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Old 21st November 2012, 07:22 PM   #1641
bristto is offline bristto  United Kingdom
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Peter or friends

Just received the kit from Peter and after plenty of reading, I feel ready to start... but one newbie question...
The LED from the rectifier.. I have a blue LED (5mm, 8,000mcd min, 3.3V, 50mA,) to go with a 25x25 transformer... On line calculators give me a 2w (then values from 480 upwards) but these figures seem low compared to Peters and the resistors seem huge in physical size...!

Is this right? Sorry for the newbie question.....
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Old 21st November 2012, 09:05 PM   #1642
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Mine LED is 4V and 25mA and I still use 62K resistor for desired brightness. Whatever the calculator says, I would still start with 10K resistor and adjust from there.
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Old 21st November 2012, 09:50 PM   #1643
bristto is offline bristto  United Kingdom
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Thanks Peter, can I just check what the supply voltage should be (is it 25v as I'm using a 25x25 transformer?) .... and is there any benefit in using the rectifier for the power or wrapping wire around the transformer to produce the voltage?
Thanks again....
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Old 21st November 2012, 09:52 PM   #1644
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With 25V transformer you will see approx 36V DC
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Old 8th December 2012, 06:46 PM   #1645
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Quote:
Originally Posted by Peter Daniel View Post
By stereo version I mean the use of a single transformer powering both channels. You could still use two separate rectifiers boards, but depending on wiring it may produce hum in some systems, so I always stick with a single rectifier board when using one transformer.

For demonstration purpose, I will install all the boards inside 3 x 1.5" U-channel, 1.25" aluminum extrusion. For normal listening, this is enough to dissipate heat from the chips, and when things get hot, you can always attach it to larger aluminum panel.

I will show a version with a potentiometer, and without, so stay tuned.


Please appologize if this question has been asked somewhere else in this thread.

But the potmeter You have a picture of there, is it one with the good oldfashioned loudnesstap on it?
If so, I am VERY interrested in where to buy theese.
I am repairing a lot of vintage stereo and pots with loudness-tap is very much asked for.
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Old 18th January 2013, 11:30 PM   #1646
elsnibo is offline elsnibo  Australia
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Peter, I Am putting together the kit I bought at the moment and was looking for a little feedback. I am planning to run a minidsp to actively cross over my speakers. I bought two kits to supply four channels, 2 tweeters and two woofers. To power this what would be the best solution? Do I run one toroid to power all of the channels or a toroid per kit? Is the anything special I need to consider for the wiring?
Regards,
Snibo
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Old 6th May 2013, 12:21 PM   #1647
glenv6 is offline glenv6  United States
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Quote:
Originally Posted by Peter Daniel View Post
If amp and PS are in separate enclosures, I would suggest to place rectifiers with the transformer, that way you will have only DC in the amp. This may not be really critical, as I've built amps with rectifiers right beside the chip (see below) and they performed well, but placing the diodes in a PS enclosure is a common practice.

There are 4 wires in the umbilical: V+, V- and two grounds separate for each rail. While the example integrated amp had separate power wires for each channel (that's why you see 6) the Patek has power wires run from one channel to another channel (board).
Hello! Newbie here, first post... I rigged up a star ground between the two OG OUT points on the main boards and connected the V+ to V+ and V- to V- points just as Peter does for the umbilical power on the Patek from the post above. Now after nearly completing my build I realized I only used one wire in my umbilical for ground. What if any downside is there to not separating the grounds for each rail? I used #18 guage wire for V+, V- and the ground.

Thanks in advance for any advice! -Glen
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Old 9th May 2013, 01:26 AM   #1648
glenv6 is offline glenv6  United States
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Default Down the drain...

Well, I had a great few hours last night with the AudioSector amp I just finished building. It sounded great, no hum and the audio was crystal clear. I was listening to it through a pair of cheap KLH speakers and was really looking forward to hearing it through something better once I ran it in for a while. Here's a link to some pictures...

Chip Amp Photo Gallery

That was all short lived however. I got home from work today excited to settle in for some listening pleasure with my newly built amp. This was the first time I had it plugged into main power without the variac. When I switched it on, there was a brief loud hum from the transformer and a sharp crackle emanated from the speakers. That was it. From then on the amp was distorted and the heat sinks were burning hot. I checked the rails and they were uneven. 24.1v on one side, 26v on the other.

So the question is, how can I avoid another blow up like this after I rebuild this thing? Would a slow start circuit work? No one slow start circuit design seems to stand out on this site, which one works the best for this amp?

Thanks! -Glen
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Old 9th May 2013, 08:21 AM   #1649
AndrewT is offline AndrewT  Scotland
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Beginners should never omit the "optional" stability and filtering components.
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Old 9th May 2013, 10:19 AM   #1650
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Quote:
Originally Posted by glenv6 View Post
So the question is, how can I avoid another blow up like this after I rebuild this thing? Would a slow start circuit work? No one slow start circuit design seems to stand out on this site, which one works the best for this amp?
Quote:
Originally Posted by glenv6 View Post
Hello! I just finished building one of the excellent Audiosector LM3875 kits by Peter Daniel. I was inspired by Peter's Patek design, so I borrowed heavily from that design for my amp.
If the LM3875 kit is built correctly, you shouldn't need a slow start circuit. If you "borrowed heavily from that design," what did you do different? Was it only the physical layout, or did you make any circuit changes from the kit specs?
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