SBT pickup: Dummy experiment II

[Cuki79]

This thread is the following of https://www.acousticguitarforum.com/...d.php?t=542977



I did not post picture of the 2nd install of pickup v8. The sensors are the same.
Pictures 1&2) But this time I put RCA connectors to be able to listen to them while installing. I recorded each sensor (clamped, non clampes... ) and taped them for 24h. Unfortunately I forgot to sand & cleanthe bridge plate. I ended up with -6dB volume but less or no 3 Khz resonances.
Picture 3) I made a Lego foot for the turnbuckle clamp (from Trance Audio). It made each sensor installation MUCH easier.
Picture 4) I transfered the preamp demo board to a PCB (forgot a decoupling capacitor in the schematic: Ouch!). Debugged a lot. Changed the values of the charge amp capacitor and resistor. There is a trade-off between high-pass filter frequency, gain and noise.
Picture 5) Finally put everything in an old project box (The Lyric gilgaus mod project)

It has two pots.
* One pot scoops the mids. I did not have any linear pots anymore so it's a log pot and all the EQing occurs after 60% turn
* One pot that changes the balance of tone. One side is "warm" (can't really hear it with mp3 compression and headphones) and the other is "bright".

Here is a video of the pot FX. I did not tune well the fingerstyle first part which is a bit too "scooped", It's hard to tell while having the guitar acoustic tone. The flat picking part is better, maybe a bit too bassy. Overall it's not that bad.


... sorry for the english mistakes (not a native speaker).

[SpruceTop]

Again, Cuki, your system sounds as good as anything out there. If you could make it for a reasonable cost and sell it for a reasonable cost people would buy it if you could get the word out. Also, for marketing, you'd need to come up with a catchy product name to stimulate the senses of prospective buyers. How about The AcoustiPhonic Acoustic-Instrument Pickup/Preamp System?

[Cuki79]

Originally Posted by SpruceTop

Again, Cuki, your system sounds as good as anything out there. If you could make it for a reasonable cost and sell it for a reasonable cost people would buy it if you could get the word out. Also, for marketing, you'd need to come up with a catchy product name to stimulate the senses of prospective buyers. How about The AcoustiPhonic Acoustic-Instrument Pickup/Preamp System?

Thanks SpruceTop,

I have no plan on selling. I did make pickups v5 for friends but with time & covid they never made to the guitars.

In this case, there is nothing special. I don't see why people would buy pickup v8 from me, they should buy local (Dazzo or Trance Audio). Pickup v5 was very different from other manufacturers pickups.

My conclusion so far with pickup v8 is:

• Most soundboard transducer sensors placed under the saddle line seem mid forward sounding.
• Many onboard pickup preamps are voiced
• Quack is also related to poor headroom from your onboard/outboard peamp. [My preamp has 24V headroom from a 9V battery, thanks to the KLON centaur power supply stage]
• Making a voiced preamp specially for your guitar and pickup is less difficult than looking for the sweet spot position of each sensor. [Because you don't know what you are looking for...]
• Once done, you have a VERY usable pickup with no quack.

So if you are looking for Flat-EQ great sounding SBTs (in no specific order):

• Buy a Trance Audio Amulet and have Maury from Maury's music install it
• Buy a Dazzo and have it installed by an experienced guy who knows how to do it
• Buy a James May Ultra-tonic pickup

Listen to Doug Young pickup page to make your mind.

If you want to improve your tone and don't like what acoustic IR brings (muddiness, lack of cut...), but still want a more "efficient" tone.

Learn to EQ... or

• Make an IR with my free app
• Use the png file to see what is the global EQ curve of the IR file
• Use this information to learn how to EQ your pickup with a free EQ plugin like Melda EQ.
• Buy/Make the proper pedal to perform these EQ corrections.

PS: I don't know what is next. Maybe a crossover between Pickup v5 and v8.
Getting the sweetness-organic feel of v5 blended with the directness/straighforward nature of v8 would be cool. I'd need another dummy guitar for that... The Eastman deserves to retire from experimental pickup adventures.
PS2: The temptation to get rid of the EAE stompmix is high too... Because now I know how to make both a better all analog guitar & mic preamps... But the EAE stompmix is so convenient feature wise ...

[martingitdave]

This is excellent work as usual Cuki!

I agree with all of your conclusions. In fact, I would go a step further and say that most of the QUALITY made sound board transducer systems: Trance, Dazzo, K&K, JJB, JM Ultra Tonic, make for great sounding acoustic guitar pickups with a matching preamp.

I've been arguing for some time, since completing my years long pickup quest, that the best overall tone and features for me have been accomplished with a passive SBT (in my case K&K) and a decent preamp.

The occasional consternation for me has been finding the right plug and play ONBOARD preamp for a SBT that brings the features of a pedal to your fingertips without weighing down the guitar.

In my experience, the two best sounding internal preamps for K&K are made by K&K and the other is Seymour Duncan Wavelength. The K&K works exactly as advertised. But, I happen to like the SD Wavelength better because it includes an electret mic and independent dual source controls.
Finally, the headroom in the Wavelength is 24 volts. That makes it quack free. It really just works great with a K&K if you know how to solder.

I think the user needs to consider the acoustic guitar itself before applying any internal electronics to it. So far, I have had ZERO luck putting anything more than a passive SBT or Fishman Matrix in any lightly built acoustic guitar. I can hear and feel the difference in tone almost immediately. Believe me, I've tried them all. Taylor's ES2 is the only onboard electronic system that does not seem to degrade tone and feel. All the others do in my experience.

So, it is my independent conclusion, verified by thousands of dollars spent, and hundreds of hours wasted, that fine acoustic guitars should have no more than a simple passive pickup and/or perhaps a bare condenser mic. Pair it with the right preamp and enjoy. If you need a fully onboard solution dedicate a guitar for stage use and put whatever pickup you desire with the right set of features. But, don't spend too much money on it because it's not going to sound like a fine acoustic one you get everything setup inside of it. This is the route I am going. One fine Martin with a passive K&K. One Taylor 12 string with it's lightweight ES2, and a RainSong with the K&K-Wavelength pairing for gigs, travel, etc.

Cheers!

[Cuki79]

Hi everyone,

I decided to experiment with dual-source.


1) I bought a few $ capsule and soldered it. (It's the little mic on the top right of the pick)
2) put the mic in foam
3) double tape the foam with the mic next to the soundhole, by the X-bracing facing the neck joint. The white triangle under the saddle line are the pickup v8 SBT ("Dazzo" shape inspired)
4) You can see the gray foam at the bottom of the soundhole.
5) setup for 2-track recording. (internal mic and sounboard transducer)
6) DIY preamp. Top IC is the mic preamp, middle IC is the charge-amp for SBT and bottom IC is the power supply (KLON centaur inspired)
7) I set the crossover to 400 Hz so the soundboard piezo transducers handle the frequencies below 400Hz while the mic handle everything above.


1) SBT (Pickup v8) alone (no EQ)
2) Internal mic alone (no EQ)
3) mix + crossover:
* below 400Hz: SBT
* above 400Hz: internal mic

Now I need to design the EQ and controls of the preamp

Note: I am pretty sure I can get a better sound by letting the mic exceed the soundhole

[SpruceTop]

That's a lot of great work, Cuki, and Thanks For Doing It!

[martingitdave]

I listened to the samples and I think they sound excellent. My favorite part is the bread board with the girls' LEGOS. A great engineer and even better Daddy!

[Cuki79]

I tried to pull out the mic from the foam



Also there was a major mistake on the mic preamp (not sure I corrected everything)



1) SBT pickup v8 alone (no EQ)
2) SBT pickup handling everything between 80Hz and 400 Hz (low end) + internal mic handling everything above 400 Hz

[Marty C]

Impressive Cuki. I don’t understand 75% of what you are talking about, but the sound samples keep getting better and better.

[Cuki79]

Originally Posted by Marty C

Impressive Cuki. I don’t understand 75% of what you are talking about, but the sound samples keep getting better and better.

Thanks,

I am sorry for the technical terms...

now the filtering (EQ) and mixing are done by the computer.

I am designing the circuit to make preamp pedal with everything onboard.

I have also to adjust the gain and Signal to noise ratio also on the mic....

I found out that electronic can be as demanding as pickup design in order to achieve the tone you want.

[Cuki79]

...mmm I added the filtering to the analog preamp board...

Well, it does not run on battery anymore, it needs a wallwart.

It brings also a lots of noise... also I half burned ones of the power supply Integrated Circuit... I have only one left in stock. The one in my go-to preamp...


Going digital for the EQ and mixing is actually easier... not sure I want to go this way though.

...to be continued...

[Cuki79]

Ok

starting from scatch but taking more time to make it better.

Here is now the internal mic alone.


Gain is better set, and HPF too. Previous did not make any sens... lol.

Note that I get a lots of room noise.

1) If one wants to use the crossover idea, the internal mic must be buried in the box (like the Anthem) to catch the least room noise. It's doomed to be boxy without EQ. (Thus the need for reflexion cancelling idea of the Anthem/Lyric mic)
2) If one wants to use the mic positioned like Doug Young does, in my opinion, the mic must be a complementary source. Because you want to be able to balance between the benefit (more air, natural tone) & drawbacks (room noise) . The crossover solves the feedback problem not the room noise.

The more I investigate that problem, the more I think dual source needs elaborate electronics... It can't be done cheap & dirty with high expectations....

UPDATE: Most of the noise comes from a ground loop. I get it when recording but not in direct monitoring. It tames when touching the ground...

...to be continued...

[Cuki79]

Here is the problem.

I mounted a standard Bass/Treble Shelf EQ (I could add Mid easily). It's a pretty simple circuit (see upper left picture in the red red square).

The EQ correction is shown on the lower left part of the picture.

HOWEVER, Sunny from Sunnaudio kindly pm me that it was not the best circuit for EQ... So I started to gather as much information I could on the internet and found that a better EQ curve would be something like the correction on the lower right:
* A 12dB/octave Highpass filter (like Grace Design Felix or Sunnaudio Stage DI-2 & MS-2)
* Some bandpass/peak EQ that you can set at strategic frequencies.
* The low frequency is about 100 Hz which makes sens since it is generally where the breathing mode is.



For the treble, my choice would tend to 2-3 KHz (Doug Young told me 2 KHz).

The only problem is that this EQ section would require 6-7 Op-amps, plus 1 if I add a parametric mid pots. It's 8 times more than the regular bass/treble EQ. (Sunnaudio customers, you know what you pay for!)

I designed the circuit as shown on the higher right part of the figure and ran simulations and it would work perfectly.

However building it would take the whole board room... and I'd still need room for the second channel... and the mixer...

FACTS:

• Can I do it? : YES
• Would it work? : Probably... But after huge time spending in debugging, trial & error
• Would I end up with something usable? : I would probably end up with a Huge noise monster full of ground loops and electromagnetic antennas...

so the question is Why not going digital?

So I took 15 min to reprogram my axoloti based pedal and... it works!

To be continued...

[Cuki79]

I just set up the Focusrite to sinesweep (scan) the Axoloti pedal EQ and here is what I get.

Note: the little waves on the treble boost are measurement artefacts.

It works flawlessly with minimal effort and pain.

Bonus: The pedal can do easily the MS decoding (i.e. stereo imaging "à la Doug Young"). It's just a programing...

PS: Of course the quality will never be as good as Grace Design or Sunnaudio nice analog circuits.
The question is: "Will it be good enough?"

...To be continued...

[martingitdave]

Originally Posted by Cuki79

Here is the problem.

I mounted a standard Bass/Treble Shelf EQ (I could add Mid easily). It's a pretty simple circuit (see upper left picture in the red red square).

The EQ correction is shown on the lower left part of the picture.

HOWEVER, Sunny from Sunnaudio kindly pm me that it was not the best circuit for EQ... So I started to gather as much information I could on the internet and found that a better EQ curve would be something like the correction on the lower right:
* A 12dB/octave Highpass filter (like Grace Design Felix or Sunnaudio Stage DI-2 & MS-2)
* Some bandpass/peak EQ that you can set at strategic frequencies.
* The low frequency is about 100 Hz which makes sens since it is generally where the breathing mode is.



For the treble, my choice would tend to 2-3 KHz (Doug Young told me 2 KHz).

The only problem is that this EQ section would require 6-7 Op-amps, plus 1 if I add a parametric mid pots. It's 8 times more than the regular bass/treble EQ. (Sunnaudio customers, you know what you pay for!)

I designed the circuit as shown on the higher right part of the figure and ran simulations and it would work perfectly.

However building it would take the whole board room... and I'd still need room for the second channel... and the mixer...

FACTS:

• Can I do it? : YES
• Would it work? : Probably... But after huge time spending in debugging, trial & error
• Would I end up with something usable? : I would probably end up with a Huge noise monster full of ground loops and electromagnetic antennas...

so the question is Why not going digital?

So I took 15 min to reprogram my axoloti based pedal and... it works!

To be continued...

You're making an excellent point! While I am not an EE like you, I am an engineer, so I understand the rudimentary basics of what you are saying. One peak inside my new Sunnaudio DI-2 device show how complex and well built Sunny's design is. While others are just looking to make their designs cheaper for mass market, this really is the kind of boutique electronics and analog circuit that audiophiles would appreciate. Besides that, for me, the most important consideration is that it sounds great! I guess it should be no surprise that it sounds better when it's better designed and made with better components. I am looking forward to putting it through its paces in a live setting.