Archive for April 27, 2014

Celestion G12T-100 Guitar Speaker Driver

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Hello,

I recently got a Marshall JCM2000 DSL401 in the shop for repairs. This amp is equipped with a 12 inch Celestion speaker labeled GOLD BACK. On a side label you can find the G12T-100 markings tho.

Checking to see if the problem wasn’t with the speaker itself i measured it and got the T/S parameters and impedance curve. Subscribers will find that zma and frd files are available.

Parameters (pdf): celestion g12t-100

Celestion G12T-100 Marshall Gold Back

Celestion G12T-100 Marshall Gold Back

 

Thanks for visiting

 

Guitarists, prepare for a live session

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Hello,

This post is for beginner guitarists.

Ever happened to you that you unplug the cable from the guitar? It must have! Either you stepped on the cable or you moved around too much. Here is a cheap and quick way how to take care of this problem.

Leave a loop of 10-20 cm between the clip and the jack. Adjust this length until you are comfortable and its not bothering you. When you are finished unplug the jack first then remove the clip. Keep cables in their own space and its best to hang them in long loops. Don’t wind them around your hand.

Do this every time. Don’t get lazy and leave the cable in just because you will play again tomorrow!

Thanks for visiting.

Guitar Cable Trick

About Field Coils and Magnetic Circuits

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Hello,

I’ve been studying the past couple of months some ways to improve the field coil performance and in a way to make my tools better, to sharpen them. My goal is to get the most flux density in gap for a given current in field coil.

I tried many magnetic circuits meant to take advantage of the shape of a field coil because being a solenoid it will work better having a length per diameter ratio above unity. Works better means a more uniform field in the core.

I managed to get a simulated result of 1.5T in a 1mm wide and 12mm high gap using standard 1010 steel and a field coil consuming 7.231 Watts!

Field Coil Loudspeaker Design フィールドコイルスピーカーデザイン

 

Field Coil Loudspeaker Design フィールドコイルスピーカーデザイン

Field Coil Loudspeaker Design フィールドコイルスピーカーデザイン

The field coil is made with 1 mm EC wire so it will be able to handle a lot more current. You will get more flux density this way but the curve will get more and more bell-shaped.

Field Coil Loudspeaker Design フィールドコイルスピーカーデザイン

Field Coil Loudspeaker Design フィールドコイルスピーカーデザイン

As you can see for 1 Amp you get a very nice increase in flux density. Its not as linear but the difference is small.

There is a balance, hard to achieve, between linearity and maximizing flux density. And this has to do with the magnetic circuit and saturating the pole plates. I usually want to saturate them right at the gap. This way it’s less prone to modulation.

In placing the saturation area, the central pole piece and the top plate geometries have a large role. Always remember that the thin parts of steel saturate faster and zones with transitions from one dimension to another or sharp angles are also prone to saturation.

Below you can see a motor with a linear flux density curve over a 20 mm travel. The central pole piece is of the same diameter as before. You can see that making the top plate thicker killed the saturation around the gap. To bring it back, we must use a larger diameter for a voice coil. But more on that in a future article.

Field Coil Loudspeaker Design フィールドコイルスピーカーデザイン

Field Coil Loudspeaker Design フィールドコイルスピーカーデザイン

 

Thank you for visiting

Project Ryu Lagger Guitar Pedal Take 2

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Here it is, the pedal version of Project Ryu Lagger. For more details on this pedal check the first article Ryu Lagger.

Project Ryu Lagger Guitar Pedal

Project Ryu Lagger Guitar Pedal