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Haunted foglifter

 
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ricky
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Joined: 20 Sep 2011
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Location: Bozeman, MT

PostPosted: Fri Oct 02, 2015 12:20 am    Post subject: Haunted foglifter Reply with quote

What might it mean when all controls on the foglifter are at zero and there is this low pitched "whup, whup, whup" kind of noise? When I actually have the guitar signal in it it sounds like a tremolo. When I turn up either the density or presence just a little it starts to go away and at around 10:00 it is gone. Nothing potentially damaging I hope.
This is on my JF RM20. The RM 50s do not do this. I had not noticed it on the 20 until tonight. Maybe it is normal and I just have never had all of the foglifter controls at zero?
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Jaded Faith
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PostPosted: Fri Oct 02, 2015 2:38 am    Post subject: Reply with quote

If you have the NFB, Presence and Density all the way down there is probably too much negative feedback being applied for the power amp/bias/speaker combination. Those controls are broad on purpose and I can't really conceive a situation where I'd want all three knobs fully down. I imagine that would sound like a blanket over the speaker? Simply turn something up to correct the condition.
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ricky
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Joined: 20 Sep 2011
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PostPosted: Fri Oct 02, 2015 9:00 am    Post subject: Reply with quote

I had all of them down as a starting point for getting a tone and to see what each control did little by little. that is kind of a cool thing with the NFB and it makes sense to me.
I am a little curious about the whole foglifter/mda/density/presence control. I understand that it is about the power section. Is it kind of an eq for the power section only? In some ways it seems like it is a "mastering" deal....I get a nice sound with the preamp section and then add a little polish.
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Yatagan
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Joined: 20 Jul 2015
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PostPosted: Fri Oct 02, 2015 10:38 am    Post subject: Reply with quote

In a sence you can say it is an EQ for the power amp section, but it is designed to be used at lower volumes.

Both are there to boost bass and treble in the power amp section when you are playing at low volumes. Bass in particular can disappear at lower volumes.

Density in particular are there to enhance the sound when you are playing at lower volumes (read loudness/ bass boost when compared to a regular home stereo system). The Presence is also there to enhance sound at lower volumes but can also be used somewhat similar as a presence control that you find on a lot of guitar amps.

Use the density with great care on higher volumes as it can quickly ruin your sound, the presence can also destroy the sound but is not as sensitive as the density.

Master is exactly that, overall volume for the power amp.

Play around with it and you'll figure it out.
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Jaded Faith
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PostPosted: Fri Oct 02, 2015 11:00 am    Post subject: Reply with quote

Everything you want to know and more can be found well explained here: http://www.aikenamps.com/index.php/what-is-negative-feedback

To quote the article and explain your initial question:

"There is a danger in using too much negative feedback, however, as the amplifier can become unstable and oscillate, particularly with reactive loads.
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ricky
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PostPosted: Fri Oct 02, 2015 2:21 pm    Post subject: Reply with quote

Thanks Rob.I have the density presence thing dialed in as far as sound goes. It is interesting to know how they work. The negative feedback article was a lot above my pay grade after the first few paragraphs, but I got the gist of how to utilize it better especially as far as getting a a more even tube distortion or clean sound.
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Caine
RM100


Joined: 31 Jul 2006
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PostPosted: Sun Jan 31, 2016 9:35 am    Post subject: Reply with quote

I'm still trying to get a handle on getting all of the controls to work together (D, P, NFB); It seems I am wanting to change the settings when going from a TD module (cleans and dirty blues) to the high gain modules--but I'd really like to have one overall setting with the D, P and NFB and then fine tune the rest with the module(s). I'm trying to avoid the blanket effect when controls are turned down too far; or too harsh or ice pickish when they are too high. But the settings that seem about right for the Egnater TD module are too conservative for the high gain modules--but the setting for the high gain mods are too harsh for the TD mod. I'm also getting a bit of "ear fatigue" thing with the higher gain modules that I didn't used to have. Is there such a thing as a neutral setting for any or all of the controls?
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Caine
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PostPosted: Sun Jan 31, 2016 5:41 pm    Post subject: Reply with quote

Well, so far it seems the best "all around" settings are NFB @ 9 o'clock, P between 11 and 12 o'clock; D @ 9. I can dial in things the rest of the way with the controls on the T/D and Brahma modules and they sound pretty good; the Mr. Scary module sounds pretty good but the bottom is a little weird still.
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Jaded Faith
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PostPosted: Tue Feb 02, 2016 7:49 am    Post subject: Reply with quote

Setting the NFB around 10:30 is generally about what a stock MTS amp is set at. Density and Presence will have the greatest effect at the lower settings of NFB because they are controls within that loop. The higher you turn the NFB, the less there is and the less those other controls do.
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ricky
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PostPosted: Fri Feb 19, 2016 12:43 pm    Post subject: Reply with quote

I have two RM50 style amps with the foglifters in them. One of them is fine and the other has a pretty loud 60 cycle hum that gets louder as I turn up each of the foglifter controls. It is there when everything is turned down, but very minimal. As I turn up the density, the hum increases and the same goes for the other two controls, but the density has the most impact. Using it live is kind of a minor annoyance, but in the studio I have to really gate it which impacts the decay of my notes. I checked the bias on the tubes and when set really low, the hum is lessened, but the tone is not quite right as it is set way too low. Any hints from anyone?
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