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Old 30th March 2012, 02:44 PM   #131
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A Zobel network is an impedance correction network. It makes sense in speakers that are connected to amplifiers that react sensitively to changing impedance, e.g. tube amps due to the high inner resistance of the output transformers or class D amps due to their passive output filter.

There is no Zobel network in an amplifier. The RC circuit from output to ground is an RF snubber circuit composed of the snubber capacitor and a current limiting resistor. The capacitor shunts unwanted RF to ground. The resistor makes sure that the amplifier does not operate into a short circuit at high frequencies, where the capacitor has nearly zero impedance.
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Old 30th March 2012, 02:46 PM   #132
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AndrewT and Pacificblue, please check posts 112 and 130 when you get a chance.

Thank you.
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Old 30th March 2012, 02:47 PM   #133
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Quote:
Originally Posted by Aguilabrava View Post
I was thinking about removing two little pieces of insulation from the wire coming from the PCB, like 2mm each, and then solder the inductor on top side and the resistor on the bottom side, then putting some heatshrink to cover both resistor//inductor. My question is, would this work since I am not cutting the wire, just two 2mm sections of its insulation to solder the components, or the wire has to be cut and then joined together by the resistor//inductor?.
The wire has to be cut, otherwise you short the resistor out and it cannot fulfil its function.
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Old 30th March 2012, 02:53 PM   #134
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Great, Pacificblue, that's what I wanted to know.

Can you please check the post regarding the speaker protection board, I think it is post 112?
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Old 30th March 2012, 03:12 PM   #135
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Quote:
Originally Posted by Aguilabrava View Post
Also, do I just solder the + LEFT and + RIGHT outputs coming from the amp PCB's to the holes in the other end of the board, and then simply attach the speaker output connectors to the board?
You should ask the seller of the board for a connection diagram.

A speaker protection board should have three connector strips. One is the board's power supply. Then there should be a place where the amp output connects and another place where the speakers connect.

The terminals where the amp comes in should have connections to the protection circuit. The speaker terminals should only be connected to the relay contacts.
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Old 30th March 2012, 09:34 PM   #136
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Default The "Thiele" R//L at the + Speaker Output Cable

Here the pictures of the Thiele network, resistor and inductor connected in parallel in the + output speaker cable. I used a 10 Ohm resistor and a 1.5uH inductor.
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File Type: jpg DSC01084.JPG (925.2 KB, 385 views)
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Old 31st March 2012, 06:21 AM   #137
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That inductor looks a bit small. Is that an iron core indcutor? Did you check the saturation current and DC resistance?

The saturation current should be greater than or equal to the amp output current. If the current drives the inductor core into saturation, you will get audible distortion. With your 40 V rails and 8 Ohm speakers the saturation current should at least be 4-5 A.
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Old 31st March 2012, 09:48 AM   #138
AndrewT is offline AndrewT  Scotland
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About 10Turns of 1.2mm enameled copper wire for the inductor.
It's resistance should read near enough zero ohms on most DMM set to ohmmeter.

I can't tell anything about the pics in post12.
We are back to the same problem: Retailers selling kits without any customer/builder support.
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Old 31st March 2012, 11:46 AM   #139
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Quote:
Originally Posted by AndrewT View Post
...Retailers selling kits without any customer/builder support.
... but it's cheap...
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Old 31st March 2012, 04:48 PM   #140
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Default API Delevan 1.5uH Inductor.

The inductor is a RF inductor API Delevan 1.5uH, 5% tolerance, maximum dc current 670 mAmps, maximum dc resistance 0.5 Ohms, self resonant frequency 160 Mhz and Q minimum 33, and it is "unshielded". This is the information I found at the place where I bought it from.

Here is the data sheet of the manufacturer:

http://www.delevan.com/seriesPDFs/1537.pdf

The seller of the speaker protection board replied with a *.doc file with instructions. It says that the board can be powered by 12-15 volts AC, the inputs are the holes/pads, and the outputs are the big holes where the speaker terminals connect to the board. I am attaching the *.doc file to this post. Please take a look at it.

I am also attaching a picture of the boards mounted on top of an old PC desktop, this is just to test it, I will get a nice amplifier enclosure for all the stuff, but I'm dying to hear it. I am not using the input selector board yet.

Again, thank you very much AndrewT and Pacificblue, this would have never been possible without your help.
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