quinta-feira, 26 de junho de 2014

À bolina, rio acima (beating, upriver)


My pride and joy sailing in Alhandra, Portugal, in June 14th.

50 years after her construction, this Piver Nugget still rocks...

quarta-feira, 25 de junho de 2014

"The Buffer"

The unity gain amplifier, aka, “The Buffer”








1-      PROBLEMS:
a.       To have an extra output from my guitar so I can feed a low impedance input without loading the pickups, or keep my favourite tuner (which is a little noise box) in the signal chain.
b.      For the input of the chosen circuit to present a high impedance to the guitar;
c.       To be noise free and lean on power consumption;
d.      Easy to build with a minimalist parts count and featuring easy to obtain components;
e.   Suitable for point-to-point wiring (no PCBs or Veroboard)
f.      Not to modify the signal in an audible manner- No metaphysics here. If I can’t hear a difference, than there’s no difference.


2-      SOLUTION: A single stage FET unity gain amplifier, or a buffer as it is also known, with two parallel outputs:




Some theory on the subject here.


Here are the simulated signal comparisons:





A little signal attenuation (around -2dB @ 1kHz into a 10k load), as expected, but in practical terms nothing to worry about. I’ve implemented the circuit with 220nF caps both at the input and output. If you can hear a loss in bass response (I can’t) please do increase the value of the output capacitor. A 1uF cap will result in a slightly better bass response:



 You can obviously go for higher values but be prepared to pay extra for film capacitors of high capacitance.


Drawing only 0.7mA of current, a standard alkaline 9V block should be good for more than 150 hours of continuous use (assuming a lowball battery capacity of around 100mAh):




Parts list (circuit only):

1x N-channel JFET (I’ve used 2N3819 devices. 2N5457 and MPF102 should also work fine)
2x 220nF polypropylene "orange drop" film capacitors
1x 1.5MΩ 1/4W resistor
1x 3,3kΩ 1/4W resistor



Have fun!

terça-feira, 24 de junho de 2014

Rota Alhandra- Valada

Para quem quiser navegar rio Tejo acima até Valada aqui ficam as rotas seguras:

Para dispositivos Android (utilização com o Google Maps): Rota Alhandra-Valada KMZ

Para outros GPS: Rota Alhandra-Valada GPX

Notas:

-A rota nos ficheiros foi traçada em 14 de Junho de 2014.
-Pode ser seguida por embarcações com até 3m de calado SE PLANEAREM A VIAGEM PARA CHEGAR A VALADA COM MAIS DE ¾ DE MARÉ CHEIA! À baixa mar na entrada de Valada (que é a zona mais crítica do percurso) apenas é segura para embarcações com um máximo de 1.5m de calado.
-Atenção às artes de pesca mal sinalizadas.
-Aconselha-se uma visita às RIO TEJO-AJUDAS NÃO OFICIAIS À NAVEGAÇÃO para observações adicionais.
-Estas rotas e recomendações são fruto do melhor do meu conhecimento e boa vontade e a sua utilização não dispensa o responsável pela embarcação de se munir e usar dos melhores conhecimentos de navegação, marinharia e bom-senso que lhe são exigíveis. Não me responsabilizo por acidentes, incidentes, aborrecimentos, ferimentos e outras chatices que possam ocorrer durante a utilização destas rotas.

Divirtam-se!


For those who want to sail the river Tejo up to Valada here are the safe routes

For Android devices (use with Google Maps): Alhandra-Valada Route KMZ

For other GPSs: Alhandra-Valada Route GPX


Notes:
-The route available in both files has been plotted in the 14thJune2014.
-It can be safely followed by boats with drafts up to 3m IF THE TRIP HAS BEEN PLANNED TO ARRIVE IN VALADA LATER THAN ¾ OF HIGH WATER! At low tide in Valada’s entrance (which is the most critical section of the trip in what regards depth) the route is only safe for boats up to 1.5m drafts.
-Keep an eye out for poorly signalled traditional fishing apparatus.
-A visit to RIOTEJO-AJUDAS NÃO OFICIAIS À NAVEGAÇÃO is recommended for additional remarks.

-These routes and recommendations are provided at the best of my good-will and knowledge and their use does not free the skipper from gathering and using the best knowledge in navigation, seamanship and good-sense that he’s required to . I’ll not be held accountable for accidents, incidents, hassles, injuries and other annoyances that may occur while using these routes.

Have fun!

sexta-feira, 28 de março de 2014

quarta-feira, 26 de março de 2014

Fixing a BOSS FW3 wah pedal

Just the other day I found a BOSS FW3 wah wah on an auction site and got it for 40€. Although the previous owner stated it was in “mint condition” it was somewhat far from it. The slider pot (yes, this wah has a slider pot instead of a rotary one) had been messed with, removed and placed back again with hot melt glue. Fortunately is it working fine and I’ll worry about it when the need comes. Some of the screws holding the base plate were also missing and the pedal was soaked in oil , grease an fuzz…

The pedal was in good working order though, the seller even threw in a brand new Duracell 9V block, and the only real problem was what led me to write this post:

-          An annoying malfunction with the indicator LED was making it unable to keep lit when the effect was engaged. Instead it flickered or remained off…

This really upset me since the indicator is in my opinion a major feature on a pedal that more established brands (when it comes to wah wah pedals) incomprehensibly opt to rule out of their designs… The BOSS FW3 is also built like a castle and, even if it didn’t work at all, 40€ would be a fair price for the case alone as a DIY start point…The wah circuit was working fine though…

Anyway, I set myself to give the thing an overhaul.

I’ll refrain from posting pictures and details of the cleaning process since there’s really not much to it: Cleaned the PCBs with Isopropyl, completely disassembled the case and pedal and degreased it with hot water and soap,  LIGHTLY lubricated the shaft with car motor oil and that was it. Now, for the LED:

After a quick look at the small PCB where the LED is placed I found a Zener diode in series with the LED and somehow got suspicious about that fellow:



 I went on to search the web for reports about the same problem and, although I found none, I managed to find the circuit schematic here: http://nicosonic.com/sites/default/files/pics/BossFW3.pdf

Here's the important part for this case:



I suppose BOSS designers put the Zener there so the LED could double both as a status indicator for the effect AND as a battery charge indicator. I’ll try to explain:
Zener diodes act upon electrical flow the same way spring loaded valves act upon water: They only let the flow through if a preset pressure (voltage) builds up upstream of them. So, as the Zener only lets electricity pass through it if the voltage rises above its preset point, the LED will only light up if the battery is able to provide a certain voltage. This way BOSS ensures that the user is made aware that the battery is getting low on charge but the pedal keeps on running for a while because the Zener diode is only in series with the LED. Think of this system as the reserve light on your car’s fuel gauge:
When it lights up you’re still good to go, but you have been warned that it won’t last much longer.

As this, if this Zener is malfunctioning it will affect the indicator LED:

-          If the Zener is shorted the “warning” effect is lost and the LED will keep lit for far longer into the end of the battery’s life
-          If the Zener is open (or if its Zener voltage is somehow out of spec) the LED will not light up at all or will show an erratic behaviour

One good way to check if a Zener diode is doing what it is supposed to do (in simple regulator circuits such as these) is to measure the voltage between a point immediately downstream of it and ground and between a point immediately upstream of it and ground. If the voltage upstream equals the voltage downstream the Zener is shorted. If the voltage downstream is 0 the Zener is open.
In my case the downstream voltage read 1.3V so, although not completely open, the Zener obviously was not letting enough juice through to power the LED.

Since this pedal is to be kept in a pedal board powered by an external supply and there’s no need for low battery warnings, I simply put a jumper across the zener diode D4 to solve the problem:




Now the pedal works perfectly and the LED lights up and shuts down as it is supposed to:



If a more “professional” solution was desired I could have simply replaced the Zener by a new one (any 5.6V Zener would do) and the pedal would have been restored to its original condition.

This fix should be OK for all pedals that use similar circuitry.

Cheers!


Pedro , from Portugal.

sábado, 4 de janeiro de 2014

A new chipamp project part II- A simple DIY guitar power amplifier

 ...for use with an external speaker and some sort of line level preamp (for example, a Behringer VAMP3)



still on a very initial stage (little more that the marine ply box done)

sexta-feira, 29 de novembro de 2013

A new chipamp project

With the new family member almost here it was time to confine the prototype to a box:

.




It's just a straightforward application of TI's datasheet circuit:
http://www.ti.com/lit/ds/snas193b/snas193b.pdf





Still to do:

- An impedance matching buffer for the CD/MP3 input: http://beavishifi.com/projects/JFET_preamplifier/

- Incorporate the RIAA preamphttp://www.vellemanusa.com/products/view/?country=us&lang=enu&id=350492 in the box:

- Improve the volume control

- Make an output attenuator

domingo, 20 de outubro de 2013

Regata Belém Alhandra Belém 2013


Mais uma vez a velejar com rating 0.000..., o que é uma pena, lá viemos rio acima... Desta feita eu e o Paulo Garrafão.


domingo, 14 de julho de 2013

Finally!

After the exams, a weekend upriver with Fulô, the Piver Nugget and Neil, the First Officer...

We left Alhandra on the early morning of Saturday 13th to Valada and returned on the 14th arround noon.

The wind was not so great, under 1kt on the way up and arround 5kt on the bow when we came back, so the sails were kept on their covers and the 5hp Tohatsu was our little helper for the trip.

Here´s a few pictures of the trip.











Fulô is now ashore for routine maintenance so no more sailing until August or September...

See you all then

quarta-feira, 1 de maio de 2013

Freedom day

Fulô, the trimaran, on the 25th April 2013 club race


segunda-feira, 11 de março de 2013

One more weekend at the mooring...

Stormy weather has been keeping us tied down for much too long...

My feet are beginning to grow roots from being ashore...

This weekend was no exception...

Cheers

Pedro

segunda-feira, 25 de fevereiro de 2013

Vox Pathfinder 10 mod pack

Here are the mods I've implemented to my Vox PAthfinder 10



PROCEED AT YOUR OWN RISK AND KEEP IN MIND THAT EVEN LITTLE AMP'S CIRCUITRY CAN CARRY LETHAL VOLTAGES. IF YOU'RE NOT FAMILIAR IN DEALING WITH SUCH CIRCUITS LEAVE THE MODS TO SOMEONE COMPETENT TO IMPLEMENT THEM.

1- External speaker jack
2- More powerfull power transformer. The unrated original unit (probably 1A) was replaced by a  2A transformer.
3- Original 14W TDA2030 chipamp replaced by a 20W LM1875 
4- Original distortion circuit's red LEDs replaced by 1n34A germanium diodes
5- Original OPAMPS replaced by JRC4558DD mounted on sockets for chip swapping on the go.



The Pathifinder 10 is a great little practice amplifier that you'll find to be a wolf in sheeps clothing...
The miniature stock speaker does not make justice to the circuit's capabilities and you won't help a very sincere WTF! when you first listen to this little box roar through a proper 12 inch driver. So the first and most cost effective mod is the external speaker jack socket.
Mine is wired in the usual fashion in such cases: Using a switched jack. Whenever an external speaker in connected to the jack, the onboard driver is shut off (thankfully).


As for the electronic mods the changes are somewhat less noticeable, nevertheless very rewarding:

- The 4558s rounded things of a little bit in what concearns the high frequencies;
- The distortion is smoother after the replacement of the original red leds by 1N34A germaniums in the clipping circuit;
- At max output there may be an increase in undistorted sound volume, courtesy of the higher capacity transformer and LM1875 chip in place of the original TDA2030 and tiny transformer.

Although this may be just my ears playing me I've had very good previous experiences in Hi-Fi DIY with the 1875 and the general opinion out thereregards the 1875 as a generaly "better" chip than the 2030, being more dynamically responsive


More on this work in progress later

Regards!

terça-feira, 19 de fevereiro de 2013

DIY Optical Tremolo

In the course of this crappy winter for sailing I have to limit my past-time activities to electronics.

After many experiments arround the subject of optical, LDR based, tremolo for guitar I decided to go ahead with the concept of a rotating disc unit. I tend to always prefer electromechanical devices in opposition to purely electric/electronic gadgetry...

Still on the breadboard, I allready found myself face-to-face with the issue that I was more afraid of: DC noise from the motor making it to the audio signal...

So, plenty to reseach and test for the time being. I'll keep posting developments...

Meanwhile here's a picture of the prototype array and respective schematic.





Note the addition of my own do-it-all mighty clean booster. Tremolos don't have to decrease overall output by definition do they?


Next to include:

1- Eliminate DC motor noise issue
2- Depth adjustment: A pot in series with the led
3- Tru bypass switching

See you!

sexta-feira, 14 de dezembro de 2012

Ashore

The mighty "Azul" (Blue) is ashore for general maintenance and to repair of a minor crack in the hull.

Azul is a Philippe Harlé Gros Plant (a minitransat 6.5m) built by my dad. She's been sailing arround Alhandra for about ten years now:


http://fr.wikipedia.org/wiki/Philippe_Harl%C3%A9 
http://www.pzsc.org.uk/history/minitransat/index.html

terça-feira, 11 de dezembro de 2012

Arsénio Novo Tube Sound Overdrive

Oh no, another solid state circuit claiming to sound like a tube based one...Well, as you'll find out on your own, this time it's true.

Following a very convincing recomendation from a friend and some positive criticism at the forums out there about this amazing little circuit I finally decided to give it a go.

Image

I never liked the onboard distortions of any of the amplifiers I've owned over time* and I've been in the search for quite a while now for the perfect distortion stompbox to go somewhere in between my tube fueled Guyatone FLIPVALVE PD1 Power Drive and my Guyatone SD2 Sustainer D. Well, I guess the search has ended.

*A cheap Legend 15, a not so cheap but indeed VERY unreliable Rocktron Rampage R80, a massive Crate GX212, a Vox Pathfinder 10, a Fender Champion 600 and a Roland Cube 40

Has it happens this awkward "back to back" PNP-NPN arrangement is likely to be the more juicy distortion you'll ever ear from a solid state distortion ciruit. I'm still trying to force myself to believe that a parts count as low as this can supply the goods in such a competent manner...

Here's the circuit:

P2 being a trimpot to help set the bias (should be set at half, approximetely, or wherever you find the best sound) and P1 being the output level control. No gain, no tone, no complication. The guitar controls are very effective in controling the behaviour of the circuit, as I'm sure you'll have a chance to confirm by yourself. Also, nevermind the switches. Those are there as a part of my own experimentation.

To ease your troubled minds, yes, I've tried a FET buffered input. I didn't like what it made to the sound though, but you're of course  free to go ahead and try one for yourself!

Here's the TINA-TI simulator simulation (@0.25Vpp/1000Hz input)

Instead of a written description of the sound (which would never make justice to the A.N.T.S.O.D) I thought it might be best to record a demo, so here it is:

Recorded using the following soundchain: Yamaha Pac311 (Fender Noisless e Gibson PUs) -> ANTSOD -> Roland Cube 40 (line out) ->PC

I've also made your rookie DIYer's life a bit easier by compiling a stripboard layout of this pearl:





Here's the almost finished product, in a very nice aluminium box available in Portugal at: http://www.sonigate.com/pt/product/show_details/58502/Caixa-Aluminio-115x65x35mm




Also of great interest is the descriptive memory of the circuit (dated back to '95) by the man himself:


    From: Arsenio Novo
    Date: 04 Jul 95 23:04:50 
    Newsgroups: rec.music.makers.guitar
    Subject: New Overdrive Circuit


    Hi,

    I've noted that talk on this echo always comes back to the subject of
    overdrive distortion. Whether generated by a vacuum tube amplifier or
    a transistor amplifier there seems to be undeniable differences to me
    as well.

    Lately, I was tinkering with an unusual transistor circuit
    configuration I had come upon a few years ago and made a few
    modifications to the circuit that turned it into one beautiful
    screaming "tube-like" overdrive but without the wall of noise these
    things usually make. When pushed it even makes that distintive
    "zoo-zoo" sound...!!!

    The original circuit was simply a complementary matched pair of
    transistors connected so that all the terminals overlapped. i.e. both
    bases tied together, emitter of the PNP connected to the collector of
    the NPN, and the collector of the PNP connected to the emitter of the
    NPN. Thus:


    This transistor pair is then biased by 2 equal value resistors in each
    of the compound legs, one to the positive supply and the other to
    ground common. The signal is coupled to the base pair leg and the
    output is picked off either of the other 2 legs.

    The result is that the above circuit exhibits the behaviour of a
    multiplier over a range of signal values. It basically performs a
    sin function: in other words a frequency doubler.

    This doesn't have a very good distortion sound though because it is
    rather "burpy and buzzy". However, lately I was toying with the
    circuit when I offhandedly decided to try doing something to it just
    to see what would result.

    After adding a large cap from the NPN's emitter to ground the thing
    went wild on me... WANGO ZE TANGO! SUPREMO DISTORTION! I then
    proceeded to refine the circuit a little more and got a better
    understanding of what it was doing.

    The final schematic follows but first a couple of notes on the
    circuit. The "bias balance" trimmer should be adjusted for a
    symetrical clipping threshold of the output signal as viewed on a
    scope. Short of this it can be easily set by "ear" for the most
    sensitivity somewhere around mid-turn.

    The input should be driven by a lo-z stage if your electric guitar
    doesn't have a built-in pre-amp. You can alter the emitter capacitor
    value in a range from 0.1uF to 1uF in order to obtain various basement
    characteristics but I found the indicated value is a good compromise.
    The input capacitor should not vary much either though because if it
    is made too large the circuit goes balistic and cuts out on the tutti.


    "Tube-sound" Distortion Overdrive Circuit:


    The operation of the circuit more closely resembles a vacuum tube than
    a diode clipper does because of the strong square law characteristic.
    This is due to the negative feedback around both base-emitter pairs.
    This feedback accentuates the junction non-linear behaviour manyfold.

    Thus each transitor drives the other even harder so that the transfer
    curve ends up more logarithmic than is typical of a single transistor.
    In other words: the clipping is gradual and not abrupt like it is in
    the case of a silicon diode. Typically a lot more 2nd harmonic is
    produced as well. As a bonus the waveform folds over on itself when
    the circuit is overdriven!

    Now in the interest of the common good I donate this design to the
    public domain for personal use but retain copyright and reserve all
    rights for any commercial purpose. In other words build one for you
    and your friend but if you have it massed produced for profit I only
    ask a fair share.


    Please, do try the circuit and leave any comments in private at my
    e-mail address: arsenioDOTnovoATmbaDOTorg

By the way, does anyone know who's Arsénio Novo? I'd like to thank him...

Have fun!

Pedro

segunda-feira, 15 de outubro de 2012

Regata Belém-Alhandra-Belém

Nem só de trabalho, estudo e afazeres terráqueos me governo...De vez em quando é preciso ir à água...

A chegar a Lisboa de manhã bem cedo.

 Um pouco antes da Vasco da Gama

 A passar Alverca, já depois de acabar a regata (que foi encurtada na baliza 1A)

Idem

 A caminho de Alhandra com a Nau dos Corvos e o Nichu's




segunda-feira, 8 de outubro de 2012

Alhandra à Vela

Há dias que, em Alhandra, a gente se se lembra daquilo para que servem os barcos à Vela...







Oxalá se repitam estes dias, por muitas e muitas vezes...