Epidrake Messages: 28 Registered: July 2016 Location: NYC
Junior Member
Hi guys,
I know some people recommend changing out the old ungrounded cord for safety, but will changing it reduce background noise and hiss on my K200b-5?
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
No, hiss is due to the transistors of that era that where used, also some of them tend to get more noisy with age .
Also in the circuit certain caps will / can change value with age, they can plan old go bad ,or go up or down in uf value.
If they go up in value then certain caps can make a gain stage produce more gain then the amp was originally made with, and this in turn will make for more hiss.
Replacing just the first two transistors in the signal chain in both preamps with modern ones will cut the hiss level a good bunch.
The same issue can be found at times with the input stage transistors of the output driver board .
I have also found that replacing the diode bridge with modern fast recovery type diodes will drop the noise hash heard also.
Epidrake Messages: 28 Registered: July 2016 Location: NYC
Junior Member
Thanks Stevem,
The amp had been in a closet unused for at least 20 years, maybe much longer. Now that I have been using it, background noise has gone down significantly. Maybe the caps needed to be juiced up because now it sounds pretty quiet. If I'm still bothered by the noise, I'll look into changing some of the transistors. Thanks for letting me know where to start. You are an amazing wealth of knowledge. Thanks again.
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
Yes, the best thing you can do to a amp that has been sitting that long is let it just sit and idle over night and any caps that are not too far gone and can be what's termed reformed will do so.
Thanks for the pat on the back , but Bill and Pleat here are a blessing to have also!