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Old 6th December 2012, 01:06 PM   #4881
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thanks a lot Uriah!
will take a look at Jung's article and later try stabilize Salas reg. Indeed, it might be more than 15min when voltage starts to drop/ increase, unfortunately do not remember precisely. Anyway it would be good to compare this shunt reg with 7805 as no one reported any results here before. Hope to find some time for that in December
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Old 6th December 2012, 11:41 PM   #4882
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As AndrewT has stated "A 7805 or 317 is perfectly good enough for the LDR supply."
In posts by me way back, I did noise/hum measurements on the production Lightspeed Attenuator with standard 7805 regulated power supply and linear wall wart.
With the input shorted the noise (there is no hum) on the output was at 100uV!!!!(microvolts) not mV(millivolts), this is so low that even my Tektronic scope had trouble measuring it above it's own noise floor, sure if you put on a smp wall wart this went up to around 200uV but this is still considered to be very low.
I've always stated my dislike for smp wall warts as the noise from these comes in anywhere even the air. They are dirty as can be.
As far as driving this circuit, it consumes so little it can almost be driven by rubbing two sticks together.

Cheers George
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Old 7th December 2012, 05:55 AM   #4883
DRONE7 is offline DRONE7  New Zealand
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Quote:
Originally Posted by georgehifi View Post
As far as driving this circuit, it consumes so little it can almost be driven by rubbing two sticks together.

Cheers George
I have three sticks..... 1xOak, 1xBeech, and 1x Yew.

Which combination would you recommend.... ?

EDIT...... now a moot point as the Beech broke when I first tried rubbing it together with the Yew.
Then the dog ran off with the Oak and I can confirm that one stick is not enough to power the unit. :-(

Last edited by DRONE7; 7th December 2012 at 06:05 AM.
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Old 7th December 2012, 01:09 PM   #4884
wlowes is offline wlowes  Canada
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Smile Noise floor of Beech vs oak - scope pictures soon

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Originally Posted by DRONE7 View Post
I have three sticks..... 1xOak, 1xBeech, and 1x Yew.

Which combination would you recommend.... ?

EDIT...... now a moot point as the Beech broke when I first tried rubbing it together with the Yew.
Then the dog ran off with the Oak and I can confirm that one stick is not enough to power the unit. :-(
Just make sure the Beech and the Yew do not create noise and you will get great sound. If they do make a higher noise floor, you'll still get darn good sound, maybe just a little wooden sounding .
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Old 19th December 2012, 05:38 AM   #4885
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George,

I found a little problem on my volume lately. I had it on 24/7 for several months and it sang for me with no problem, but lately I've found the left channel sounds louder than the right when I turn it up to above 11 o'clock. I have both channels checked and the resistance of both channels are the same when in 9 o'clock but starts to vary from 1100 ohms to 1306 ohms when I turn the pot up to 11 o'clock. The more I turned the volume the larger the variation. I have the 1k pot tuned but with no avail. I then put another 1k pot on the other channel but it doesn't work either. The 5v B+ is absolutely stable. Is something fired or ?? Please do advise.
Thanks

Albert
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Old 19th December 2012, 03:15 PM   #4886
troystg is offline troystg  United States
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.... Is something fired or ?? Please do advise.
Thanks

Albert
Did you flip the RCA's from the source into the attenuator to prove it was the attenuator?

Just being thorough...
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Old 19th December 2012, 03:23 PM   #4887
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Did you flip the RCA's from the source into the attenuator to prove it was the attenuator?

Just being thorough...
I have it checked unload - No hookup to anything.
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Old 19th December 2012, 07:32 PM   #4888
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I can't remember Albert did you build this diy Lightspeed inside a pre or poweramp or is it a stand alone unit?

Cheers George
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Old 19th December 2012, 09:39 PM   #4889
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Originally Posted by georgehifi View Post
I can't remember Albert did you build this diy Lightspeed inside a pre or poweramp or is it a stand alone unit?

Cheers George
A stand alone unit.
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Old 19th December 2012, 09:49 PM   #4890
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Seems to me then if it was not a fluctuating heat issue, that can happen if instaled inside pre or poweramps.
That maybe you could have had some very strong dc offset or test bench type audio signal come into the input or output that has given your ldr's a bit of a hammering, this can change their resistance character and unmatch them. Time to get another matched set.
Am I right from your pictures that you have separtate left and right led volume controls? And did you say they were 1Kohm?
Cheers George
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Last edited by georgehifi; 19th December 2012 at 10:01 PM.
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