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

[speaker]

Originally posted by staggerlee



$17,000! I hope it comes with K-Y!!!

Hey, at least they include the 274B rectumfryer!

[mach1]

Please reccomend a choke if you would.... No, I won't try an output tranny if you held a .357 to my head!

Try a Handmade Electronics H3007 (60H @30ma): they mate very well with the 12B4 and won't break the bank.

pm

[lawbadman]

Does anyone have a schematic of a tube regulator circuit for the 12b4?
I have 2 OA2 tubes on hand, can they be used?
Can anyone point me to the datasheet for the oa2?




Thanks
Lawrence

[pengboon]

Originally posted by Mark A. Gulbrandsen
I have no problem trying a choke in there, thats a sensible thing to try. I also have not tried a solid state regulator at the plate either. Someone had reccomended the IXYS type....

Please reccomend a choke if you would.... No, I won't try an output tranny if you held a .357 to my head!

Mark

Mark, do give the plate chokes a try. I have, and I ain't removing them anytime soon! I am using 100H 50mA. I have to add "wider and deeper soundstage" to what Zen_mod has mentioned too...

I had a humming on one channel initially and just could not figure it out. Until I moved my PSU choke. Orientation didn't matter, physical distance did...

[pengboon]

Originally posted by lawbadman
Does anyone have a schematic of a tube regulator circuit for the 12b4?
I have 2 OA2 tubes on hand, can they be used?
Can anyone point me to the datasheet for the oa2?

Are you going to use plate chokes? If you are, then you can use 1 OA2 on each side giving 150V regulation. If not, then you're going to need 300V and (recommended) 2 OA2s per channel (total of 4). Look for Zen_mod's schematic some posts ago...

[lawbadman]

I guess I dont understand how tube regulators work, but why would I need two per channel? Dont they work like zener diodes???

[Mark A. Gulbrandsen]

They do work like zeners.... You have to stack them in series to get the needed voltage.

I will try plate chokes as soon as time permits. The KSA-100 thread is comming back alive too and I have very limited time....

Mark

[pengboon]

Originally posted by lawbadman
I guess I dont understand how tube regulators work, but why would I need two per channel? Dont they work like zener diodes???

One 0A2 with regulate to 150V, so to get 300V, you will need 2 stacked together as Mark mentioned. If you use plate chokes, you need only one for the required 150V.

[pengboon]

On the topic of plate chokes, what are the sonic differences between a setup using plate choke and that which is using a OPT? I guess plate chokes still has the effect of the output capacitor, and higher output impedance?

[Wavebourn]

Originally posted by Mark A. Gulbrandsen
They do work like zeners.... You have to stack them in series to get the needed voltage.

Mark

Unlike Zeners they need a higher voltage to fire up, after that they drop voltage down to a regulated level. Slightly different resistors across them is the way to fire them up one by one and make resulting fire-up voltage less, if you connect them in series.