ZIM Schematics

ZIM Overdrive Schematics and Blank ZIMcard DRVF

Do you like to experiment with different chips and modifications? Then the ZIMcard is a dream come true. Modular ZIMcards make modifications and circuit swapping fun and easy. ZIMcard schematics and circuit board layouts are now available, along with blank ZIMcards. You can configure your ZIM dual drive pedal to sound the way you want it. 

Get our free PDF download containing a circuit board layout diagram for the ZIMcard DRVF and schematics for ZIMcards T9, B9, CS, H9 and VT. Modify existing ZIMcards and build up your own by using a blank DRVF ZIMcard.

DRVF is a small circuit board that is laid out to accommodate the basic diode-clipping overdrive circuit, commonly called the Tube Screamer, or TS. This is the card from which all of the overdrive-based ZIMcards are built. Using the ZIMcard DRVF schematic PDF, you can create the perfect ZIMcards for your ZIM. You can modify your ZIMcards over and over again without any wear and tear to your ZIM pedal.A blank ZIMcard comes with basic, necessary parts installed and you supply the rest of the parts. Parts that are already installed: IC Socket, 8-pin plug, 10 Ohm current limit resistor, 2X47K resistors and 2X10uF caps for power decoupling and voltage reference. With this card, you can build a TS-based circuit with the parts and values you choose.

ZIMcards Based on the Tube Screamer Circuit:
T9 - Classic Overdrive (TS) - The basic, stock tube screamer circuit with a 4.7K resistor and a .047 capacitor shaping the tone in the clipping section. A 1Meg resistor in the feeback loop, in paralel with the 1Meg drive control limits the amount of available gain to be the same as a stock TS.
B9 - TS with Increased Low End and Gain Range - Close to T9, with a 3.3K resistor and a .1uF cap. Also, there is no 1 meg resistor added to the feedback loop to limit the available gain, so the max gain is set by the 1meg drive pot. One of the silicon-clipping diodes has a germanium diode in series.
CS - TS Drive with No Mid Hump - Same as B9 with the addition of a feedback circuit that returns post-clipping midrange back to the pre-clipping input, but out of phase. This subtracts midrange in a dynamic way and creates a clean sounding overdrive, without the type of mid hump you hear in the stock TS circuit.
H9 - TS with Even More Low End and Gain Range - Close to B9, with a 1K resistor and a .22 uF cap. This provides more gain and low end. The clipping diodes are double in series, which gives more dynamic headroom and output level, so there is a resistor that backs it down to a reasonable level.
VT - TS Drive with No Mid Hump and Extended Gain Range - Same as CS, but the clipping diodes doubled in series like H9. And like H9, there is a resistor to cut the resulting output level. This was introduced as an improved version of CS. Compared to CS, VT has more range and a slightly different mid-range voicing.

Earlier Versions of the ZIM Drivecard
In the first year or two of making ZIM pedals, I went through some different versions of the drive card before settling on DRVF. The earlier cards have the same circuitry and basically the same functionality, but their parts layout is completely different. The earlier versions of the ZIM Drivecard are shown below. Both of these early cards have been re-assigned and re-used over the years as current DRVF ZIMcard type. They all have the same basic topology, so each one of the circuits can occupy any of the circuit boards. In 2006 I designed DRVF, the same old ZIMcard with a better layout. It's a little larger with more breathing space and some pads for optional parts. The majority of ZIMcards out there are DRVF. The schematics in this documentation apply to the ZIMcard types regardless of which ZIMcards they're built on. The parts layout information in this documentation applies only to DRVF cards only. Some of the early ZIMcards may contain undocumented differences compared to the current schematics.

ZIM Drive - This is the first version of the ZIMcard. This card was included in the first 100 ZIMs. There were two versions, one with more gain than the other. There were no letter/number designation on the cards.
DRVD - This is the second version of the ZIMcard. These came into use around 2005, when other versions of ZIMcards became available. The top left part of the card is left blank and the card's type is written with silver paint pen.