Tube Amp Archive

nice pics guys
I will check the stage who hum by removing one per the preamp tube and rewiring the hum stage

Hello
replace the yellow wire who make loop in front of the filament wire and the hum was decrease good news
But is still here ...and I don't have an idea to solve !
nobody have an idea ?
thx

hello i just checked all the voltage and all is on the tolerence ....good news ;) I pushing the yellow wires around with an insulated tool and it's don't remove the hum i a see a mistake on my wiring ....see pics [img:912:608]https://lh6.googleusercontent.com/_WkVlvTVF6xo/Tb2VZWpryuI/AAAAAAAAEE4/x0-...

hello i just cheked the frequencies of the hum and it's 50 hz (i'm in europe > paris france)>>>>edit ,it's normal is the france frequencies voltage :) So I found a another problem (a big one ) when a push the standby , i have half time a big hum and the half time a little hum !! i think it' a VVR pr...

oky thanks
i will check the ground connection and replace the yelow wires loop far from the filament wires

yes i saw this technique on TAD pics

Oky so i see a little proximity between the cathode and the filament on V3 tube see pics ia had another if you want [img:912:608]https://lh3.googleusercontent.com/_WkVlvTVF6xo/Tb2Vf7tKbMI/AAAAAAAAEFQ/TGTHaLCBseQ/s912/IMG_0312.JPG[/img] [img:912:608]https://lh5.googleusercontent.com/_WkVlvTVF6xo/Tb2V...

hello thanks for your answer i i have installed 3 12ay7 and 1 12ax7 as seen on original layout it's a brand new TAD tube I d'ont have multimetre yet to check the cathode voltage but a will check maybe tomorow do you think it's a grounding problem ? because i don't have so hum when the pot is all way...

nobody have an issue ?
thanks in advance

so
i make a full reviews of my amp
the vol bright pot is not linear .....
the treeble pot buzzz
and a did hear any difference when a turn the presence pot !!!

a have a VVR but i don't think it's the cause
for the cruch ,perharps it's the brand new tube ?
i will check tonight with the vvr full and ground sheme on the treeble pot !

Hello
i just finish my 5e8-a and i have a big hum on the treeble pot !
anyone have a solution ?
also i have a sound like a cruch ,not always but it apears after 5-10 min !
thanks a lot !

So if i understand i can change the 56R by a 56K bias pot ? I'd rather build a voltage divider by keeping a series R with a 25K trimmer connected as a variable resistor to ground. Tap bias at the junction of the R and the pot. Values should be calculated according to the raw bias voltage you've got...

FYL wrote:

the Bias layout it's ok ?

The bias section is OK. You'll have to fine-tune the 56K dropping R if post-VVR bias voltage isn't acceptable.

So if i understand i can change the 56R by a 56K bias pot ?

Ok thanks
do you think it's a better performance in insert VVR between C1 and L or between L and C2
If the voltage is twice filtered ,it's better ?