[Doublej]

Do solid state amplifiers need to be rebiased every so often? I have a B&K EX4420 that is at least 15(?) years old. I am wondering if it would sound better with some sort of tuneup.

While I am on the subject, are there any B&K forums like there are for some of the other vintage brands?

[G Georgopoulos]

That's a great idea but you know how to set the trim pot do you have a scope etc...

[rikhav]

I would also like to know if ss amps need to be rebiased every few years
I have any odyssey stratos which has a rather shrunk sound stage and solution to this on odyssey circles a rebias
My amp is little more then 4 years old and I am the second owner

[Pete Schumacher]

I would also like to know if ss amps need to be rebiased every few years
I have any odyssey stratos which has a rather shrunk sound stage and solution to this on odyssey circles a rebias
My amp is little more then 4 years old and I am the second owner

It's not something that I'd recommend someone doing unless they're very comfortable with a soldering iron and inserting a current meter in series with the power rail.  Or if there are fuses in line with each rail, the meter could be used in its place.  A competent tech could verify bias in less than a half hour, or adjust it to another value that is deemed better now.

In most cases, solid state components are pretty stable over time and should not need to be re-biased.  But if your local line voltage is significantly different than what was used to bias the amp in the first place, there could be an improvement to set it with your local line voltage as the AC input.  In any case, 4 years should not mean much, if any drift of the bias level due to component stability issues.  Tube amps would be far more likely to drift over the same time frame.

[rikhav]

Thank you pete for the detailed reply
I am in india and amp was build in usa by klaus of odyssey. The first owner was also from india as well so I guess klaus would have kept in account the power conditions here in india. Still I will speak to klaus and see what he has to say

Also I will try and change the pre as some suggested that it can be the prr which is the culprit. I am using a passive prr which has tvc (promethius standard edition)

[G Georgopoulos]

It's not something that I'd recommend someone doing unless they're very comfortable with a soldering iron and inserting a current meter in series with the power rail.  Or if there are fuses in line with each rail, the meter could be used in its place.  A competent tech could verify bias in less than a half hour, or adjust it to another value that is deemed better now.

Hi Pete

if you measure current from fuses the reading will include current from vas and input stages
a better way is to measure the voltage of the o/p stage emmiter/source resistor and by
using ohms law (i=v/r) you find the bias current...

the above is for 1 pair of o/p devices

for 2 pairs of o/p devices is (i=v/r) x 2
for 3 pairs of o/p devices is (i=v/r) x 3
and so on

i also think is better leave it to a pro rather than doing it yourself...

cheers 

[G Georgopoulos]

components last 50,000 hours

it all depends how long are used each day

say 4 hours a day, a year is 365 x 4 = 1460 hours

then the life expectancy is 50,000/1460=34 years

so it makes sense to check the bias after 15 years or even 10 years etc...