The D*A*M FZ-673 is a germanium fuzz box released in March 2011 as a strictly limited run of 10 units, now discontinued. D*A*M describes its circuit as the Zonk Machine and Tone Bender MKI circuit with a few subtle tweaks, and says the pedal delivers "op-amp quality overdrive like smoothness but with all the complex glory and freaky exhaled responsiveness of a primitive germanium fuzz circuit"1. It is a variant of the Holy Roller, the D*A*M MKI style fuzz box the builder made around 200412.
The Swell control is not a regular volume adjuster: around noon it tames high end, and past noon, in the last quarter of its travel, it pushes gain and saturation into fierce fuzz, so set it with that in mind1.
Where it came from
D*A*M's product page introduces the pedal in the builder's own voice: "I am the fuzz box system demon ~ FZ-673". The name breaks down as FZ for Fuzz, 67 for 1967, the guestimated year of the main study Zonk, and 73 for the year of the film Enter the Dragon2. The maker dates the pedal's "Manifestation date" to March 2011 and states plainly that "10 units were produced in total. Will never be made again."1
The circuit descends from the Holy Roller, the D*A*M MKI style fuzz box from circa 2004, and the maker describes the FZ-673 as that Zonk Machine/Tone Bender MKI design with a few subtle tweaks12. Compared with the original, D*A*M lists the addition of a tone filter, a boost in output volume and gain, plus modern fixtures: a status LED, a battery drawer and a DC tap1.
Controls
| Control | What it does |
|---|---|
| Swell | The volume control, but with a different nature to a regular volume adjuster: around noon it tames high end, and past noon and in the last quarter it pushes gain and saturation into fierce fuzz1 |
| Fuzz | A gradual increase from chunkiness to full-on fuzziness with little in the way of dead spots, more gradual than a stock Zonk Machine fuzz control1 |
| Filter | A very crude but effective dial for tuning your guitar and/or amp to the FZ-673's circuit; pickup type and cabinet size come into play1 |
D*A*M describes the enclosure graphic as only the second time the builder used a two layer graphic, with a sci-fi theme intended to appear almost toy like, made from Lego style elements1.
Transistors and the DIY layout
For builders selecting transistors for the circuit, the maker recommends a leakage of 0.800 to 0.900 mA for Q1 with an HFE of 60 to 802.
Builders who worked from that layout left detailed reports in its comments:
- Travis reported, "It sounds pretty sweet with these AC125s… it's by far the best MKI I've built" (6 December 2014)2
- Jimijam built one with a leaky OC75 for Q1, a non-leaky AC125 for Q2 and another leaky OC for Q3, and found it "simply amazing build and sound" (17 June 2015)2
- JaviCAP called it "One of the best fuzzes I've ever tried. It's picky about the trannies, but more forgiving than the Tonebender MKI." (29 July 2014)2
- Brad Graham built one with Toshiba transistors (HFE 25 to 140) pulled from an old portable radio and reported "Sounds killer so far." (22 January 2018)2
Not every build went smoothly. johnk reported that "while adjusting the trimpot it fried my trimpot twice, and two different OC75's (in Q2) are now shorted (dead)."2 Bret608 had a similar experience: "The trimmer basically went up in smoke after I adjusted it while playing. Before that it had a weak sound for just a min"2. Builders adjusting the internal trimmer on this circuit should be aware of those reports.
FZ-673 in D*A*M's catalog
The FZ-673 sits in a line of D*A*M fuzzes built around Tone Bender family circuits. The maker's own history includes the D*A*M System Tone Bender MKI style work behind the Holy Roller, the D*A*M Tone Bender MKII SCB, the D*A*M Tone Bender MKIV, the D*A*M 1965 Tone Distorter and the D*A*M Dark Flesh MKII. For the wider family, see Fuzz Pedals12.
Videos
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Questions
What does FZ-673 stand for?
According to the Guitar FX Layouts write-up of the circuit, FZ stands for Fuzz, 67 refers to 1967, the guestimated year of the main study Zonk, and 73 refers to the year of the film Enter the Dragon. The maker's own page introduces the pedal with the line "I am the fuzz box system demon ~ FZ-673".
Is the D*A*M FZ-673 still in production?
No. D*A*M's product page states that the FZ-673 was discontinued and will never be made again. It was released in March 2011 as a strictly limited run of 10 units in total, so secondhand examples are the only way to encounter the original pedal.
How many D*A*M FZ-673 pedals were made?
Ten units were produced in total, according to D*A*M's own product page, which also states the pedal will never be made again. That makes it one of the smallest runs in the maker's catalogue.
Which circuit is the FZ-673 based on?
D*A*M describes the FZ-673 circuit as the Zonk Machine and Tone Bender MKI circuit with a few subtle tweaks. The maker also links it to the Holy Roller, the D*A*M MKI style fuzz box from around 2004, and adds a tone filter plus a boost in output volume and gain.
What transistors does the FZ-673 use?
The maker combined Motorola OC75 transistors, described as ex-military stock, with CV7004s, which are the military version of the OC45. Builders reproducing the circuit have also reported good results with other germanium types, including AC125, AC128 and even Toshiba transistors pulled from an old portable radio.
How does the FZ-673 differ from the D*A*M Holy Roller?
The FZ-673 is a variant of the Holy Roller, the D*A*M MKI style fuzz box from around 2004, but it adds a tone filter, a boost in output volume and gain, and modern fixtures including a status LED, a battery drawer and a DC tap. Its circuit is the Zonk Machine and Tone Bender MKI design with subtle tweaks.
Sources (2)
- FZ-673, D*A*M (stompboxes.co.uk), 2017
- Guitar FX Layouts: DAM FZ-673, tagboardeffects.blogspot.com, 2014-12-06
