I using mine in MM with a Shure V15111, and it sounds amazing.
Strangely enough, after trying TF, Siemans and Mullards, I've found that a dirt cheap Mazda PCC189 in V3 makes it sound spectacular. Although it's branded Mazda, it's a Blackburn Mullard,and best of all cost a fiver.
I've done it accident and it just doesn't work, nothing shorts.
I imagine the jumper changes the path from pin 9 to pin 4 or 5 and vice versa, so it's either putting 6.3 volts through a 12.6 series filament, or just connecting the shield to the heater ground, (the shield is meant to go to ground anyway) depending on which way round it's wrong. I certainly stand to be corrected on that, I'm no tube expert.
But, as I've said, I done it accidentally with no issues other than silence
Haven't had the chance to compare it, but it sounds very good with either tube, just a little bit different. I have some NOS RCA 7025 aswel, TAD 7025, Mullard 12AX7 etc etc
My cartridge is Nagaoka MP-300.
Variable mu means variable gain
As far as I'm aware, the purpose is to reduce distortion, It's achieved by varying the spacing of the control grid windings which act as a sort of sieve, when the control grid has a low negative charge, electrons pass through the whole grid, and as the negative charge increases, they will only pass through the wider spacings.
It sounds counter intuitive to me as it sounds like it would just reduce gain, but apparently it actually produces a smoother curve. I don't believe the fact it's variable mu makes any difference when used in V3 of the BB.
Again, I'm no valve expert, so I stand to be corrected
Final and finished almost
I finally finished my build. At first, things worked very well - no hum only a big sound and a smile on my face. After 20 min the beast shot down. all lights went out. NO music.
After 10 minutes I turned it on again and to my surprise, everything worked again for 15 minutes
Could it be the transformer that is defective in some way ( Audiophonics)
I do have another transformer(r26-90) but I am not sure how to mount the transformer. It has two black wires and 2 brown wires labeled 9V. Do I put 2 wires in zero( one black and one grey) ??????
Regards Jeppesen
I finally finished my build. At first, things worked very well - no hum only a big sound and a smile on my face. After 20 min the beast shot down. all lights went out. NO music.
After 10 minutes I turned it on again and to my surprise, everything worked again for 15 minutes
Could it be the transformer that is defective in some way ( Audiophonics)
I do have another transformer(r26-90) but I am not sure how to mount the transformer. It has two black wires and 2 brown wires labeled 9V. Do I put 2 wires in zero( one black and one grey) ??????
Regards Jeppesen
Attachments
Yes, you centre one black and one grey. I assume that's a typo when you say brown labelled 9v, the brown are 165v.
I have the same traffo, but didn't use it as the voltages are all over the place. (Have a look a post 165 in this thread)
As Ryssen says, connect it and measure voltages.