Yet another 12B4 line stage, or is the 12B4 better than the Grounded Grid.....

[Mark A. Gulbrandsen]

Hi Brian,

Thanks for the formulas!! Now all I need is a scientific calculator to do them.... Math is not my forte by any means. Would you also be willing to share the general layout of the LM317 as a CSS with the 12B4 for us? I would love to incorporate that feature into my line stage. I think I can figure out the correct resistor for the current sense.....

Thanks,
Mark

[Brian Beck]

Here is a schematic showing a 12B4 with a cathode current source which I used in the output stage of a cheap, but decent, Pioneer DVD/CD player from a couple of years ago. The LCR low-pass filter is only needed for the CD application and should be deleted for line stage use. I found I didn't need a grid stopper and I won’t use them where they’re not needed. Your mileage might vary with a different grid circuit (like a volume pot, etc.) I ran this triode fairly hot (at around 3.6 watts of plate dissipation) because I wanted 30mA of plate current which is needed to give the 12B4 a low plate resistance and high transconductance. The circuit has worked flawlessly for two years and sounds superb. I plan to implement something similar in my Sony SACD player.

[Mark A. Gulbrandsen]

WOW!

Thanks a ton Brian. I will work on that when I get back from my next buisness trip....

Best,
Mark

[Klimon]

Hello Brian;

Aaaah, the magic formula

I've changed to 1µF a few days ago and it sounds much better; to my surprise not only more bass but the whole (mids?) sounds much more relaxed now - your description as 'presence and air' describes it nicely. The power amp I'm currently on has 220k input r. ; I'll do my homework later to see what I had been missing (and should install as definitive cap) -

Do you know if for a power amp Rtotal equals the grounding resistor or are there here also other variables that constitute Rtotal?

Cheers!

[Mark A. Gulbrandsen]

I had a one day reprive from leaving on this service trip so I installed Brian's CSS mod. Result is that the sound is now alot cleaner than it was... I also did install 5 uf coupling caps (nothing fancy yet just Electrocubes), am driving a pair of Aleph 2's and they have a pretty low input impedance. The combination is quite breathtaking. Now for a change I am listening to whats IN the music..... you can'y miss annything running with this linestage...... Absolutely fantastic!

I have to laugh... over the past 25 years I built and owned alot of line stages, only to end up with something so simple.... I hope that everyone that builds line stages will someday end up here...

Mark
Live.... From the armpit of Wyoming....

[Zen Mod]

Originally posted by Mark A. Gulbrandsen
I had a one day reprive from leaving on this service trip so I installed Brian's CSS mod. Result is that the sound is now alot cleaner than it was... I also did install 5 uf coupling caps (nothing fancy yet just Electrocubes), am driving a pair of Aleph 2's and they have a pretty low input impedance. The combination is quite breathtaking. Now for a change I am listening to whats IN the music..... you can'y miss annything running with this linestage...... Absolutely fantastic!

I have to laugh... over the past 25 years I built and owned alot of line stages, only to end up with something so simple.... I hope that everyone that builds line stages will someday end up here...

Mark
Live.... From the armpit of Wyoming....

simplicity is hard to achieve.........
I know that-after all this years






ps. I'm still for (at least-trying) lower value of anode resistor

[blaaberg]

"I had a one day reprive from leaving on this service trip so I installed Brian's CSS mod. Result is that the sound is now alot cleaner than it was... I also did install 5 uf coupling caps (nothing fancy yet just Electrocubes), am driving a pair of Aleph 2's and they have a pretty low input impedance."

Sound very interesting, how low is your input impedance? Do you think it can drive my 17Kohm input Zappulse.....?javascript:smilie('')
angel

Venlig hilsen Jan

[Mark A. Gulbrandsen]

Sound very interesting, how low is your input impedance? Do you think it can drive my 17Kohm input Zappulse.....?

Shouldn't be a problem, just be sure the output capacitor is large enough.... use Brian's formula above to calculate that. The input impedance of my Aleph 2's is only 10K annd it drives them quite nicely.

Mark

Just don't let your amp Zap the signal......

[pinkmouse]

Hey Mark, tried it with the Krells yet?

[Sherman]

Originally posted by choky



simplicity is hard to achieve.........
I know that-after all this years ...

As Einstein said- "Everything should be as simple as possible, but no simpler."