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In Reply to: Re: Biasing a Scott 299 posted by dadbar on April 13, 2007 at 18:28:55:
Thanks,
I recently sent the amp out to get a filter cap changed. Also had a quad of Ei Elites installed and the selenium rectifier was changed, along with a new pair of gold RCA inputs on the phono stage. The amp was given a thorough service and works great. However, I prefer the more 3D sound of the Sovteks and put them back in. The bias voltage did not change when I rolled the tubes. I have some EH EL84's on order and will try them as well. I just want to be sure I don't damage the tubes or tranny. I will check the grid voltage if you can explain that.
Much appreciated,
Larry.
Follow Ups:
Larry
There is a quick accurate way to set the Dc balance and what you do is get the amp fully warmed up and then put your dc voltmeter across the grid of each output tube of each channel..For intance take your meter and put it across the grids of the left channel tubes and set it for zero volts potential between the two tube's grids..This way if one tube draws more cuurent than the other,the DC balance pot proportionates enough voltage to each grid so it ultimantely draws the same amount of current..Then you can bring up your bias to -18to 21 is where I usually end up and I have seen some at -12 but thats usually when the tubes are real weak.Do the same procedure for the other channel..You have to go over it a few times once in a while.
Thanks Michael, I will give that a try.
Regards,
Larry.
You better go to hhscott.com forum. There are a lot of info about setting bias on your Scott 299A.
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