Sunday, 17 August 2014

Resonant Electronics Acceleron Fuzz

This is a really great sounding fuzz and definitely something different from the norm, so props to Resonant Electronic Design.  You'll notice on the layout there's a cap marked ??? and as you can probably guess the guy who did the trace didn't get the value of that one.  Looking at it though I suspect is may be a 2u2 poly cap because it is next to a 1u poly cap on the board but is physically larger.  I would definitely suggest socketing that one to test, but I think 2u2 is the value I'd try first.  The polarised 1u and 10u caps in this are tantalum and the 470u at the bottom left is rated at 6.3V which should allow you to keep the dimensions down for that one.  The 470u cap in the centre is the main supply filter cap and so will need to be rated sufficiently for the supply you intend to put in it, but if you're using 9V then a 10V cap should be fine as the series reverse polarity protection diode will be shaving around 0.7V off the voltage anyway.  Thanks to skywise for the pics and trace and mmolteratx for the scheme.

Info about the original:
Most guitar players either love or hate fuzz pedals. We found ourselves on the fence. We love the classic tones of Fuzz Faces, Tonebenders, Big Muffs, and other early fuzz designs, but many of them are prone to splatty, overly-compressed sounds when set to anything but the optimal settings. Modern fuzzes can do some amazing tricks and can produce some unique tones, but often they are one-trick-ponies relegated to the bridge of a song, random use during late-night jams.

We wanted to design a fuzz pedal that could do it all and never sound out-of-control or unusable. The task was to create a circuit that could produce vintage fuzz style tones, explosion-esque modern-fuzz-style tones, and everything in between - all without ever getting overly noisy or misbehaving. It took some serious tinkering and an entirely new approach to fuzz circuits, but we did it. This thing will roar, scream, and sing - all at the turn of a knob, and it will never let you down by being unpredictable or unusable.

Just like all of our Field Effects pedals, the Acceleron Fuzz uses a discrete Class A topology and is built with audiophile grade components. This is the fuzz that will replace a pedal board full of other fuzz pedals.

Friday, 15 August 2014

Walrus Audio Mayflower

Thanks to Matt for his schematic for this buffered Timmy.  Info about the original:

The Mayflower is a true bypass, midrange overdrive pedal that falls in-between the Voyager’s low gain preamp settings and the Iron Horse’s full and harmonically rich distortion. The Mayflower boasts a transparent, midrange signal that is great for cutting through or adding to the rhythm. It includes Level, Drive, Bass and Treble controls for a large range of tonal versatility. The Mayflower provides a transparent and organic sounding breakup that allows tweaking and shaping to boost your original tone.

Only one channel of the second IC is being used, and that is only being used to buffer the reference voltage.  There are a lot of pedals that work perfectly well without doing this, not least of which the pedal it's based on, and so as this is a low-ish gain Timmy with buffers I'm not too worried about excess noise.  So to save space this layout removes the second IC completely and just uses a normal unbuffered voltage divider for vref.  I don't expect any significant audible differences between the two so I think this is the one I'd build.

Wednesday, 13 August 2014

Negative and Positive Ground Effects

This question comes up frequently and many of the articles you read about it online can be a little difficult to get your head around sometimes, so I thought I'd just do a short write up on negative and positive ground effects and the problems associated with mixing them.  I am writing this in a way that I think will be easy to understand, but if I over simplify or miss out anything important then by all means post in the comments and I will edit where necessary :o)

One thing that makes this topic confusing for some is that we can often think of the supply having a +9V positive side and a 0V negative, but although this is often perceived to be true, it isn't exactly the case.  With a floating supply like from a battery or isolated power supply there is no point of reference until it is in a circuit and so the only thing we know for sure is that the positive side is 9V greater in potential than the negative.  In a common negative ground effect this makes perfect sense to us, ground is 0V and the positive supply is +9V, but when we build an effect and are instructed to connect what we think of as the +9V side to ground it doesn't compute.

When you have a chain of effects, ground is fixed at 0V by the negative ground effects, and more importantly your amp which is connected to all effect grounds via the sleeves of the connecting cables.  So that "9V connection" to ground you made in your positive ground build is set at 0V by the local connections.  This gives a reference point for the supply, and remembering the negative side going to the supply point of the effect circuit is 9V lower, that determines it must be -9V.  This is why it is never a problem to mix negative and positive ground effects in your chain.  Ground is always 0V with each pedal having either a +9V or -9V supply when in circuit depending whether the ground connection has used the negative or positive side of the source of supply. 

The problem with mixing negative and positive ground effects comes when people try to power them with the same source of supply.  In this instance the power supply isn't floating any more, negative is 0V and the positive is 9V and so making that non-computing connection from positive to ground creates an immediate short which will usually destroy your power supply unless you have one with a fuse or some other sort of short circuit protection. 

So what can you do? 

This is why power supplies with multiple isolated outputs can be very useful.  Because the channels are isolated from each other, they find their point of reference independently and so you can have one powering negative ground effects at 0 to 9V and the other isolated side powering positive ground effects at -9 to 0V.  Then there is no problem in daisy chaining all your positive ground pedals together from one isolated output channel, and likewise daisy chaining all your negative ground pedals together from another.  Always ensuring of course that the current available from each output isn't exceeded by the pedals combined consumption.

As an alternative, and something I always recommend trying with the layouts on this site is to use a charge pump IC to provide a negative voltage.  The charge pump takes a 9V input and gives a -9V output, so instead of connecting the positive side of the supply to ground this allows you to keep all ground connections 0V, and supply the positive ground effect with the -9V from the charge pump.  Common ground, common power supply.

Thursday, 7 August 2014

Danelectro CD-1 Distortion

After checking a few things out, this turns out to be slightly modded Maxon DS-830 (thanks johnk for noticing). The 47p, 10n and 180n cap values are measured on board, so i'd suggest using sockets for those and see what values work the best for you. Anyway. This should be safe to build.

Playing around with the original, this may be one of the most underestimated drive pedals around. You won't be saving any money building one for yourself, but this way you'll be able to tweak the gyrators and clipping diodes to suit your taste.

Heavy British to classic hard rock

Tuesday, 5 August 2014

EHX Big Muff Pi with Tone Wicker

Thanks to Miro for his great work with the trace for this one.  This is more an adaptation than a verbatim clone, but will give you the same results.  The original used a CD4066 quad bilateral switch to do the Tone Wicker switching which seems very much like an unnecessary inclusion when you consider all it is doing is bypassing the 470p base collector capacitors, so it seemed that instead of using a DPDT switch and CD4066 with the associated increase in required board space, it makes much more sense to simply use a 3PDT toggle for exactly the same results.

Info about the original from Electro Harmonix:
The Big Muff Pi with Tone Wicker taps into the sonic power of the legendary Big Muff Pi, but creates new tonal possibilities at the flick of a switch -- or two. Use the Wicker switch to open up three high-frequency filters for raspy, sustaining distortion with top-end bite, or flick on the Tone switch to bypass the tone control for unabated tonal slam. Want the original Big Muff sound? Just switch off the Wicker and turn on the Tone. The ability to create your own personal Big Muff sound is what truly makes this the Wicked Wicker.