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Old 16th March 2012, 04:59 PM   #41
AndrewT is offline AndrewT  Scotland
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The PCB is OK.
There is sufficient copper trace still there to maintain continuity.
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Old 16th March 2012, 05:08 PM   #42
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Thank you Andrew.

I also received the toroidal transformer I am planning to use, it is Antek AS3428, 28V, 300VA. This transformer is a "shielded type", and because of that it has an additional "purple color wire" in the input section. What do I do with that wire?. Do I connect it to the chassis?. Do I connect it together with the other grounds?.
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Old 16th March 2012, 05:09 PM   #43
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If you want to check the specs of the toroidal, here is the data sheet:

http://www.antekinc.com/pdf/AS-3428.pdf
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Old 23rd March 2012, 05:41 PM   #44
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Default Still confused...

Quote:
Originally Posted by AndrewT View Post
There is no provision for an output Zobel.
Use the locations of R1 and the speaker terminal to fit an R+C Zobel.
R1=2r0 to 10r
Speaker terminal=47nF to 220nF.
Add the other half of the Thiele Output Network, the R//L, off the PCB. R=2r0 to 10r L=0.5uH to 1.5uH
Insert a thick copper wire in this pad first, The top end of R1, nearest the output PIN.
Attach R1 to the copper wire.
Take the speaker output from the top end of R1. Attach the speaker wire to the copper wire. I suggest you fit the speaker wire on the bottom side.
You could bend over the top side of the copper wire to lie on top of the output PIN. Solder this connection. But fit a temporary tab heatsink next to the package since quite a bit of heat will try to travel along this PIN during soldering.
Hi:

Little by little I have been receiving most of the items I need to finally begin the assembly process of the amplifier, I'm still waiting for some, including the speaker protection board that seems got lost in the mail.

Anyhow, in the next few days I will have everything I need to at least solder the components into the boards. As AndrewT mentioned, the only things I am using from the kit are the LM3886TF, the two PCB's and the connection blocks, I discarded the capacitors and resistors because the quality didn't look too good. I just want to do this once, in this case, so I ordered better quality items from USA suppliers.

I am still confused with the Zobel and Thiele networks and how to implement them in these PCB's.

I understand that what AndrewT calls the R+C Zobel is basically a resistor and capacitor connected in series, and the R//L Thiele is basically a resistor and inductor connected in parallel.

Now, he says to use the space left empty in these boards for R1, which I don't need to use. The space for R1 has two holes, one at the top close to Pin #3 of the LM3886TF and one at the bottom close to the Output + terminal. Is it OK to install the 10 Ohm resistor in the R1 location two holes, then attaching the 220nf capacitor in the bottom hole of R1 space and the Output + terminal right next to it?. Then, I will take the speaker connection (Output +) from the bottom of the PCB, and the Output Ground will go from the chassis speaker terminal to the common ground where ALL grounds will join the amplifier chassis, is this right?.

At the same time, the chassis speaker terminal will have the 10 Ohm resistor with the 1.5H inductor connected in parallel attached to the Output +, correct?.

Or, if someone here could help me understand his quote above where he mentions using a copper wire as a terminal, etc., I'd be very happy to do it that way, the problem is that I can't picture how to connect the resistor plus the capacitor plus the copper wire, making an arch with the three of them that go from top of R1 to bottom of Output +....????

I have the 10 Ohm resistors, the 220nF capacitors and the 1.5uH axial inductors. I also have the capacitor that goes in parallel either on top or bottom of R5 to filter RF.

Thank you.
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Old 23rd March 2012, 05:53 PM   #45
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Default C4 and C5 capacitors...

I have another question. My kit calls for a 22uF capacitor in the C4 space, and a Wima 1.0uF in location C5 in the PCB. All other locations on the board call for 100uF capacitors.

After doing some research, I think I've seen some other kits that use a 47uF capacitor for what I think is C4, instead of the 22uF that my kit calls for. What would be the difference if I replace the C4 22uF with a 47uF?.

They still use the same 100uF 50V in all other locations.

I am already replacing the C5 Wima 1.uF with a Audiophiler MKP 4.7uF 400V.

Thanks again.
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Old 23rd March 2012, 07:00 PM   #46
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Good questions to ask. Please post some close up pictures of the modifications when you are done so that we can see how to modify these boards for the better. Hopefully when this is done and working to your satisfaction, it can be documented as a kind of how-to for these boards. dunno, just an idea.

Call me a cheater but, I'm kinda following along here
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Old 23rd March 2012, 07:51 PM   #47
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Yes, absolutely, Fabricated.

The goal is to find the best way to do all the necessary modifications in these boards with the help of the experts here at Diyaudio and post good pictures of them. I have been searching lots of documents where all these questions have been asked many times but I have not been able to get conclusive answers, I'm pretty sure you have gone through the same yourself.


I was happy to find a link about building a gainclone based on the LM3875 from a place called "Audiosector". When I opened the PDF file I realized it was actually extracted from here written by Peter Daniel, very well written and explained with great detail and excellent pictures as well, but his chip amps and boards are different, he doesn't use Zobel and Thiele networks and the grounding scenario is not clear, at least for me. I want to do something like this but with the XY boards we have from the auction site so people will be able to put together the amplifier getting all the answers from one place so “Pacificblue”, “AndrewT” and company can take a break. If you want to look at this excellent manual, here is the link, it doesn't answer most of the questions we have, but I'm pretty sure it can help you with other concepts:


http://www.audiosector.com/nigc_kit-users_guide.pdf

Keep in touch...!
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Old 23rd March 2012, 08:00 PM   #48
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Default Gainclone Grounding Scenario

I just found this diagram showing the grounding scenario in a 4 channel Gainclone amplifier. I hope it helps... I found it taking a quick look in a thread about "favorite threads related to chip amps".
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File Type: jpg GaincloneGrounding2.jpg (51.8 KB, 750 views)
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Old 23rd March 2012, 11:22 PM   #49
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I have actually printed off that last picture you have and put it on the back wall of my bench, along with a few others. It seems some of the threads started about these boards have, at one point or another, hit a dead end and just stopped. Either they gave up or just didn't have the drive to see it through. I have learned alot from guys like "Pacificblue" and "AndrewT". I'm looking into putting in a donation when this is all said and done for their efforts.

My wife has caught me looking at alot of Planet10's stuff and just shook her head when she had seen that i had "enabled" an old pair of drivers. She asked me "What on earth are you doing now?" just walk away hun.....just walk away lol
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Old 24th March 2012, 10:58 AM   #50
AndrewT is offline AndrewT  Scotland
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I'll come back a little later and see what still needs answers or explanation (from post44 and after).
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