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Old 2nd September 2009, 07:24 AM   #131
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Hello,

I still can't find 1.8V LED. The things i find are 2.0V above. Is it okay to use this value? Or, are there suggestions using zener? What type would be then?
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Old 2nd September 2009, 01:53 PM   #132
Salas is offline Salas  Greece
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Hmm, use the little over 2V ones, but make the 68R to 82R and use one less LED in the reference string. I.e. 4 instead a row of 5 and jumper the empty position.
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Old 2nd September 2009, 03:16 PM   #133
AndrewT is offline AndrewT  Scotland
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over 2V at what current?

Measure the voltage after your have assembled the circuit.

Once you know the voltage you can calculate the current that flows due to the voltage drop across the resistor.

Try fitting a mix of red and yellow and green LEDS. They will all have a different volts drop.

Short out one of them using a long leg that you did not snip off.
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Old 3rd September 2009, 05:09 PM   #134
CeeVee is offline CeeVee  Portugal
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Originally Posted by sutantoroy View Post
Hello,

I still can't find 1.8V LED. The things i find are 2.0V above. Is it okay to use this value? Or, are there suggestions using zener? What type would be then?
How's about this...lots to match from :-)

http://www.ledshoppe.com/Product/led/LE1018.htm
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Old 3rd September 2009, 05:29 PM   #135
Salas is offline Salas  Greece
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Adequate. Size may not make them that orderly looking, when stuffed on PCB though. Any 3mm with Vf like those?

http://www.ledshoppe.com/Product/led/LE4008.htm
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Old 15th September 2009, 12:46 AM   #136
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Default My Buffer Finally Done

Here it is....

It took a bit long time to find closest voltage of LED (finally i found around 1,8V LED, but then i realize that even i have all same voltage on LED, it won't give the same output voltage to supply the buffer because we dont match the transistor and other components, so we should compromise this by adjusting our LEDs. Therefore the LED voltage between positive and negative side isnt the same but resulting the same output voltage). The output voltage is about 10,7V - 0V - (-10,7V) with +/-0.05V ripple. Offset is about 0.7mV at positive voltage and 1.7mV at negative voltage.

I can feel more detail in sound. There are some resistors valued different from the schematic. They are:
37.4R 1W instead 34R 1W
464R instead 470R
215R instead 220R
Is this okay? Or is it degrade the sound quality from this buffer should offer actually?

Thank you all, especially for Salas the designer and crt as i use his file then modify it properly to fit the components i used.
Attached Images
File Type: jpg SantPcb.jpg (159.3 KB, 1609 views)
File Type: jpg SantDCB1.jpg (203.6 KB, 1589 views)

Last edited by sutantoroy; 15th September 2009 at 12:52 AM.
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Old 23rd September 2009, 08:02 PM   #137
Salas is offline Salas  Greece
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Congratulations! Your values are OK, and you did great work. What you mean ripple? Maybe 50mV regs dif? Any more subjective comments after enough usage by now?
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Old 23rd September 2009, 08:29 PM   #138
Salas is offline Salas  Greece
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For those who don't follow the DCB1 group buy, the news are that Tea-Bag is the new GB manager. He has already given proto PCBs that Crt designed, out to several members and the protos are testing OK. He has opened a google document for everybody originally interested in boards to sign up. If we hit more than 100 pcs we are talking sub $10 per board. There are 2 options. The Hypnotize with only a delay relay on output for avoiding DC offset hick ups during on/off and it can be used as a one input buffer or augmented with a classic input switch, and Mezmerize, that sports 6 inputs via relays. Both need a 15-25k stereo log pot.

If you had your name on the original old wiki GB or new to it, sign up here:
http://spreadsheets.google.com/ccc?k...3WnpDRnc&hl=en
Attached Images
File Type: jpg Hypn.jpg (147.0 KB, 1598 views)
File Type: jpg HypnKan.jpg (253.5 KB, 1539 views)
File Type: jpg Mez.jpg (137.1 KB, 1473 views)
File Type: jpg MezGru.jpg (169.2 KB, 848 views)
File Type: jpg mesmerizeflipsideC.jpg (98.9 KB, 805 views)
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Old 24th September 2009, 11:39 AM   #139
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Quote:
Originally Posted by jean-paul View Post

5. Risks are: If you are not careful and there is no input capacitor in your power amplifier, or DC output sensor and relay, you can burn woofers, if you connect a source device with much DC offset, or one symmetric B1 supply fails during service. Be warned.
Does the above 'risk' still exist in this buffer?
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Old 24th September 2009, 11:54 AM   #140
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Originally Posted by pmchoong View Post
Does the above 'risk' still exist in this buffer?
You can build a DC sensing / off set protection circuit - to avoid this problem. Power amps generally should have either a coupling Cap in most of the cases or should have a DC sensing /shut off system if it is DC coupled to the speaker.
kannan
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