not, remember that if you pull 2 tubes, you'll want to match the impedance to the speakers by using the lower impedance taps on your amp, the lowest of which on the M-125 is 4 Ohms. For example, if your speakers are 8 Ohms and you pull 2 tubes, use the 4 Ohm connections on the amps. If you are using nominal 4 Ohm speakers already, you will have a mismatch.
Hi GKT
I did not know that. Show's how much I have to learn still.
My Speakers are nominal 4 ohm speakers.
I am guessing the mismatch is occurring on the primary side of the OPT?
So if I am understanding this correctly:
The output tubes are not driving the (in my case) 2200ohm primary but 4ohm load on the other side.
With only 2 output tubes, each tube is looking at double the resistance it would be looking at were there 4 output tubes.
Therefore the output tubes are going to operating outside of their ideal conditions.
The output tubes are not driving the (in my case) 2200ohm primary but 4ohm load on the other side.
With only 2 output tubes, each tube is looking at double the resistance it would be looking at were there 4 output tubes.
Therefore the output tubes are going to operating outside of their ideal conditions.
Chassis have been shipped out for some special treatment.
I am starting to work on the driver boards.
Bob talked me into using the standard boards instead of the octals
Started to mount electro caps on top of board, but am going to move to bottom, for aesthetics. I plan to make a cover of some kind for the ugly green PCB, with only the two driver tubes protruding.
Will post pics later
I am starting to work on the driver boards.
Bob talked me into using the standard boards instead of the octals
Started to mount electro caps on top of board, but am going to move to bottom, for aesthetics. I plan to make a cover of some kind for the ugly green PCB, with only the two driver tubes protruding.
Will post pics later
Rayma, you are very right in you advice. I have done about three psuedo complete designs and 4 nearcomplete -to-complete speaker designs and have found some great results, and some very to exceptionally good cost/performance ratios. My last project, and it was so good that I stopped doing new speakers after that, was Joe Rasmussen’s design “Elsinore” on these pages that had since continued to evolve. However, I stopped at about Mk V and I am so satisfied that I know my hearing ability is now the biggest limiting factor in hearing better music. Perhaps this post would be better in the Speaker area.
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@rayma & Francois - I have been involved on the speaker building hobby for the better part of 30 years. While my design skills are far from deficient, I do intent to build a tried and tested design. Mostly because, I simply lack the time and budget to go through multiple iterations and have been out of the loop for many years.
I am looking at the elsinore very hard, but am a bit concerned about the extreme directionality and the narrow sweet spot for listening. I am looking at SEOS designs as well, for their wider dispersion, but most of the design use unavailable drivers.
I will cross the speaker bridge once the monoblocks are done.
My biggest issue now is designing the outer chassis. There will be wood... that is all I know at this point. I have to wait for the SS chassis to come back from their special treatment place. Once I see them, I will get a better idea of how to move forward 😉
I am looking at the elsinore very hard, but am a bit concerned about the extreme directionality and the narrow sweet spot for listening. I am looking at SEOS designs as well, for their wider dispersion, but most of the design use unavailable drivers.
I will cross the speaker bridge once the monoblocks are done.
My biggest issue now is designing the outer chassis. There will be wood... that is all I know at this point. I have to wait for the SS chassis to come back from their special treatment place. Once I see them, I will get a better idea of how to move forward 😉
teaching VTA M-125 to sing
As built by VTA, my M-125 mono-blocks were very noisy, ≈55db unweighted
After fixing build and design errors, the amps quietened almost 40db to ≈93db unweighted.
I suspect many DIY and retro designs may suffer similar problems.
In an effort to help others with similar problems, complete instructions:
ieLogical VTA M-125
As built by VTA, my M-125 mono-blocks were very noisy, ≈55db unweighted
After fixing build and design errors, the amps quietened almost 40db to ≈93db unweighted.
I suspect many DIY and retro designs may suffer similar problems.
In an effort to help others with similar problems, complete instructions:
ieLogical VTA M-125