I have a Beard P50 power amp. Its part of an all valve setup feeding a pair of rebuilt Gale 401s
The P50 was aged when I got it. I first recapped most of the signal and all of the psu sections.
Bypassed the input level pot
Fitted Mazda tubes and GEC KT88s
It has ran for a few years of light use since (tubes don't have many so hours on them).
It does still have some low level hum but not sure if this unavoidable. It can be heard when close to the speakers with no signal playing.
I previously looked at this, added a balance pot as per instructions on here to the AC heater lines. Adjusting that did not do much.
I also fitted a few diodes to lower the heater voltage by 0.6v as due to running an isolation transformer my incoming mains is a shade high.
Not sure what the source of the hum is.
I will be taking another look at the amp in the coming weeks. I still need to fix the panel lights but have not figured an easy way to access those as sandwiched between front panel and chassis. Not sure if removing the rack mount handles and all panel knobs will release the front panel or a chassis strip down is required. Lots of hidden screws that would be invasive to reach.
I have new diodes ready to replace the 240v input rectification. Just as an age replacement and better spec.
Any aged looking resistors I replaced when did the caps.
My next thoughts are the signal wires.
These run from the rca's at the rear to the front of the chassis. They are solid core, layed neatly on sticky pads but not twisted.
I will check to see if the path can be improved/shortened.
Thoughts on these please,
try new twisted signal wires? If so what type.
I want to order any bits I may require first. I will then post pics for any further advice. I may have some earlier ones I can dig out.
Another mod I was thinking was to add some extra caps to the large psu items I replaced. I gather the P80 version of this amp had these but have no diagrams for either despite several attempts to find any. The Gale 401s like some grunt to wake them up so maybe lots of reserve in the large caps would be useful.
All the tube sockets are original. I nipped in the female legs rather than replace last time. I don't get any of the rustling leaves sound so assume they are not a weak point sonically as is.
Thanks Rob
The P50 was aged when I got it. I first recapped most of the signal and all of the psu sections.
Bypassed the input level pot
Fitted Mazda tubes and GEC KT88s
It has ran for a few years of light use since (tubes don't have many so hours on them).
It does still have some low level hum but not sure if this unavoidable. It can be heard when close to the speakers with no signal playing.
I previously looked at this, added a balance pot as per instructions on here to the AC heater lines. Adjusting that did not do much.
I also fitted a few diodes to lower the heater voltage by 0.6v as due to running an isolation transformer my incoming mains is a shade high.
Not sure what the source of the hum is.
I will be taking another look at the amp in the coming weeks. I still need to fix the panel lights but have not figured an easy way to access those as sandwiched between front panel and chassis. Not sure if removing the rack mount handles and all panel knobs will release the front panel or a chassis strip down is required. Lots of hidden screws that would be invasive to reach.
I have new diodes ready to replace the 240v input rectification. Just as an age replacement and better spec.
Any aged looking resistors I replaced when did the caps.
My next thoughts are the signal wires.
These run from the rca's at the rear to the front of the chassis. They are solid core, layed neatly on sticky pads but not twisted.
I will check to see if the path can be improved/shortened.
Thoughts on these please,
try new twisted signal wires? If so what type.
I want to order any bits I may require first. I will then post pics for any further advice. I may have some earlier ones I can dig out.
Another mod I was thinking was to add some extra caps to the large psu items I replaced. I gather the P80 version of this amp had these but have no diagrams for either despite several attempts to find any. The Gale 401s like some grunt to wake them up so maybe lots of reserve in the large caps would be useful.
All the tube sockets are original. I nipped in the female legs rather than replace last time. I don't get any of the rustling leaves sound so assume they are not a weak point sonically as is.
Thanks Rob