The Aefea Drive - a simple one-chip diversion

[nocentelli]

The 4k7/220nf an 3k3/47nf networks exploit the Proco Rat trick of providing differing amounts of gain for the lows and low mids, and the upper mids and highs.  The 3k3/47nf network provides a bit more gain for content above 1khz.  At absolute maximum gain, the gain is 228x for stuff above 1026hz, and 160x for stuff below that. 

I would also assume both resistors caps are hanging off the inverting input.

[Kipper4]

Mark (Bluebunny) All those are joined.
I can confirm Simons Layout too. I built mine in perf.
Mr Hammer this has to be one of the most tonally adjustable drives I've ever built. I made the change to 30k and 39nf this morning just to test and its awesome.
I'm gonna see if i cant scrounge an on off on switch tonight at work.
Anything from a rat to a screamer to a zen and i havent even tried it with humbuckys yet.
Thanks Mr H

[bluebunny]

Mark (Bluebunny) All those are joined.

Thanks Rich - thought so.  Eager now to build and hear this one for myself!

[Kipper4]

PS I'm using a 500kA for the shape.

[Mark Hammer]

Mark (Bluebunny) All those are joined.
I can confirm Simons Layout too. I built mine in perf.
Mr Hammer this has to be one of the most tonally adjustable drives I've ever built. I made the change to 30k and 39nf this morning just to test and its awesome.
I'm gonna see if i cant scrounge an on off on switch tonight at work.
Anything from a rat to a screamer to a zen and i havent even tried it with humbuckys yet.
Thanks Mr H

Well that put a big smile on my face, so thank YOU.
BTW, I'm assuming the "39nf" you refer to above is merely a typo and is supposed to be 3n9?  or have you stumbled onto something that improves it?
Finally, thanks for confirming the layout.  I also built it on perf, so it's nice to know I have something more reliable to turn to.

[samhay]

Looks like a nice design Mark. I simmed it and the tone section certainly looks nice and useful.
I guess the two pots in the op-amp feedback loop are fairly interactive and I wonder if replacing the 250k pot with another on-off-on toggle switch might work better (at least in terms of being able to find that sound again).

[Mark Hammer]

Yeah, I think there are a wide variety of other options, such as the one you describe.  Heck, it could be as simple as sticking a 3-position toggle to select three different resistances in series with the diodes, and just leaving the gain pot and feedback cap in the more traditional arrangement.  Essentially, an SD-1 clone with a choice of resistances for softer or harder clipping.

Me, I just liked the idea of the reciprocal control that essentially says "Oh, you want harder clipping?  I'll show YOU harder clipping!"  .  But that doesn't have to be everyone's taste.  The softer clipping thing works fine without it, and the co-star tone-section can be tacked onto just about anything you want.

[vigilante397]

Does anyone have sound clips of this one yet? I've been considering finding something to replace my RAT but haven't found anything that can quite do the job yet?

[Kipper4]

Yep my mistake  I meant 3n9.
I played with the drive a fair bit this morning it has lots of different tone and gain possibilities.
I found it to interact nicely with with the guitar volume and tone controls too.
I.really liked how I.could set a low amount of gain, shape the tone with the 500k and low pass post and it responded well to the different playing dynamics.
I liked some of the fuzz like tones and TS type settings too.
It's small footprint and low parts count is also a bonus.
Maybe some more power supply filtering might be something I'd consider in future.
I used 1N914 diodes too.

[Mark Hammer]

Does anyone have sound clips of this one yet? I've been considering finding something to replace my RAT but haven't found anything that can quite do the job yet?

It's flexible, but I doubt it would cover ALL the terrain of a Rat.  Big difference in max gain.  But having a Rat clone, I will say that it covers some of the same turf.  Like the name says: *almost* everything for everybody....almost.

But you have me curious now.  I 'll pull out my Rat and try to A/B them.

[vigilante397]

Does anyone have sound clips of this one yet? I've been considering finding something to replace my RAT but haven't found anything that can quite do the job yet?

It's flexible, but I doubt it would cover ALL the terrain of a Rat.  Big difference in max gain.  But having a Rat clone, I will say that it covers some of the same turf.  Like the name says: *almost* everything for everybody....almost.

But you have me curious now.  I 'll pull out my Rat and try to A/B them.

That would be awesome. And frankly it still might do everything I need. There was a time when I was younger and I had to crank the distortion to '11' or every riff, but I'm finding with my RAT clone and my current playing style I rarely if ever turn it much past 12 o'clock. It still sounds great even maxed out ("this thing doesn't have a single unusable setting!"), but it's not what I need for the band I play in right now.

[deadastronaut]

There was a time when I was younger and I had to crank the distortion to '11' or every riff,

yep , me too, but now i find i like tone too...in fact i dug out an old multi fx and went through a few patches ''all on 11 ' ' dropped the distortion level

and what dya know, i could hear the notes, not a load of fluff ''around'' the notes...at around ''3-4'' was nicer and still had an edge. ...its surprising how much not maxing it matters...especially loud.


looking forward to clips/vid of this mark...or whoever builds it..

[bool]

The math behind the "11" phenomenon is simple. Very simple in fact.

When you "hear" a record, it was in most cases recorded with multi-tracking (n * "doubling") guitar and other tracks, even on older records. Higher harmonics add together just as the root tones do. IOW, distortion "adds up" with the amount of multi-"doubled" tracking.

This is what you hear from the record, and this is what you want to hear when you (alone or with a bandmate or two ...) want to reproduce tonally. So, IOW, you want "11" to fill up the void.

Especially with slightly untrained ears that just want to hear "the oomph" and not really the exact tone they're playing. Which changes somewhat proportionally with the amount of time you play your instrument.. I'm not going onto details but there is a time when young guitarists discover "tonal nuances" and go reall nuts for a while trying out to find "their tone".

What in the world are you spending your time on forums like these if not for the above truism, haha?

[vigilante397]

I agree completely with the above explanation, but I had another reason for cranking to '11,' which was simply that I wasn't a very good guitarist Sloppy playing sounds less sloppy when you have a sloppy amount of distortion on it. I used my distortion to cover my mistakes. I don't claim to be a great guitarist now, but I've come a long way and have gone from distortion on 11 to a nice overdrive between 3-5 depending on the song. As I said, the RAT does it very well, especially when I want it a little heavier, but it's not quite what I'm looking for when I just want a tiny bit of breakup on my drive.

looking forward to clips/vid of this mark...or whoever builds it..

Also 

[Mark Hammer]

Okay, some crude sample clips.  Two are comparing a Rat and Aefea, and two are extended trips through the tone controls at different lighter and a few harder clip settings.

Clips are my Turser Nashville Tele w/pickups I wound into the pedals into a 5F2-A Princeton and a Blue Snowflake to pick it up.  Since I shot it at low res to make the upload fast, I should mention that the controls are - clockwise from lower left - Level, Shift, Clip, Gain, with the 3-position Mode toggle in the middle.  Clockwise on the Shift pot moves the lowpass rolloff upwards.  Clockwise on the Clip pot reduces the resistance in series with the diodes, and increases the feedback resistance to produce more gain.  The Mode switch is scoop setting when flicked towards the stompswitch, variable lowpass-only in the middle position and variable lowpass+ full-spectrum-bypass in the upwards position. I futz around with the Shift and Mode controls a lot to show how tonally flexible it is.  The Rodent is a GGG layout and I use an LM308.  Not crazy about the taper of the gain/drive pot in it, though.

Enjoy

https://www.youtube.com/watch?v=sWiRd-N2_ik
https://www.youtube.com/watch?v=wSGYA11LRSg
https://www.youtube.com/watch?v=kJut7j00PYQ
https://www.youtube.com/watch?v=Fe_hnEMbG1A

[J0K3RX]

Sounds great! Curious how this would sound driving an already over driven/high gain amp? Wonder if it will have that tube screamer effect on the bottom end with the gain almost all the way off and the level almost all the way up? .... hmmmmm  might have to build and see..  I like the 20k pot notch thingy at the output!

[deadastronaut]

I like the 20k pot notch thingy at the output!

yeah looks/sounds interesting, might have to try that

3rd clip sounds almost identical to ratty at the beginning.. ..cheers mark.

[Mark Hammer]

The Rat clone does have more bottom.  Hard to tell, I guess, with an 8" speaker (albeit a nice JBL 8") at a level that lets people elsewhere in the house watch TV. 

As for overdriving a ready-to-break-up amp, well that's clearly going to have to be someone else's task.  I did try to go back and forth between effect and bypass levels to give a sense of how much increase in level is attainable.  It's certainly not a lot, but there are a variety of settings where it is comparable to a TS-9 in output level.  Because of the level-limiting effect of the diodes, highest output levels will be achieved in soft clipping settings.  And rotating the Shift control to its highest rolloff point will also allow for greater output level.  As a happy coincidence, that probably yields the most useful overdriving signal.

[charger]

I'm digging this one, I built it off Mark's vero layout from tagboard effects.  I subbed 30k and 3n9. The output level is good, it's at unity at around 1-2 o' clock depending on the switch and Hardness settings.  Realized after I built it I should have used an on-off-on switch instead of on/on.  I've been looking for a pedal for my Epi Valve Jr which is on the dark side... this fits the bill. Was previously using a home-built Morning Glory, but after I sold that, and my replacement build failed, I thought I'd try something new. Definitely bright, gainier than the morning glory, and I like the increased clarity of low freq vs high freq distortion.  A lot of tweak in the hardness knob.

[Mark Hammer]

Thanks for the feedback.  I'm tickled that a tagboard layout appeared so quickly and that folks have already built it (although that's the sort of response one ought to expect when describing something as a "simple one-chip diversion", I guess).

Realistically, there are probably a few alternatives for shaping the high end.  One is certainly to drop the value of the 4n7 cap down to 3n9.  That will raise the corner frequency where high-end passes through unobstructed, and in so doing chop the level a bit. 

On the other hand, if you like the content brought in by 4n7 but just wish it was so in-your-face, you can simply stick a fixed resistor in series with the cap.  I'll suggest 3k9 to 4k7 might yield a suitable balance between bottom and top end.  Alternatively, a person could stick a 5k or 10k trimpot in series with the cap, wired up as variable resistance, and just dial in how much top end they want, and leave it at that.