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Old 29th March 2012, 06:02 PM   #101
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Default Pictures.

I have included some pictures here. I know the wires in the connector strip don't look nice, but this was made just for testing purposes, the finished amp will have them nicely attached.
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Old 29th March 2012, 06:03 PM   #102
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Quote:
Originally Posted by AndrewT View Post
Tell me, do you have one PSU?
How many wire connections is it expecting from the transformer?
Yes, only one PSU for two amp PSBs.
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Old 29th March 2012, 06:03 PM   #103
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Your second question will be answered when you check these pictures... :-)
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Old 29th March 2012, 06:07 PM   #104
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Quote:
Originally Posted by Corpius View Post
Could anybody explain to me why one needs a tranformer with lower secondaries for 4 ohm speakers then with 8 ohm speakers?
Because power = voltage x current. A 4 Ohm speaker needs less voltage but more current to get the same power.

An ideal amp that delivers 60 W into a 4 Ohm speaker will only deliver 30 W into 8 Ohm. On the other hand, if you optimise the amp to deliver 60 W into 8 Ohm and connect a 4 Ohm speaker to it, then the amp will try to deliver 120 W and may switch off due to internal protecion circuits or be damaged in the process.

Quote:
Originally Posted by Corpius View Post
I`m building the same amp also with the XY lm3886 ebay kit. I have a dual 24V tranformer lying around. Would this be OK for both 4 and 8 ohm speakers or just 8 ohm speakers?
It would be OK for 8 Ohm speakers. With 4 Ohm speakers it would mean pushing it a bit, and it depends on your listening habits, heatsinking and complexity of the speaker load whether it will work in the long run or not.
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Old 29th March 2012, 06:09 PM   #105
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Default Finished Boards.

By the way, I just finished the amp boards, I ended up using a Elna Silmic II 47uf 50V in C4, and the Audiophiler MKP 4.7uf 400V in C5.

I soldered the speaker output wire to the bottom part of the copper that comes from pin #3 and includes the Zobel network, I just need to add the Thiele part to that wire, I just don't know how...

Well, here are the pictures, the black stuff in the bottom is liquid electric tape.
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Old 29th March 2012, 06:12 PM   #106
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Great, Pacificblue!!!! I was waiting for someone to answer that question, I couldn't do it, but I remember you mentioning it before at another thread, that's why I decided to get the 28V transformer, I only care about 8 Ohm speakers...

Thank you.
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Old 29th March 2012, 06:30 PM   #107
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Location: Des Moines, IA
Keep it up Aguilabrava! you're getting there one step at a time and getting help from the pro's is a huge plus!

I'm still following closely,yet, I'm at a standstill for a little while.... my new baby boy will be here tomorrow. Good luck!
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Old 29th March 2012, 06:38 PM   #108
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Quote:
Originally Posted by Aguilabrava View Post
How do I connect the power from the transformer to the speaker protection board?
You can use one of the 15 V windings and add a voltage regulator to it to bring the 21+ VDC you get after rectification down to 12 VDC. It is recommendable to use a resistor in series so that the regulator need not dissipate 9 V times the protection board current.

Quote:
Originally Posted by Aguilabrava View Post
On the secondaries side I have 4 pairs of wires, blue and green, blue and green are each 28 volts, then brown and brown, orange and orange are the two secondaries that produce 15 volts each.
If you measure 28 V from blue to green, then one blue wire goes to AC, the green one that belongs to it and the other blue wire go to GND and the green that is left over goes to the other AC.
Click the image to open in full size.
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Old 29th March 2012, 06:47 PM   #109
Corpius is offline Corpius  Netherlands
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Quote:
Originally Posted by pacificblue View Post
Because power = voltage x current. A 4 Ohm speaker needs less voltage but more current to get the same power.

An ideal amp that delivers 60 W into a 4 Ohm speaker will only deliver 30 W into 8 Ohm. On the other hand, if you optimise the amp to deliver 60 W into 8 Ohm and connect a 4 Ohm speaker to it, then the amp will try to deliver 120 W and may switch off due to internal protecion circuits or be damaged in the process.


It would be OK for 8 Ohm speakers. With 4 Ohm speakers it would mean pushing it a bit, and it depends on your listening habits, heatsinking and complexity of the speaker load whether it will work in the long run or not.
Thanks. Would it be possible to use a 4 ohm power resistor in series with a 4 ohm speaker to achieve 8 ohm or would this do good to the sound?
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Old 29th March 2012, 06:49 PM   #110
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My speakers have a 8 ohm resistance, so no problem here. Just curious.
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