Salas hotrodded blue DCB1 build - Page 34 - diyAudio
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Old 15th September 2010, 10:26 AM   #331
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Salas, i did as you suggested the 39r are underneath the board and used the 10r in lieu of the 8r2 since the ones I had were 8k2 by mistake. The voltage of 2nd cap is 23v & -24.8v.

I'm not sure if this is the correct reading you want for the audio out offset, but I measured from ground to out and it is 0.002v.

Only using the teddy reg since I have boards on hand already built with few minor changes to resistor values, I would prefer the salas mini shunt and I do have the board from quangho but not the parts.
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Old 15th September 2010, 10:33 AM   #332
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by wendell c View Post
I'm not sure if this is the correct reading you want for the audio out offset, but I measured from ground to out and it is 0.002v.
0.002V = 2mV
That is unusually high for a DCB1 build.

How accurate is the voltage scale of your DMM?

It is good to have a meter that can read 199.9mVdc and can also read 199.9mVac. these can be bought cheaply with <=+-0.5%+-1digit accuracy.
+-1%+-2digits should be very cheap and the worst you should buy.
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Old 15th September 2010, 10:36 AM   #333
Salas is offline Salas  Greece
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One English guy using an optivol recommended taking out the local 317 and just using a v1 dedicated reg for that as his best, after he used it as pre reg even.

Your Vin is not bad for 35V filter caps. With 8R2 it will give more mA and drop also. But it works fine as for now. 2mV is good enough offset for no problems but it can go lower.
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Old 15th September 2010, 10:42 AM   #334
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Andrew, using a cheap little DMM. I tested again with a chinese fluke copy and I am getting 1.8mv and 0.2mv
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Old 15th September 2010, 10:57 AM   #335
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Now, with ok from Salas. I need to figure the best way to implement the LDR. I've read in previous posts some people having noise or hum. I have both oliver and uriah boards, Does anyone have a diagram of how to connect the LDR to the DCB1.

Much appreciated!
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Old 15th September 2010, 11:08 AM   #336
AndrewT is online now AndrewT  Scotland
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Hi,
0.2mV is good. That offset is typical of well selected Idss pairs.
1.8mV is poor for a selected pair. This low output offset will not damage any following equipment.
Will the following equipment multiply that 1.8mV to a value that could interfere with performance? An AC coupled power amplifier will accept 1.8mV of offset without any problem.
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Old 15th September 2010, 11:11 AM   #337
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by wendell c View Post
I need to figure the best way to implement the LDR. ........... I have both oliver and uriah boards,
the originator of the Lightspeed volume attenuator says that the LED/LDR alone will perform better than an LED/LDR + buffer when following his design. You must decide if that applies to your implementation.
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Old 15th September 2010, 11:24 AM   #338
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Andrew, so it's better to just use a volume pot for the DCB1? the LDR alone is superior to the DCB1? I'm assuming you are talking about if buffer is not needed,yes?
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Old 15th September 2010, 11:55 AM   #339
Marra is offline Marra  United Kingdom
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I have just installed my transformer with 0-15v secondaries but with everything fired up its outputting 17v is this a problem?
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Old 15th September 2010, 12:06 PM   #340
Salas is offline Salas  Greece
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Where is the 17V? On filter caps? Or is your AC? How much is the DC on filter caps?
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