Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: RoadShow on October 21, 2024, 09:50:19 am

Title: Hmm, does red plating make a sound to reveal itself?
Post by: RoadShow on October 21, 2024, 09:50:19 am

I understand what red plating is and what causes it, but I've never actually experienced it.

I see people mention that they had a tube red plate, but is there something that made them look to see it?

I suspect that the amp doesn't sound right when it occurs, so what is the change in the sound?

Or, should I be looking in the back of the amp whenever I use it... just in case.

Thanks...

Title: Re: Hmm, does red plating make a sound to reveal itself?
Post by: pdf64 on October 21, 2024, 09:58:09 am

By definition, a redplating valve draws a lot of idle current.
That imbalances a push pull stage / typically increases HT ripple, to such a degree that the amp hums at twice mains frequency.

Title: Re: Hmm, does red plating make a sound to reveal itself?
Post by: Merlin on October 21, 2024, 10:00:51 am

Redplating can be due to hot bias in which case you won't necessarily hear anything unusual. Or it may be a symptom of a significant fault that is audible. So both options are possible!

Title: Re: Hmm, does red plating make a sound to reveal itself?
Post by: tubeswell on October 22, 2024, 08:26:35 am

If you happen to be playing some power chords, the amp can sound incredible as it’s red plating, and then it dawns on you what might be happening, but by then it’s too late…

Title: Re: Hmm, does red plating make a sound to reveal itself?
Post by: stratomaster on October 22, 2024, 09:36:40 am

In my experience, the worst cases both look and sound like Darth Vader waiting in the dark to strike your amp down.

Title: Re: Hmm, does red plating make a sound to reveal itself?
Post by: acheld on October 22, 2024, 09:54:20 am

The good news is that neither Darth Vader or red plating are subtle.   

At least, not subtle once you have experienced it.   When I hear that increasing 120Hz hum, I know what switch to reach for!

Title: Re: Hmm, does red plating make a sound to reveal itself?
Post by: shooter on October 22, 2024, 10:12:44 am

was at a local outdoor jam weekend, one of my amps was "on display" for the various guitarist to try out.  That night the "headliner band" jammed out, during a break I was backstage, told the lead guitarist "Your twin sounds like the PA tubes are on their last legs"
He smiled, said; "It's amazing the sound I get, I have my tech ONLY install tubes that are ready to die, I get one or two shows on each set"