Modding Epi Valve Junior !! MORE content added!
- Thread starter JE
- Start date
the mods done are:
high inpedance input to let more guitar signal thru
rebias the preamp tube for smoother driven sound
change the coupleing cap to have tighter low frequency response
add screen grid resistor to protect the tube
increase cathod capacitor to stablize the power tube
rebias the power tube
basically the amp is voiced now somewhat like a vox.
high inpedance input to let more guitar signal thru
rebias the preamp tube for smoother driven sound
change the coupleing cap to have tighter low frequency response
add screen grid resistor to protect the tube
increase cathod capacitor to stablize the power tube
rebias the power tube
basically the amp is voiced now somewhat like a vox.
Indigo_blues
New member
any soundclips?
Indigo_blues
New member
ah, you may pop by my place if you want and bring the amp along.. i have some recording gears all setup.
but timing may be an issue.. I'm only free mostly on saturdays.
but timing may be an issue.. I'm only free mostly on saturdays.
Indigo_blues
New member
ok. haha should be interesting. can try different tubes in the thing. 
more stuff done to my (poor) epi head today.
poor man's attenuator!!!
okay.. it started with this
yes, it's a toilet roll (told u it's the poor man's version).. okay.. just too lazy to get a proper housing for a trial build. then:
2 power resistors (they cost 70c each...), installed thru a pen-punched hole on the toilet roll. flip:
wiring at the back : look at the sloppy job.. nah.. just want to get it done with. tape it with flameproof electrical tape to make sure it (and me) survives.
as it so turn out, the toilet roll is a perfect fit :? on the valve junior head handle. not only it's easy to install, the exposed power resistors can dissipate heats rather easily.
okay.. the problem: the attenuator brings the head from 5W down to 1.25W, it's still WAY TOO LOUD (i'm not crazy!! really!!!). it resulted in only -3dB effect.. so most likely i will make a newer, proper one.. still.. it's CHEAP!!! (about 5 dollars). by changing the resistor values, one can achieve ANY level of attenuation (for 5 dollars
)
poor man's attenuator!!!
okay.. it started with this
yes, it's a toilet roll (told u it's the poor man's version).. okay.. just too lazy to get a proper housing for a trial build. then:
2 power resistors (they cost 70c each...), installed thru a pen-punched hole on the toilet roll. flip:
wiring at the back : look at the sloppy job.. nah.. just want to get it done with. tape it with flameproof electrical tape to make sure it (and me) survives.
as it so turn out, the toilet roll is a perfect fit :? on the valve junior head handle. not only it's easy to install, the exposed power resistors can dissipate heats rather easily.
okay.. the problem: the attenuator brings the head from 5W down to 1.25W, it's still WAY TOO LOUD (i'm not crazy!! really!!!). it resulted in only -3dB effect.. so most likely i will make a newer, proper one.. still.. it's CHEAP!!! (about 5 dollars). by changing the resistor values, one can achieve ANY level of attenuation (for 5 dollars
)
Indigo_blues
New member
attenuator (2nd edition): this is a much better (cosmetic and function) attenuator, yet it's still very cheap to make
power resistors are used to drain some power from amp output
5-way switch to select from bypass to high attenuation (about -20db)
cables and plugs. i chose not to use any jacks to simplify the structure and at the same time, make sure the contacts are as little as possible.
and the housing/chassis. staying true to the DIY spirit, this is actually a gift box :lol:
first: the knob and switch is fitted on to the chassis (lid of the box)
it worked okay, but need more cosmetic touch-ups, worry about that later.
flip the lid around, lay down the resistors neatly, not forgetting insulate them with flame proof tape.
notice the soldering grid on the side? well. i intend to fit everythin on that.. clearly it was a BIG mistake.. anyway, just do without it.
now comes to the most tedious part: point to point wiring!!
now you know why boutique ptp amps are so expensive. not necessary because they are better, but certainly because it takes LOTS of effort!
finally assembled, and seated on top of my valve junior
it works very nicely, i can *finally* dime the amp and still don't disturb people(much) at night. now.. just need to find some silver marker..
cost tally:
resistors: $0.7*8 =$5.6
cable and plugs =$4.5
switch and knob =$2.5
box =$2.5
total =$15.1
still (dirt) cheap (cheaper than a JJ EL84 by the way)
power resistors are used to drain some power from amp output
5-way switch to select from bypass to high attenuation (about -20db)
cables and plugs. i chose not to use any jacks to simplify the structure and at the same time, make sure the contacts are as little as possible.
and the housing/chassis. staying true to the DIY spirit, this is actually a gift box :lol:
first: the knob and switch is fitted on to the chassis (lid of the box)
it worked okay, but need more cosmetic touch-ups, worry about that later.
flip the lid around, lay down the resistors neatly, not forgetting insulate them with flame proof tape.
notice the soldering grid on the side? well. i intend to fit everythin on that.. clearly it was a BIG mistake.. anyway, just do without it.
now comes to the most tedious part: point to point wiring!!
now you know why boutique ptp amps are so expensive. not necessary because they are better, but certainly because it takes LOTS of effort!
finally assembled, and seated on top of my valve junior
it works very nicely, i can *finally* dime the amp and still don't disturb people(much) at night. now.. just need to find some silver marker..
cost tally:
resistors: $0.7*8 =$5.6
cable and plugs =$4.5
switch and knob =$2.5
box =$2.5
total =$15.1
still (dirt) cheap (cheaper than a JJ EL84 by the way)
yep.. it is not reactive. after all, it's only about 5W's of power.. not much difference it will be.
about the resistance value. it depends on what level of attenuation you want..
.................................___ speaker ___
.................................|.........................|
"amp+"----7.5ohm---+----- 0.5ohm----+---- "amp-" (ignore the ... s)
this setup outputs about 0.02W of power to speaker. perfect for night practice pm me if you got more questions.
about the resistance value. it depends on what level of attenuation you want..
.................................___ speaker ___
.................................|.........................|
"amp+"----7.5ohm---+----- 0.5ohm----+---- "amp-" (ignore the ... s)
this setup outputs about 0.02W of power to speaker. perfect for night practice
pm me if you got more questions.
Reth
New member
Yo JE! Thanks alot for helping me out with the attenuator! Mine's finally done!
For all you guys out there, this is almost the same as the one above. Just that this one's for my valbee
Some pics:
My first attempt at soldering. Completed
In the amp cab
Nasty speaker-section job. But it works nonetheless (note the melted rubber)
And now it sits beside my valbee! Kinda big compared with the valbee..
The best part is- it works! Played for a couple of hours today, and it sounded really great at turned-down higher levels, and it distorts just as it should with volume maxed. Of course, nothing beats a fully cranked, un-attenuated amp! (except maybe the police) I notice that the selected resistors can get pretty hot- should I worry about that? Can the whole box catch fire or something?
Big thanks goes out to JE for helping me with the scheme and the sources! I must say you've helped me alot!
We'll keep in touch!
For all you guys out there, this is almost the same as the one above. Just that this one's for my valbee
Some pics:
My first attempt at soldering. Completed
In the amp cab
Nasty speaker-section job. But it works nonetheless (note the melted rubber)
And now it sits beside my valbee! Kinda big compared with the valbee..
The best part is- it works! Played for a couple of hours today, and it sounded really great at turned-down higher levels, and it distorts just as it should with volume maxed. Of course, nothing beats a fully cranked, un-attenuated amp! (except maybe the police) I notice that the selected resistors can get pretty hot- should I worry about that? Can the whole box catch fire or something?
Big thanks goes out to JE for helping me with the scheme and the sources! I must say you've helped me alot!
We'll keep in touch!
suckasucks
New member
hows the valbee compared to a valve junior?
want a VJ so bad but no one bring in locally.. no one brings int e new fender champs either..
want a VJ so bad but no one bring in locally.. no one brings int e new fender champs either..
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