The Aefea Drive - a simple one-chip diversion

[vigilante397]

Mark, your demos have pretty well sold me. I'm going to have to build it. It doesn't seem to have as much face-melting distortion as the RAT, but I think that's probably fine for me.

Did we establish that the PCB transfer earlier in the thread was verified?

[maartendh]

First one of the Hammer Palindrome series?

Hope to build it soon.
Maarten

[Kipper4]

I built mine on pref from the layout in this thread

[Mark Hammer]

First one of the Hammer Palindrome series?

Hope to build it soon.
Maarten

Actually, because we're in the midst of a provincial election here, I was all set to call it "The Candidate".  But then I thought, well, if it's trying to be everything to everybody, then why not just call it that?  I was going to call it Almost Everything For Almost Everybody, but that would have been AEFAE, whjich just sounded weird (Ay-Fay).  Aefea sounded more exotic, so I went with that.  Never really thought about it being a palindrome.

[vigilante397]

I built mine on pref from the layout in this thread

That should mean the layout is fine and it should be good to etch, yes?

[bluebunny]

Never really thought about it being a palindrome.

AEFEA = chords to a song, perhaps?   

[Frank_NH]

Hi Mark,

Thanks for this design.  I plan to build it based on IVIark's vero layout at tagboardeffects.blogspot.com.

Some have reported that the sound is "bright" depending on the gain control settings (perhaps too bright), and I was wondering if (in addition to your suggestions) this could be tamed by modifying the the 4k7/220nf an 3k3/47nf networks in the gain part of the circuit.  Maybe reduce the high frequency gain?  Or would this change the character of the sound too much?

[Seljer]

Hi Mark,

Thanks for this design.  I plan to build it based on IVIark's vero layout at tagboardeffects.blogspot.com.

Some have reported that the sound is "bright" depending on the gain control settings (perhaps too bright), and I was wondering if (in addition to your suggestions) this could be tamed by modifying the the 4k7/220nf an 3k3/47nf networks in the gain part of the circuit.  Maybe reduce the high frequency gain?  Or would this change the character of the sound too much?

The 4k7/220nf an 3k3/47nf networks control the low end gain

If you want to tame the high end increase the 100pF in the feedback loop

[Mark Hammer]

Very reasonable suggestion.  Note hat the feedback cap will interact with the gain and "hardness" pots such that the higher the total feedback resistance, the lower the rolloff (i.e., it gets brighter at lowest gains, and rounded off more at highest gains.)

I find the middle position on the mode switch, where the signal can only reach the output via the variable lowpass filter, yields the tamest highs.  I imagine most folks will only find it useful when the gain is turned up to some appreciable amount.

[earthtonesaudio]

Never really thought about it being a palindrome.

AEFEA = chords to a song, perhaps?   

I propose that all future demo clips of this pedal must include this chord progression.

[Mark Hammer]

I just strummed that progression now, and boy, if that doesn't have The Ventures and The Shadows written all over it.

[mitchelr]

Not made it yet but I've got my   A.E.F.E.A  chord sequence backing track ready.
https://dl.dropboxusercontent.com/u/54139522/aefea.mp3

[Frank_NH]

Well, I have the veroboard prepped, but had to order some pots and a 3.9 nF cap    Getting all that from SmallBear (thanks Steve).  Hope to have it done by next weekend.

I'm still thinking that modding the 4k7/220nf an 3k3/47nf networks would be interesting, but I'll build it stock for now 

[bluebunny]

All this interest triggered me into doing a perf layout at the weekend, with onboard pots.  I should have all the parts, so I'll gather them together this evening and try to get it built.

[Kipper4]

Can't wait to see what you think of it Bunny.

[Mark Hammer]

Well, I have the veroboard prepped, but had to order some pots and a 3.9 nF cap    Getting all that from SmallBear (thanks Steve).  Hope to have it done by next weekend.

I'm still thinking that modding the 4k7/220nf an 3k3/47nf networks would be interesting, but I'll build it stock for now 

The dual ground legs employ a strategy similar to the Tube Screamer in providing a gain advantage for the mids, such that they are nudged a bit closer to the clipping threshold in order to provide about as much clipping of the lows AND highs (lows will nearly always be higher amplitude, therefore clip more, if not adjusted).  The TS and its kin employ only one ground leg, with a bass rolloff that starts around 720hz, and lops off 6db at 360hz and another 6db at 180hz.  The dual-leg approach I used is essentially flat from around 150hz to a little over 1khz, and then adds more gain above that.  So there is a midrange advantage, as in the TS, but not quite as much bass loss.  A happy medium.

But there is no reason that it needs to be that way.  So, strapping a 12k or 10k in parallel with that 4k7 would get you a bass boost, and effectively de-TS-ify the circuit.  That may, or may not appeal to some, but at least is simple to implement, and reverse, with a SPST toggle.  It will certainly make the mid-scoop setting on the Mode switch more obviously bottom heavy, and create a greater impression of midscoop...which, I suppose would make it even more for almost everybody. 

[vigilante397]

Well I finally got around to etching it as per the transfer earlier in the thread. Got it all drilled out and populated today. Everything was great and I was ready to try it out...until I realized I don't have any TL071's  They should be here Monday, so we'll see how it goes.

[Mark Hammer]

I suspect any single op-amp with the same pinout will do.  I just happened to use a TL071.

[vigilante397]

I'm going to have to look through the bins to see what I have. I know TL072 is a different pinout, it looks like NE5532 is different as well. I know I have some OP something-or-others lying around but I can't quite remember the number so I'll have to check the pinout after work

Do you know of anything off the top of your head with the same pinout?

[Mark Hammer]

LM741, TL061, TL081, CA3140

NE5534 has the same pinout and is half a 5532.