• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

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

Official Court Jester
Joined 2003
Paid Member
arnoldc said:


choky, is that your LR phono?


nope;
as I said-that was a sin from youth-my variant of something (for me later) known as "RCA lookalike" or simpler- two triodes per channel with nfb EQ......

hehe
my LR riaa will be at least 10 times bigger
you can see at www how tiny line stage looks when I make them in this age...
regarding plans for LR riaa-seems that I found source for TFK EC8010;
just must check that source (I don't trust anymore to www stock lists)......when I lay my dirty hands on at least few pairs of these beasties,I'll start breadboarding

too much started projects in this moment :clown:
 
Official Court Jester
Joined 2003
Paid Member
arnoldc said:

DC for filaments? this is just me but i don't find DC a must for my General Electric 12B4A. Good layout *and* star grounding always do it for me. Anyway with 12.6V filaments, you will need half the current (300mA instead of 600mA) so the power transformer can be smaller, less heat.



Cheers!


I'll go with 317 based CCS for filaments

regarding gas stabs- I have impression that 400V is lowest usable margin if 300V is working voltage

anyway-it's just me :clown:
 
Official Court Jester
Joined 2003
Paid Member
Mark A. Gulbrandsen said:
Neat little glow bottles all the same... I gotta admit that this is a gas!

Mark

OK, You guys can shoot me for saying that.......

BTW: I am running at 300 volts and about 28 ma. CSS on the cathode.

Mark-mebbe is redundant to say this-but try to put those regs as close you can to 12B4 anodes
also-if something start to itchin' ya ,especially if you have golden ear and expensive CRO-try to connect 5 to 10 nf in parallel to each OD string (values are really from top of my head,but-smaller is better)
that way you will get rid of last trace of grain,if something is still left
 
Official Court Jester
Joined 2003
Paid Member
pengboon said:
There is a strike voltage i the OD3 specs, how would we take ito consideration this attribute in the design of the PSU?

Choky, can you share the reason why 400V to get margin for 300V B+. For 400V, I guess I will need a transformer voltage of about 350-0-350?



study schmtc and imagine case when mains voltage is 10% down

yes-you need higher voltage than 280Vac

hehe-posting from Croatia,from my sister's place
 
hi pengboon,

the VR150/0D3 has max voltage of 185V, strike voltage of 160V and operating voltage of 150V. Max of 40mA, min of 5mA to maintain regulation.

you will need two of these stacked, with individual small cap across each as choky said.

Here's how they're wired for my Gordon Rankin 807 amp before (but this one is VR105+VR150)
 

Attachments

  • gordon rankin 807.jpg
    gordon rankin 807.jpg
    44.6 KB · Views: 1,206
arnoldc said:
hi pengboon,

the VR150/0D3 has max voltage of 185V, strike voltage of 160V and operating voltage of 150V. Max of 40mA, min of 5mA to maintain regulation.

you will need two of these stacked, with individual small cap across each as choky said.

Here's how they're wired for my Gordon Rankin 807 amp before (but this one is VR105+VR150)


OK, understood. I can use only 2 VR150s for both channels right, not necessary to have 4 VR150s?
 
GG design

GG is good sonically, but not the best I heard. I built a simple one tube per channel Tung Sol 6P5GT linestage that is better sounding- more musical.

I used a Mullard EZ81 square getter rectifier to an LCLC PS filter to another LC per channel with plate chokes on each tube. Also, Vitimin Q PIO coupling caps. The plate chokes brought out the last bit of micro details without being edgy sounding.

Simple design cost less than 1/2 of the GG.
 
Well it is on.
Another Pass Shootout in Salt Lake City. We will be using Mark's 12b4 linestage with the gas shunt regulator, and also the solid state regulated power supplies, one for each channel, and comparing them both. Mark is trying to be open minded, but I sense he is leaning towards the shunt, and I, after spending another $40 on used tubes for the Eico, am definitely going to make my first build using one of these sweet solid state boards from Germany.
Lyndon
 
Amperex,
I would like to hear your preamp.

Just a quick note here. Choky, I am sorry, but I couldn't discern any difference between the solid state regulated power supply vs. your
gas shunt one.
Mark differed, and felt the gas had a better sound. If looks count, yes, the purple glow off those things was pretty dramatic in a darkened room. But I think I am going ahead with the solid state when I build mine.
Lyndon
 
Lyndon,

I had to share your views on the gas reg. Last week I rigged one of my PSU to feed stacked VR150+VR105 (same voltage as my MOSFET) and I cound not hear any difference. I have not put them up the scope tho. I have to admit though that I miss that purple glow.

Pengboon,

That entirely depends on your source if it has enough output to drive the 12B4. Also on the sensitivity and driveability of your cans.