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Prostheta

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Posts posted by Prostheta

  1. I think that's a common description, for better or for worse. Whether this is down to any tonal colouration by the preamp or the coil being very "by the numbers and uninteresting" is debatable. I certainly think that both can be tested if coils can be extracted without destroying them. I'm of the opinion that taking the old EMG preamp, running it at 18v and it using a passive pickup like say, an SD Invader would be a nice combination. I don't see how the preamp is a bad design aside from the disco'ed parts. I can't recall off the top of my head if the EMG coil output is comparable to a passive, or whether they are lower and the preamp pickups up the slack or not. There's little unique magic going on here aside from the ultra-conservative current limiting.

    Regardless, I'm a strong believer in active circuits even if the electronics simply function as a "line driver". This being said, the compromise is losing some of the niche things that passive enthusiasts love, such as the interaction between coils when dialling in/out the volume/tone pots. This can be allayed by putting the active electronics downstream of the coils, switches and pots but by that point noise is baked in and just becomes powerful low impedance noise instead!

    I'm in the classroom today, so can't shouldn't check out the sample until later.

  2. I used to build in a brass mesh to my preamps bent over the board as an attempt at a Faraday cage. I didn't notice any difference. A strong ground plane both sides seems good enough. Your recordings sound great. Are you noticing any particular characteristics, such as sweeter sustain, blooming notes evolving in sustain, etc? 

    • Like 1
  3. I've never seen preamps set in singles before, however from what I am aware Fishman's Fluence singles have a "master" pickup that the others slave into, presumably sharing one preamp. It still requires that one pickup has the preamp, however this does imply that you can consider moving the preamp offboard. This isn't anything novel, since a preamp separate to the pickup itself is no different to one being onboard....in principle an EMG81 could have the preamp externally to the casing, however this then becomes a question about how many connections the preamp needs to the coil. Fluence humbuckers are probably very deeply integrated with the "coils" at several points during their "wind" in order to manipulate the voicing.

    I'm of the opinion that a preamp within the pickup form factor isn't necessary unless factors such as the Fluence humbucker necessitate it. Actives also have a really narrow variety compared to passive. This is where I'm getting into personal opinion. I'd rather have an in-cavity preamp paired with readily-available passives unless a certain active delivers out of the box. I'm yet to weigh in with the Fluence Classic neck pickup and how smoothly it pairs with a rolled-back tone control, specifically with how well compares to a simple Seymour Duncan '59 SH-1N, my favourite neck pickup.

    On 9/13/2023 at 1:59 PM, nakedzen said:

    @curtisa I'm getting pretty much the same amount of emi from the active pickup as from passive humbuckers, from pc cases and speakers. EMG's are dead quiet in comparison.

    I didn't have ground planes built into the prototype pcb, so that might explain it. :D

    Did you manage to get past this specific issue? An op-amp circuit running in true differential mode connected to either end of the coils with no reference to ground being made usually works very nicely. I can send you a preamp (albeit one that requires 2x 9v batteries) to experiment with that does this. Bang the pickup coils either side of two pins and instant inky-black quietness is achieved.

    • Like 1
  4. 1 hour ago, henrim said:

    Maybe it would work better with less stick out on the blade. Also I find it odd that the sliding surface is knurled. I can’t see the whole tool in the picture but if there is a flat surface on either arm that would make a better support. Round tool tend to rotate in unwanted ways. 

    It looks upside down, perhaps. Yes, most Gramil-like tools that I have seen are something like a 20 x 30mm block with a radius of say, something like 3-5cm on the bearing face. Round looks difficult to dial in.

  5. You'll love it as long as you do small quantities and keep the process under control. A bunch of wooden forks for mixing, precision scales and plastic or paper shot glasses. The thing that always bothered me about epoxy was me not being organised enough or able to mix small batchs of a few grams at a time. Done over multiple sessions and taking off as much as you can each time, and it's magical.

  6. That being said, I bet you Taylor cut their channels on CNC....because that's the sort of thing they seem to see as a challenge to best.

    I agree about a hot iron. It might be useful in the long term to make a brass block with a threaded handle to judicious application of heat. Similarly, a nice brass Gramil or one made from say, African Blackwood or other wood that takes a thread nicely may be in your future.

  7. Even CNC cannot do it to the point of what I would call geometric perfection. The objectives as I see it are to produce crisp edges. Internally, they can be cleaned by hand for areas that are missed or left to fill with glue in voids.

    An example that I rolled about my head was the binding channel over the curved arm contour of my Mirage bodies last year. If done by CNC (I did them manually in the end) with the cutter following an XY path around the perimeter with adjustment in the Z, the nature of the cutter would leave it inconsistent. The ideal path would be a rectangle swept around the profile with the direction changing perpendicular to the profile in a pure XY shape. With a cutter being cylindrical, it cannot be perfect. The exact same issue that you are describing.

    The small ridge left if acceptable in my view, since it can either be cleaned manually as mentioned, or the inner edge of the binding can be scraped. Either or both. The main objective is for the seams to be tight and clean. Any slight deviations internally are neither here nor there, and have to be accepted at some point as a consequence of geometry.

    I like that machine, but really it seems like something that may still need to be supported by a Schneider Gramil or even manual cutting. My jig is literally like the Z axis of a CNC with my Makita palm router fitted, and using a modified white plastic Thor hammer face as the bearing. In the extremes of curvature, the channel reduces in depth significantly compared to the flat areas. It works, but needs final tuning.

  8. DCR is only a rough hint at the output of a coil, however it does conveniently sidestep the complicated aspects of a pickup such as the field strength, inductance, etc. 10k is still pretty hefty.

    Yes, it looks like the LM4250 is out of production so I wonder how EMG are sidestepping that one? Yes, a chip shouldn't have its own sound in the regions where it is running linearly however the tradeoff of the LM4250 is that it has a lower frequency range when run in ultra-low current ranges (). Without researching further, this may exhibit high-end rolloff, crossover/slewing distortion or perhaps reduced headroom. Not sure. None of these things are good in the way that we otherwise characterise the aspects of other pickups.

    Given the schematic that Andrew @curtisa posted above, the quiescent current of the LM4250 with R8 at 1MOhm is ridiculously low. Using a different op-amp would indeed work in principle, however you'd be lucky to get that silly battery life that EMGs provide. Sticking with TI, I would consider something more modern and quality. Briefly looking at the site, I'd say that the OPA1637 might be an interesting one to test. It is very much a precision part but not super hungry either.

    https://www.ti.com/product/OPA1637

    Not the most expensive op-amp I've seen (I use some that cost 3x that in my "no holds barred" preamps) and certainly worth a look. I'd snag some TSSOP8 > DIP8 PCBs to do a bit of testing.

    • Like 1
  9. The LM4250 doesn't really offer anything specific beyond being able to be massively current limited for immense battery life. I mean, that's a great thing but I started running all my EMG circuits with 18v as they have very little headroom. I don't know whether it's the current limiting and frequency response that makes them run less linearly, or whether the headroom within the circuit is less than ideal (I suspect the former) but 18v opens them up a lot, especially with basses but also the 81 as well.

    Interesting aside. Fishman Fluence don't discernibly change in response to being run with 18v which makes the double Gotoh battery box on the back of my white Mirage a bit superfluous to needs....

    • Like 2
  10. On 5/30/2023 at 9:54 PM, mistermikev said:

    well no expert here... but I can relay what I've read, and that is that the emg version of a difference amp actually is running the two coils of a humbucker into sep inputs... then dropping voltage for anything they have in common, and amplifying anything they don't have in common.  This keeps the noise floor really low.  it requires some really underwound singles.

    the schematic you linked to... that's just a garden variety booster.  anything at the input is being boosted -noise included.  Just like a pedal running after the guitar.  Nothing wrong w that... just isn't anything like what is going on in an emg pickup (not being critical here... just observation).  you could, essentially take any booster circuit and put it in a guitar.  I've done it with micro booster, linear power booster, mid boosters, sho boost... and enjoyed it quite a bit.  IMO it's a very useful and cool thing to do.

     

    All of this. Interesting project! From what I am aware, the original EMG preamp based around the LM4250 is a circuit that is current-limited by function of that silicon. This has the effect of reducing high frequency response, which is fine in the audio spectrum.

    A bit of an aside, but here's a preamp from a 1980s Aria Pro II SB-Integra which I reproduced a few years back:

    AHEQ2s.jpg

    aheq2.jpg

    This preamp was external to the pickups, however those pickups were also made similar to the approach EMG use in their 81s by being hugely underwound, or at least using lower gauge wire in the coils. The circuit is hard-coded for 6db of amplification per pickup (10x gain). This also works as a differential amplifier. Rather than having the circuitry within the pickups themselves (a P and a J) we had this outside of the pickups. The silicon is a plain old JFET TL072CN, but in principle could work using an 074 or even an 064 for lower current with a bit more noise. Like @curtisa states, the function of a differential amplifier is to reject common mode noise. This can be done by removing reference to earth and running a differential amplifier off a split supply or creating a floating reference as per EMG and this circuit with a single-ended supply. The Aria Pro II SB bass project I made a while back uses the latter approach, so has 2x PP3 batteries for a -9v/0v/+9v split supply, with a nice amount of headroom. The pickups are floated with no reference to ground and they're inky-black silent. It also worked wonderfully for the single coil in my 5-string 1951 P-bass.

    • Like 2
  11. There's a number of different solvents you can use. Tru-Oil uses one called "Stoddard solvent" which is just another name for white/mineral spirits, or Turpentine substitute. The difficulty when choosing the right thing to cut BLO is finding a good solvent, but once you'd done that the product becomes stupidly cheap to mix to specific applications. Tru-Oil is nice because of the consistency, and the fact that BLO is not too cheap "because Finland".

    • Like 1
  12. 2 hours ago, Bizman62 said:

    Which brings me to this question: What is the naphtha you talk about? Not the Zippo filling stuff, I guess? Even in the Finnish language there's several names for common solvents and if their labels are multi-language, the mix is even more confusing.

    Yep. Pretty much just lighter fluid, but check your tin of course. I've seen it called kerosene or lamp fluid. I used some basic "Mustang" junk from Tokmanni last time and it works fine. Behlen also sell VM&P Naphtha ("Varnish Makers & Painters") which gives you more than a clue about its end use in this respect, and you know what you're getting if it's labelled VM&P. We call it nafta, same as a lot of central and eastern European states, however its meaning can be less specific place to place.

    The only thing one can say with any level of certainty is that it's terrible for your health. I'm fairly sure that @ADFinlayson will allow me this indulgence mid-thread 😉

     

  13. A bit of an aside, but "Crimson Finishing Oil" is an grossly overpriced product (or variants of the same product now, it seems) that are simply an analog of Tru-Oil or otherwise cheap BLO cut with a varying fraction of solvent. Get a tin of naphtha (light fluid) and cut your own oil. It's way cheaper, and you can control the flow of the oil throughout your finishing process whether it's for a penetrating flood, bodying or flashing final coats. Work smarter. I buy Tru-Oil 960ml at a time for our Sapele furniture and house fittings and divide it up into jars of 8:1 cut and 4:1 cut.

    • Like 1
  14. Exactly that sort of jig, yes. Given the right design, it shouldn't be too difficult to tune in the shoulders to tenths of a degree. How did yours turn out, Andy?

    I know I shouldn't think about acoustics for more than a hot minute otherwise I lose focus on all the other silly things in my head and find a new one to roll over and over....

  15. Absolutely! Acoustics are very much dialled in at the time of build. I always feel that if I cannot bring these factors under my command at every stage, it becomes a guessing game....which I refuse to do any more. I would say that angles in the neck are the best way to locate these string loft changes, however by the same coin I think one needs a real command over dialling in angles on a very small footprint that yield changes of tenths of a degree. The place where a porpoise-made jig is required. I can't recall off the top of my head, but isn't that the sort of adjustments that Taylor build into their adjustable shim system? Not that it applies here, but that sort of ability to work in fractions where it matters?

  16. On 8/26/2023 at 4:35 AM, ADFinlayson said:

    Well when it comes to action .33mm is a big number. I don't think I need much anyway now that I've done some tape pulling. The bridge is currently 8.5mm, I can bring that down to 8mm, then there is the height of the frets too, I think I should be able to obtain decent action depending how much lift there is on the top. Worst case scenario I need to tilt the neck back a bit more and stick a veneer under the fretboard extension. 

    I think I will increase the break angle in the soundboard on the next one though, all it would have needed was an extra few mins sanding on the ribs. 

    Agreed, it can make the difference. I see it as a large and somewhat unorthodox way of achieving that end, especially since it is fundamentally baked in from that point. It sounds (and looks) like these other factor are making a bigger difference than this one. This is a bit of a world away from what I do, as acoustics have so many other different factors to work with than a - simple by comparison - solidbody.

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