The filter capacitors in many amps are mounted in a metal can, which can be an obstacle to successfully recapping the amp. These days, filter cans are only made in a limited values, so it's hard to find the exact match. Mounting the caps outside of the can is another option, but finding the space can be tricky. Removing the can can leave a giant hole, which can allow dust to enter the chassis over time. So, what's the best way to replace can-style filter capacitors?Read More
In Part I of our guide on fixing hum, we listed some easy fixes. In Part II, we’ll go into further detail on techniques that require some prior electronics experience to execute. It’s worth checking out Part I first, because it listed some simple, non-invasive things that you should always be tried before diving into the amplifier’s circuitry. For the purposes of this article, we’ll assume that you already tried everything in Part I. This includes:Read More
Before we start, a disclaimer: hum should be addressed on a case-by-case basis, because every vintage amp is special and degrades in its own way. What cures one amp may not work for another. That said, reading this guide should give you a good starting point on how to address your own hum problems. This guide is pretty basic and going to assume that the only piece of test equipment that you have is a multimeter.Read More
The heaters of your vacuum tubes are one of the most critical parts of your amplifier. A well-designed heater circuit is quiet and unobtrusive: truly an unsung hero of any quality amp. On the other hand, flaws in a heater circuit can produce noise.Read More
Wurlitzer tube amps are in fact very similar to guitar amps.
But before we talk about that, let’s back up a little. The Wurlitzer itself is very analogous to an electric guitar: the heart of both instruments is a pickup that converts vibration into an electrical signal that is ultimately sent to an amplifier. In a guitar, the amplifier is almost always external, but a Wurlitzer’s amplifier is tucked into the body of the instrument.Read More
We’ve discussed the differences between the GA-5 and 5F1, both historically and in terms of the circuit. Here’s how one circuit could be converted to the other, in list form.Read More
This Dynavox was originally a so-called widowmaker amplifier. We completely rebuilt it with all-new components, installed a power transformer, and revised the circuit to eliminate the obsolete widowmaker tubes. It is now a safe, functional 1.5 watt practice amplifier. It can be used alone for bedroom practice, or plugged into a second amp for interesting tube overdrive tones.
Here’s some details on how we redesigned this amp.Read More
A widowmaker amplifier has no power transformer or fuse. Instead, the two-prong, non-polar power cord is wired directly to the rectifier tube. It is very unsafe, because under even minor failure conditions (such as a shorted capacitor or even - in some models - plugging the power cord in backwards), the mains voltage might end up on the guitar strings and the user will be shocked/electrocuted.
On the plus(?) side, power transformers are expensive so widowmaker amps could be manufactured and sold at a lower price. This ensured that every aspiring guitarist in America could own a low-fi death trap if that’s what they really wanted.Read More
This vintage tube hi-fi-turned-guitar amp is one of our favorite past restorations.Read More