Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Schematics and Layouts => Topic started by: blues dog on September 21, 2011, 11:43:28 AM

Title: LR Baggs Piezo-Pickup preamp
Post by: blues dog on September 21, 2011, 11:43:28 AM
My effort of tracing the LR Baggs Piezo-Pickup preamp from a Godin guitar (the guitars belongs to my customer). I triple check the trace.. Hope don't miss something there..  :D

(http://farm7.static.flickr.com/6073/6058662418_1e3aaf80f7_b.jpg)

(http://farm7.static.flickr.com/6075/6058114469_6f164fdc4b_b.jpg)

(http://farm7.static.flickr.com/6158/6169740546_952e7218a3_b.jpg)
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on October 05, 2011, 10:04:50 AM
Thankyou for the effort,, but I'd check that again as Q4 does not seem to go anywhere?
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: J M Fahey on October 06, 2011, 12:12:40 AM
Q4 looks suspiciously like a gyrator, peaking some frequency.
Too sleepy to calculate it just now, might provide sparkle, body, or anything the designer thought was needed.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: blues dog on November 02, 2011, 09:30:44 PM
Agree with JM. Q4 used to maintain some freq for the piezo.
I guess this make the preamp character for the piezo sounds smooth in treble area.

BTW I succesfully made the circuit for the owner of this preamp.
So now he has 2 guitars with similar preamps:
- Godin (I forget the model) with this original LR Bags preamp
- budget Greg Bennet Les Paul with the "replica preamp"

Both of us love the tone. Even the customer feel sooo satisfied with the project   :)
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: J M Fahey on November 03, 2011, 03:57:50 AM
Goooooooood !! Congratulations !!
PLEASE post some pics of your work. :tu:


Hey !! What a funny thumbs up we have now !!
Dear joecool, are you sure it´s OK?
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: joecool85 on November 03, 2011, 09:34:14 AM
Hey !! What a funny thumbs up we have now !!
Dear joecool, are you sure it´s OK?

New forum software, new emoticons.  I'll see what I can do though.

**edit**
Fixed and even added a double thumbs up ->  :dbtu:
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: J M Fahey on November 06, 2011, 04:24:29 PM
Well, all I can say is  :dbtu:
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: zedonetx on October 28, 2015, 06:22:27 AM
do you know the model of this Godin guitar? I need something for my classical-flamenco guitar. and i want to make a good natural tone Preamp. :)
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: J M Fahey on October 28, 2015, 08:59:40 AM
That L R Baggs preamp is *very*  good.
I just calculated the "mystery gyrator" frequency and it's surprising (or not? ) 95 Hz
Clearly it adds body to turn usually famigerated "Piezo shrillness" into nice warm fat sound, without losing top frequency transparency.
AFn excellent design ... although you'll have to design your own PCB .

This one is for dual mics, Piezo and Magnetic, if you use just the Piezo, you can simplify the design quite a bit, since you need neither the Magnetic preamp nor the mixer, in that case V1 volume pot can straight go to output jack.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: Enzo on October 28, 2015, 01:51:12 PM
And Baggs and others already make a selection of such pickups and preamps.  Unless you are just into making a project, you might consider a commercial product, one that has a pickup designed to work with it.  My friends at Elderly can help you, and other places like Sweetwater as well.

http://www.elderly.com/accessories/cats/PUA.html

http://www.sweetwater.com/c985--Acoustic_Guitar_Pickups
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: dogbox on November 02, 2015, 08:27:52 PM
That L R Baggs preamp is *very*  good.
I just calculated the "mystery gyrator" frequency and it's surprising (or not? ) 95 Hz
Clearly it adds body to turn usually famigerated "Piezo shrillness" into nice warm fat sound, without losing top frequency transparency.
AFn excellent design ... although you'll have to design your own PCB .

This one is for dual mics, Piezo and Magnetic, if you use just the Piezo, you can simplify the design quite a bit, since you need neither the Magnetic preamp nor the mixer, in that case V1 volume pot can straight go to output jack.

That's very interesting JM. Can you explain how you calculated the frequency affected by the Gyrator, I'm geussing the Gyrator (i had to google gyrator to find out what it was :-[), acts as an Inductor, so is it some kind RLC filter..maybe a bandpass?? Am I completely on the wrong track?? I've been recently playing around with some homemade piezo disc pickup/contact mics. Still yet to get that magic sound. There sure are a lot of schematics on the web and ideas about how to tame these piezo devils.

Have tried Tl072 chargeamp based circuits, and various well known things like Tillman and offshoots. I got a some largeish discs, some salvaged from buzzer, and these really small ones that are very trebley/high end. Have tried mounting the bassy one and the treble disc feed into a 2 stage jfet preamp that I found on a ham radio site, I added 10m input resistor. I then added a passive mixer - just 2 -  10k pots - 10k resistors. It works but the larger disc really over powers the smaller. I only have 1k, 10k, 20k pots on hand. I tried a 20k pot on the smaller and got more signal in the mix. But it lacks a bit of sparkle, and its now lost a bit of volume.

keen to give this one try on the breadboad before I get out the soldering iron and commit to my lastest version. I have mpf102, and some BC 54x . Would they be ok this LR Baggs circuit?? If you have suggestions..I'm here to learn..cheers
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on November 03, 2015, 06:27:58 AM
This might help explain some of the issues you will face.

http://www.ozvalveamps.org/pickups.htm

I know it's fun to muk around with pz elements but there are many hurdles to overcome.
These days piezo elements are cheap and plentiful and all the initial bugs are already well researched.

Even with the above sorted the preamp can be a mine field. I doubt few manufactures take the type of guitar into account as most just use of the shelf electronics in cheap plastic cases and no matter how impressive the specs Low frequency Feedback is often big issue with ElAcoustics.

Any large cavity with two parallel planes (Classic acoustic Guit shape) will resonate in sympathy at certain frequencies. The smaller body guitars tend to have less FB issues.

Ovation may not be everyone's fav axe but they did get one very important factor dead right, that is the bowl back minimizes the dreaded feedback. <3)

As I play a lot of open mic gigs these days I've resorted to a cheap plastic Acoustic and although unplugged it will never compete tone wise with Martins or most other exotic instruments it's a massive sound when amplified. I've been asked many times about how I get such a huge sound.  8) 8)

The guitar is a Hornby Skewes Vintage Synergy Vr6 with a bridge piezo and onboard Fishman Isys preamp. it has no tone controls just a volume and a contour push button,, oh and a stupid tuner which I hardly ever use.  See here; http://www.jhs.co.uk/vintageelectroacoustic.html

Like a lot of these preamps the output signal can be anywhere from average to insane loud causing many headaches.  :grr :grr :grr My unit's output was too hot past halfway and that was rectified by simply wiring a passive 25k master volume control on the output. The first volume is then used as a gain control and hardly ever gets moved.

The added passive master volume is mounted on the face which makes for super fast volume changes.
When playing solo you can't access side mounted controls fast enough and that is very frustrating for me as I use volume control a lot on both Electric and Acoustic.

All the rest of the sound comes from a dedicated tone circuit I designed > then pedals and amplifier setup do the rest.
Hope it helps, Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: dogbox on November 03, 2015, 01:24:42 PM
Thanks Phatt that was a great link you posted. Yeah it is a bit like re-inventing the wheel, but playing around with piezo is fun, and educational..and safe for the kids (as they say). Currently living in Bengkulu , Indonesia and chances of me being able to get brand name pickup are slim to none. I've only got an Indo made acoustic nylon string, masonite fretboard, and cheap but surprisingly good sounding ukulele. I really want get some kind of rig together so I can jam with a few mates.

I just try get as natural sound, try eliminate the bass loss as much possible. My rig is a powered no name one hung low PA bin that definitely needs something between the piezo and the amp. Straight piezo with no buffer equals, distortion, horrible tone..feedback, due to its 100k input resistance, this thing was designed for fynamic mics. Been trying various simple preamps on a breadboard. They all work to an extent, but feedback is defintely an issue, and certain notes on certsin strings can cause a vibrational buzz. Fine tuning the placement of the piezo on the body can get different tones, using a couple at the same time yields better results when attached to the outside. In the Oz valve article, he talks about putting a couple of caps in series, I geuss hes really talking about use of piezo into a valve amp. I just bypassed my preamp and a tried a couple of cap values as suggested 5000pf and worked pretty good..one cap is ok, 2 is better. Its late and I can't crank the amp, but i just fed my passive blender into the caps..totally surprised..sounded pretty good??? Why?. LOL

I have got the Baggs circuit on my breadboard, minus the gyrator. Not sounding any better/worse than the ham radio one i already had. Gonna add the gyrator tomorrow see if magical sparkle appears :). The passive circuit defitely seems to tame this disc, and still getting a nice amount of bass tones. How it that even possible??
Anyways mate....cheers for the info
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on November 04, 2015, 08:40:21 AM
Ok now I think I understand ,, you want to do this as cheap as possible.

Then go with the first schematic and tweak until you are happy. :tu:

My only concern is that some of these circuits require specific Fets to work correctly.

If it helps there are a lot of Ovation drawings here:
http://www.ovationtribute.com/Schematics.html

Also this is very simple to build and may work ok with your idea.
http://www.hawestv.com/amp_projects/fet_preamp/fetpreamp2.htm

Yes try a small value cap directly across the piezo element it may help, maybe start with 50nF
better minds here may know more about selecting values. all my research was a long time ago but I did once mess around with some ceramic transducers and found them to be very quirky things to work with. You can't directly mount them and expect good sound as they need a small amount of mechanical suspension otherwise they feedback.

Try a strip of double sided tape or something similar between the element and sound board.
If you are familiar with those old ceramic phono pickups (found on old budget record players) you will notice the needle is not directly mounted to the ceramic strip,, it's got a small rubber shock absorber between the needle and ceramic element. Without that tiny rubber mount the sound would be very peaky and likely render it useless. :'(
I did once remove the needle and just rested the tiny rubber foot onto the sound board of a guitar and got signal that was passable but hard to mount it all and gave up.
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: dogbox on November 08, 2015, 05:40:25 AM
After a little bit more experimenting with ideas contained in ozvalve I'm convinced that you can improve the performance of the piezo by soldering a cap and resistor directly to the disc. My results...
I tried a 100n/1m resistor. Just that on its own was enough to open up the disc and get all useable  frequencies passed. I was able to plug directly into my macbook laptop audio port which has 20k impedance. I recorded some audio ..ended up a pretty low level around -10db to -20db., and it is obvious that the disc i used must have a resonant frequency around 2.5-3k hz. That makes sense I geuss those are the most easy to hear frequencies for humans, and these disc are generally used as alarms. When I pulled those frequencies down in the mix with a parametric eq plugin, it really sounded pretty good. So I geuss my next step is to create a preamp that boosts the signal, and has a filter/ pot that allows me to reduce those frequencies that make it sound harsh. I also tried a band stop to roll off the high frequencies afte 10k..that helped a bit too. The bass didn't really need much..pretty well all there. On k&k sound website they say for contact mcs to try nd get the pickup direct onto the guitar body, if you use tape put it over the back of the pickup. I definitely got better results that way. But maybe playing into amp, or with a pre it might be too hot a signal. Having fun playing around. Definitely worth experimenting with a couple components on the disc. With my limited knowledge I believe i have set high pass filter on the disc..thus reducing the need for a such a high value input resistor in the preamp?
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: paosal on June 05, 2016, 03:05:44 AM
Does anyone knows what kind of fet to use? J201, 2N5457, MPF102 and what for the PNP
Thans

Paosal
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on June 06, 2016, 09:17:19 AM
The device is not that important. You work with what is at hand and adjust Drain and gate Resistors to get the best clean signal output.  MPF102 is likely the easiest to come by.

As for the BJT they are just followers so any ~ 25volt pnp transistor will work much the same.
It's a high Z input so watch the grounding as it will pickup noise if not well shielded at the input.

Phil.
 
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: paosal on June 18, 2016, 02:18:57 PM
thanks a lot phatt, i'll try with some 5457

paolo
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on June 19, 2016, 04:35:53 AM
I've just been running some tests of the LR Baggs circuit as well as something I built a few weeks back to fix a friends guitar which had a dead preamp module.

This Screen shot is an A/B comparison of the 2 circuits output curves. Green is Morris Yellow is LR Baggs

My Preamp circuit is a copy of an old Morris preamp with a couple of slight mods to fix the excess bandwidth which is a common issue for Piezo pickups.

Active Piezo's are a brilliant idea but the outputs are often very different. The output signal strength as well as the response cuves vary a lot. As can be seen here the LR Baggs output is almost half of the Morris and quite different curves.

You may need to experiment with a few circuits to find a happy solution.

I've found that most of the bridge under saddle transducers don't need excessively high Z preamp inputs. Past 2meg is just asking for low freq FB issues, especially on large body guitars. The early bug type transducers did tend to suffer bass loss without really hi Z,, like 10meg.

Regarding low freq FB; I've found that a central post wedged between bridge and back can help in some instruments, A case of suck it and see if it helps. As it's only wedged in place the mod is usually reversible. for those that may think it a rather non professional fix up,, Violin luthiers are known to use a post to reduce resonance between the face and back, moving it around to find the sweet spot. I'd guess guitar luthiers would reject the idea as folly.
Try it if you have bad FB, you might be surprised.
Phil.   


(https://s5.postimg.org/faouweyqf/Morris_preamp02.png) (https://postimage.org/)image url upload (https://postimage.org/)

(https://s5.postimg.org/6tpclhu1j/Ph_Abb_Fet_LRBaggs.png) (https://postimage.org/)upload a picture (https://postimage.org/)
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: paosal on July 06, 2016, 01:29:59 AM
I tried to build a stripboard version but it seems that does not work , very very low signal . I used BC177 and 2N5457. Here is the stripboard version.  Can someone help me?
I've tried a lot of other preamp but no way to have a good bass frequency response like Element LRBAGGS or NaturalI Fishman
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on July 07, 2016, 09:29:36 AM
Maybe draw up the schematic of what you have built,, then take some voltage readings on the running circuit.
You need to note down the DC voltage at the drain and source of the Fets and other places if asked.
Then some of the better minds here will likely be able to help you.
This will also help you to work from a schematic rather than a layout.
Sadly layouts are very much harder to fault find and I think most technical people do not have the time to draw out your circuit from that layout.  You will get help a lot faster if you go to the extra effort and draw up a schematic to reference with numbered components and some DC voltages.    :tu:
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: paosal on July 07, 2016, 11:30:45 AM
Thanks a lot Phatt, in the meantime I've tryed the Phabb fet boost, very nice, warm and big headroom
could be used together with a magnetic p.u. like the lrbaggs? Maybe can I use the same buffer like in lrbaggs schematics?

Thx again

Paolo
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on July 08, 2016, 03:38:23 AM
Great! thanks for the feedback :tu: Good to know it's working for others.
I actually built this into my mates acoustic and while testing the idea I found it also worked well as a clean boost on my Strat. In the end I built it into a pedal and very happy with the outcome.

Assuming you are building this with the intention of running both types of PU in the one guitar then the only real issue I can think of is the output of Mag and Piezo will be at different levels so a bit of testing might be in order before you build.
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: paosal on July 08, 2016, 11:36:26 AM
When I go into the input with the mag it souns good but the piezo disappears. Could work use a simple tillman preamp to gain the mag signal and go straight to the output together?

paolo
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on July 09, 2016, 07:53:55 AM
Whoops! Now I see what you mean.

No Magnetic and Piezo don't mix as the Z of each is VASTLY different. :-[

A Mag pu has a much much lower Z (impedance) and will just load down the piezo and it will hardly work.
Yes you will need two separate preamps if you want to use them both at the same time.

Be aware that the frequency response of these two types of PU's will be quite different and two independent sections with separate tone circuits might be worth exploring.
Then blended in a final mix stage.

If recall right,, you might only need to use a unity gain preamp on the piezo. The output is then mixed into the passive Magnetic circuit using a high value pot.
i.e. in the case of a passive wired Strat circuit you would use a 250k pot and join the output of that to the output of the passive pot.

You would need unity gain on the piezo output and even then the signal will likely be louder than the passive magnetic PU.  Long time ago but I think that was how I remember it all.

The Morris preamp idea has +20dB gain so that won't work with the above.

Some help in understanding these piezo elements can be found here;
http://ozvalveamps.org/pickups.htm 
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: paosal on July 09, 2016, 04:15:19 PM
So, I use a modified tillman preamp to obtain quite the same level. The sounds both really good, the èickup is a Benedetto, so a low output p.u. The mixing of two p.u. is not so udible, you ear it only with both vol opened. Maybe I can post a sample and schematic

paolo
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: paosal on July 12, 2016, 05:01:41 AM
Hi Phatt, if I hitt hard the strings I have a little saturation, is due to the 20 db gain or is a 2n5457 biasing problem? I put a 50k trimmer instead of the 15k drain resistor to obtain 4.5v
The VR2 is a gain control?
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: J M Fahey on July 13, 2016, 04:15:58 PM
No 9V powered preamp can have 20dB gain and stay clean, because signal peaks will try to go beyond rails (9V and 0V), thus clipping.
AFAIK the original Tillman had 6 to 10dB tops (3X max.)  which is about all you can get away with.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: zedonetx on October 24, 2016, 02:24:45 AM
thanks for reply , and sorry for topic resurrection  xP A time comes and i am so much eager to make my own preamp project for my acoustic nylon string guitar. Then after a time, i forget it. then i remember again and search. and i find my postings here again. :) kind of weird, isnt it?

thank you for your info. i would rather like to make my own preamp since im an electronics engineer and a amateur musician.

And Baggs and others already make a selection of such pickups and preamps.  Unless you are just into making a project, you might consider a commercial product, one that has a pickup designed to work with it.  My friends at Elderly can help you, and other places like Sweetwater as well.

http://www.elderly.com/accessories/cats/PUA.html

http://www.sweetwater.com/c985--Acoustic_Guitar_Pickups
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: zedonetx on October 24, 2016, 02:30:11 AM
Can i ask some terms in the schematic?

BRIDGE?
RING?
TIP?
Can i learn what they refer to? I am trying to match "piezo", "under-saddle pickup", "jack" and "microphone" terms with them. thank you

My effort of tracing the LR Baggs Piezo-Pickup preamp from a Godin guitar (the guitars belongs to my customer). I triple check the trace.. Hope don't miss something there..  :D

(http://farm7.static.flickr.com/6073/6058662418_1e3aaf80f7_b.jpg)

(http://farm7.static.flickr.com/6075/6058114469_6f164fdc4b_b.jpg)

(http://farm7.static.flickr.com/6158/6169740546_952e7218a3_b.jpg)
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on October 24, 2016, 07:16:28 AM
Hi zedonetx,

*Bridge* refers to the Piezo element usually located in the bridge of the guitar.
*Ring and Tip* is the term used to describe the 6.5mm plug/socket of the common guitar cord.
A Mono plug is called a TS (Tip Sleeve) and a Stereo plug has the extra contact ring, TRS (Tip Ring Sleeve)
It is common practice in guitar preamps to use a TRS Socket in combination with a Mono 6.5 Plug to switch on the preamp.
The Ring contact in the socket is bridged by the mono plug and connects the negative of the internal battery to the ground/common of the preamp turning on the power.

The same idea is also used in most battery powered pedals,, inserting your guitar cord completes the circuit and power stays on until you remove the plug.

As you have an *Nylon* string guitar you can't make use of the Magnetic section as they only work on steel string guitars.
That means you only need the top part of that circuit so you can delete everything after C4 (the cap after the Volume pot).
hope that helps.
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: zedonetx on October 24, 2016, 08:41:41 AM
Thank you very much for your answer. it really helped me. one more question: Ok, i will take the upper part of the circuit for my classical guitar. but can i also add a microphone to this circuit? microphone gives more natural sound. i mean the circuit can be with Mic and Piezo at the same time? i want to used both. :)

thanks in advance,

Hi zedonetx,

*Bridge* refers to the Piezo element usually located in the bridge of the guitar.
*Ring and Tip* is the term used to describe the 6.5mm plug/socket of the common guitar cord.
A Mono plug is called a TS (Tip Sleeve) and a Stereo plug has the extra contact ring, TRS (Tip Ring Sleeve)
It is common practice in guitar preamps to use a TRS Socket in combination with a Mono 6.5 Plug to switch on the preamp.
The Ring contact in the socket is bridged by the mono plug and connects the negative of the internal battery to the ground/common of the preamp turning on the power.

The same idea is also used in most battery powered pedals,, inserting your guitar cord completes the circuit and power stays on until you remove the plug.

As you have an *Nylon* string guitar you can't make use of the Magnetic section as they only work on steel string guitars.
That means you only need the top part of that circuit so you can delete everything after C4 (the cap after the Volume pot).
hope that helps.
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on October 24, 2016, 09:05:02 AM
As you are likely not yet fully conversant with this type of setup I don't recommend a microphone addon.
Yes it has been done but requires a special mic and some specialized knowledge.
Even the best on board mic setups can have feedback issues and still will not sound as good as a normal outboard mic.

A piezo PU is ideally suited to Nylon guitar and in my experience actually often better sound reproduction than most microphones. (outside of a pro studio setup) 8|
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: zedonetx on October 25, 2016, 04:03:11 AM
As I am very interested in that topic, I decided to make a PCB schematic with PCBwizard v3.5. I added *.pcb file now to let you see the diagram. After making sure of the drawing, i will make auto-routing and it will be ready for PCB print-out. :) As you see, i only did the piezo part of the circuit, as @Phatt said, i didnt take the magnetic part of the circuit as long as it is for my nylon string guitar :) thanks to @Phatt

Battery should be supplied with 9V, right?

Any suggestions for the schematic that I have drawn is appreciated!

As you are likely not yet fully conversant with this type of setup I don't recommend a microphone addon.
Yes it has been done but requires a special mic and some specialized knowledge.
Even the best on board mic setups can have feedback issues and still will not sound as good as a normal outboard mic.

A piezo PU is ideally suited to Nylon guitar and in my experience actually often better sound reproduction than most microphones. (outside of a pro studio setup) 8|
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on October 25, 2016, 07:54:29 AM
OK you score 10 for your enthusiasm :dbtu: but don't get ahead of yourself this is not as simple as it looks. :-X
Auto route is fine if you are making mother boards but this is not the same on several levels. 8|
For audio circuits like this auto route is the fastest way to make more land fill. :'( :'(

This is a very high impedance input and highly prone to picking crud noise.
Keep the input away from output.
Don't make very fine tracks and pads (I'm assuming you are going to hand etch & drill this PCB)
You are bound to end up needing to change a component and tiny tracks & pads are only good for one or two shots. There should be a global menu to set pad and track dimensions,, so use it. :tu:

I've edited your schematic to give you some idea of how to wire it up.

Hand route the PCB and try to keep the layout much like the schematic i.e. power on one side and ground plane on the other and that should work ok for a small board like this.

Note:  I changed D1 to be in series with the battery,, works either way,,, fors and against both ways.
If IRC, Diode in series puts less stress on the diode if battery is inserted wrong.
Oh the extra cap is just extra filtering and I have read it may even help the battery.

Now;
I forgot to mention,, you might want to consider an output buffer (to drive long cables better)
just a simple BJT is all that is needed. See my PhAbb Fet Boost output on previous page for how to insert that. The circuit will work without it but a buffer covers any situation.
If there is anything I've missed I'm sure others here will see any mistakes I've missed and chime in to help.
Cheers, Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: J M Fahey on October 26, 2016, 08:17:24 PM
I´m a little worried about D1 and C9  ???
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on October 27, 2016, 01:44:04 AM
I´m a little worried about D1 and C9  ???
That is perfectly understandable as it was a complete balls up by me :-[ :-[
Thanks for keeping an eye on me :tu:

I've now edited that schematic and corrected that mistake.
Now excuse me,,, I have to go bang my head against a wall.
and no Anzac biscuits for me today. ;)
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: J M Fahey on October 27, 2016, 08:58:51 AM
    Hey !!!!!!  Those look GOOD!!!!  :tu:
Missing them must certainly be unbearable punishment  :'(

(http://www.taste.com.au/images/recipes/tas/2009/04/anzac-biscuits-16116_l.jpeg)
Quote
Ingredients

    1 1/4 cups plain flour, sifted
    1 cup rolled oats
    1/2 cup caster sugar
    3/4 cup desiccated coconut
    2 tablespoons golden syrup or treacle
    150g unsalted butter, chopped
    1/2 teaspoon bicarb soda

Title: Re: LR Baggs Piezo-Pickup preamp
Post by: zedonetx on October 28, 2016, 05:12:17 AM
Thanks to j.m.fahey and phatt.

-Arrangements were made according to the warnings.
-Piezo and battery is far from each others :)
-pcb layouts were designed by me after auto routing (it must be double-checked).
-I tried to make the minimum space for the board.
-A board with 50mmx65mm sizes would fit. The rest is your ability :)

Of course, first i would like to test the circuit on a breadboard. It is important. Firstly test it :)



OK you score 10 for your enthusiasm :dbtu: but don't get ahead of yourself this is not as simple as it looks. :-X
Auto route is fine if you are making mother boards but this is not the same on several levels. 8|
For audio circuits like this auto route is the fastest way to make more land fill. :'( :'(

This is a very high impedance input and highly prone to picking crud noise.
Keep the input away from output.
Don't make very fine tracks and pads (I'm assuming you are going to hand etch & drill this PCB)
You are bound to end up needing to change a component and tiny tracks & pads are only good for one or two shots. There should be a global menu to set pad and track dimensions,, so use it. :tu:

I've edited your schematic to give you some idea of how to wire it up.

Hand route the PCB and try to keep the layout much like the schematic i.e. power on one side and ground plane on the other and that should work ok for a small board like this.

Note:  I changed D1 to be in series with the battery,, works either way,,, fors and against both ways.
If IRC, Diode in series puts less stress on the diode if battery is inserted wrong.
Oh the extra cap is just extra filtering and I have read it may even help the battery.

Now;
I forgot to mention,, you might want to consider an output buffer (to drive long cables better)
just a simple BJT is all that is needed. See my PhAbb Fet Boost output on previous page for how to insert that. The circuit will work without it but a buffer covers any situation.
If there is anything I've missed I'm sure others here will see any mistakes I've missed and chime in to help.
Cheers, Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on October 28, 2016, 08:19:46 AM
Thanks to j.m.fahey and phatt.

Of course, first i would like to test the circuit on a breadboard. It is important. Firstly test it :)

Wise move :dbtu:
Yes I can can see a few things on the layout that don't look right but hard to tell as part numbers are hidden.

By using a breadboard you will become more familiar with what goes where and find which nodes are sensitive to noise and it will also help you fix any PCB mistakes.

The hard part is being patient and working methodically through the whole project ironing out any potential problems *Before* you commit to a PCB.
Anytime i find a circuit that looks like a good idea I go build it on the breadboard,,I've worn out 3 breadboards over a ~20 year period.

The breadboard is your saviour,, the difference between a success or more land fill.
No need to ask how I know this to be the fastest way to make a good circuit. :lmao:
Phil.
Title: Re: LR Baggs Piezo-Pickup preamp
Post by: phatt on October 28, 2016, 08:25:18 AM
    Hey !!!!!!  Those look GOOD!!!!  :tu:
Missing them must certainly be unbearable punishment  :'(

(http://www.taste.com.au/images/recipes/tas/2009/04/anzac-biscuits-16116_l.jpeg)
Quote
Ingredients

    1 1/4 cups plain flour, sifted
    1 cup rolled oats
    1/2 cup caster sugar
    3/4 cup desiccated coconut
    2 tablespoons golden syrup or treacle
    150g unsalted butter, chopped
    1/2 teaspoon bicarb soda


I thought you might pickup on that one ;)
I was buying the store biscuits but they have changed the recipe and now they are rock hard and lack the flavour of the real thing,, probably no treacle. :'( :'(
Phil.