Introductory Hello & My M125 Build

Just a quick hello to introduce myself and show my m125 build so far.
First one wired but with the populated TDR board not yet installed. (I'll tidy up the wiring once that's done.) It will likely be another week until I have tubes to first fire it up but until then...

https://ibb.co/bvTocQ

Welcome! Look forward to hearing your impressions of it. What are you currently running?

slate1 wrote:Welcome!  Look forward to hearing your impressions of it.  What are you currently running?

Thanks!
Very much lookingappreciated forward to sharing my impressions.

I've currently got quitea a mish mash of stuff. Set up now though; a Lenco L75 in a birch plinth. Audiomods arm with an Ortofon 2m Black. A Les Box'd Yaqin 23b into an old Linn lk100. Speakers are Magnepan 1.7qr with the Peter Gunn crossover and I've also got some Alpair 10p FHXL.
As far as my road to the m125's, I tried out a friend's Unison Research and a Vincent but I had no love for either. I felt sure I'd go with a Line Magnetic but the power of the m125's along with the appeal of DIY lured me in.
Preamps will be next after this. While I love the Les Box, I have a very nearly finished EAR834 TRLH and a half completed ph16. (I know. I start new projects faster than I can finish them).

I like the appearance of the Line Magnetic products....industrial ...reminiscent of electrical products from the 50's and 60's. But I've heard there are issues with some of the amps and preamps.perhaps that's simply not true. I wish there was a place to audition them in person that's close to home. Maybe Axpona next year.

Welcome!

Welcome to the zoo, Denizen!
Remember our primary rule here is: The only dumb question is the one not asked.

Thanks all!
And deepee, that's an excellent rule!

The first amp is pretty much buttoned up. TDR installed and working, seemingly as it should. Pins 4 and 6 on the rectifier fluctuating between 396 & 400 vac.
I ordered Weber rectifiers early last week and tubes were ordered from Tube Amp Doctor here in Germany on Saturday. They've always been good but always a bit slow too. Still I hope to have everything here this week so I can finish things up and play some music!

For now here's a quick pic of the TDR's happy, green light.
https://ibb.co/cQQNRv

While mentioning tubes, nothing too exotic.
TAD Premium Select12BH7A-STR and 12au7,
KT120 and Weber wz68.

Oh, more importantly. Can I get a show of hands, how many here did the diode mod?

Good tube selection. I have KT120's in one of my M125's and looking forward to eventually switching the other one over.

One hand up here wrt to the diode mod. Got tired of rectifiers arcing. No arcing since the mod.

LeGrace wrote:Good tube selection. I have KT120's in one of my M125's and looking forward to eventually switching the other one over.  

One hand up here wrt to the diode mod. Got tired of rectifiers arcing. No arcing since the mod.

Thanks LeGrace.
I'll see if the local shop has those diodes on hand.

My only comment is that Maggies are difficult loads for a tube amp. By no means impossible, but difficult. I keep a pair of vintage IIIas, and although I have a 75-watt-per-channel 6550-based vintage Scott LK150, I wound up having to drive the Maggies with a Citation 16, a true brute-force device. Otherwise, even at moderate volumes, I was clipping far too much. Now, the maggies are in a large room (5.5m x 8.5m x 3m), so I suspect that has something to do with it.

Enjoy, and please tell us how your maggies do with the 120s. I may be tempted....

IMHO, the diode, or "yellow sheet" mod (on the stickies here) should be compulsory. Takes a lot of heavy lifting off the rectifiers, whether tube or Webers.
A good way to prolong the life of the Webers is to remove the "copper cap," drill a pattern of small cooling holes in it, and put it back on. You're not breaking a vacuum. The rectifier position is exposed to a lot of heat, so this will help. The Webers are consumables, just like tubes, so bear this in mind and order a spare or two if you can.

Peter, deepee, thanks.

I'm currently running the Maggies with a Linn lk100 so into 4ohms they're only getting around 90 watts. In our aprx. 7x9 meter listening room (with fairly high ceilings) I can push it into clipping but at a level that I wouldn't enjoy listening to. I will say though, before I did the Peter Gunn crossover, they hit a brick wall fairly quickly. I'd turn them up loud but they wouldn't go louder than, I'd guess, 85-90 decibels. The new crossovers defintely lightened the load. I can now get them louder than I would ever actually listen to them. So... I'd dare say the m125 will do just fine.
Knowing that Bob runs his with them plus talking with Noir et Blanc hifi shop in Brussels that says the Line Magnetic 508ia (48 watts) can drive 1.6qr has me feeling confident.
Either way though, I will certainly let you know how they do.

DeePee, the Weber mod is a sure thing. I love any chance I get to use my drill press so it'll be a pleasure. I've been curious though if there's any best glue to use. I've got contact cement (which I'm hesitant to use with high heat) and super glue on hand but thought there must be a go to glue that I just haven't seen mentioned.


I was able to pick up some 1N4007's from the local shop so I'm set for that. Checked the status of the wz68's and they've cleared customs AND I got shipping notification that the tubes shipped express today. Knock on wood, it's looking like I'll get these running this week.

The steps you are taking will help you avoid many of the rookie mistakes I made. ie I did not know about the diode mod and my first 5AR4 rectifier blew up in less then a week after first time switching on my M125's due to arcing. Panic attack! I was advised some tubes are just weak. Replaced it and the next one lasted all of 3 weeks. Any every time you lose a fuse. I powered up in between a couple times as I didn't know what was happening and of course more fuses down the drain. Once they arc they are basically toast.  Anyway the diode mod + webers you will avoid all that. Also the KT120's are a more robust tube IME, another good move. Plus they sound great.

Denizen wrote:Peter, deepee, thanks.

I'm currently running the Maggies with a Linn lk100 so into 4ohms they're only getting around 90 watts. In our aprx. 7x9 meter listening room (with fairly high ceilings) I can push it into clipping but at a level that I wouldn't enjoy listening to. I will say though, before I did the Peter Gunn crossover, they hit a brick wall fairly quickly. I'd turn them up loud but they wouldn't go louder than, I'd guess, 85-90 decibels. The new crossovers defintely lightened the load. I can now get them louder than I would ever actually listen to them. So... I'd dare say the m125 will do just fine.
Knowing that Bob runs his with them plus talking with Noir et Blanc hifi shop in Brussels that says the Line Magnetic 508ia (48 watts) can drive 1.6qr has me feeling confident.
Either way though, I will certainly let you know how they do.

DeePee, the Weber mod is a sure thing. I love any chance I get to use my drill press so it'll be a pleasure. I've been curious though if there's any best glue to use. I've got contact cement (which I'm hesitant to use with high heat) and super glue on hand but thought there must be a go to glue that I just haven't seen mentioned.


I was able to pick up some 1N4007's from the local shop so I'm set for that. Checked the status of the wz68's and they've cleared customs AND I got shipping notification that the tubes shipped express today. Knock on wood, it's looking like I'll get these running this week.

I would get some Loc-Tite for re-assembly. It's used on gun-chambers and is thus fairly tolerant of heat. Once the critter blows, toss it.

Denizen wrote:

Oh, more importantly. Can I get a show of hands, how many here did the diode mod?

I did, although I guess there's no point in running a tube rectifier now, or not.

jfine wrote:

Denizen wrote:

Oh, more importantly. Can I get a show of hands, how many here did the diode mod?

I did, although I guess there's no point in running a tube rectifier now, or not.

With the mod the only thing the tube is doing is dropping the B+ down to normal values. It definitely looks better than a copper cap though.

Tubes4ever wrote:
With the mod the only thing the tube is doing is dropping the B+ down to normal values. It definitely looks better than a copper cap though.

funny I heard a difference between a GZ37 and a 5AR4 though

jfine wrote:

Tubes4ever wrote:
With the mod the only thing the tube is doing is dropping the B+ down to normal values. It definitely looks better than a copper cap though.

funny I heard a difference between a GZ37 and a 5AR4 though

That's probably because the GZ37 has a higher voltage drop than a 5AR4. Your B+ was lower with the GZ37.

The 5AR4 still delays the delivery of B+ to the plates of your pentodes after the yellow sheet mod.

j beede wrote:The 5AR4 still delays the delivery of B+ to the plates of your pentodes after the yellow sheet mod.

Yes it does. So does the GZ37. But good point!

"I would get some Loc-Tite for re-assembly. It's used on gun-chambers and is thus fairly tolerant of heat. Once the critter blows, toss it."

Ah, great choice. Gun chambers definitely get very hot. (I used to go to the gun range all the time). Used Loc-Tite on car and motorcyle parts all the time too. Best of all, I happen to have some that I forgot about. Very glad I asked.

You would think you'd remember having a spare Mullard gz34 stashed away but it took all the other tubes arriving to remind me.

Anyway, happy days! Quickly doing the diode mod I risked the Mullard because there was no way I could wait. Tubes biased up nicely and grabbed the nearest record. Now spinning an original 10" of Ella & Louis's Porgy & Bess. Happy days!

Denizen wrote:You would think you'd remember having a spare Mullard gz34 stashed away but it took all the other tubes arriving to remind me.

Anyway, happy days! Quickly doing the diode mod I risked the Mullard because there was no way I could wait. Tubes biased up nicely and grabbed the nearest record. Now spinning an original 10" of Ella & Louis's Porgy & Bess. Happy days!

Hot damn and good for you!
What you really need are GZ-33s. Absent some catastrophic failure below decks they'll live longer than you.
PeterW may know where there's a couple.

deepee99 wrote:

Denizen wrote:You would think you'd remember having a spare Mullard gz34 stashed away but it took all the other tubes arriving to remind me.

Anyway, happy days! Quickly doing the diode mod I risked the Mullard because there was no way I could wait. Tubes biased up nicely and grabbed the nearest record. Now spinning an original 10" of Ella & Louis's Porgy & Bess. Happy days!

Hot damn and good for you!
What you really need are GZ-33s. Absent some catastrophic failure below decks they'll live longer than you.
PeterW may know where there's a couple.

Thanks!!!

Yep, I had decided on gz33's if or when I run rectifier tubes rather than Webers. For now though, I wanted to test and bias this first one so I can finish the second before my father in law visits.

I realize the tubes are brand new and I'm only running one speaker but I was surprised that I didn't hear any difference between pentode and triode modes. What might be the reasons for that?