Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: belf on February 02, 2014, 06:08:15 am
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When the tone knob on my 5e3 clone is set at anything greater than 7 I can hear a "white noise"/shhhhh sound as soon as the volume knob for the bright channel is turned past 2. The hiss gets louder as I turn the volume knob. Here's a short video to demonstrate the hissing : https://www.youtube.com/watch?v=BYI_41DYOh0 (https://www.youtube.com/watch?v=BYI_41DYOh0)
What I've already tried:
Removing V1 (12ay7) (v2 still plugged) -> hiss is still there but slightly lower.
Removing V2 (12ax7) (v1 still plugged) -> hiss completely goes away.
Exchanging V2 with another tube -> almost no difference.
All resistors carbon composition. Any ideas ?
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I look at your video and first thing I saw is many wires are to long and you need to clean all your wiring . Push all wires close to the chassis. Wire must be shorter as possible . Not for heater wires
You said you remove V2 and almost all hiss goes away ; this mean hiss is coming between V1 and V2 . Most of the time is from the wire from the volume pot ( or close ) to the V2 grid . Long wire act like antenna . Best is shielded wire at each tube grid OR you solder the cap or resistor directly on tube's socket. This stop the hiss .
Look any Fender Blackface amp wiring picture, you see how is the wires.
V1 ; if too long wire coming from the jack OR bad wiring dress = hiss . You can use shielded wire if you can't do proper wiring dress.