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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Ideas for preamp box design
Ideas for preamp box design
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Old 26th August 2006, 06:27 AM   #1
paulspencer is offline paulspencer  Australia
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Default Ideas for preamp box design

Now I'm working on a design for a preamp box (with remote vol control). Here is the concept I'm working on at the moment:

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There are a few features I want to include:

* vivid blue backlighting similar to that on "indiglo" watches, or the Logitech harmony remotes, or many mobile phones
* curved front face plate and curved top of box
* seamless box construction
* no visible holes
* minimal screws


Question: how critical is ventilation for preamps? I prefer not to have holes except in the bottom which can't be seen


I'd like to make it out of sheet metal which I have, but avoid the seams you get where they are normally folded over. I have thought of a few ideas:

* MDF front panel
* inner layer of sheet metal with 3mm MDF slipping over to give seamless look and curve on top
* composite construction panels with a layer of sheet metal with 3mm MDF in the middle - this could achieve the curve and seamless look


IDEAS


Any ideas on how to pull off the backlighting?

* will I have problems with powering lots of LEDs off the preamp power supply?
* any ideas on the best way to get that vivid blue colour?

This colour:

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* should I use plastic to get the light to carry through the front panel? If so what plastic?
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Old 26th August 2006, 06:29 AM   #2
paulspencer is offline paulspencer  Australia
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Background: (Not essential reading but just for interest)

I now (finally) have a working preamp with a remote controlled pot! It's been a few years in the works. I first built an ESP P97 preamp but couldn't get it to work - one of my first electronics projects. Later I managed to get an Altronics kit working for the volume controlled pot, and recently I've build the ESP P88 preamp - simpler and it looks a little better. Here are the kits:

remote pot:

http://www.altronics.com.au/index.as...=item&id=K5026

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preamp:

http://sound.westhost.com/project88.htm

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power supply:

http://sound.westhost.com/project05.htm
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Old 26th August 2006, 06:52 AM   #3
Calvin is offline Calvin  Germany
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Hi,

I once used 1mm thick plastic fibre (meant for conducting light anyway as in digital optical cables) and glued the LEDs onto those. The LEDs with flat hat were drilled so I could stick the fibre in and glue it tight.
I used a flat Front panel made from shist with the fibres flush with the face plate. When turned off You even couldnīt see them (try to find the 2 lights at the lower Akku-PS ).
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With this kind of lightshow You could also give the volume knob a small light

jauu
Calvin
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Old 26th August 2006, 08:18 AM   #4
paulspencer is offline paulspencer  Australia
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Nice work calvin!

How did you do those labels?

Any suggestions on where I might find plastic fibre?

What is shist?

I intend to use a light on the knob itself as well.

I'm thinking each of the dots would be an LED, other parst backlit in some way.
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Old 26th August 2006, 03:35 PM   #5
Calvin is offline Calvin  Germany
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Hi,

the fibre is for optical uses. The same as used for digital audio interconnect cables, or in bundles used in those 70s style lamps.
You should get it at any electronic supply shop.

Shist (the german word is Schiefer) is a natural matte black stone. Basically it consists of pressed layers of sediments and clay (mud ;-) ). So Itīs quite soft for a stone and its structure is layer like. You can get it with a naturally broken surface or grinded.
It has much better damping characteristics than the harder stones like marble or granit and is an excellent material for speakers, turntables and spikes/absorbers.
http://www.musicallife.de
http://www.fischer-fischer.de/start.html
have a look at the SL550 to see natural and grinded surfaces

The labels are rub-on types with a top coat using a fixative spray

jauu
Calvin
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Old 26th August 2006, 07:46 PM   #6
dnsey is offline dnsey  United Kingdom
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You might consider using electroluminescent film for the backlighting. It's easily cut with scissors etc., and available in a range of colours. The downside is that it has to be energised with an AC supply, which might cause problems with the audio side; having said that, H&H used a similar system for their PA amps quite successfully.
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