Building M125's- Which tubes, GL KT88 or KT120?

Hello, first post here, but have been dropping in to read  since I built an SP 12 a couple years ago.

I'm patiently progressing thorough an M125 assembly and will need to order tubes soon. I've  read many favorable reviews of  Gold Lion 88's and Tung Sol 120's.   From what I have gathered the 120's might be a little more durable and have a bit more "umph" while the GL's  might be "sweeter" at mid and higher frequencies.  

Anybody care to comment or suggest other options?  Obviously this is a matter of preference and perception, but  any input is  appreciated.

you hit it right on the head. It really is a matter of preference, wether to go with the KT88's, KT120's, or even some NOS 6550's. They will all sound great and work well in the M125, of course, each tube model will need to be biased correctly.
I exclusively use KT120's in my builds. They are VERY robust, tend to cover the whole frequency range very nicely and have great bass without shaking the books off the shelve!
But I also use the Gold Lion KT88's in one of my other models and they are perfect for that setup.
I know that deepee99 uses his much loved 6550's in his version of the M125 that I re built for him and he's head over heels with them!
Bottom line, which really does not help answer your question, they ALL work and sound great in the M125!

VTshopdog,
Keep in mind that you've got the pentode-triode switch on Bob's amps, and that you can adjust the bias for your output tubes. That will flavour the sound almost as much as your tube selection. Jim McShane swears by the Gold Lion KT-88s. He also sells the Russian New Sensor Tungsol KT-120s, which as MontanaWay says are quite robust, deliver great sound and are probably the best bang for the buck.
I have a rack of KT-120s and KT-88s acquired from Dr. McShane, who is my go-to guy for Russian tubes; he really torture-tests before shipping them.
I'm kinda partial to my New Jersey TS 6550s. Those 50-year-olds just look so pretty and they've got a certain sumpin' about them. Problem is you've got to sell your first-born to get eight of them NOS nowadays. They're several hundred bucks apiece.
Starting out, I would take Montana's advice and go with the New Sensor TS KT-120s. Get them from Jim at www.mcshanedesign.net and you won't be sorry.
I would also scout about for some NOS General Electric 12BH7As for your driver-board slots, especially in the front holes. They're not expensive and are very sweet, and also will very much affect the quality of your sound.
Hope that wasn't TMI. Welcome to tube-land, a/k/a Tommy's Holiday Camp.

Thanks guys - was leaning to 120s already, might flip a coin in the end.  

Have done no research on driver tubes, so that was my next question and I will search a bit for the recommended BH7.  This is extremely non rush project and have mostly spent time building some wood bits to dress up Bob's stock chassis thus far, so a tube quest will fall right in stride with pace of the project.

vtshopdog wrote:Thanks guys - was leaning to 120s already, might flip a coin in the end.  

Have done no research on driver tubes, so that was my next question and I will search a bit for the recommended BH7.  This is extremely non rush project and have mostly spent time building some wood bits to dress up Bob's stock chassis thus far, so a tube quest will fall right in stride with pace of the project.

You can't go wrong with NOS GE 12BH7As. They are very musical, excellent range and tone, and non-microphonic. Stay away from the Russians in the driver holes, IMHO.

I concur with Mr. deep on the GE 12BH7s. He was kind enough to sell me three from his stash and they are superb. I run one with GL KT-88s in my ST-120, and the combo is gold. From what I've gleaned opinion-wise, the KT-120s might have a slight edge in the M-125s, however. The only reason I went with the GL is that Tung Sol is the SOLE maker (so far) of the KT-120s. That scares me a bit. But apparently they last forever, especially with the additional insurance of the McShane Treatment.
Now if only I could procure four good ol' 6550s for less than the cost of a cabin cruiser, i'd be as happy as a porker in feces.....