help a newbie build his first tube project

[Ahmad_tbp]

hi all .
i m trying to build a marshal 50w amp w an ecc83 and two el34 with help of u guys in here ,..
it s my first tube project , and i wanna use this amp w an ampeg v3 bass preamp ,...
i just don want to fail in this project and loose everything , so i m tryin to go on step by step w help of you guys ...
thnx ...

here s the schematic of marshall amp :
http://www.drtube.com/schematics/marshall/78331-2.gif
and the ampeg preamp :
http://www.drtube.com/schematics/ampeg/v3pre-jp.gif
...
i have a few questions before starting buying stuffs ,
1-wat can i use as choke in amp ? can i use any choke ? or i should wound a choke ?
2-wat exactly transformer i need to use for pre and power amp supply ? how much ampere shoud the transformer have ? i already have a transformer w 250-0-6 secondaries , can i use it for this amp ? or if not and i should wound a transformer wat transformer i exactly need for supply ?

 

[Bas Horneman]

1-wat can i use as choke in amp ? can i use any choke ? or i should wound a choke ?

Does not matter that much I think...something between 2H to 15H will do. And if you can't find a choke... I'll send you a 5H unit I have lying around.

 

[Ahmad_tbp]

hii Bas , glad to c u here 🙂
thnx man i cant go on and take everything from you 😛 . i think 10 to 20 turns of #22 insulated wire on a .5 cm guage air core will do the job for me yeah ? or do i need a core ?
wat bout power transformer ? wat transformer i exactly need ?
can i use my old 250-0-6 transformer ? or i should order a transformer w 350-0-350 and 6 , secondaries ? ( how much ampere ? )

 

[Ahmad_tbp]

HELLO !!! , any body out there ?

 

[SHiFTY]

can i use my old 250-0-6 transformer ? or i should order a transformer w 350-0-350 and 6 , secondaries ? ( how much ampere ? )

Order the right part for the job- i.e. get a new transformer. Buy a proper choke as well- they are very difficult to get right, otherwise they buzz like crazy.

You might want to consider buying a kit with all the parts you need- it works out a lot easier.

Also be sure to read the
Safety Thread

And yes there are people out here, so no need to yell...

 

[Ahmad_tbp]

u said get a new transformer . wat kind of transformer ?
and wat s proper choke ?
buy a kit ??? lol .. i would buy if i can buy anythin from here ! thnx

 

[SHiFTY]

At a guess 350-0-350 @ 250mA with 6.3V 5A would probably be ok for the job...

And the choke say 5H at 150mA, or just use a really big power resistor (say 100 ohms / 50 Watts)- it's a guitar amp after all.

 

[selfwilly]

try here, great help available, good designs too. i've scratch built 2 of thier circuits, with my own power supply design-my guitar playing brother, literally conned me into selling him one, he thought it sounded so good!

http://www.ax84.com/dp.php?pg=home

 

[Ahmad_tbp]

thnx , i ll order the transformer , and so i can t wound the choke my self ? cuz i couldn t find it here ..

 

[Ahmad_tbp]

hii there ..
can any body plz tell me how can i wound the choke my self ?
do i need a core ?
plz

 

[Bas Horneman]

Hallo Ahmad,

Yes, you would need a core...since most chokes for a tube amp I have ever seen used a core....you could wind an air core..but I think you can't get usefull H out of that.

One thing is that the core must have an airgap....because it has to pass DC (or part DC) ..So it will look a little like a single ended output transformer.

But like I said..I'll mail you a choke.... 🙂

I'm picking up the transformer tomorrow and will post some pics.


Regards,
Bas

 

[Ahmad_tbp]

helllllo Bas
thanks a lot 🙂 .. i don t know wat i would goin to do with choke 😛 .. thanx again 😉 ...
i m startin to convert the pre amp and the power amp schematic to pcb layout 🙂 ...