Strange 'Light-sabre' Fizz from amp ??

[evh_slash]

Have started slaving my amps now that I have a Suhr Reactive Load, which means I'm now able to crank them up more.

I've started to notice a prominent harsh fizzy frequency that really rings and takes over when I let big chords ring out. I'm confused as to what it is.
It kinda sounds like a lightsaber being drawn by Obi Wan / a 60w Plasma rifle melting through robotic flesh. lol It's not noticeable while playing or riffing/soloing but if I let the notes ring out with distortion you can hear it.

I'm not sure if it was always there but now that I'm cranking that master up past 2 it has grabbed my attention. I'm not sure if its the EMG pickups/too close to the strings, or the Phase inverter is saturating/distorting, low amp filtering/ghost notes or if its something to do with the speakers... I've recorded a clip demonstrating it. please check it out.

Heres a few things to note:
- My tubes are set with a fairly hot bias and the amp has fairly low filtering (50 watt Friedman BE 50)
- The guitar I'm using currently has an EMG 85 in the bridge and its set very close to the strings (I can't seem to get it lower! This my be part of the problem)
- I'm not using THAT much gain on the amp, its set just under noon (4 and 1/2) and Master is set to noon (5), presence is around 8 and treble is at 5 (noon)
- Plugged into a closed 4x12 with Greenbacks and H75 combo. I've mic'd it DEAD Centre & harsh to emphasize the sizzle!

https://soundcloud.com/mbstudiopre/amp-fizz

Any ideas what this is and how I could look at eliminating this would be much appreciated guys!!

 

[CaptainWhizz]

Re: Strange 'Light-sabre' Fizz from amp ??

A phased plasma rifle in the 40 watt range?
Someone needs to make amps under the “plasma rifle” brand.

Sorry, I can’t help, but I had to reply.

 

[evh_slash]

Re: Strange 'Light-sabre' Fizz from amp ??

A phased plasma rifle in the 40 watt range?
Someone needs to make amps under the “plasma rifle” brand.

Sorry, I can’t help, but I had to reply.

Haha dude, that's why I said it. I'm glad you picked up on the terminator hint.

 

[67Mopar]

Re: Strange 'Light-sabre' Fizz from amp ??

Just curious... Why in the name of all that is just and worthy, would you use an attenuator with a MV amplifier?

 

[FuseG4]

Re: Strange 'Light-sabre' Fizz from amp ??

Just curious... Why in the name of all that is just and worthy, would you use an attenuator with a MV amplifier?

to hear the sound of the power tubes... you raise the master volume, driving the power tubes, and lower the volume right before the speaker.
When you lower the master, you are cutting the signal before it gets to the power tubes.

 

[Darg1911]

Re: Strange 'Light-sabre' Fizz from amp ??

I would probably go through the steps to check if amps, on their own, is contributing to the "fizz". That probably means cranking the amp briefly without attenuation. You can also eliminate the attenuator as the source if you get no fizz with guitar-amp-attenuator-speaker. I know that doesn't solve it but it eliminates some components, at least on their own. It's a starting point.

 

[67Mopar]

Re: Strange 'Light-sabre' Fizz from amp ??

Any benefits gained by driving the phase inverter/power valves into distortion are lost using an attenuator. This being said, consider swapping out the phase inverter valve, possibly the power valves as well. I would chit-can the attenuator, and go with an isolation cabinet. The "magic" you're looking for happens via output to speaker interaction. Anyone with an ear will concur.

 

[evh_slash]

Re: Strange 'Light-sabre' Fizz from amp ??

Any benefits gained by driving the phase inverter/power valves into distortion are lost using an attenuator. This being said, consider swapping out the phase inverter valve, possibly the power valves as well. I would chit-can the attenuator, and go with an isolation cabinet. The "magic" you're looking for happens via output to speaker interaction. Anyone with an ear will concur.

Guys , I'm not using a typical attenuator box. I'm using the Suhr REACTIVE LOAD, but effectively acts as a dynamic dummy 4x12 cab with greenbacks and responds exactly like a cab with the amp. In answer to some of your Q's , I have several amps some non MV, some MV, either way they are all 50 - 100w EL34 style amps so I like the idea of cranking them to the sweet spot and slaving them through a rack stereo power amp via the dummy load box with a load of post amp stereo FX racks like Eventide and 2290 delay.
This is necessary with classic amps which don't have master volume, FX loops , line outs etc.
I don't like built in loops or pedals for FX.

I'm thinking I should cool down the bias on my tubes a tad, and increase the PI filter cap values because right now they're are on the warm/saggy spongey side which is probably causing the cranked signal to become raspy and fizzy/loose. My master volume is only cranked up half way so I don't think I'm overdoing it per'se.

 

[evh_slash]

Re: Strange 'Light-sabre' Fizz from amp ??

Just to re-iterate. I'm NOT USING an attenuator box. I am using a Suhr REACTIVE Load (represents an exact reactive impedance curve of a 4x12 cab with greenbacks) and it absorbs all the power from my Amp, then sends a line level signal to be re-amped, Slaved, or for post FX processing & direct monitoring with IR . I am slaving/tramping into a VHT power amp.

 

[Phantasmagoria]

Re: Strange 'Light-sabre' Fizz from amp ??

I'm using a reactive load-box myself & the noise you hear might just be the sound of what your playing at an extremely low volume that's coming out of the load-box itself (like a speaker signal turned way down..if you put your ear close to the box it's more obvious). I believe that's normal for reactive loads ..read it somewhere. The sound is louder with certain amps than with others...

 

[evh_slash]

Re: Strange 'Light-sabre' Fizz from amp ??

I'm using a reactive load-box myself & the noise you hear might just be the sound of what your playing at an extremely low volume that's coming out of the load-box itself (like a speaker signal turned way down..if you put your ear close to the box it's more obvious). I believe that's normal for reactive loads ..read it somewhere. The sound is louder with certain amps than with others...

Yeah I know it buzzes a little but this is actually coming through the AMP and speaker.... I recorded a clip showing this. Check it out and let me know. it almost sounds like a wah pedal filter set all the way down. AWWWWWWW-tSHHHHHHHH

 

[67Mopar]

Re: Strange 'Light-sabre' Fizz from amp ??

I realize you're using a reactive load, but there should not be a noticeable difference in tone whether you're using a resistive or reactive load. Not unless the resistor bank has been subjected to excessive stress. What you're doing was of course pioneered by EVH. Just so you know, Ed wasn't using his Marshall plexi as the bi-amp. He used a VOX AC15 (attenuated) + Marshall plexi (as a PA) to amplify the attenuated AC15 signal and effects. You do not need to attenuate a 50 or 100 watt amplifier to attain that sound, but if you like what you're hearing, by all means continue.

Concerning Ed's Marshall plexi: Jose simply replaced the stock 'mustard' caps and transformers with aftermarket components. All components used were stock value. The first tech to work on Ed's famed plexi (post Jose) was Guy Hedrick. Guy rebuilt the entire amp circuit using NOS 'mustard' caps and transformers that he hand-wound himself. I asked Guy what he found when he opened the amp, and he was very specific. Everyone who inspected Ed's plexi were looking at a Guy Hedrick rebuilt plexi circuit. btw... Guy Hedricks' Guytron GT20 and GT100 amplifiers were inspired by Ed's early VOX/Marshall rig.

Replacing the PI filtering caps will do little to quell what you're hearing. You can go from 22n to say 33n to darken the output, but I don't think it's going to solve the issue at hand. I'm going to assume that you begin hearing this "light saber" sound effect, more, as you increase attenuation and amplifier volume? As far as loops go, if they're done properly, they can be quite rewarding. The best loops I've found are '87 Marshall Silver Jubilee series, Cornford, and Guytron amplifiers. Nothing will ever beat cab micing + mixer based effects, but a good loop makes all the difference.

 

[FuseG4]

Re: Strange 'Light-sabre' Fizz from amp ??

Any benefits gained by driving the phase inverter/power valves into distortion are lost using an attenuator. This being said, consider swapping out the phase inverter valve, possibly the power valves as well. I would chit-can the attenuator, and go with an isolation cabinet. The "magic" you're looking for happens via output to speaker interaction. Anyone with an ear will concur.

You literally cannot say any power tube benefit is lost by attenuation ...
Take a fender deluxe reverb and turn it to ten then attenuate it back to the SPL of the amp on six. You don't lose the interaction if the speaker, it's moving lots of air and if the load is reactive it's the same interaction as before, but not as loud. But the power tubes are compressing and distorting like they weren't before. And it sounds good.
Maybe your used to using attenuators on different amps and situations than me and some others but there's no way that the creamy power tube distortion just gets cancelled out cuz you stuck a reactive load in the chain there
With cheap, resistors+l-pad/rheostat that aren't reactive I still disagree. Yes much of the speaker reaction is lost but you it still doesn't undo the complicated filtering, clipping, and wave shaping of overdriven pi and power tubes.
Just cuz it doesn't sound as good to you doesn't mean that no one will see any benefit.

 

[FuseG4]

Re: Strange 'Light-sabre' Fizz from amp ??

I have only owned non reactive load boxes but got a really fizzy decay when I dimed the gain with it at maximum attenuation back when I used the night train 15 by vox
When I asked about it people said that's just the fizzy nature of the preamp that normally gets killed by the high end roll off of the greenback, combined with the fact that the amp had no choke and not much negative feedback

 

[67Mopar]

Re: Strange 'Light-sabre' Fizz from amp ??

It's likely that you are going to hear the same anomaly whether you use the attenuator or not. You would of course need to crank the amp with no attenuator connected to find out. The attenuator lets you to crank the power section, but that doesn't mean that it is not going to react in odd ways. If you are combining an excessive amount preamp gain into a cranked power section, I would back-off on the preamp, power amp, or both. I generally find that I prefer either a small amount of preamp distortion with a cranked power section. If using excessive preamp distortion, I back off on the output section. There is a fine-line balance between the two, no question. I had a Cornford RK100 head that, when pushed to 10, would exhibit similar sounds. I experienced the same with a Bogner 100B. It's not as uncommon as you might think.