Designing a "transparent" overdrive/distortion

[YouAre]

When someone is making a "trasparent" overdrive or distortion, are they implementing clipping onto the whole signal or what? When someone says an overdrive is "transparent" what does that really mean?


Furthermore, is it possible to clip and distort only a certain portion or certain frequencies of the signal (say, just the midrange and highs) and leave the rest of the signal untouched (meaning the bass is neither cut nor distorted)? As far as i'm looking at it now, overdrives and distortions distort a certain part of the signal, and the tone shaping of the circuit cut and boost certain frequencies of the pedal. Example: the tubescreamer cuts bass and clips the rest of the signal, and then rolls off highs later in the signal.

I'm trying to get an understanding of how to design an overdrive and what goes into it. Can anyone who's designed a dirt pedal from the ground up describe to me what they used as a base and how they built up from it?

thanks for the help.

~murad

[MartyMart]

http://www.diystompboxes.com/smfforum/index.php?topic=39172.0

Worth a read through first murad !

My take on it , leaving your guitars "sound" and "tone" as it is, ie - no loss of top/mid/bottom.
A very good quality clean full range boost could be said to be transparent - just a volume increase !


MM>

[darron]

you bet you can only clip certain frequencies!

this is probably exactly what you need to be looking at:

http://www.generalguitargadgets.com/richardo/distortion/index.html

i'd say the frequencies that you clip, and then the frequencies that you cut later, play a major roll in how a distortion will sound, from a broken up fuzz to a tight controlled overdrive. for a lot of units limiting the bass is as simple as using a smaller input cap that won't let everything though, and then they simply shunt some highs to ground. the tone control on most distortions controls the EQ after the clipping, so that it doesn't change the nature of the distortion too much, and this is usually just a treble or bass cut. the big muff has a different tone control.

get an opamp, drive it heaps to clip some diodes. then change the diodes to observe the distortion difference. now put an EQ before and after the distortion and go nuts finding all the tones you can.that will give you an idea of what characteristics to look for in future builds

hope that link helps

[YouAre]

you bet you can only clip certain frequencies!

this is probably exactly what you need to be looking at:

http://www.generalguitargadgets.com/richardo/distortion/index.html

i'd say the frequencies that you clip, and then the frequencies that you cut later, play a major roll in how a distortion will sound, from a broken up fuzz to a tight controlled overdrive. for a lot of units limiting the bass is as simple as using a smaller input cap that won't let everything though, and then they simply shunt some highs to ground. the tone control on most distortions controls the EQ after the clipping, so that it doesn't change the nature of the distortion too much, and this is usually just a treble or bass cut. the big muff has a different tone control.

get an opamp, drive it heaps to clip some diodes. then change the diodes to observe the distortion difference. now put an EQ before and after the distortion and go nuts finding all the tones you can.that will give you an idea of what characteristics to look for in future builds

hope that link helps

very interesting article! thank you!

One thing bothered me though. At the bottom where it makes a sample circuit. It says C4+R5 are a low pass filter and R4+C3 form the high pass filter. I thought it was the other way around....If you look above in the article where they make an example circuit with a low pas and high pass filter in the non-inverting opamp, it shows the opposite. Can anyone verify this?

Also, what about transistors? Where can i go to learn about their uses in distortion?

~murad

[axg20202]

Well, I can definitely point you to a perfect commercial example (IMO) - the Barber LTD Silver....the most transparent OD pedal I have ever used without question. (I'm sure others here will have their preferences). When I say transparent, I mean that it does not force it's character onto the tone of my guitar, and there is no mid-hump or cut, or other obvious EQ character. Rather, it complements the existing tone and allows it to shine through and 'bloom', while giving a little dirt if required. This pedal achieves that "my existing guitar tone through a tube amp on the edge of breaking up" tone to a T.

[skiraly017]

Boutique clichés can run amok here! 

What does transparent mean to me? With the pedal engaged, the sound coming out of my amp sound be the same as my clean sound with the exception of added grit. No adding/subtracting of bass, mids or treble. A couple of pedals I've come across that to my ear can do this...

Catalinbread Silverkiss (first version, second revision)
Timmy

IMO, both pedals have EQ's that allow me to dial out the pedal itself leaving only the grit/drive. They are an extension of my clean sound. As always YMMV.

[YouAre]

any DIY circuits of overdrives similar to the catalin/barber i can look at out there to help me out with this?

Also, i was thinking about clean blends. Like, have the clean signal on at full at all times, but blend in the overdrive, rather than blending in clean to the overdrive. This way, if we want to overdrive only the mids, we can have a pedal like the tubescreamer, layered on top of the clean signal cutting the highs and lows, and distorting everything else. This way, we get the clean sound, with select frequencies being distorted. What do you guys think?

[skiraly017]

I'm surprised more people don't incorporate a clean blend.

[YouAre]

I'm surprised more people don't incorporate a clean blend.

i'm pretty sure what i described is a little different than clean blend....its like clean blend but....in a parallel loop with the clean? I think thats what it is...

[Eb7+9]

When someone is making a "trasparent" overdrive or distortion, are they implementing clipping onto the whole signal or what? When someone says an overdrive is "transparent" what does that really mean?

transparent is a loose terms some players use to describe a signal transfer that doesn't take too much away either tonally or dynamically ... of course, a little experience is required to read between the lines and appreciate the dimension of each component in the overall picture of things ... I know marketing lingo refers to "tone sucking" but that's only half the picture - in engineering tonal/spectral refers to the steady-state properties of signal transfer while dynamic refers to the transient-response (steady-state analysis is used to describe the linear aspects of circuitry while transient-response analysis is used to describe the "mostly overlooked" non-linear aspects) ... although separately considered in circuit analysis in real life they both play out together ...

from a player's practical perspective we tend to define two main regions of dynamic operation for OD circuits, one that lies somewhat below the clipping threshold of the hard-limiting devices/mechanisms and the other that lies somewhat well within the clipping realms of the circuit ... with experience players come to realize the pre-clip sound of certain circuits sound "clearer/more-unaltered" than others (class-A circuits can be great for this) ... bypassing the FET switching on a Boss or Ibanez OD circuit is a now ubiquitous example of providing a less-altered transfer response - in this case the correction is mainly tonal ... my SRV-Special mod addresses dynamic fidelity issues in the TS topology ...

the hard-to-pin-point quality that seasoned players start looking for after a while is usually dynamics - hence the affinity for great sounding tube amp circuits and components ... the concept of "dynamic transparency" as applied to OD circuits may sound like martian to a non-player, but simply put some OD circuits have better dynamic transparency than others ... again, this quality is often judged in an OD circuit's capacity to play in it's clean region but it's not restricted to that of course ... the "focused" quality of the clipped sound, all I can think of calling it, is another dimension to the fidelity/transparency/mojo/fi quality or whatever you wanna call it that some players recognize ...

and, both are affected buy the underlying choice of topology used ... especially in op-amp based OD's

if we stick to op-amp based topologies for a second (TS, RAT, etc ...) what we know so far is one tends to produce a more focused hard-clip than the other ... what we also know from theory and analysis is that one configuration of the std op-amp gain stage exhibits less harmonic and dynamic distortion than the other (inv versus non-inv) in it's linear region - some hi-fi minded people therefore don't use that topology in their circuits ... it would be silly not to think those facts have repercussions on our design choices ...

best ...

[R.G.]

So, JC - what's that mean in plain English, and with proper punctuation?

Or, what's the Zen of loose transfer dynamically dimension tonal/spectral regions of below well within clipping realms (?) ubiquitous mainly tonal dynamic fidelity seasoned dynamics martian dynamic transparency clean region focused another dimension topology repercussions?

Ellipsis (plural ellipses; from Greek ἔλλειψις 'omission') in printing and writing refers to the row of three full stops (... or . . . ) or asterisks (***) indicating an intentional omission. This punctuation mark is also called a suspension point, points of ellipsis, periods of ellipsis, or colloquially, dot-dot-dot. An ellipsis is sometimes used to indicate a pause in speech, an unfinished thought or, at the end of a sentence, a trailing off into silence (aposiopesis).
... [note that this use of ellipses is per the surrounding quotation, as I ellipse-d out a jump table.]
The use of ellipses can either mislead or clarify, and the reader must rely on the good intentions of the writer who uses it. An example of this ambiguity is 'She went to... school.' In this sentence, '...' might represent the word 'elementary', or the word 'no'. Omission of part of a quoted sentence without indication by an ellipsis (or bracketed text) (i.e., 'She went to school.' as opposed to 'She went to Broadmoor Elementary school.') is considered misleading. An ellipsis at the end of the sentence which ends with a period (or such a period followed by an ellipsis), appears, therefore, as four dots.

[petemoore]

When someone says an overdrive is "transparent" what does that really mean?
  When 'transparent' sound is important, [ie output looks like a 'transparency' of the input, a synonym for 'clear'], eliminating or removing all distortion, [and 'overdrive' which came to mean 'distortion', a most common and characteristic artifact of 'overdriving' a sound amplification circuit] will achieve satisfactory 'transparent' results.
  Allowing overdriving and distortion to occur, fails to achieve transparency.

[sivnalem]

When I think of transparent for an overdrive pedal I think of how well the pedal allows the  "color" of my pickups through.  One of the reasons I backed away from my rack rig was that all guitars and all pickups sounded alike.  Maybe the only difference was a vaguely woollier(?) sound on neck pickups versus a vaguely brighter sound on the bridge pickups.  Since I have changed to a BSIAB 2 through my bassman (heavily modified with EL34's and trainwreck clone variant circuitry) the sound of my pickups is easily discernible.  Adjusting the guitar volume also shows different shades of tone.   From lightly overdriven to full crunch mode my guitar and pickups show their character.  I'm sure there are other pedals that do the same.  I'll just have to try building some more : ) 

[YouAre]

ok, i figured out what i mainly want!

i want to distort or color a certain part of the frequency spectrum, without cutting or boosting the others. So think of an EQ pedal, but instead of boosting or cutting volume, we're boosting gain. Anyone know how to implement that idea?

[skiraly017]

Overdrive with an adjustable 5 band EQ? 

[YouAre]

Overdrive with an adjustable 5 band EQ? 

....YA KILLIN ME! 

[R.G.]

google "Anderton Quadrafuzz"

[YouAre]

google "Anderton Quadrafuzz"

Very interesting!!!

I heard somewhere that Craig Anderton calls everything a fuzz, whether it be a distortion, overdrive, crunch or fuzz. Is that the case for this product? Also, is it possible to take out the distortion thats in there, and replace it with a distortion of my choice?

thanks for showing me that! the kit is so cheap too!

regards,
murad

[petemoore]

i want to distort or color a certain part of the frequency spectrum, without cutting or boosting the others. So think of an EQ pedal, but instead of boosting or cutting volume, we're boosting gain. Anyone know how to implement that idea?
 google "Anderton Quadrafuzz"
 And check out GEO's 'parallelyzer".
 Parallel signal chains, try not to mix inverted signals with non-inverted ones, use headroom or lack of it to your advantage, consider compression and EQ on distortion or other 'channel' [one of the signal paths].
 Something about opamps and and split/paralleled signals and mixer channels doesn't lend itself to my 'other original' meaning of 'transparent' though.
 All my trials with paralleling signals worked out pretty good when 'this source goes to that amp, that signal goes through to that amp'.
  'mixed back together through the amp' can be cool, just did the trick or tricks I set it up to do, and did take some knob fiddling to get that far, and sounded like itself more than I expected.

[johnadon]

I have to put in my $0.02 worth on this one since my cerebral cortex has been saturated with this topic for about 18 hours now. I just want to mention how easy it is to come to wrong conclusions about builds when comparing builds to others' subjective descriptions of what circuits should sound like. Last night I built about 400 boosters to compare and pair with a Big Muff I just cobbled together. I fully expected to like the AMZ Mini-Booster the best since it's pretty much universally acclaimed. Some of the descriptions I read about the Mini-Booster included 'clean', 'transparent', and 'slightly colored'. Well, my finished product sounded more like a distortion pedal so I immediately decided that I'd committed yet another dumb build error. (Why are the simple circuits the most difficult to get working?) I decided to look for more descriptions of the Mini-Booster on this site just to to be thorough before I started picking apart my board, and I discovered that elsewhere there were descriptions of the circuit as having 'warm overdrive sound' and "mild clipping". At this point I'm not sure if I have a build error or not. I'll find out tonight since I'd like to get the full experience, but I just thought it was apropos to the discussion.

Another case in point would be my Orange Squeezer build. Reviews of the circuit typically described its sound as being "transparent" with "mild but pleasing distortion". It worked right out of the box and my thought was "Wow, this really is transparent!" since I couldn't detect any compression at all. I finally convinced myself that it was compressing, and I was quite happy with it for months. Last week I decided to do some mods to the Squeezer and couldn't get any of them to work so I decided to trace my wiring once again and discovered that I'd never connected one leg of the FET that makes the compression happen. Basically I'd convinced myself that I was hearing compression, when in fact I've had a booster all along. :-)

I guess that's what led to last night's booster marathon... :-)