sandy_r Posted February 22 Share Posted February 22 (edited) Not sure how much longer i'm going to be able to successfully complete fine-detail work, so i'm going to try for a bit of a blitz to round off a few legacy projects... This one is to upgrade my DIY JFET preamp for my Aria Sinsonido travel bass (which i use as an EUB). I bought a small CNC kit a few years back, which i've used to make PCBs for a non-audio application, and i thought i'd see if it could produce a more professional-looking module than my rather scrappy-looking attempt on veroboard:- Schematic for the JFET Pre Photo below shows an initial test mill of the PCB v0 (Laid out using PCB Designer on a Linux-type platform). After a bit of a shaky start, i managed to complete the mill run and all signal traces show good continuity between pin pads (and importantly - no continuity to the infill copper!). I copied and hand-edited the Gcode drill-file to add a 3rd pass which increases the connector pin sizes up to 1mm (from the default component pin diam of 0.8mm). Hoping to do a full, clean run (without the initial glitches) next week Now waiting on delivery of new parts to populate the board - then test my eyesight, and hand-steadyness, with soldering and installing in the bass for test Edited April 13 by sandy_r 6 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 22 Author Share Posted February 22 (edited) [TL; DR...] Fast Forward to photos of v1, revised with better solder pads for battery wire connection - populated, soldered, continuity-checked, control looms made & fitted Edited April 13 by sandy_r 2 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 22 Author Share Posted February 22 (edited) [TL; DR...] Fast Forward to photo of completed CNC milled PCB installed in bass (Aria Sinsonido) Tone shaping provided: (a) 8-12 o'clock: Bass boost, Treble cut; (b) 12-4 o'clock: Bass cut, Treble boost Audio clip recorded using new CNC milled PCB (Tone at 12 o'clock; ground-wound strings; direct into Samsung tablet) Sinso-JFET-Pre-Tflat-PBPflat.mp3 Edited April 13 by sandy_r 1 Quote Link to comment Share on other sites More sharing options...
Richard R Posted February 22 Share Posted February 22 Following 👍 2 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 28 Author Share Posted February 28 Parts arrived - populated unsoldered on proto PCB: spacing ok 2nd mill-run delayed by hospital appointments 😞 3 Quote Link to comment Share on other sites More sharing options...
SamIAm Posted February 28 Share Posted February 28 OMG ... brilliant! I've a 3018 (tho I still need to clean it up from fire damage) this would be a great first thing to try it on post refurb! Sam x 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 28 Author Share Posted February 28 2 hours ago, SamIAm said: OMG ... brilliant! I've a 3018 (tho I still need to clean it up from fire damage) this would be a great first thing to try it on post refurb! Sam x This method seems to be quite widely used for low-volume, quick turn-around runs - and can give very good results Some folks seem to struggle with getting consistent depth of cut, despite Z-Axis mapping of the work+support surface but i suspect that is more of an issue on the larger machines - so far i haven't needed to go to those lengths (laminate flooring offcuts seem to provide a more stable and closely-controlled thickness for the 'sacrificial' board) Hopefully, your machine wasn't affected by the heat of the fire, otherwise you may find that some of the 3D-printed parts have warped slightly, causing misalignment of the frame and binding of the drive threads Good luck if you decide to give it a go Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 2 Author Share Posted March 2 (edited) First full mill-run looks ok - and continuity all good** - but i'm not pleased with my pad layout for the 2 thicker Veropins i have to use for +/- power; this run will probably be ok to populate and use but i'd rather edit the layout to add rectangular pads for those 2 pins (being the largest diameter holes here, at approx 1.5mm) (i'd planned to use narrower-profile pins, which i've got squirreled-away somewhere, but free time has been tight due to some unexpected hospital appointments) (** reflections from the liquid flux applied to the board look like copper 'bridges' in some places) Edited March 3 by sandy_r 3 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 2 Author Share Posted March 2 I've edited the layout to add wider pads for the thicker Veropins (and used the revision to move a decoupling cap further away from the corner of the Jack cutout) - Gcode files all exported and edited for Grbl controller s/w - full mill-run #2 within next few days hopefully Quote Link to comment Share on other sites More sharing options...
Richard R Posted March 3 Share Posted March 3 On 22/02/2024 at 10:49, sandy_r said: After a bit of a shaky start, i managed to complete the mill run and all signal traces show good continuity between pin pads (and importantly - no continuity to the infill copper!). A basic question I should have asked at the start: what is the board you are milling? I assume it is a ready-made item with a thin copper plate bonded to an insulating board? Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 3 Author Share Posted March 3 (edited) 1 hour ago, Richard R said: A basic question I should have asked at the start: what is the board you are milling? I assume it is a ready-made item with a thin copper plate bonded to an insulating board? Yes, i'm using a single-side copper-coated pcb blank This board is made of a phenolic type material, not quite as high quality as glass-fibre based boards (which are blue- or green-looking) - but it doesn't blunt the drills and bits in such short order, and the dust is not quite as nasty Edited March 3 by sandy_r 1 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 5 Author Share Posted March 5 Hah - almost snatched Disaster out of the jaws of Victory ...the Gerber Control app crashed partway through the run! Fortunately, it was possible to re-align sufficiently and edit the Gcode to continue from the previous trace Continuity all good, happy with new pads around the power Veropins, and so - on to the 'soddering', as my colleagues across the pond used to say 4 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 10 Author Share Posted March 10 (edited) PCB populated & soldered; soldered-joint continuity checked ok; control looms made ...next stop - installation, power-check and circuit test (*can't find nail-biting emoji*) Edited March 10 by sandy_r 3 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 11 Author Share Posted March 11 Completed CNC milled PCB installed in bass (Aria Sinsonido); JFET inserted in socket; battery connected, current drain measured as 1.2mA; wires from 2x electret bridge mics and switching jack loaded into connectors; control cavity shielding extended under control cover, grounded to jack ...time to try it out - annnddddd .... Silence! Ok, who put all these switches and controls on a preamp?!? Eventually, 3 brain cells later... phew, it works! For absolutely no technical reason, it sounds better than the vero protoype (will try and post some audio clips, in due course) 3 Quote Link to comment Share on other sites More sharing options...
Richard R Posted March 11 Share Posted March 11 Very neat. Which shouldn't affect the sound, but probably does. 😉 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 12 Author Share Posted March 12 (edited) 12 hours ago, Richard R said: Very neat. Which shouldn't affect the sound, but probably does. 😉 Thanks Richard, yes agreed, the layout shouldn't make a difference - no high frequencies or extreme impedances involved - more likely that variation in component values could be noticeable An ad hoc comparison** of the new PCB with a recording of its vero prototype suggests that the new PCB has a slightly more 'bassy' profile - suits me! (** based on phrases of notes played, low A to mid D, Tone at 12 o'clock for both) Red - New PCB __________ Green - Vero prototype Edited March 12 by sandy_r colour blind! 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 14 Author Share Posted March 14 (edited) here are some audio clips of the CNC PCB installed in the Sinsonido (fretless, but hopefully, not too Boingy, Richard? 😉) Ground wound strings, recorded direct into Samsung tablet Tone EQ flat: Sinso-JFET-Pre-Tflat-PBPflat.mp3 Tone EQ at max bass: Sinso-JFET-Pre-Tmaxbass-PBPflat.mp3 Tone EQ at max treble: Sinso-JFET-Pre-Tmaxtreb-PBPflat.mp3 Edited April 10 by sandy_r 2 Quote Link to comment Share on other sites More sharing options...
Richard R Posted March 14 Share Posted March 14 Boingy is good. I like the max bass version. 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted March 14 Author Share Posted March 14 1 hour ago, Richard R said: Boingy is good. I like the max bass version. ...seriously thinking of changing my username to boingybassman i was interested that the Tflat position still seems to have a reasonable 'bass' content - i think i would start there, but its useful to have some measure of boost for either bass or treble, not just cut Quote Link to comment Share on other sites More sharing options...
sandy_r Posted April 10 Author Share Posted April 10 (edited) Figure 1 shows the single-adjustment tone control which provides a symmetric EQ response that is flat at the center of the adjustment range Figure 1. Single-adjustment tone control for Bass Moving the control in one direction simultaneously boosts the bass and cuts the treble until about 5.5 dB of boost and 23 dB of cut are obtained. Moving the control in the other direction boosts the treble and cuts the bass in an identical fashion. Figure 2 shows the typical curves obtained from approx 5 Hz to 20 kHz with a 340Hz centre frequency, for the lower half and upper half of the control range, respectively Figure 2. The tone-control circuit delivers good response characteristics in both the lower half (a) and upper half (b) of the control range Insertion loss (at centre) approaches 6 dB. Since this is a passive circuit, all component values can be scaled, if required, without affecting the AC transfer-function.(Keep the source impedance low and the load impedance high. In this application the source is <10k ohm, and the load > 400k ohm) The audio clips posted above were recorded at the EQ flat, Max Bass and Max Treble positions Edited April 20 by sandy_r Quote Link to comment Share on other sites More sharing options...
itu Posted April 10 Share Posted April 10 This is so called tilt-eq. Can be found in some Steinbergers, Quad preamps and so on. 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted April 10 Author Share Posted April 10 1 minute ago, itu said: This is so called tilt-eq. Can be found in some Steinbergers, Quad preamps and so on. Actually it dates back to early wireless (er, radio) days, i believe - when the 'Tone' function was usually limited to a single control (if any) 1 Quote Link to comment Share on other sites More sharing options...
itu Posted April 10 Share Posted April 10 Yes, surprisingly rare nowadays, although very powerful in just one knob. I think Quad had also another switch to choose the desired tilt frequency. 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted April 10 Author Share Posted April 10 11 minutes ago, itu said: Yes, surprisingly rare nowadays, although very powerful in just one knob. I think Quad had also another switch to choose the desired tilt frequency. Quad amps ..."Wire - with gain"! Quote Link to comment Share on other sites More sharing options...
Si600 Posted April 10 Share Posted April 10 Wot, one of these? 3 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.