M125 monoblock Tube Rolling

There's a few tube rolling threads here, but not much for the M125 monoblocks.

Anyone have favorites?

I've run Sovtek 6550's, Genalex KT88's and Tung Sol KT120's in mine. I'd assign a slight edge to the KT120's.

LeGrace wrote:I've run Sovtek 6550's, Genalex KT88's and Tung Sol KT120's in mine. I'd assign a slight edge to the KT120's.

Been eyeing a KT120 myself,

How about the other tube positions, or did you find the power tubes provided the most change in sonics?

I have been using sovetek kt88s.  I was previously using kt120 but they expired.  I am also currently using Baldwin Raytheon 12au7 black plate in the front and they have very extended highs in comparison with the mullards cv4300.  However, the mullard have better mids and seem more focused.

I've used KT120 ever since my build back in Dec of 2014, played almost nightly. Using Tesla 12au7's in the front, made in Czech from the early 70s, very nice tubes. Also Rogers Majestics 12bh7s in the rear, circa late 1950s. This combination for me is the best I've found for my system and will keep them there till they expire.

No rectifier rollers?

From what I gather, some amps do not decouple the rectifier circuit as well as others, i.e., chokes, etc., So on those a different 5AR4 may be audible, but maybe in the M125 it is not, or barely.

I like to roll my speaker jack if you know what i mean.

PeppaPig wrote:I like to roll my speaker jack if you know what i mean.

You mean you don't change out tubes, or you don't own tube gear?

I like rolling vinyl records

jfine,
P'raps yer serious after all. Some expensive and hard-won advice herewith:
Bob's M-125s will handle anything, although KT-150s are going to put more stress on the filament taps than is warranted. If you like the New Sensor sound, KT-120s are bullet-proof and are well within the heater parameters of Bob's xformers. As Bob has said time and again on this forum, there's no audio advantage twixt the -120s and -150s, so why pay the extra bucks?
Cannot  prove this with any kind of fancy gear, but I prefer variants of the KT-88 series output tubes (Gold Lions, Shu Guangs, PSVanes, etc.) in the Dynaco architecture. Set up in one of Bob/Roy's amps and biased right and with presumably the correct plate voltage, they're running ~ 70% which is about where most any toob loves to be.
Rolling output tubes gets spendy in a hurry, especially if you don't re-tension the sockets each time and become witness to the exciting event we call "red-plating." And you won't notice results until those power tubes get 100+ hours on them, by which time you ears will have forgotten what the other outputs sounded like. So my advice is, stick a quad or octet of matched tubes into the output holes, keep an eye on the bias for the first 25 hours or so to make sure they're steady, and forget about 'em for 500 hours.
A far cheaper and more influential way to tweak your amp's sound is on the driver board. By cheaper, I don't mean, skimp. I mean, driver tubes are less expensive than output tubes and burn in fairly quickly. On the M-125s, the front tube on each driver board has the greatest influence. On the ST-120 board, the inside tube is the most influential.
To each his/her own, but that's my tuppence-worth.

Why wouldn't I be serious? (I seem to be in the minority.)

I understand the driver board front tube might be the most influential, but I ask specifically, what brands/models does everyone like?

Example, an old Sylvania 5963, or a 12BU7, maybe an old Mullard ECC82, or maybe even new production tubes.

The power/rectifier tubes same question. I'm looking for sonics, but longevity/durability are a close second.

As I mentioned, there seems to be 2 camps on the rectifier tube, even though an old Mullard GZ34 may last longer, (and is more expensive), does it really sound better, than let's say a new production tube, in the M125?

deepee99 wrote:If you like the New Sensor sound, KT-120s are bullet-proof and are well within the heater parameters of Bob's xformers.

Rolling output tubes gets spendy in a hurry, especially if you don't re-tension the sockets each time and become witness to the exciting event we call "red-plating."

2 questions, how *does* the New Sensor KT-120 sound,

and how does one re-tension the sockets on the M125? I've pulled the power tubes out more than a few times during/after the build, but was not aware of this.

jfine wrote:Why wouldn't I be serious? (I seem to be in the minority.)

I understand the driver board front tube might be the most influential, but I ask specifically, what brands/models does everyone like?

Example, an old Sylvania 5963, or a 12BU7, maybe an old Mullard ECC82, or maybe even new production tubes.

The power/rectifier tubes same question. I'm looking for sonics, but longevity/durability are a close second.

As I mentioned, there seems to be 2 camps on the rectifier tube, even though an old Mullard GZ34 may last longer, (and is more expensive), does it really sound better, than let's say a new production tube, in the M125?

jfine, I can't speak much re: novals as I've gone to the old-model octal 6SN7s for drivers as well as in the pre-amp. You can start quite a food-fight over whether the 8-pin beats a 9-pin in such applications. Once again, it's an ear thing. There are plentiful supplies of either tube type built in the 1950s and '60s, NOS or grab-bag, and unlike output tubes, they ain't that expensive. For my ears, I'll take a brand-new Changsha-made CV-181 over the best Sylvania 6SN7 old-stock and put my faith in the iffy quality-control of the Chinese tubes: Shu Guang, PSVane, they all come from the same factory. FleaBay is best place to find them, c/out the feedback. I have done business with several distributors (PM me if you want specific decent sellers) or you can purchase them from Sophia, Grant Electric, or other re-sellers in the US and Canada. You pay a hefty mark-up but their turnaround within the warranty time-line beats dealing with China Post. You can also peruse JJ's, which are made in Europe, but I have no experience with them so cannot advise.
Regarding rectifiers: you're asking an awful lot from a GZ-34 to power an M-125. Original Mullard GZ-33s and -37s have the balls to do the job. Absent those I would consider a solid-state power supply, or running the -34s in parallel pairs in each amp. And by all means, perform Roy's "yellow sheet" mod no matter what tube you select.

deepee99 wrote:
jfine, I can't speak much re: novals as I've gone to the old-model octal 6SN7s for drivers as well as in the pre-amp. You can start quite a food-fight over whether the 8-pin beats a 9-pin in such applications. Once again, it's an ear thing. There are plentiful supplies of either tube type built in the 1950s and '60s, NOS or grab-bag, and unlike output tubes, they ain't that expensive. For my ears, I'll take a brand-new Changsha-made CV-181 over the best Sylvania 6SN7 old-stock and put my faith in the iffy quality-control of the Chinese tubes: Shu Guang, PSVane, they all come from the same factory. FleaBay is best place to find them, c/out the feedback. I have done business with several distributors (PM me if you want specific decent sellers) or you can purchase them from Sophia, Grant Electric, or other re-sellers in the US and Canada. You pay a hefty mark-up but their turnaround within the warranty time-line beats dealing with China Post. You can also peruse JJ's, which are made in Europe, but I have no experience with them so cannot advise.
Regarding rectifiers: you're asking an awful lot from a GZ-34 to power an M-125. Original Mullard GZ-33s and -37s have the balls to do the job. Absent those I would consider a solid-state power supply, or running the -34s in parallel pairs in each amp. And by all means, perform Roy's "yellow sheet" mod no matter what tube you select.

I don't know what to think about your 6SN7 discussion, I'm assuming you have modified your gear to accept those, something I can research later I guess.

But about the yellow sheet mod, and using GZ33/37, I would have to now ask Bob, why would the M125 be shipped without the yellow sheet mod, (or at least an optional addendum to the build instructions), and, still recommends using GZ34?

jfine wrote:

deepee99 wrote:If you like the New Sensor sound, KT-120s are bullet-proof and are well within the heater parameters of Bob's xformers.

Rolling output tubes gets spendy in a hurry, especially if you don't re-tension the sockets each time and become witness to the exciting event we call "red-plating."

2 questions, how *does* the New Sensor KT-120 sound,

and how does one re-tension the sockets on the M125? I've pulled the power tubes out more than a few times during/after the build, but was not aware of this.

jfine,
The New Sensor tubes are labeled as new-issue Tung-Sols and are made in Russia. New Sensor,
https://www.newsensor.com/
which is based in Queens, NY, also makes or provides for most European new-issue tubes and owns the trademarks of most of the old and great US and British tube-makers.
Sorry if I confused things: a New Sensor KT-120 is the same as a newly-labeled Tung-Sol KT-120.
Your best resource for all tubes Russian is Jim McShane, who checks in occasionally on our forum, or just email him at:
jimmcshane@prodigy.net or visit his website at:
http://www.mcshanedesign.net/
Having blathered sufficiently, in answer to your specific questions:
The new Tung-Sol KT-120s are magnificent tubes. Sparkly high-end (in a good way) and very taut bass. Throw one of 'em against a concrete wall and it will bounce back to you in one piece. I prefer some others (Gold Lion KT-88s and the best of the best Chinese KT-88z-s) but if stranded on a desert island, I'd probably go with the TS KT-120s, especially the ones McShane tortures before shipping.
As regards your tube sockets, if you've been swapping out power tubes even a few times, the little feathery things that make actual contact with the tube pins are going to stretch outwards and lose their tension. The effect worsens over time. I dragged out my calipers once and measured the actual pin diameters of different makes/models of the whole 6550/KT-88/KT-120 smash and found that the individual pin diameters vary to quite a degree.
Short answer: you want those socket contacts to be as tight as possible. Here's the pissy part. Power off, everything cold, and pull the tubes. You'll see those little feathery spindly thingies sprouting from the sides of the socket towards the inside hole -- depends on the socket-maker but a few for each pin-hole. Your job, Mr. Phelps, should you choose to accept it, is to pry those little buggers towards the centre of each pin-hole till they almost touch. A very small jeweler's screwdriver, or a wooden tooth-pick, will do the job.
NOW, while you're at it, spray a little bit of De-Oxit or tuner-cleaner into each of those 8 re tensioned pin-holes, which will inhibit corrosion down the road, regardless of whether your tube pins or sockets are gold-plated or not.
It is the curse of tube gear that the most critical connexion -- that between the tube and the circuitry -- is also the flimsiest. 'Splain that to me, and I'll tell you why God in His Wisdom invented mosquitoes.

jfine wrote:

deepee99 wrote:
jfine, I can't speak much re: novals as I've gone to the old-model octal 6SN7s for drivers as well as in the pre-amp. You can start quite a food-fight over whether the 8-pin beats a 9-pin in such applications. Once again, it's an ear thing. There are plentiful supplies of either tube type built in the 1950s and '60s, NOS or grab-bag, and unlike output tubes, they ain't that expensive. For my ears, I'll take a brand-new Changsha-made CV-181 over the best Sylvania 6SN7 old-stock and put my faith in the iffy quality-control of the Chinese tubes: Shu Guang, PSVane, they all come from the same factory. FleaBay is best place to find them, c/out the feedback. I have done business with several distributors (PM me if you want specific decent sellers) or you can purchase them from Sophia, Grant Electric, or other re-sellers in the US and Canada. You pay a hefty mark-up but their turnaround within the warranty time-line beats dealing with China Post. You can also peruse JJ's, which are made in Europe, but I have no experience with them so cannot advise.
Regarding rectifiers: you're asking an awful lot from a GZ-34 to power an M-125. Original Mullard GZ-33s and -37s have the balls to do the job. Absent those I would consider a solid-state power supply, or running the -34s in parallel pairs in each amp. And by all means, perform Roy's "yellow sheet" mod no matter what tube you select.

I don't know what to think about your 6SN7 discussion, I'm assuming you have modified your gear to accept those, something I can research later I guess.

But about the yellow sheet mod, and using GZ33/37, I would have to now ask Bob, why would the M125 be shipped without the yellow sheet mod, (or at least an optional addendum to the build instructions), and, still recommends using GZ34?

jfine,
If you've not yet made the jump into purchasing, the octal (6SN7) driver board is an available option. The VTAs ship with the 9-pin set-up as standard, but you can talk to Roy M. (tubes4hifi) or Bob L. on this board or go to the VTA page to see if there's a cost differential. I believe several on the forum have taken their existing 9-pin boards and modified them to octals; a socket conversion (i.e. 9 pins to is available from several socket-makers. I don't know what you have to do "under the hood" for the conversion, but again, a number of folks have done it so it can't be rocket science. I've had both octal and noval drivers on my VTA gear but did not make the conversions myself
Destructions on the "yellow sheet mod are here:
https://dynacotubeaudio.forumotion.com/t1006-tube-rectifier-diode-mod
And why it's not standard, I dunno, except to keep costs down without compromising quality. But I wouldn't own any VTA amp without that mod if you're going with a tube rectifier, regardless of model. I'd also argue that the slow-start relay (TDR) option in the kits and finished products should be standard equipment. Basically, it lets the tube warm up to operating temperature before the high B+ voltage applies, which saves wear and tear on the power tubes. It also protects the power supply from quick on'/off events in your wall voltage by shutting the amp down and letting the caps drain before restoring full voltage, so there's no train-wreck of incoming and outgoing electrons, for want of a better analogy.
I ran Jim McShane's Russian Gold Lion 5AR4 rectifier tubes with no worries in my old M-125s without a problem, and if you're custom-building the chassis you can set it up to run a pair of them in parallel. Just drill an extra octal hole.
Again, a lot of this is Ford/Chevy stuff. Bob L. likes noval drivers; Roy M. likes octal drivers. Economics and tube availability are not really an issue; there's plenty of good choices out there no matter which way you go.

Personally I do not hear much if any difference with rectifiers. I currently use the webers solid state. I also have a pair of mullards gz-33 but they are just in the drawer. I have been using the same weber solid state rectifiers for two and a half years.

pedrocols wrote:Personally I do not hear much if any difference with rectifiers. I currently use the webers solid state.  I also have a pair of mullards gz-33 but they are just in the drawer.  I have been using the same weber solid state rectifiers for  two and a half years.

Pedro, I'm with you on the Webers. They got a bum rap early on for burning out. Their design flaw is that they concentrate way too much heat in a tiny enclosure. Air them out with a couple of cooling holes drilled into the enclosures, let them ventilate, and their WZ-68s are every bit as good as my antique GZ-33s, plus the Webers don't yank any juice out of the xformer. The cooling holes are a no-brainer. The Weber is not a vacuum tube. That pretty copper cover that makes it look like a vacuum tube is there to keep tiny hands from grabbing 600 volts and is not there to protect a vacuum; it can be removed and replaced with a bit of heat and glue.
Maybe the whole rectifier conversation is a tad over-wrought. All a rectifier does is convert alternating current into pulsating DC. Fancy names and brands aside, all these things are is diodes. It's what happens downstream to smooth out that pulsating square-wave DC into a nice sine wave that matters.

pedrocols wrote:Personally I do not hear much if any difference with rectifiers. I currently use the webers solid state.  I also have a pair of mullards gz-33 but they are just in the drawer.  I have been using the same weber solid state rectifiers for  two and a half years.

In some amps, apparently some do hear a difference. I found this comment on another forum:

"How much sonic difference a tube rectifier will make in an amp is directly related to the power supply design of the amp. Most vintage amps with original power supply designs will benefit from a better rectifier since the rectifier is not decoupled by large filter banks & chokes from the rest of the circuit and even then the difference may not be audible until the amp is pushed hard. In my amps in electrical terms the rectifier is effectively miles away from the audio circuits of the amplifier. I'd be shocked if someone could hear the difference in a Mullard in a blind test".

If I end up having longevity issues with tube rectification, even after the diode mod on the socket, I will try the SS rectifier.

deepee99 wrote:Air them out with a couple of cooling holes drilled into the enclosures, let them ventilate, and their WZ-68s are every bit as good as my antique GZ-33s, plus the Webers don't yank any juice out of the xformer. The cooling holes are a no-brainer.

Anyone can post a photo of the drilled holes in the weber?

jfine wrote:

deepee99 wrote:Air them out with a couple of cooling holes drilled into the enclosures, let them ventilate, and their WZ-68s are every bit as good as my antique GZ-33s, plus the Webers don't yank any juice out of the xformer. The cooling holes are a no-brainer.

Anyone can post a photo of the drilled holes in the weber?

God, Linux and right-brained wiring won't let me post photos. Gawd knows I've tried . .
Surely, somebody else could help.
I could talk you through it verbally. Just grab the Weber by its base (not in the socket!) with your lame hand, then heat the base-copper top with a heat gun or hair dryer, and worry the copper top off. Again, we're just dealing with fairly low-temp glue here.
Once you get the cap off, insert a piece of dowel to support it, and drill a pair of 3/8ths or 1/4-th inch holes thru the copper (near but not at) near the bottom of of the thing, 180 degrees apart. Or four holes at 90-degree spacing.
Then do the same thing at the top.
Wipe the innards of the copper clean so no errant drill-shavings are there. Clean, wet rag will do the trick.
Then glue the cap back onto the base.
The whole trick is just to get some air moving through the thing to cool it. It's sitting right next to the power transformer and close to one of the power tubes, so let it ventilate.
I've got one around here, if you want to PM me I'll send it to you for a look. Postage is on you.

deepee99 wrote:
God, Linux and right-brained wiring won't let me post photos. Gawd knows I've tried . .
Surely, somebody else could help.
I could talk you through it verbally. Just grab the Weber by its base (not in the socket!) with your lame hand, then heat the base-copper top with a heat gun or hair dryer, and worry the copper top off. Again, we're just dealing with fairly low-temp glue here.
Once you get the cap off, insert a piece of dowel to support it, and drill a pair of 3/8ths or 1/4-th inch holes thru the copper (near but not at) near the bottom of of the thing, 180 degrees apart. Or four holes at 90-degree spacing.
Then do the same thing at the top.
Wipe the innards of the copper clean so no errant drill-shavings are there. Clean, wet rag will do the trick.
Then glue the cap back onto the base.
The whole trick is just to get some air moving through the thing to cool it. It's sitting right next to the power transformer and close to one of the power tubes, so let it ventilate.
I've got one around here, if you want to PM me I'll send it to you for a look. Postage is on you.

Xubuntu here, another linux man. I guess you're back on my christmas list.

Saw a photo right here on this forum:

https://dynacotubeaudio.forumotion.com/t2360-weber-copper-cap-discoloring#18793

thanks for the tips.

.

Here's a fairly comprehensive review of rectifiers. I prefer the GZ37's over others I've tried. (5ar4/GZ34/weber)

https://www.head-fi.org/f/threads/dubstep-girls-massive-5ar4-5r4-5u4g-rectifier-review-comparison-rectifer-tube-rolling-thread.694525/