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Wednesday, November 16, 2016

El cheapo power soak

Many years ago, when I was but a lad of 19 I had a 50watt valve amplifier and lived in a flat.
That amp was the Peavey Classic 50 head. It sounded great, but boy hoh by was it loud.

Back then I had a job repairing turntables and as a result had access to a catalogue of stuff that just wasn't available in the local Dick Smith (remember when they sold electronics components?).

Anyway, in said catalogue they had this thing called a speaker attenuator. It was a little pricey for my measly wage, but I thought that it might do the trick. It didn't and it has been sitting in one box or another for the last 17 years. That was until this afternoon when I fished it out and took to it with the soldering iron.

You see, I had an idea this morning, it was the same one that I had back in 1999.

I'd been on ebay and was searching for something when I saw a "power soak" that was cheap and looked suspiciously like the thing that I had in my workshop.

After a bit of searching on the commute, I came across this instructable and it turns out I'd been doing it wrong.

You see there was only solder on two of the three terminals, so I guess that I set about wiring it the wrong way.

Wiring it up the same as the instructable yielded the result that I was after so many moons ago!

I don't have the 50 watter any more, but I do have two Fives and a Fifteen.
Now the five can be cranked and not annoy the neighbours, but everything in my crappy little sound booth rattles and its a little unpleasant on the ears after a few minutes.

The fifteen on the other hand, gets too loud at just #3 on the dial.
Nice and clean at this point, but the sweet spot is a little further up the dial.

I've only tried out the attenuator on my Epiphone Valve Jr Half-Stack so far, but it worked flawlessly.
The amp can run full tilt and yield a nice gritty distortion, but be dialed down to almost nothing.

With this design, the amp sees 8 ohms at any level and is now at a nice neighbour friendly volume.

Update:
I got around to placing the power soak into an enclosure this weekend and try it out on my Fender Princeton. The results are good, but not as good as they were on the Valve Jr.

There are a couple of factors at play here at least.
The two biggest that I can identify are A: Power and B: Speaker interaction.

The Epiphone overdrives well and doesn't get nearly as loud as the Fender.
Sure its 1/3 the wattage, but that doesn't mean its only 1/3 as loud.
I've run them in stereo and they're not too different side by side.
The Epi isn't being drowned out by the Fender.
Though the fender does cause more rattling of the fixings in the booth.

The Fender does overdrive, but at maximum it is pretty fizzy and not anything like what you hear when running raw into the speaker at full volume.
From what I can tell, the amplifier / speaker interaction is where the great tone of this amp comes from. When the amp begins to distort, the speaker is working hard and lending its owe character to the overall sound. This seems to complement the amp's natural overdrive and also round out any unpleasant fizz. Either that or the assault on your ears means they can't pick out the nuances.

Dialing back the volume of the amp to (around 4 & 5) the zone where it straddles the clean/breaking up threshold and setting the power soak to just slightly higher than where I had it on the Valve Jr yielded a pretty nice tone. Clean and jangly with nice overdrive when hitting the strings hard.

I usually play with a neck pickup, but the bridge was better when using the power soak.
At a guess, its due to the same reason the overdrive at max volume wasn't great. The speaker plays a big part in the overall tone and maybe the lower frequencies are being rolled off a bit as well.

In conclusion, the price can't be beat for the control it provides over neighbourhood relations even if the unit does change the way your amp sounds. I'd love to try out a more expensive unit to see if they too suffer the fizziness that I experienced. I'm guessing that the answer would be yes due to the speaker not being driven the way it is intended. I still had very useable tone, but it is markedly different to the raw amp experience.

Your milage may vary.


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