{"id":8372,"date":"2021-06-04T14:17:20","date_gmt":"2021-06-04T13:17:20","guid":{"rendered":"https:\/\/origineffects.com\/?p=8372"},"modified":"2022-01-21T15:42:48","modified_gmt":"2022-01-21T15:42:48","slug":"tech-tips-the-more-pres-control-what-is-negative-feedback-why-should-i-care","status":"publish","type":"post","link":"https:\/\/origineffects.com\/2021\/06\/04\/tech-tips-the-more-pres-control-what-is-negative-feedback-why-should-i-care\/","title":{"rendered":"TECH TIPS: The MORE PRES Control – What Is Negative Feedback & Why Should I Care?"},"content":{"rendered":"

What Is Negative Feedback & Why Should I Care?<\/strong><\/span><\/h3>\n
By John Dines –\u00a0 OE Product Manager<\/span><\/h6>\n

 <\/p>\n

So, what is negative feedback \u2013 other than what I receive on school reports, first dates and job interviews? By clicking the link to read this article you have admitted that, to some extent, you are a guitar gear nerd, so you\u2019ll have almost certainly heard of negative feedback in relation to amplifier design, and with good reason. It has a huge impact on the character of an amp and can affect the clean headroom, dynamic response and the all-important transition into breakup (no, we\u2019re not talking about my dating life again). We all know these clich\u00e9s from reading the guitar press \u2013 \u201ctight, percussive and articulate\u201d or \u201ctouch-sensitive, natural compression\u201d \u2013 but it\u2019s useful to understand the electronics behind the marketing and, more importantly, how the Origin Effects RevivalDRIVE range of pedals can offer a whole spectrum of amp-tone personalities (spoiler alert: it\u2019s the MORE PRES control).<\/span>\u00a0<\/span><\/p>\n

\"RevivalDRIVE\"<\/a><\/p>\n

 <\/p>\n

Negative feedback is a simple concept that can have a big effect on an amp\u2019s behaviour.\u00a0In basic terms,\u00a0an amp\u00a0takes\u00a0some signal from the speaker output and feeds it back to an earlier part of the circuit.\u00a0The important part is that the signal is fed back\u00a0<\/span>out of phase<\/span><\/i>.\u00a0\u201cOut of phase\u201d means that polarity of the signal is reversed \u2013 imagine a sound wave with positive peaks and negative troughs.\u00a0Inverting the phase means the peaks become troughs and the troughs become peaks.\u00a0It\u2019s\u00a0exact same sound wave, just upside down.\u00a0If we add this\u00a0out-of-phase signal to our original signal, they cancel each other out and we\u00a0are left with nothing. If, however, we add\u00a0just\u00a0a small amount of the out-of-phase\u00a0signal, the level of our original signal is\u00a0merely\u00a0reduced. Still with me?<\/span>\u00a0<\/span><\/p>\n

This is where I hope it gets interesting. By taking the out-of-phase signal from\u00a0<\/span>later<\/span><\/i>\u00a0in the circuit\u00a0\u2013\u00a0the speaker output and feeding it to an earlier part\u00a0(before the power amp)\u00a0we can change the power amp\u2019s behaviour.\u00a0More output from the speaker = more signal fed back =\u00a0more level reduction = more clean headroom\u2026until the output section finally distorts. This is when\u00a0we hear a\u00a0sudden transition into overdrive, like\u00a0you\u2019d\u00a0expect\u00a0from a Fender Twin Reverb or a Marshall Plexi.\u00a0This is a trick from the\u00a0good\u00a0ol\u2019 days, when clean headroom was the goal, but it\u2019s just as desirable in the world of\u00a0rock distortion.<\/span>\u00a0<\/span><\/p>\n

This type of circuit will typically\u00a0<\/span>feel<\/span><\/i>\u00a0percussive,\u00a0stiff\u00a0or aggressive to the player. It will usually\u00a0have excellent definition and a huge dynamic range, as well as being much more stable.\u00a0You\u2019ll\u00a0also notice quite an abrupt transition between clean and distorted\u00a0sounds,\u00a0for the reasons described above. To a great many players, these are all desirable traits, especially if you like your guitar to have a loud, clear, authoritative voice. But what if you lean the other way?…<\/span>\u00a0<\/span><\/p>\n

Amps with\u00a0little or no\u00a0negative\u00a0feedback have a very different character altogether.\u00a0The Vox AC30 and the Fender Tweed Deluxe are both great examples of this.\u00a0Instead of a\u00a0clean, clear amp which suddenly distorts,\u00a0you get a very gradual transition into overdrive\u00a0that can be wonderfully expressive, especially if\u00a0you\u2019re\u00a0a player who lives on the edge of\u00a0breakup.\u00a0Once you push these\u00a0amps over the edge, they can become quite raucous and unhinged\u00a0\u2013\u00a0almost to the point of your guitar\u00a0tone completely falling apart. Let me be clear:\u00a0<\/span>all<\/span><\/i>\u00a0of these are good things!<\/span>\u00a0<\/span><\/p>\n

\"\"<\/a><\/p>\n

Between noon and fully anticlockwise on the RevivalDRIVE\u2019s MORE PRES control, this is exactly what you\u2019re affecting. Don\u2019t forget, these all-analogue pedals emulate a whole amp circuit in miniature \u2013 even the output section and reactive load \u2013 so it\u2019s happening for real! Turning the MORE PRES control down from the 12 o\u2019clock position reduces the negative feedback in the pedal\u2019s emulated amp circuit all the way down to nothing (yes, the pedal\u2019s push-pull output section has variable negative feedback. We really have gone that far in recreating a valve amp\u2019s signal path). But what about when you turn it <\/span>above<\/span><\/i>\u00a012 o\u2019clock? Time to learn about presence controls.<\/span>\u00a0<\/span><\/p>\n

We already know that you can feed some out-of-phase signal back into an earlier part of the circuit to help clean headroom,\u00a0stability\u00a0and dynamics.\u00a0This\u00a0is what happens when our out-of-phase signal is full-range. But, if we\u00a0filter some treble out of this signal and\u00a0feed back\u00a0only the low end, only the lower frequencies will be cancelled out\u00a0\u2013\u00a0or, to put it another way, we\u00a0<\/span>boost<\/span><\/i>\u00a0the top end\u2026 Presence!<\/span>\u00a0<\/span><\/p>\n

This is exactly\u00a0what\u2019s\u00a0happening\u00a0when you turn up the presence control on an amp,\u00a0such as a Fender\u00a0Bassman\u00a0or a Marshall Plexi. This\u00a0is not the same as turning up the amp\u2019s treble control, and it can have a really big impact on the way the amp feels,\u00a0as well as\u00a0the character of its overdrive.\u00a0Basically,\u00a0it\u2019s\u00a0a\u00a0<\/span>really\u00a0<\/span><\/i>important part of what valve amps do\u00a0so we\u00a0<\/span>had<\/span><\/i> to include it in the RevivalDRIVE pedals. When you turn the MORE PRES control above 12 o\u2019clock, it becomes a presence control, boosting high end and changing the way the pedal breaks up, just as it would do on a vintage amp.<\/span>\u00a0<\/span><\/p>\n

To summarise,\u00a0this one control is possibly the single biggest difference you can make to your overdrive tone and should not be underestimated.\u00a0It\u2019s\u00a0what helps these pedals capture such a variety\u00a0of classic amps sounds, and what gives them the all-important feel that is often missing from \u201camp in a box\u201d type circuits.\u00a0The best part is that\u00a0these properties are endlessly variable, meaning you can mix and match\u00a0the different\u00a0characteristics of\u00a0your favourite classic amps.\u00a0You\u2019re\u00a0pretty much\u00a0designing your own vintage amp every time you turn the knob!<\/span>\u00a0<\/span><\/p>\n

\"\"<\/a><\/p>\n

To make sure you enjoy the MORE PRES control on your RevivalDRIVE pedal with maximum rocking and minimum fiddling, here are some handy hints:<\/span>\u00a0<\/span><\/p>\n

MORE PRES at 12:00<\/strong> \u2013 Some negative feedback. Good clean headroom and more abrupt breakup, like a Fender Twin Reverb or a Marshall Plexi with its Presence control on 0.<\/span>\u00a0<\/span><\/p>\n

MORE PRES fully anticlockwise<\/strong> \u2013 No negative feedback. Gradual and touch-sensitive transition into overdrive with a \u201cwild\u201d character at higher gain settings, like a Vox AC30 or a small Tweed Fender.<\/span>\u00a0<\/span><\/p>\n

MORE PRES fully clockwise<\/strong> \u2013 Lots of negative feedback boosting high end. Crisp and cutting, like a Marshall Plexi with its Presence control cranked all the way up.<\/span>\u00a0<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

What Is Negative Feedback & Why Should I Care? By John Dines –\u00a0 OE Product Manager   So, what is negative feedback \u2013 other than what I receive on school reports, first dates and job interviews? By clicking the link to read this article you have admitted that, to some extent, you are a guitar…<\/p>\n","protected":false},"author":1,"featured_media":7236,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[74],"tags":[],"acf":[],"_links":{"self":[{"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/posts\/8372"}],"collection":[{"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/comments?post=8372"}],"version-history":[{"count":2,"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/posts\/8372\/revisions"}],"predecessor-version":[{"id":9077,"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/posts\/8372\/revisions\/9077"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/media\/7236"}],"wp:attachment":[{"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/media?parent=8372"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/categories?post=8372"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/origineffects.com\/wp-json\/wp\/v2\/tags?post=8372"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}