Amps with no negative feedback and guitar vol knob

5F6-A

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We all know that an amp with no negative feedback sounds louder, dirtier and wilder than the same amp with a NF. That might be good or bad depending on your desired tone. However, I wonder if the extra gain and dirt of a non NF amp can be tamed by just turning your guitar vol knob a tad. Never done the experiment but it sounds plausible. At the moment I only have amps with NF. What do you think??

Mighty Uncle Doug summarised it really well here:
NFL.JPG
 

The Ballzz

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Play for "AWHILE" through a generally bone stock 5E3, Tweed Deluxe and get back to me. It's not an overnight or even few days thing understanding it. It's more of a "feel" thing than an actual sound thing and it takes a bit of time to truly "get" it!

Just Sayin'
Gene
 

Case24

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Both my 5E3 and Marshall 18 watt clones that I built have no NFL and they both clean up well by turning done the volume knob on the guitar. I’m not getting Twin Reverb cleans but there is definitely less dirt.
 

5F6-A

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Cool! In my limited experience, what I hear in NFL amps is a familiar 'chinky', compressed clean tone. Polite, safe and warm. With Non NFL amps I hear a raucous, loud, sweet-but-dangerous feel. A bit like Johnny Cash.
 

Geeze

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I agree with @The Ballzz about the feel. I have a Satellite Barracuda [Satellite's take on a JTM45 with no negative feedback, NMV and just a tone knob] with KT66's. Warm Marshall cleans that thicken into early Billy Gibbons tones as I dial up the volume. I don't get a ton of gain from it until it's dimed [holy crap loud though] but the feel / attack is desert island amp amazing. Every show I take it to I get offers for it.

The reason I'm responding is to question the circuit design/path & power tube affect in addition to the NF level. For instance the KT66 doesn't go into full square wave when pushed so it's adding a noticeable addition to the tone/feel. I've replicated the smoother gain with noticeably better note separation with a Marshall 2555X running a quad of them. But the 2555X doesn't have the same feel [I haven't turned the presence off at volume yet] as the Barracuda. So based on this limited data sample I'm concluding there are many bits contributing to the sonic stew.

Russ
 

sonar

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I agree it's more a feel thing, but also dependent on the amp.

Most of the time amp builders get it right with (or without) using NFB in their respective designs.

For instance, eliminating or even decreasing NFB on some BF designs (excluding the CBS "NFB within NFB" weirdness on the AB165) kind of wrecks the feel, and note definition falls apart when turned up.
 

5F6-A

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My new amp is a 5F2A Princeton type but it has ss rectification and no NFL in a Valco style cab. I get what you mean in terms of feel. It 'feels' bolder, wilder and more mid focused. I use a Mazda Chrome plate ECC83 and RCA 6V6GT. Both from the 50s. Amazing, bold and in-your-face. Time to relearn how to play again....
 

Splattle101

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I have a late 60s Super Reverb. I re-purposed the earth switch on the back panel to defeat the negative feedback, so if the switch is on the amp is stock, but if it's off the amp has no negative feedback.

Without NF the amp is louder, wilder and hairier at any given setting. In addition, it also has WAY more top end. So much so, in fact, that I could never use it with the treble settings the same as for the stock amp.

I find it does clean up just fine when I turn the guitar volume down. It still sounds like a different amp, though.

I also have a 5E3 clone (no NF). It's a four-holer with interactive volumes so bear with me here. If I plug into either channel and set that channel's volume to ~75%, then set the OTHER channel's volume to ~35%, I get good distortion that I can boost into filth, or clean up by rolling back the volume on the guitar. However, the clean is not really clean. It's still got some hair around the edges.

However, if I leave the volume settings as they are, and plug into the other channel, the amp can produce a real clean with the guitar vol down a bit. Not an almost-clean, but a real, genuine clean. And the amp still sounds like a 5E3, and more so if I kick the front end with a boost.

BTW, I use a 12AY7 in the preamp of the 5E3, and a 12AX7 in the preamp of the Super Reverb. The preamp tube for the normal channel of the Super is removed (this affects the bias of the preamp for the reverb channel).

I also have a tweed Super 5F4 clone. This amp has a presence control, which is a high-pass filter on the NF. The tweed amp has more low mids than its blackface sibling, and on first listen it's got less treble. However, if I run the presence high (minimum NF) I get more top end than the blackface amp in stock condition. This means I can roll off the volume at the guitar and get real cleans from the tweed Super that are hard and glassy enough to play funk. I really didn't expect that from any tweed amp, but there it is.
 

Wrench66

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I removed the NFB from my 5f1 clone. It distorts at around 3.5/12 on the amps volume with the guitar volume dimed (humbucker). With the NFB in the circuit, it wouldn’t distort until about 5/12 on the amps volume.

The amp “breaths” a little better with out the NFB IMO. It still gets beautiful cleans with the guitar volume rolled down, but sweet bluesy overdrive, especially on the neck pickup, with the guitar volume dimed.

Picking dynamics are better with out the NFB also. Sweet cleans to overdrive with just the pick. Pretty sweet in my opinion .
 

cooljuk

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You can put a switch or pot inline with the NF to turn it on or off or adjust the amount. I've got one rig that has something of a NF EQ on it, where the bass resonance and presence are both independently adjustable in the NF loop. It's an awesome way to shape the sound.

I think Uncle Doug actually has a video where he shows a schematic for adjustable NF, somewhere. Maybe the same one you mentioned above?

That'd be the easiest way to test your theory in your amp/rig. Personally, having messed with NF just casually, I don't think that a guitar volume knob tweak, altering the very front end loading of the signal, will respond anything at all like changing the NF, altering the phase in a non-linear way at the far end of the signal chain.
 




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