How to easily determine if an early JP-2C has had the loop update.
As you are likely aware having searched out this article, the earliest of JP-2C amplifiers (a few hundred) shipped with the effects loop circuitry different from what is now standard in the amplifier. For those players who received an early JP-2C and wished the effects loop to function differently, we offered an update.
The update addresses the concerns most commonly associated with the feedback we noted on user forums. These concerns arose in applications where the playing volumes were low and/or a high setting of the MASTER in Channel 1 (as compared to Channels 2 and 3) produced excessive volume in the first repeats using a Delay. The update addresses these concerns and provides a well-matched Effects blend–again–when the amplifier is used for the intended use stated above and the Channels are relatively close volume-wise.
However, since the performance of the Effects Loop is greatly affected by the settings of both the preamp (GAIN and Tone Controls) and power amp (MASTER and PRESENCE) in each of the Channels, it is still possible to experience SEND and/or RETURN level differences under certain conditions. Namely, those which deviate from the Clean/Gain/Gain Channel dedication noted above and/or extreme GAIN and MASTER differences Channel to Channel. In an amplifier with this much GAIN and output power, as with any hot-rod, an application must be determined and a relative tuning for that application applied to achieve stability for the widest number of “drivers”.
JP-2C amplifiers starting at serial number JP-000345 and those with a higher serial number all have the "loop update" incorporated into their build as the standard design. Most all of the JP-2Cs built prior to serial number JP-000345 have now had the loop update done.
There is a simple test that can be done to determine if a JP-2C below serial number JP-000345 has had the loop update.
- Plug a guitar into FX Return jack
- Power up the amp and take it out of Standby after 30 seconds of warm-up time.
- Select Channel 1
- Set "FX" switch for the Effects Loop to its On position (its LED will light up when on). It is located near the Graphic Equalizers.
- Turn the volume of the guitar up and play an open string on the guitar while turning the amplifier's Channel 1 MASTER knob/potentiometer. If adjusting this MASTER level control affects signal level then this amp has the loop update.
Should you determine that you have a JP-2C where the loop update has not been performed and you would like to have it done, you’re welcome to call 707-778-6565 (Monday through Thursday, 9AM to 5PM PST) to speak with a Customer Support Representative directly about making service arrangements or request a RMA# online.