header image

JP-10 (2003)

2003_jp10
This model of the JP series was designed to be a “home use” or “recording” single-channel guitar amplifier. The JP-10 uses three tubes for its preamp and has an output of approximately 10W using a single output tube.

Front panel controls

Low, Mid, High – EQ controls function as expected, and have an additional mini boost switch associated with each knob (earlier models do not have a mini boost switch for the Low EQ knob).

Gain – sets the overall gain/distortion level.

Master Volume – controls the overall volume level.

Low Boost – a three-position switch intended for a low boost beyond the range of the Low EQ knob and has a different feel from using the Low knob’s mini boost switch. Higher settings yield more low-end response and overall depth. The setting 2 is considered normal, 3 is deeper. The setting of 1 is for keeping the response tighter and more even, especially at higher volumes.

Bias – controls the bias of the output tube (within a safe range) for a different overall sound and feel. The amp is self-biasing, but this feature helps give more versatility since what’s considered an optimal bias point can be subjective. This control has three settings–L, M and H (meaning “Low”, “Medium” and “High”). Lower settings bring the amp’s dynamic response a tighter, more contained feel. Higher settings loosen the response and bring more depth and bounce to the low end. Depending on your volume setting and specific power tube, you’ll probably find either the M or H settings to be best for the response you want. (Note: If using a 6V6 output tube, avoid using the H setting as it may stress the tube more than normal.)

Voicing – selects one of four overall gain voicings:

Voicing 1 – The voicing with the lowest gain and distortion. Capable of achieving lower-gain classic rock sounds or with the Gain turned down, some bluesy/cleaner sounds. NOTE: this is not a “clean channel”. If you’re considering buying a JP-10 second-hand, be aware it was not intended to be very good at getting clean sounds.

Voicing 2 – Takes Voicing 1 and adds some more gain, snarl, and growl. Sounds reminiscent of late 70’s to 80’s rock can be achieved.

Voicing 3 – Another preamp gain stage is engaged. At lower gain settings, Voicing 3 starts where Voicing 2 leaves off. As the gain level is increased, a transition to a more “modern high gain” sound occurs.

Voicing 4 – A variation on Voicing 3 which allows the amp to have more solid lower midrange for a tighter attack. While not always immediately noticeably different from Voicing 3, it’s something you will feel. Allows for a more modern hard rock aggressiveness.

Rear panel controls

Output Drive – This control has 4 settings to set the amp’s overall sound for more or less punch. This adjusts the amount of gain in the last gain stage of the preamp. Higher settings of the Output Drive control are not recommended with use with higher Gain settings and higher volume settings, as feedback can occur more easily.

Loop – (Note: the Loop was optional for the JP-10 design, so some earlier models do not have this feature.) This is a basic series preamp out / poweramp in type of effects loop best suited to rack effects. Some pedals will still function well in this loop, depending on their design (generally speaking, this loop is not suitable for most pedals for anything other than lower to moderate volume levels).

The Preamp Out is the send, the Poweramp In is the return.

Speaker Outputs – generally meant to be used separately. Use either the 4 ohm jack, the 16 ohm jack, or one of the two 8 ohm jacks. When connecting two 16 ohm cabinets, both 8 ohm jacks can be used for a proper impedance match. (Note: Early units have a 4/8/16 ohm selector switch and two parallel jacks.)

Attack – used to allow for a different overall feel of the amp. Shallow has a more contained feel and Deep feels deeper overall as the name suggests. (Note: Early JP-10 amps have a Pentode/Triode switch instead of an Attack switch. Triode mode puts the amp in “lower power” mode, reducing headroom and output power.)

Fuses and lamp bulb

Mains = 2A Slo Blo

HT = 0.125A (1/8A) Slo Blo (fast-acting types can also be used for this fuse)

Both fuses should be rated for 250V.

Early units had a separate power lamp instead of an internally illuminated power switch. The bulb for that lamp is rated for 6.3V / 150mA (0.95W).

Tubes

The JP-10 uses three 12AX7 preamp tubes and one EL34 output tube. It can also accept a 6V6, 6L6, KT66, KT88 or 6550 output tube. Doubling the impedance is recommended when using 6V6, 6L6 or KT66 tubes. (Hook a single 16 ohm cab to the amp’s 8 ohm jack, or hook a single 8 ohm cab to the amp’s 4 ohm jack.) It’s safe to use without doing this but this will result in the optimum sound/feel intended for this model.

There is no bias adjustment required for different output tubes, however note that 6V6 tubes may wear prematurely if using the H bias selection.

Removable protective bar

The metal bar on the back of the amp is a quick-release type. Just pull the bar and it unhinges from a couple clamps that hold it in place. To replace, push until it snaps into place.

Note: This document is meant as a reference for JP-10 models only. The JP-50 and JP-100 amplifiers have different features, functionality and sound from the JP-10 model.