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  #31  
Old 05-18-2019, 01:53 PM
Gordon Currie Gordon Currie is offline
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Wow, nice job. Although it is a little bright it has no piezo quack that I could hear (and I'm pretty sensitive to it).
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  #32  
Old 05-18-2019, 02:38 PM
Cuki79 Cuki79 is offline
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Quote:
Originally Posted by Gordon Currie View Post
Wow, nice job. Although it is a little bright it has no piezo quack that I could hear (and I'm pretty sensitive to it).
Thanks, I am back to the drawing board



1) I tried full folding: It kills the tone (I guess high end). I need the film to be free to vibrate.
2) I tried half folding (see picture), it just lose half of the signal.
3) I tried to add feet (think HFN): it CLEANS the low mid growl much...

So I need to find the proper feet size to 3D-print...

Also I think I will not avoid half of the pickup standing in the air...
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  #33  
Old 05-18-2019, 03:57 PM
jonfields45 jonfields45 is offline
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You getting results that sound quite good. I wonder if it would be possible to have some sort of know reference pickup recording so we can place what your achieving given all the recording and playback variables...
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  #34  
Old 05-18-2019, 06:00 PM
Vancebo Vancebo is offline
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Itís very clear to me we need a new forum category. We can call it Pickup University. Professor Cuki and James May can be the professors and we can add others as needed.
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  #35  
Old 05-19-2019, 12:18 AM
Cuki79 Cuki79 is offline
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So I made more Lego experiments

1) I tried different feet size but using the same position behind the bridge (First 3 upper pictures). This time I recorded simultaneously the undersaddle transducer (UST) from the Yamaha FG.

2) I positioned the Lego on the bridge, behind the pins, half standing in the air as it is inside the Eastman (Lower 2 pictures). I have very similar results as Pickup v1.0. Then I tried with the smallest feet at the same position.



Experiment 1)
3 first strums are for 3 differents feet sizes of the LEGO suspended PVDF. 3 last strums are the exact same but recorded with the UST.


Experiment 2)
First is with a full length contact (see lower left picture)
Second is for the smallest feet (see upper right picture)
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  #36  
Old 05-19-2019, 08:16 AM
SpruceTop SpruceTop is offline
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Thanks, Cuki! With your ongoing research and experimentation, there's really no reason why you couldn't develop a really good-sounding system and market it if you could secure the necessary financing.

Do you feel that a system needs to be located at the focal point of vibration, i.e., the bridge-saddle area as Ovation research determined for best gain-before-feedback, or could a system be developed that would provide a more mic-like signal and still be feedback resistant if located somewhere else on a guitar's top? How about a thin electro-generating film of vibration-sensing material that could be applied directly on and over a larger area of the underside of a guitar's bridge plate and top. Perhaps an electro-vibration spray could be developed that could be sprayed on the bridge plate and underside of the top over areas the size of which could be determined to generate the best-amplified tone. Electric leads placed at positions at the edges of the film would then feed a preamp. There could even be two or more large-area sensing regions feeding a preamp. Likely, larger-area sensing would present some phasing issues but it may be a concept worth some research?
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Last edited by SpruceTop; 05-19-2019 at 10:02 AM.
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  #37  
Old 05-19-2019, 09:59 AM
Cuki79 Cuki79 is offline
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Quote:
Originally Posted by SpruceTop View Post
Thanks, Cuki! With your ongoing research and experimentation, there's really no reason why you couldn't develop a really good-sounding system and market it if you could secure the necessary financing.
Thanks Ken, similarly to the IR project I don't think I'll ever make a penny with my little project. I am French, we are poor business people. We don't know how to monentize the stuff we do.

Quote:
Originally Posted by SpruceTop View Post
Do you feel that a system needs to be located at the focal point of vibration, i.e., the bridge-saddle area as Ovation research determined for best gain-before-feedback, or could a system be developed that would provide a more mic-like signal and still be feedback resistant if located somewhere else on a guitar's top?
I don't think you can be feedback resistant away from the saddle-line. It's physics. The more you sens the top, the less feedback resistant. If you only sens the strings then you are super feedback resistant because the strings have poor coupling with air vibration. I think the main job of the top is to provide acoustic impedance matching between the vibration of the strings and the vibration of air.... The good working top is well coupled to the air vibration and will feedback easily.

If feedback is the problem, you'd better cut the relation ship between the air moved by the loudspeaker and the guitar top... like playing behind a plexiglass wall ()

Another way to kill that relation ship would be for example to work on the frequency domain and psycho-acoustic. If you make a digital FX that supresses the fundamental frequencies that correspond to the guitar top frequencies and wisely boost the harmonics: You could maybe still keep the feeling of "bass presence" to the audience and remove the offending frequencies.

Quote:
Originally Posted by SpruceTop View Post
How about a thin electro-generating film of vibration-sensing material that could be applied directly on and over a larger area of the underside of a guitar's bridge plate and top. Perhaps an electro-vibration spray could be developed that could be sprayed on the bridge plate and underside of the top over areas the size of which could be determined to generate the best-amplified tone. Electric leads placed at positions at the edges of the film would then feed a preamp. There could even be two or more large-area sensing regions feeding a preamp. Likely, larger-area sensing would may present some phasing issues but it may be a concept worth some research?
I don't think it would be feedback resistant but it could indeed sound great and help providing a stereo image of the guitar projection. I've been thinking of things similar... But this kind project is way to time consuming for me.

I started the pickup project because I thought there was a way at "low volume" to compete with IR.

I think the biggest challenge would be to get rid of the comb filtering effect of a magnetic pickup. If you can do that, you can apply IR to a magnetic pickup and the acoustic amplification problem at loud volume is solved.


My initial project started from a Doug Young post or pm saying that PUTW #54 was the most mic-like pickup, quickly followed by a bunch of drawbacks experienced by Doug Young and MartinGitDave:
* Poor tape fixation
* Handling noise
* Weak output
* Feedback prone
* Needs really high impedance preamp

I have a feeling that many SBT have poor high end... So you push them too hard to make them loud, resulting in a lower feedback resistance. So my idea was:
* Find an Amulet red tape equivalent (I am pretty sure I have found one). I have tests showing no significant difference between superglue and this tape when proper clamped.
* Find a way to damped noise. I thought the Perculens (see one of my previous thread) cable dampers was a good idea.
* Suspend the PVDF film to let it vibrate: huge loudness improvement: probably both because of decreased damping and better high end.
* Feedback: Well... we will see that if my theory works
* Onboard FET voltage preamp or outboard "charge amplifier"
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  #38  
Old 05-19-2019, 10:12 AM
Cuki79 Cuki79 is offline
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Quote:
Originally Posted by SpruceTop View Post
How about a thin electro-generating film of vibration-sensing material that could be applied directly on and over a larger area of the underside of a guitar's bridge plate and top.
I forgot to say: each part of the film that is not vibrating acts as a load capacitor and decreases the signal strength.
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  #39  
Old 05-19-2019, 01:01 PM
Cuki79 Cuki79 is offline
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I moved pickup v1.1 toward the center (still behind the pins)



Well without the preamp it is very bright, even with the preamp.

1) Direct
2) Through 4.2 Mo input impedance FET preamp



It seems that there is a resonance in the high-end that is shared by both positions. For both position the tone is different, but there is that harshness.

I guess the size of the suspended PVD Film counts.

Probably I should try an enclosure half way between v1.0 and v1.1
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  #40  
Old 05-19-2019, 01:41 PM
SpruceTop SpruceTop is offline
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Cuki, you're a mad scientist with around-the-clock experimentation! Do you ever sleep? Thanks For All You Do!
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  #41  
Old 05-19-2019, 02:08 PM
Cuki79 Cuki79 is offline
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Quote:
Originally Posted by SpruceTop View Post
Cuki, you're a mad scientist with around-the-clock experimentation! Do you ever sleep? Thanks For All You Do!
Lol

I live in France. I do my mad experiments when you sleep!
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  #42  
Old 05-20-2019, 06:27 AM
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martingitdave martingitdave is offline
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Great work Cuki! Perhaps you should look at the Trance model and try two pickups on either side of the bridge plate?
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  #43  
Old 05-20-2019, 07:02 AM
Cuki79 Cuki79 is offline
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Quote:
Originally Posted by martingitdave View Post
Great work Cuki! Perhaps you should look at the Trance model and try two pickups on either side of the bridge plate?
I definitely thought of it... But I also thought that the Trance brightness might come from the sensor more than the position.

When I place pickup v1.1 in the middle I get a much brighter sound than pickup v1.0.

It could be either:
* The coupling surface
* The supended PVDF surface
* the suspension wall that are twice thicker for the pickup v1.0 (I stretched the drawing to make it larger)

So right now I cancelled the adjunction of a second pickup... Although I do think the second pickup on the bass side will bring some balance it might not counter the high end harshness if it is due to the sensor itself.

I will first try
1) Add feet to the pickup v1.0
2) Make a smaller sized pickup v1.0

Then we will see...
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  #44  
Old 05-20-2019, 07:04 AM
Cuki79 Cuki79 is offline
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If the PVDF suspended lenght plays a key role. One can imagine a tunable enclosure that let the user choose how long the PVDF film will be suspended and tune his sensor response to his taste...

Also a smaller enclosure could probably fit in under the saddle line....

This is also something worth experimenting.
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  #45  
Old 05-21-2019, 01:40 PM
Cuki79 Cuki79 is offline
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I gave pickup v1.0 wide enclosure a try again. But with double tape only on each side and not on the whole surface.

I've put the PVDF film of pickup v1.1 so it still have the fold trauma and is not perfectly suspended... Also I forgot the clamp overnight... Just go it out.

It sounds much more balanced than the first time with full tape...



1) With preamp 4.2 Mo input impedance
2) Direct

I have the new enclosure but I might want to wait one day before trying.

I am sure with 1 Mo input impedance I can clean the boom and get something good.

Strumming with a pick leads to no quack.

UPDATE: I tried plugged into the JAM 150. I needed the input impedance of my FET preamp to be reduced to 220Ko again to keep the low end under control (still when you tap on the bridge, you hear the feedback woof starting). The sound is also a bit distant.

UPDATE 2: The pickup was just taped on the treble side, when I removed the strings later on. The bass tape did not hold.... Don't know how it was during the recording...

So I need to try the new designs.
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Last edited by Cuki79; 05-22-2019 at 06:52 AM.
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