low gain distortion unit

[scaesic]

i want to use a distortion unit on a microphone, mainly for the clipping, but i dont want to give it a shit load of gain as this plays havok going into a pa.

is it feasable to modify a pedal to still give a high gain clipping sound, but with greatly reduced gain without using a compressor or anything, just a distortion unit?

[petemoore]

  k...here's my theoretcal take on this:
  distorted vocal amplification as you noted can be alot different than guitar distorting, as far as what you 'want, and the same as far as getting what you want without what you don't want.
  If the PA has horns, you probably want much less complex HF content, especially of any 'unsmoothed clipped' variety, for this a 'sharper' LP filter arrangement at/near output, so as to 'catch anything 'HF-hashy' as it exits. See the amp and speaker emulators at ROG for filters ideas near output.
  Then you have the actuall clipping stage, for that I'd theorize soft/medium clipping, of the 'smooth variety' would be well suited for the task, again this points to the ROG circuits using Jfets, known for 'tube like' clipping sound.
  Tone control of complex or 'simple...just what you need' variety..to adjust the thing for 'more of this without feedback' etc. ...iow very adjustable or basically tuned about where you want it with 'limited/simple' adjustment...I'd cut the bass at the input [with chosen input cap value] at least so the gain stage isn't amplifying a bunch of 'not used' bass content, choosing the value carefully to retain bass response before bass feedback with your system. Putting some tone control before and/or after...choices/alternatives which would increase tunability/flexability over what gets distorted, what gets filtered after distortion etc.
  ...2 or 3 Jfet gain stages seriesed? You can probably get plenty of distortion, adding another Jfet for total of 4, but limiting the gain more on each stage...lots of options here.
  There are lots of circuits at ROG that you could use as a starting point. Listen to and read the soundclip text.
  VOcal distorters can be finnikky, I'd build up probably a couple circuits with flexability built in [say like socket a source to ground connection to adjust gain/use pots sockets here and there like that...breadboard]...
  Here's one I suggest for this...a Jfet Mu amp with voltage starve...build a minibooster, then throw a voltage regulator on the supply, so you can drop the supply voltage down around 2-3v.  high frequency gain drops with higher input levels...compression...soft distortion. It's *my 'Starved Mu' design...but I guess it's very well suited for the application you've described, the only circuit I know of that does 'those' exact things I theorized would be good for PA Distortion.
 
 

[scaesic]

that reply reads like its like extreme modernism prose poetry

[Mark Hammer]

Don't confuse "gain" and output.

When one uses diode-based clipping circuits, the amount of amplification/gain needed to achieve noticeable clipping will depend on two things: the amplitude of the signal you feed it, and the clipping threshold dictated by the composition of the diodes and their number.  As has been discussed here several thousand times, use of different diode types (Schottky, germanium, silicon, LED) will result in being able to achieve different clipping amounts, and combining multiple diodes, and sometimes diode types, will permit zoning in on a specific clipping threshold that results in a given clipping quality/amount.

Given the "natural" thresholds imposed by the diodes themselves, and the typical guitar signal, I have yet to see anything that achieves clipping worth talking about without imposing at least a gain of 50 on the input signal.  Gains of several hundred are more typical.  That's for one stage.  Things like double clippers are a little more complicated because all the gain applied in clipping stage 1 does not necessarily show up as greater amplitude at the input of stage two - after all, it has been clipped in stage 1.  You may have a gain of x100 in stage 1 and a gain of 100 in stage 2, but that is not exactly equivalent to a cumulative gain of 10,000 across the entire frequency spectrum.  But all of that is a digression.

Of course, the key thing to remember is that microphone outputs are significantly lower than guitar outputs.  Unless there is some sort of on-board preamp, you can expect many mics to be about 20-30db below what the average whacked guitar puts out.  Ineed, it is the irritatingl low output levels of mics that makes mic preamps require so much attention to noise and preserving frequency response while maintaining some immunity to hum and noise.

That is the long way of saying that if you plan on getting some sort of distortion out of a voice mic that strives to be "fuzzy" like a guitar, you are going to have to use MORE gain than is normally found on a guitar distortion pedal.  Ideally, you know, the best spot to stick any sort of deliberate distortion circuit in a mic's path would be in the send/eturn loop of a mixer, after it has been boosted.  This will reduce the gain requirements imposed on the distortion so that any noise added will be acceptably low.

[Paul Perry (Frostwave)]

Would a low to high impedance audio transformer help? Maybe you could get the mic signal up to a more guitarish level, and then instead of running the distortion output into a mic input, treat it as though it was a guitar level. Or run it to a DI box to get it back down to mic level.
This problem must come up all the time, as people do the audi thru fx thing more. (OK so Throbbing gristle did it 25 years ago..)

[Paul Perry (Frostwave)]

Can anyone recommend a "universal" mic to line level adaptor circuit? (or commercial schems for same  )
Just looking for something that will get "any common type" of mic up to guitar level. Keen to hear any "mic to stompbox" experiences (shit, I'm sounding like a singles ad )

[R.G.]

Mikes are often about 1/10 the signal level of a guitar. Give it a gain of 10.

[petemoore]

  Some of my favorite ol recordings ...Doors, Elvis, old Blues dudes, early Stones...had a marked 'Tone' to the vocals.
  Sounded like...tube preamp, tube amp, overdriven tube amp, tube reverb etc.
  Sometimes even taking on a 'Harmonica through cranked Champ' type tone.
  Other times sounding like a speaker driven to have less extended freq response.
  Sometimes like a large Horn/Driver only, with mids allowed in...
  With the exception of overdriving a DYNA St 70 into 12's for vocals, [which was great for jamming, but not quite up to 'pro-giggin' standards], distortion in PA is something to be out and out avoided, modern PA's simply don't respond well to any types of distortions, and arent designed to do distortion themselves.
'Demonizing' [see below] being the main exclusion.
  The possible exception I haven't really explored, that being the processor inside the new mixer board our band is using // I've tried the internal effects SP90 [which are probably quite similar] in my Recording mixer, but wasn't too thrilled with any of the distortions on vocals.
  What'd be nice is a Pedalboard beside and for the Microphone, toe down for more distortion/compression/eq change.
  Having a separate tube amp system just to do the 'good 'ol days of tube distortion for vocals is impractical. Big 'ol Tube PA w/alotta low '^scale', low watt 12's or 10's to drivew/horns might be nice...
  Notes:
  Introducing distortion also introduces a multiplicative opportunity for accoustic feedback to get started, as does reverb, echo. This introduces new challenges to using it, building it, tuning it.
  Starting with clean PA system headroom [since this is what most of us have for vocals amplification/reproduction to begin with] will allow more 'room' to play with distortion, eq, reverb, dynamics..
  I suspect it is a similar to the 'road to tube amp like distortion' that circuit tweekers use to make guitars sound 'like tube amp w/load' @ low volume, or utilizing Si outputs...long, bumpy, easily straying the designer farther away, closer, near, but never quite 'on' the target tones, variability that a killer tube rig'll getcha. It can probably be done, or at least something nice and similar.
  Something that distorts Only when sufficient input is 'there' [like when vocal chords emanations are dominating the mic diaphram, thereby intercepting and preventing any accoustic feedback loop from speaker into mic]...because distortion only happens when you're 'on it', when you're 'off it' distortion induced feedback isn't such a problem.
  I've tried amp sims, speaker sims, OD's dist's etc, with limited degrees of succes, but that 'ol tube amp was always big fun.
  There's the modern 'Grunge Death Distortion / sometimes OCtave Down Demon Grind Metal Tone'...a couple bands made cool song with this, seems to be served as the 'main course', from beginning to end of songs it's used in, I'd prefer at most a split a'la Carte order [cameo apperance only]...gets way too 'salty' for me real quick. I don't know what they're usin' to get that...
  It's quandrous to me that they get away with it, must be some sort of noise gate...it Should feedback.
  I'm guessing, and should look, but ask what does that, how variable can it be, and guess it's a digital vocal demonizer type unit 'they' are using. Perhaps there is a unit avialable intended for providing soft distortion for vocal PA use.
 

[Paul Perry (Frostwave)]

PeteM, I would have thought that the more processing done to a vocal before reaching the amp, the LESS feedback there would be. Because, feedback being caused by the amplified sig going back thru the mic and around & around... if you apply distortion, you are chopping off the top of the sig, which should help against feedback, plus if you are pitch shifting, then again you are breaking the loop. In fact those commercial PA system anti-feedback rack units are actually pitch shifters  that push the signal up by .1 to 2 HZ or so.
I expect that the human mind is so set in what it expects to hear from a voice, that it is very sensitive to vocal distortion. Meaning, a little might go a very long way, compared to a guitar.
I'm sure that specialised vocal DSP will be the Next Big Thing. In the same way that movie studios are backing computer generated characters to get away from paying *stars*, the next thing will be completely synthesised character voices.

[petemoore]

if you apply distortion, you are chopping off the top of the sig, which should help against feedback,
  Well here's a point of topic...that's why a guitar sustains at lower output levels with distortion, when distortion is present, instead of a 'smooth waveform, much higher 'transient levels [pressure differences when in the air, voltage differences say in a clipping circuit], the same increased transient forces present with a distorted signal compared to clean is what impact guitar wood/strings to allow amp type feedback at lower volume levels than clean, also what lets you get volume levels much higher before feedback with a more substantial PA system that doesn't distort and 'hit' the diaphram of the microphone in a frequency that is 'sympathetic vibration sensative'.
  plus if you are pitch shifting, then again you are breaking the loop. In fact those commercial PA system anti-feedback rack units are actually pitch shifters  that push the signal up by .1 to 2 HZ or so.
  >  Thank You...that makes sense...
I expect that the human mind is so set in what it expects to hear from a voice, that it is very sensitive to vocal distortion. Meaning, a little might go a very long way, compared to a guitar. All a matter of taste, this sounds like a good recipe to me.
I'm sure that specialised vocal DSP will be the Next Big Thing. In the same way that movie studios are backing computer generated characters to get away from paying *stars*, the next thing will be completely synthesised character voices. AKkkkk...already happening to some degree or another I suspect...could be cool, but I'd guess artistic use of such effects would be limited, time consuming...isn't that kind of the thing Cher uses for 'Life After Love'? A digital replication of her voice, inflections, prununciation are played on a keyboard...there are a couple other songs, actually quite a few with recognizable 'tuning alignment' processing sound.

[d95err]

...isn't that kind of the thing Cher uses for 'Life After Love'? A digital replication of her voice, inflections, prununciation are played on a keyboard...there are a couple other songs, actually quite a few with recognizable 'tuning alignment' processing sound.

(A bit off topic I suppose)

The "Cher" effect is just a regular auto-tune, AFAIK. You can set it up to allow only a few notes in the scale and anything in between will be pushed to the closest value. Once it starts pushing the vocals more than half a step or so, you get the effect.

I could write a long rant about how much I HATE that effect. On Life After Love, it was done elegantly, subtle and really lifted the song to a new level. Nowadays every B-producer uses it to hide the fact that their big-breasted models actually can't sing at all. Hearing it on any song (except Cher's "original") is like a big neon sign saying "THIS ARTIST AND THIS SONG REALLY SUCKS, BUT WE'RE TRYING TO HIDE IT!". My hand instintively switches channel on the radio within a few milliseconds of such an effect appearing in a song...