6DJ8 Linestage

[DoomPixie]

Hey all, I have been experimenting with my 6DJ8 linestage and have changed a few component values and came up with the following, It sounds better than it did originally, anyone got any suggestions for me to improve it further?
Owen

 

[Zen Mod]

Hey all, I have been experimenting with my 6DJ8 linestage and have changed a few component values and came up with the following, It sounds better than it did originally, anyone got any suggestions for me to improve it further?
Owen

is it 0,2uF enough for your power amp?

suggestions?

toss that SRPP ,wire both halves in para,then use some nice choke in parafeed ,mebbe even in WE config, burn them on some 90V and 20mA
and enjoy


after that -you can use some other tube in WOT style

 

[DoomPixie]

i built 3 6DJ8 pre's last year and this one sounded best out of the three (to my ears at the time anyway)
Since then i have changed the value of the output capacitor from 0.6uF to 0.2uF and it sounds better BUT i was useing some really cheap 0.2uF caps to get 0.6uF and now i am useing some nice 0.1uF caps i got out of an old osciloscope that was going to the scrappers. so mabey the change for the better has to do more with the quality of the cap's than with the value?
Owen

 

[DoomPixie]

ok, just thought i would revive this thread, i have just replaced the output cap's with some nice 2.2uF cap's i bought... yet to test it with the new cap's in.. anyone have any sugestions how to improve this further?
Owen

 

[hacknet]

whats the kinda current running through those babies? it might be a good idea to float the heaters so the top valve's heater insulation doesnt give problems.

 

[DoomPixie]

i'll measure the current tommorow. not sure what it is of the top of my head. might ad another RC stage to the power supply aswell to get rid of the remaining hum (only just noticable with volume maxed out and no input signal) and tweak it a little so the B+ is closer to 200V..
Owen

 

[Burnedfingers]

Why don't you convert it to the Aikido circuit? This will get rid of any noise and from a performance aspect the Aikido will smoke it.

 

[DoomPixie]

to be honest, i dont think there will be any noise problems atall when i have sorted the power supply out properly. have you got any schematics for the Aikido? how many tubes does it use?
Owen

 

[lt cdr data]

turn it into a mu stage, definately improves the srpp no matter what some say.

a 10k or 20 k resistor above the top resistor, a 1MEG also and a coupling cap is all you need.

 

[Burnedfingers]

Tube count increases


I will try to post a schematic

 

[bucurb]

1.2 V in the cathode of the input tube

As a curiosity about schematic presented by burnedfingers:
1.2 V in the cathode of the first (input) tube isn't inappropriate for a CD input signal (2V), please? Thanks.

 

[Zen Mod]

you can't think in that way;
that tube needs what she gets with 1V2 in cathode.
if you change cathode bias to,say,(-)2V ,tube will have smaller current through.

besides ,1V2 means that your signal can have +- 1V2 ,and thats 2V4p-p.
in any case-every decent preamp have 10K in line with CD and 10K to ground ;in other words -voltage divider on CD input with 10K-10K

 

[SY]

That input will never see 2V. A 2V input there will result in something like 40-50V output! That's why there's a volume control.

 

[bucurb]

2 V ....

I'm using Russian 6N1P for about 30 years, being currently available in my country, and it's not at all pleasant to hear sound of it when it's not healthy biased, in my opinion. It could be easily tested. Maybe it’s question of usage of this nice valve.
Approaching, only, 0V will introduce unpleasant distortions. I would wish to consider here dynamics of well recorded music.
If you think that's necessary to divide input signal in order to preserve linearity of this stage, ok but it's not the best solution, however (S/N and so on).
I would suggest you other biasing approach, if you please. Use 240 - 250 V in anode with about -5V in cathode, 8 mA about, and this tube will sound very very well at any CD input signal level, IMHO. Thanks!

 

[Burnedfingers]

bucurb


I bought a dozen of the 6N1P tubes and after listening to them under various plate voltages and biased differently I am under the assumption there isn't much hope for the valve. However, I could be mistaken and need someone like you for guidance.

Could you please post tube curve chart to show the sweet spot?

 

[DoomPixie]

I have some nice old mullard ECC88's im useing at the moment, got some russian 6n1p aswell but they are nowhere near as nice sounding .. i'm not sure about upping the valve count, want to keep it as small as possible, i will build it and see what it sounds like though.. 🙂
Owen

 

[lineup]

I bought a dozen of the 6N1P tubes and after listening to them under various plate voltages and biased differently I am under the assumption there isn't much hope for the valve. However, I could be mistaken and need someone like you for guidance.

Could you please post tube curve chart to show the sweet spot?

Here is one of the best tests of 6N1P curves.
It is a russian website, so it is not too fast pages.
But it is good!

http://klausmobile.narod.ru/testerfiles/6n1p.htm

 

[morfeas]

I use a similar circuit 🙂

http://audio.dynatech.gr/toppage11.htm

After listening thru various tubes ended up with 6N1P. Still have to try 6N23.

6DJ8 Amperex Bugle Boy sounds more hiend 😉

 

[DoomPixie]

that circuit is very simmilar yes.. 🙂
I will have a bit of a play around with mine and see what i can do. 🙂
Owen

 

[hacknet]

i've got to ask a silly question bout the heaters.

say i've got a silly transfomer lying around that only has one 6.3v filament taping. i was thinking of raising the heater voltage to the upper valve's voltage, would this prove detrimental to the lower valve?