Overdrives - To clip or not to clip

[Electric_Death]

I've been tinkering with some overdrives completely op amp driven and have been unsure about adding clipping diodes. I'm curious to know what the veterans here think or prefer anyway, a massive clean boost, a large boost with some soft clipping or a large boost with hard clipping?
Is there a huge benefit to hard clipping?
I'm sure I'll be building a variety of all 3 as time goes on but the hard clipping I suspect will deliver the best pinch harmonics but will probably have the most noise issues due to the level of gain needed for it to have an efficient amount of output. From what I've seen here, a lot of you guys have probably built easily 2 or 3 dozen distortion boxes alone! So far all I've built are clean boosts and soft clipping circuits designed from scratch, I'm awful happy but of course I'm also now awfully addicted

Another preference I'm curious about is tone stacks, bandpass filters, active EQ's and of course, the ever so popular parametric EQ's. The parametric designs I've looked at really have me interested but I have to wonder about the highs. My experience has been that when you start toying with your treble bandwidths, the best sound comes from picking a select frequency rather than a parametric range.

The one thing I have learned for certain from these DIY sites and forums is that no matter what I see on the market, the stuff I see guys designing and building in their own workshops beats the snot out of the commercial products be it amps or pedals and for that matter, chip, transistor or tube driven.

[Minion]

Generally you won"t get a Very Good overdrive sound useing Just opamps because Opamps do not clip very gracefully ,you might get a better Clipping sound useing a Fet Input opamps but generally even these don"t sound very good when overdriven.....

Maybe try useing an Opamp to Overdrive a Jfet or Transistor (simular to a rat) and/or use several trypes of Clipping Diodes in different Places to get a wider Variety of Clipping sounds ,Like Try a couple different types in the Feedback loop connected to a switch so you can enable or disable them and try a couple types at the opamp output with a switch to enable or disable them and then you shoul;d be able to get a wide variety of Overdrive/Distortion......


Cheers

[petemoore]

I've been tinkering with some overdrives completely op amp driven and have been unsure about adding clipping diodes.
  Overdrive is a funny word, I'm not always certain I catch it's intended meaning.
  I'm curious to know what the veterans here think or prefer anyway, a massive clean boost,
  I'll answer like it's a poll:
  a massive clean boost: see Large boost
a large boost with some soft clipping: That'd be a Mini-Booster @3 after TC into small tube amp, yes.
  or a large boost with hard clipping?
  Is there a huge benefit to hard clipping?
  If you like the tone of it as I do...
  I'm sure I'll be building a variety of all 3 as time goes on but the hard clipping I suspect will deliver the best pinch harmonics but will probably have the most noise issues due to the level of gain needed for it to have an efficient amount of output. From what I've seen here, a lot of you guys have probably built easily 2 or 3 dozen distortion boxes alone! So far all I've built are clean boosts and soft clipping circuits designed from scratch, I'm awful happy but of course I'm also now awfully addicted
   The clean boosts and soft clipping circuit may lend themselves to being part of [circuit fragments of] the hard clipping circuit of choice.
  Amp type has lots to do with it too, this can a large part of the clipping sound equation.
Another preference I'm curious about is tone stacks, bandpass filters, active EQ's and of course, the ever so popular parametric EQ's. The parametric designs I've looked at really have me interested but I have to wonder about the highs. My experience has been that when you start toying with your treble bandwidths, the best sound comes from picking a select frequency rather than a parametric range.

The one thing I have learned for certain from these DIY sites and forums is that no matter what I see on the market, the stuff I see guys designing and building in their own workshops beats the snot out of the commercial products be it amps or pedals and for that matter, chip, transistor or tube driven.

[shredgd]

I'm not a veteran, but I can say you usually need some diode clipping in overdrive pedals because they let you acheive a balance between clean and overdriven tones. If you never use a clean tone, then you *might* like just pushing the front of your tube amp with a booster; otherwise you will always end up with a drop in volume whenever you turn your dirt-box off or, even worse, a nasty 30dB increase in volume when you engage it... Ouch! My eardrums are already aching!!..

Giulio

[GibsonGM]

To add to Shredgd's answer, yeah - to get a nice fat dirty sound from a tube amp, using a clean booster like AMZ Mosfet boost, requires such an increase in the output from the booster, that you have to have your amp on 1 and pedal on 10!! 

Any circuit with diodes in the feedback loop of the OA will be a softer clip than diodes at the output.   Looking at many schematics, you'll start to see patterns by which the amount of clipping is controlled.   Check out the AMZ site for some ideas on this....a pot can be inserted before the clipping diodes on the output to "dial in" the clipping level, etc.
 
So it really just depends on what you want to do, what your amp is like, and how much headroom you have.  Pushing an already-dirty amp doesn't take much....making a clean amp sound like Angus takes either a LOT of volume or some clipping elements in there to create some mud ) 

[bipedal]

FWIW:

I'm toying with building diode clipping + opamp circuit a la Tube Screamer and kin, but adding a dual-ganged pot to serve as dual variable resistors on either side of the clipping diode series - sort of like gates between the main gain loop and the diodes.  Thought this might be an interesting way to tune the amount of diode clipping flavoring within the gain loop.   

Anyone tried something like this before?

This idea just occurred to me, so I'm not sure what's a good starting point for the dual pot's resistance.  That control ought to be quite interactive with the Drive pot when it comes to the distortion grit.  Also, I suspect that there will be a significant impact on output volume when diodes are blocked by the resistors compared to when Vr is 0 and the diodes are "all in"...

Cheers,

- Jay

[Minion]

I am actually doing the Same thing for a Simple Bass amp I am designing......I have 2 Clipping Diodes at the output of an Opamp with a switch to put the Diodes in curcuit or out of Curcuit and it has a 10k Pot between the Diodes and Ground so you can tune it the amount of Clipping ....I sort of Got the Idea from looking at the Dirty Sanchez Pedal project..... For the Bass amp Tone controlls I am useing a 15 band EQ from a Old busted Rane ME15 eq that had a Bad Channel.....

[bipedal]

Minion,

I'm curious: how did you arrive at the 10k value for the clipping "blend" pot in your projectt?

I know diodes won't start to clip until a certain current level is achieved (germs and LEDs clip at lower current than silicons, IIRC).  I was thinking that in a Screamer type of circuit I'd need rather large resistance values on either side of the diode loop to effectively pull them out of the signal path -- like in the 500k range -- but perhaps I'm overshooting significantly...

Regards,

- Jay

[Electric_Death]

I'm not a veteran, but I can say you usually need some diode clipping in overdrive pedals because they let you acheive a balance between clean and overdriven tones. If you never use a clean tone, then you *might* like just pushing the front of your tube amp with a booster; otherwise you will always end up with a drop in volume whenever you turn your dirt-box off or, even worse, a nasty 30dB increase in volume when you engage it... Ouch! My eardrums are already aching!!..

Giulio

shredgd I think that's where the title of the pedal is misleading. The term overdrive is in terms of what this pedal/preamp is to do to your amp. Whether it has distortion or not doesn't change it's purpose. I find this with all things in life though, you hear a term for your entire life and it takes on almost a folk lore definition but one day it clicks and you catch on to the fact that we're taught by the world around us to misinterpret things.

I recently designed an op amp circuit from scratch. So far it's two versions, one that is just a clean boost and another that has a clipping stage. The clean boost is low gain and I really liked it but the one with a very mild level of soft clipping(you really can't even hear it), definitely outperforms the clean. I'm waiting on some parts so I can step up the non-clipped version and let the two battle it out. The huge factor leading me to believe I'll prefer the clipped version is the way it works with my high value linear pots.
I get all the richness of my volume set on 10 as I do with it on 2 but it's tame enough for blues and other low gain styles without compromising response, sustain or bandwidth.

Why am I still talking......
Maybe overdrives should be more straight forward, simplistic circuits since their purpose is so basic. Most overdrives are really just distortion pedals and don't overdrive our amps distortion much at all.

[johngreene]

shredgd I think that's where the title of the pedal is misleading. The term overdrive is in terms of what this pedal/preamp is to do to your amp. Whether it has distortion or not doesn't change it's purpose. I find this with all things in life though, you hear a term for your entire life and it takes on almost a folk lore definition but one day it clicks and you catch on to the fact that we're taught by the world around us to misinterpret things.

So how does your definition of an 'overdrive' differ from that of a 'booster'?
What if someone calls a pedal an overdrive because it sounds like an amplifier being overdriven?

[Minion]

Minion,

I'm curious: how did you arrive at the 10k value for the clipping "blend" pot in your projectt?

I know diodes won't start to clip until a certain current level is achieved (germs and LEDs clip at lower current than silicons, IIRC).  I was thinking that in a Screamer type of circuit I'd need rather large resistance values on either side of the diode loop to effectively pull them out of the signal path -- like in the 500k range -- but perhaps I'm overshooting significantly...

Regards,

- Jay

I just chose that Value because it is the Value used in the Dirty Sanchez Pedal project, it suggests useing a 10k or 25k pot but I am sure that you can get different sounds useing a different Value or maybe bypass one of the Diodes with a Low Value Cap to get different tones...??

[Electric_Death]

shredgd I think that's where the title of the pedal is misleading. The term overdrive is in terms of what this pedal/preamp is to do to your amp. Whether it has distortion or not doesn't change it's purpose. I find this with all things in life though, you hear a term for your entire life and it takes on almost a folk lore definition but one day it clicks and you catch on to the fact that we're taught by the world around us to misinterpret things.

So how does your definition of an 'overdrive' differ from that of a 'booster'?
What if someone calls a pedal an overdrive because it sounds like an amplifier being overdriven?

It's job is to overdrive your amp, not overdrive itself which is why it's called an overdrive. Doesn't matter whether it does it with clean gain or clipped gain.
If you want a pedal that fits your misunderstanding of the definition, you can always make a pedal called the overdriven booster or the overdriven overdrive

[oldschoolanalog]

I know diodes won't start to clip until a certain current level is achieved (germs and LEDs clip at lower current than silicons, IIRC). 

IIRC diodes don't conduct until their forward voltage is exceeded. This conduction manifesting itself as clipping.
As always, I could be wrong... Anybody have some thoughts/insight on this?

[bipedal]

oldschoolanalog -

Thanks for the correction, I used the wrong terminology in regards to the operation of clipping diodes -- it is voltage, not current.

I just stumbled across this nice primer on diode clipping -- looks like it was part of Aron's "old" stompbox site, don't know if it's linked to the wiki:
http://www.diystompboxes.com/pedals/diodes.html

- Jay

[oldschoolanalog]

I just stumbled across this nice primer on diode clipping -- looks like it was part of Aron's "old" stompbox site, don't know if it's linked to the wiki:
http://www.diystompboxes.com/pedals/diodes.html
- Jay

Good stuff! Thanks for the link.
osa