hi Sinsonido owners
i found this thread whilst looking for any info online about faults occurring with the preamp
i bought a used fretted model a few years back and gigged it with my pub band (blues, rock, soul covers) - great action and bonus of light weight (for the person who had to ship the heaviest gear! - plus the PA)
the only downside was the preamp - one control did nothing and the other only produced a musically-related sound in the centre of the control rotation - the thing also eats 9V rechargeable batteries for breakfast
since the pub band became de-funked (!) i started playing more with some guys miking up acoustic instruments & percussion and i decided to get the bass converted to fretless - i now use it as an upright bass on a stand
variation of volume & tone is now more important throughout a gig and so i started looking to see what other owners had done about what seems to be a fairly common problem
i wasn't keen to replace the preamp with another from the manufacturer, if the design is flaky, so i've looked at several designs for preamps using FETs for low-current drain, high-impedance 'valve' sound performance
i've just successfully replaced the faulty preamp with my homebrew design and i'm very pleased with the results - i now have a working volume control and a tone control which can vary the sound from a slightly boosted low-end 'thud' all the way across to a thin 'twang'
current draw has reduced from 10mA to 1mA, so i should get about 20 sessions between needing to swap the battery out for a recharge as opposed to two sessions as previously
i'm hoping to use the button below to upload a schematic and photos to help anyone who is also trying to replace a faulty preamp on their Sinsonido
in addition to the regular external Vol & Tone controls, i've added 2 preset controls: the 5K preset varies the overall gain of the preamp, the 500K preset enables the level of one pickup mike to be varied relative to the other, in case the strings at one end of the bridge are louder than than at the other end
i've re-used the original switching jack socket which acts as the power switch when you plug in the cable - i had to file out the mounting-holes slightly for the Vol & Tone controls - the green areas in the photo of the new preamp are insulating tape to prevent the conductive shielding paint in the preamp recess from interacting with the high-impedance circuit
(NB. the output is now mono only - and no longer supports headphone operation)
hope this info is of some help to a fellow Sinsonido convert
rock steady!
