A box arrived.
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Eminence1963
Active Member
Enjoy Welcome to the VTA club/Rabbit hole.
Lavane
Lunatic Member
I've already built a VTA ST-70 that I've been using for about 10 years now along with a Dynakit ST-35 I built awhile back. Both have been pretty trouble free.
Oh man this is going to be a fun ride. Please post photos and narrative as you build this amp. I read many good things about the quality of material, instructions, and final product. There is an interesting post and webpage dedicated to the improvements to this amp that is gained by paying particular attention to certain construction details. I noticed in the one photo it did not include the transformers. How massive are they?
epifanatic
acoustically suspended
This should be fun.
Lavane
Lunatic Member
I haven't opened the two boxes-0-iron yet, but both boxes are pretty heavy.
Lavane
Lunatic Member
I already have a quad of JJ KT-88's to start with. Depending on how they sound in these amps, since I can run just two per amp, I'll either buy another quad of them, or KT-120's. For drivers I have some RCA clear tops and some old stock 12BH7's. I'm using WZ68 SS copper top rectifiers, but I think I'll pop the covers off and drill holes near the bottom and top to help cool them.
Lavane
Lunatic Member
Yup, will do. It may be a slower build. Now that the weather is getting better outside stuff is needing attention.
The options are endless as you note. This amp allows 2 or 4 power tubes to operate. And that includes KT-88, 6550, KT-120 and who know what else. The combinations are many. But from what I read it is the front end smaller tubes that factor into the sonic quality. RCA clear tops are hard to beat in performance and value. I have less experience on the 12BH7 or (7A). And when it comes to the 12AU7 variants oh boy it is endless. So much choices and so much to learn. Let us not forget all the other components that cumulative contributes to the overall experience. This is going to be a fun ride.
From what I read the modern Gold Lion KT-88 is hard to beat in quality, performance, and value. Make sure to purchase from a reputable dealer. The difference between the TS KT-120 and GL KT-88 are not very noticeable. But the front end tubes do matter.
Lavane
Lunatic Member
Thanks. I have other 12AU7's also to try. I like how the old manufacture 12BH7's sound in my VTA-ST-70, hopefully they sound as good in the M-125's. I'll be rerouting some of the wiring as well. I don't like the A/C wires going parallel and under some of the D/C and signal wiring. Swapping the power switch to the rear and putting the input jack on the front makes more sense to me. I'm adding resistors from the 16 ohm taps to ground and moving the feedback circuit to the 8 ohm tap. I ordered the resistors and caps for that also, along with adding snubbers and a few other odds and ends. It all should be fun though for sure.
I have been meaning to ask you this for a while now. Are you using the low gain or high gain VTA board in your ST70?
Lavane
Lunatic Member
Whatever he is shipping in the kits now. I never thought to ask.
Lavane
Lunatic Member
That I don't know yet, I haven't read through all the paperwork yet.
Ya, that would have been better. My fault, I took forever looking at other options.
Pio1980
AK Member
Afaik, standard (low) gain is the default version, because most users couple them to active line stages.
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