Hughes & Kettner Warp Factor

Hughes & Kettner Warp Factor

Hughes & Kettner Warp Factor

The first thing you notice about this pedal its the unusual round shape: there are other effects with the same shape (Dallas Arbiter Fuzz Face and Expandora , just to mention two), but no one is dark, heavy (700 g) and menacing as this one :)

In addition to the usual “gain” and “level” knobs, there are 2 more controls: a “warp” knob and a “sub” button.

The “warp” knob is actually a tone control, which doesn’t work in the usual way: to the left it boosts mids from 250 Hz to 1 kHz. When set to the right, it cuts mids at 500 kHz with a subtle boost at 3 kHz.

Hughes & Kettner Warp Factor - front

Hughes & Kettner Warp Factor - front

The “sub” button is a low-end boost at 90 Hz (!) and is recommended for use with a 4×12 cabinet as you can see on the manual and on the reverse of the box.

By the way, as you can see in the photos, the input and output jack are reversed: I mean that the input jack is positioned on the left side while the output jack is on the right side…pretty weird choice imho, since the standard is exactly the opposite.

Hughes & Kettner Warp Factor - back

Hughes & Kettner Warp Factor - back

This pedal needs a whopping 180 mA of 12 V current: forget about using batteries, however a 700 mA power supply is included.

This effect was included in H&K catalog for year 2006, but is now discontinued: my personal opinion is that the sound isn’t bad, but probably its quirks were enough to condemn it to a fast “phase-out”. At the moment they can be found second-hand at reasonable price.


Weight: 700 g

Max. current consumption: 180 mA

Power supply: 14 V~

Input sensitivity: -14 dB

Input impedance: 1 MOhm

Output level: +6 dB

Output impedance: 3 kOhm


Original manual and catalog from H&K site


Bixonic Expandora II – Exp 2001

Bixonic Expandora - Exp 2001

Bixonic Expandora - Exp 2001 (front side)

As far as I know, this pedal has gone through 3 main versions: the original (and much sought after) Expandora, the 2001 version in this page, and a “reissue” version, called 2000-R.

Moreover, I am reasonably sure that Bixonic is no more in business, so we’ll probably will not see a new version anytime soon.

The 1st version had only three knobs on the outside, and some internal dip-switches that required to open the box to change settings: definitely not “user friendly” imho. The second version has no dip-switches, but a fourth knob labeled “Drive”, while the third version is similar to the 1st but the dip-switches can be easily accessed on top of the unit. All the knobs on this version are red, (yes, that’s why you can ofter hear about a “red knobs version”) smaller, difficult to spot and not really comfortable to use: however I admit that you can’t really change settings by accident, and that’s a plus.

Another difference is this: both the 1st and 2000R have a standard footswitch, while the 2001 has a large pad as you can see in the above image. Under the pad you can find the battery compartment.

Bixonic Expandora - Exp 2001 - Right side

Bixonic Expandora - Exp 2001 - Right side

However, another difference which you can’t miss is the light coming from the LEDs under the “Expandora II” badge on the top while playing with the unit switched on: I am sure its not just related to the input level alone, but I can’t tell :) . You can easily see this, in the videos at the links below. On a schematic on GeoFex site (see links below) it seems that LEDs are used as part of a compressor circuit, but I hadn’t open my unit to check it out.

All the units can be powered by a standard Boss style PSU, using the plug on top, or a 9V battery.

Bixonic Expandora - Exp 2001 - back side

Bixonic Expandora - Exp 2001 - back side


The Expandora II – 2001 on YouTube

A nice shootout/comparison between 2001 and 2000R version on YouTube

A supposed schematic for the Expandora on GeoFex site, use the link : ‘Schematics and More’ on left menu

Ibanez TM5 Thrashmetal

TM5 Thrashmetal (Ibanez)

Ok, I know: I shouldn’t expect anything from the name of a pedal. I mean, effect names are otfen *very* loosely related to what the circuitry in the box does. However, I’d have expected from the TM5 something able to scare the hell out of me (or at least out of my cat, which is usually easier :) ). A more correct name would have been “Heavy Overdrive” which was what Ibanez actually said, by the way. If you are into trash metal or any similar kind of music, look somewhere else.

The effect in the photo has been thrashed around from the previous owner, but is still perfectly working. While this pedals looks tough, the box isn’t entirely metal: the battery cover, which you can see open in the next photo, is made of plastic. Since this was the first pedal I’ve got in this series, I thought all of them were made in the same way: I found out later that this is not true, when I got hold of a different one which used a plastic case :(

TM5 Thrashmetal (Ibanez) with battery compartment open

Another thing I don’t like about this pedal and its “soundtank” brothers, is the kind of control knobs: you can’t check their positions at a glance while playing, the white markers are almost invisible unless you have a very long neck…

Apart from those notes, the TM5 is worth checking if you need an inexpensive overdrive, since it can usually picked up second-hand at very low prices.

Ibanez Soundtank Series page on Web Archives

Hand drawn schematic on Effects Heaven site

TM5 page on DiscoFreq’s FX site

TM5 page on NoiseGuide site

Dirk Hendrik offers a mod from TM5 ro ProCo Rat: you can mail him on his site if interested

MXR ZW44 Zakk Wylde Overdrive

ZW44 Zakk Wylde Overdrive (MXR - Dunlop)

This is the signature overdrive pedal for Zakk Wylde, and sports a peculiar black and white bullseye drawing favoured from the guy himself.

I personally think this is a good overdrive, however you shouldn’t think that putting this between your guitar and a bad amp will give you the same sound :( A *good* tube head is mandatory.

The build quality is usual MXR: compact size, solid metal and built to last. Notice the rubber covers on the pot knobs: I’ve been told that should allow turning the pots using your feet, but I’m still thinking it was a joke :) .

One thing I don’t like is that you have to remove the 4 screws on the bottom plate to replace the battery.

ZW44 Zakk Wylde Overdrive (MXR - Dunlop) side view

Official page on Dunlop’s site, with info and audio samples

Some videos of people using this pedal on YouTube:

A review from ProGuitarShop

A review

A video in french language

Another video

Another video (last one :) )

Schematic on Analogguru’s page

Boss OD-1 Overdrive

OD-1 Over Drive (Boss)

This is one of the hundreds of pedals built around the JRC4558 operational amp chip and its variants. It has been built from 1977 to 1985. There are 2 controls: “Level” and “Over Drive”. Moreover, there are at least 5 versions of the circuit board: the first versions probably didn’t even use the JRC4558. This pedal isn’t particularly rare, even considering that has been out of production for more than 20 years, however it has a lot of fans. It has a pretty good sound when used to crank up a Marshall tube head, however may not sound so good with other amps. Building quality is standard Boss, which means they are built like a small tank. This was one of the first pedals to use FET switching instead of “True Bypass” switching: however I’m not sure if this can be considered as an improvement :) . The fact that 30 years later some pedals are still made in this kind of box means that the overall design was really good (compact size, easy battery access, anti-skid panels on top and bottom).


- Input Impedance: 220 kOhm

- Output Impedance: Over 600 Ohm

- Signal/Noise Ratio: 80 dB

- Current Draw: 3.5 mA

Samples coming real soon


OD-1 schematics and nice images – on fffworks site (text is in Japanese language)

OD-1 Schematics at Schematic Heaven: OD-1 schematics

Short description on Boss USA site

OD-1 on Boss USA site

And some videos from YouTube:

Video 1 (in japanese)

Video 2 (in japanese, too)

OD-1 mods from Analog Man