james low

I’ve been experimenting with some of the cheap class d amplifier boards available on eBay from china. This is the PAM8610 board with a Wampler Euphoria clone as a preamp. I added a footswitch that footswitches between clean and overdrive. It switches between two separate gain pots for clean and overdrive, removes the clipping diodes for clean, and adds a lead master in overdrive mode. I did some tests with this setup in separate enclosures, and there was very little hum, but as you can see from the video, there is tons when in the same enclosure. Maybe I have something poorly soldered, or maybe things are just too close together. Still it would be cool if a real manufacturer did something like this and sorted out all the issues because it doesn’t sound bad other than the hum. I might get another one of the boards and put it by itself in it’s own box. I’m powering it with a Mooer 2000mA power supply, but a one spot or anything over 1000mA should work, and it should take anything up to 12V.

Here’s some pics of the project. Notice I had to cut some of the plastic housing from the input jack, as well as bend the legs to make it all fit. The chassis is grounded, but the speaker output is isolated from the chassis. I kind of wish I’d used the deeper 1590BS instead of a 1590B so that there was a little more room.

After building a 2 in 1 overdrive, I’ve got interested in building more pedals, so here’s a few of the PCBs manufacturers I’ve found. Please let me know if you have more to add.

I had the idea that it might be more useful to have an overdrive with a contour control rather than a traditional tone control on it. I found this mid boost/cut circuit and added an overdrive section to it. It’s no the best sounding overdrive in the world, but here’s the schematic and a quick demo.

Just a couple of volume pedal ideas I had; To modify something like the Hotone volume/wah, and instead of having it manually switchable between a wah and volume, to use the built in footswitch to determine what mode its in.

1) The first idea I had was to have a volume pedal with a built in footswitch (like a wah). When you use the volume pedal normally its between 0 and unity gain. When you click the footswitch a boost is engaged.

2) The second idea I had was to have a volume pedal/expression pedal in one. It would have in/out jacks for the signal, then and additional TRS jack for expression. When you click the footswitch the pedal changes to become an expression pedal (and the audio signal just goes straight through).

I’ve been wondering about tinkering with a guitar amplifier that runs of a 9V power supply for a while now. I tired a Diago Little Smasher which was loud and great for distorted tones, but not quite loud enough, or enough bass for clean. There are some cheap preassembled boards on eBay using the PAM8610 chip, they rated 10W, but this is probably only at 12V into 4ohm. I got a couple and these are the results:

Summary:
Red board:
– More expensive
– More bass
– Treble roll off
– Quieter (but can be as loud with a boost/preamp before it)
– Smallest enclosure probably a 1590LB

Black board
– Cheaper
– More hum
– Less bass
– More Treble
– Louder (without preamp)
– Smaller, would fit in 1590H enclosure to make a tiny but loud amp!

Overall I think I liked the tone of the red board more, but I’ll probably put both in some projects.

Another one of those contentious topics that seem to have strong supporters on both sides. I can’t change what most people think, but it helps me to just get my ideas out somewhere. Here are a few random ones:

• Are boutique pedals that much better than mass produced pedals (whether made in the west or in the far east)? Probably not, but that doesn’t mean that the price isn’t justified. Labour costs are more in the west, as well as more stringent environmental practices.
• So is it just ethics and there’s no difference in tone? I would say no to this too. There will be some differences. The amount you pay for a product made in America is also going towards skilled designers that spend more time tweaking a pedal till it sounds good. This not only includes the circuit, but the layout of the PCB, which can affect things too. Some boutique companies also individually test components to find the ones within really tight tolerances.
• Which should I buy then? Buy what you can afford, support people doing new designs, because part of the cost of the pedal isn’t just the components, but the time taken to design it, which fewer people will do if their designs just get made for cheap in China. Finally think about how a company is treating it’s employees or the environment. There are some places in China where electronics waste is just being dumped, hurting people there, but eventually all of us as it gets into the food chain.
• Are there any people doing unique designs in China? J. Wong who has worked with many of the well known Chinese brands now has his own pedals with Tone City. Some of these seem to be unique designs. JOYO too seem to have moved on from just copying other designs to some more unique products in recent years.

Much has been written about this, it seemed that there was a preference for true bypass. This has slowly shifted towards believing buffered bypass results in less “tone suck”. You still see people on forums simply saying one is always better, but it is of course more complicated than that, and you may want one of the other depending on the situation. Here’s my list of reasons why.

Reasons for true bypass:

• You may want true bypass if the pedal has a bad buffer in it. This seems to have been the problem with lots of BOSS pedals in the 80s and 90s, which is probably why the true bypass fad started.
• You may want true bypass if you’re putting the pedal before a fuzz or other germanium vintage vintage pedal. These pedals sound classic when they’re working with your pickups impedance, not with the impedance of the output of a buffer.
• You may want true bypass (or at least analog bypass/dry through) if you have a digital pedal, and find that you don’t like the sound/feel of your signal going through the digital converters.

Reasons for buffered bypass:

• If you have a good buffer, you may get less loss of high end through long cable runs / multiple pedals.
• If you have a time based effect like delay or reverb and you want “trails”, the effect to continue till fade out after you turn it off.
• For things like long press or tap tempo in a single switch (although this is possible with relay true bypass as well).
• You can have switching with things like MIDI or other remote options (again possible with a relay too).