“.”

“.”

Advertisements

Poster Art in Lisbon : Diogo Barros Pires

 

Street Art In Lisbon: A few pieces from Downtown

A few pieces of public art from Lisbon.

Tile Art in Lisbon’s Metro: The Great Portuguese

If you arrive at Portela airport in Lisbon,Portugal , its possible to travel to downtown by metro. At the Aeroporto metro station,the visitor is greeted by a modern homage to all the remarkable Portuguese individuals through history. Actors, painters, architects and doctors all say “Bem vindo a Portugal!”.

How to prototype with valves / vacuum tubes? 12AX7 or 6N2P adapter !

Tibetan freedom inspired murals in the city center of Warsaw!

GREAT and FREE online applications for BLOGGERS!

Summer is coming and with it some TRAVELING . For most bloggers taking a laptop, smartphone or pad, is essential to keeps those posts reaching the followers. But perhaps this year an application will get corrupted or your tool cant be taken or you are borrowing from a friend.

 

Here is a list of a few FREE web based application to assist with your content and blogging:

 

Photo and image editors:

 

Statistics:

Utilities:

 

 

 

Port Czerniakowski : Lost camp!

Port Czerniakowski  in Vistula, is quick walk from the city center, and has a semi abandoned camping park.

Wonderful and unique fat smooth overdrive: Pentode tubes!

Bands like The Beatles, Rolling Stones and guitarists such as Brian May from Queen, Peter Green from Fleetwood Mac, or more recently Rory Gallagher from Oasis, are known users of Vox AC-30 guitar amplifiers. Turned up loud it has a fat smooth overdrive, harmonic and unique, but whats the secret?

Most of the recent versions use parts that are quite standard and the same as any other valve amplifier, meaning noval triodes tubes in the pre-amplifier and pentodes in the power amplifier, but the most favored and sought after AC-30 tones, are the in the late 1950’s and early 1960’s versions, the main difference being the EF86 tube in the pre-amplifier.

So what is so special about the EF86?

The EF86 (datasheet) is a high-gain pentode designed to amplify low-level audio signals in the late 1950’s. It is usually found as a pre-amplifier tube in audio equipment and instrument amplifiers. The EF86 is much more sensitive than other common preamp tubes like the 12AX7, and achieves more gain. Pentodes still offer with a little more odd-harmonic content and a ‘glassy’ sound. Their overdriven  sound is an expressive compression effect.

What is the issue with pentode tubes?

A complex mechanical structure, combined with a high gain design, make a pentode like the EF86 very susceptible to vibration and the resulting microphonics, meaning noisy, which is not very good for music in busy loud stages.

How do reduce the noise floor of a EF86 pentode?

The easiest ways, if you really want to use a EF86 pentode quietly ( some ways are cheaper  than others) : add dampers, shock mount the tube, buy a few tubes and test until a quiet one is found.

Another way? 

But lets think a in a non linear way, perhaps we can find a pentode that can allow us to have all the good things like the glassy compressed overdrive but with low microphonics.

I started looking around datasheets from  both from east (USSR) and west ( rest of the world) and started noticing that some tubes would withstand greater amount of G-force . The submini tubes, specified  for reliability and designed for long service life under conditions of severe shock, vibration (up to 20,000G), high temperature and high altitude. These tubes were some of the most meticulously built and most rigorously tested of all tubes, as their main intended use was extreme military applications.

The cheapest and easiest submini pentodes for me to obtain  were the russian made ones, I found and tested a few, in the first tube position of a guitar amplifer, submini pentodes such as the 6S31B (datasheet; in cyrillic 6С31Б), 6P30B (datasheet; in cyrillic 6П30Б-P), 6J5B-V (datasheet; in cyrillic 6Ж5Б-В).

But just for standard size tube enthusiasts I also tested a few noval and heptal options.

I will keep improving the circuit until it sounds great and  is stable. A post about it soon.

 

 

 

 

Budapest for a day : Historic, Detailed and Stickers

A beautiful historic city in the heart of Europe. 24 hours walking around.