![]() The other SRAM address lines are accessed through latch U17 (Schematic p2) and the 16 bit data lines with latches U16 and U30 (Schematic p2), all controlled by the CPU. These lines are used as sort of a memory page selector by the CPU. U13 is driven by latch U18 (schematic p2) called PD (Port D). Here are some notes for the schematic (I always do this to help me understand the schematic): Analog circuit: LF353N Dual Opamps LF311N Voltage comparitor LF357N Dual Opamps Digital circuit: 74HC157 Quad 2-input multiplexers LH2464-12 (DRAM) (4464 in schematic) VGT7764-6024 (DSP) LH5116-12 (RAM) HD63A03RP (CPU) HY6264LP-12 (Static RAM) PCM54HP (DAC) - warms up - replaced it.Ī8, A9 and A10 are not wired to the DSP!, but come from U13 (Schematic p1). So anyone willing to take a look at the schematics and help figuring out what could be wrong. Control of the unit, recalling presets and responding to buttons, driving display etc. I thought this might be oscillation in the analog circuit but to be honest, I have no idea how that works. ![]() After one second or so, the scope image becomes a jumble of lines. When switching the unit on, after the CPU/DSP has booted up, there is a clear tone 'visible' on the output. When I insert even one, the problem comes back. I have tried to switch around the DRAM the DSP uses but only when I remove them all, is the tone gone. The problem is currently that it generates a tone without any input. I have replaced the DAC (U39) with a new one and that fixed a distorted sound (when none was desired -) that was the initial problem. The GSP-5 is quite a complex beast and I cannot say that I have all parts of the schematic (attached) figured out. ![]() Although I am not willing to spend a whole lot of money, I wouldn't mind taking it further than you would usually. Note that this repair is more for my experience/learning than it is to make it profitable. I also used a stereo system with a preamp and a GMP1 Marshall stereo power amp in a more rock style and in this context it shall work very well (delay, chorus, stereo spacialisation).I have been sitting on this for some time now and I decided it was time to either fix it, or get rid of it. Caution, however, not to adjust the volume settings at the bottom because it promotes a slight hissing sound, like all digital cameras of this type. I use this multi effect with an electric guitar by plugging it into the loop to insert a combo amp Mesa Bogie Caliber 50 +, so after the preamp, for delays and chorus. Many parameters can be edited via MIDI but I have never experienced. I had the manual in English, but publishing is simple enough not to mess. In short: you choose a memory location, we choose a config effect among the 13 available, we adjust the parameters of each effect according to its taste and it remains in memory! It may well be securely copied to another location of your choice (99 locations). ![]() The settings are easily editable the front and are automatically stored in the memory location where you are. This annoyed me at first, but eventually they are wise enough to forget this constraint. The effects are not all available at the same time, but grouped according to 13 configurations set by the manufacturer. ![]() Itional input, two outputs (stereo), taken to two pedals, two MIDI. On the front panel: input jack, a knob gain with LED level, output level, all the necessary buttons for editing effects. The box thus contains: a distortion (digital), graphic equalizer, parametric equalizer, a low pass filter, chorus, flanger, delay, delay slapback, 4 and 8 tap sync delay, a simulation of analog delay, reverb, gated reverb, spectral enhancer, boost voicing (which is a kind of enhancer). The big advantage is sure to have all the classic effects in one box. This is a preamp / digital multi-effects rack mount unit dedicated to the guitar. ![]()
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