Ruby Mod, snubbers - 18 watt

[Deric]

I just used the closest value that was ~1-2v higher.

[Lindz]

Thanks for all the replies - very helpful.

FYI - my amp has a Mercury Magnetics 018RS-L output tranny

I would venture it is not way underpowered, although I am certainly no expert about transformers.

there are pics of my board in my "noob questions about 18 watt" thread.

Experts... what is your take on the Guitar Player mag article and mod? Anyone install something like that on their amp??

[Zippy]

FWIW I think it's worth a try. I've built several 18 Watters (with both very good AND very questionable output transformers) and the Ruby mod made most of them sound better.

Could you specify which "Ruby mod" you used?

It would be nice to learn exactly what ailment the mod in the OP's post addresses.

[Deric]

"Ruby mod".....

http://www.18watt.com/storage/18-watter ... fo_311.pdf

[Zippy]

So it's NOT the mod that the OP shared...

[jelle]

Isn't that like a conjunctive filter on the output?

My thought exactly!

[ampgeek]

The OP references two mods to potentially solve a swirly/buzzy condition observed in two similarly built 18 watt plans. The "Ruby" mod and what appears to be a conjunctive filter affair.

Both of the presented sound clips clearly indentify the offending condition.

My understanding is that conjunctive filters are often used in PA system applications that have long, low(?) impedance speaker cable runs that are sensitive to radio wave range interference. Is that true?

Could radio wave range interference cause the problem heard in the clips?

Cheers,
Dave O.

[Lindz]

Thought I would update this thread now that I had time to work on my amp

A couple weeks later and I installed the "Ruby mod" on my amp and it worked like a charm ... I am pretty stoked!

Installed 14 watt zeners (measured 12 on my amp) w the 1N4007's and voila.. very little swirly buzz on the decay of notes and chords as in my original sound clips - there is a TINY amount still but I am quite happy with it and as other posters suggested a little give some pretty cool overtones

thanks for the input everyone

[bgkyt1]

Lindz,

Thanks for this post. Very informative. Can you tell me what the circuit the ...TMB_fizzz.mp3 clip is in your original post?

https://tubeamparchive.com/viewtopic.php?t=15332

Thanks.

[Lindz]

Its a Trinity Plexi TMB 18 watt - semi standard tmb layout but I changed a few cap and resistor values to mimic an amp another builder made over in their forum

[Masco]

Here's the Zimmerman GP article the OP was talking about: http://www.guitarplayer.com/article/smo ... -ride/5505