6BL7 power pre amp
A real power pre amp here , one that will drive your headphones
to the cemetary if you dont watch out and fun too build as well,
accesible to anyone , it is very good and very cheap .At least on the
amplifier side , but it is very sensitive to the PSU so the power supply
must be perfect or at least as good as possible .
Ps in any amplifying device : the ps must allways be good .
Compared to the 6SN7 now we have 2 tubes handling the operation ,
but its still a very classic schematic :
The first tube is a 6SN7 parallelled which means that it's best to use matched
Triode sections and the second tube uses the very power full 6BL7
The first part is not decoupled , the second neither , so we avoid electrolytics
In the signal path and the last part is your classic everyday low impedance
tube output with a 100 ohm resistor to (protect and serve) in case of a short
You can allways remove it .
I have to mention that I was a bit overzealous with the capacitors ,actually
Sometimes less is more , you are free to experiment.
This monster of simplicity drives the 300B PP amp perfectly ,
which means it can swing quite a voltage .the soundstage is excellent ,
deep spacy & airy.
I will try to choke load the first plate that is the other improvment left .
The potmeter is a Panasonic stereo 50Klog , it is the only pot you should ever use.
(i gave up on stepped volumecontrols since the panasonic)
I do not use silver wiring allthough i sell it , (i am not a big fan of all
these expensive stuff)
and I dont use shielded wire , just common hook up wire ( shielded is necassary if the cables are long )
From our local telephone company , it is some sort of metal alloy (nickel
tin copper I guess)
The groundplane is cabled with 1.5MM2 OFC loudspeaker wire with lots
of fine strands , it's easy to work with ( you don't need that 75W welding
And finally the schematic :
Have fun building , and if you need anything let us know
Kit offer :
1 pcb all componets and tubes 160 euro for stereo version ( no housing or powersupply )
with transformer and choke and simple housing total cost 350 Euro
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