Exar MT-02 Metal / BM-02 Bad Metal [schematic]

[VitaliiBobrov]

Another Exar pedals tracing, this time it is not one but two effects at once - MT-02 Metal and BM-02 Bad Metal. I traced both at once, as it appeared that they shared a single PCB.

Exar MT-02 Metal

Exar BM-02 Bad Metal

Both units seem to be manufactured same year - 1995 according to dates on potentiometers. I have boxes for both of them, but Bad Metal has a user manual, an Exar products catalog, and even a receipt from the store. It was old in 1997 in Warsaw for 77 PLN.

Exar BM-02 user manual 1

Exar BM-02 user manual 2

Exar products catalog 1

Exar products catalog 2

Exar BM-02 receipt

The description of pedals in the catalog clearly says that Bad Metal is an extended version of Metal pedal with an additional frequency band controlled by High pot.

Exar Bad Metal vs Metal

It wasn't a big surprise that they are sharing a single PCB, with a bunch of parts unpopulated in Metal pedal.

Exar MT-02 PCB top

Exar MT-02 PCB bottom

Exar BM-02 PCB top

Exar BM-02 PCB bottom

So the differences between the two were in the additional gyrator attached to the High pot, different pot values 22k for Metal and 10k for Bad Metal and op-amp bias resistor (470k vs. 453k, however, my guess is it was just about of availability of certain resistors values).

The differences between series 1 MT-1 Metal and MT-02 are minor changes in component values and symmetrical soft clipping instead of asymmetrical in MT-02. Attached are schematics with buffered bypass-related parts omitted.