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EL84/6SN7 tube amp

riktw

Member
2007-09-16 5:33 pm
Hello

i got some tubes laying around and i want to make an amplifier with them :)
with some help from the internet, especially this sites i tried to design one.

How to design valve guitar amplifiers
How to Design an SE Power Amplifier

i want to make an EL84 amplifier, EL84 as triode and an 6SN7 as input stage.
i already got the transformers (got them on a dutch ebay site, 30 euro's for 2 OPT and a power supply transformer) and i got the tubes.
The OPT's have a 1:30 winding ratio, i got 4 ohm speakers so that means 30*30*4 = 3600ohm

for the questions:
the EL84 stage requires a 20V swing to get max power, the 6SN7 stage amplifies 15 times.
so i would need 1.33V input fox max output.
as far as i know a CD player delivers roughly 2Vpp but do i need 1.33Vpp fox max output of 1.33Vrms?
i expect at least 50 different mistakes :p but did i make some and so yes what and where?

here is my design with the formula's i used in them:

Thanks, rik
 

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  • 6SN7 stage.png
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riktw

Member
2007-09-16 5:33 pm
i will put an RC network in the power supply, 100uF 47ohm 100uF should work good enough :)
input capacitor is a good point indeed, shall add it.

and yes, 2 watts is enough, if this works properly i can start thinking about making a bigger tube amp with good new transformers.
the GM70 tube is one i really like lookwise, who knows if this works out perfectly i can build a nice GM70 amp
this is pure practice :)
 
I don't use input capacitors, as they say the best cap is no cap, however and this is a big however; I always make sure that my sources (a line stage in most cases) have no more than a couple of mV of DC on their outputs.

All of my digital sources are balanced and transformer coupled so no DC there. The line stage is also transformer coupled so again no DC there.
 
I don't use input capacitors, as they say the best cap is no cap, however and this is a big however; I always make sure that my sources (a line stage in most cases) have no more than a couple of mV of DC on their outputs.

All of my digital sources are balanced and transformer coupled so no DC there. The line stage is also transformer coupled so again no DC there.

I have a guitar effects pedal that puts out 4V5 DC so I would need a capacitor on the input. 4v5 on the grid would change the voltage on the cathode too and screw things up.