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Lightspeed Attenuator a new passive preamp
Lightspeed Attenuator a new passive preamp
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Old 21st July 2011, 01:41 AM   #4211
georgehifi is offline georgehifi  Australia
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Here are some updated distortion measurments for those interested from Silonex and then AP ones done by a member here.

Cheers George
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File Type: jpg Silonex NS32SR2S Distortion Measurments.jpg (224.1 KB, 600 views)
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Old 21st July 2011, 05:29 PM   #4212
jonclancy is offline jonclancy  United Kingdom
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Thanks George.

The text on the AP slide is a bit small. Is the LS THD figure 0.000282%?

Many thanks!

Jon
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Old 21st July 2011, 06:02 PM   #4213
h22 is offline h22  United States
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I am very interested in building one of these for use with a B22 headphone amp, I am planning on building this in as small a case as possible. I am wondering if it would be possible to use the +1/2 of the sigma22 power supply to feed a small (TO92) sized
lm7805 with a couple of caps as the power for the LEDs, the sigma22 has is a very clean power sorce, so I am assuming that this would result in a very clean voltage to the LED side.Anyone tried this or a similar scheme?
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Old 21st July 2011, 10:05 PM   #4214
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by jonclancy View Post
Thanks George.

The text on the AP slide is a bit small. Is the LS THD figure 0.000282%?


Many thanks!

Jon

The .000275% was his calculated distortion, plus the noise floor he says he measured of.000282%



Quote:
Originally Posted by h22 View Post
I am very interested in building one of these for use with a B22 headphone amp, I am planning on building this in as small a case as possible. I am wondering if it would be possible to use the +1/2 of the sigma22 power supply to feed a small (TO92) sized
lm7805 with a couple of caps as the power for the LEDs, the sigma22 has is a very clean power sorce, so I am assuming that this would result in a very clean voltage to the LED side.Anyone tried this or a similar scheme?

That will be fine even overkill with the Sigma 22, I use a 7805 in my final regulation with nice 470uf smoothing cap then a .1uf MTK and it is indistinguishable from the purest form of dc, battery.

Cheers George
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Last edited by georgehifi; 21st July 2011 at 10:09 PM.
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Old 21st July 2011, 10:29 PM   #4215
jonclancy is offline jonclancy  United Kingdom
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Thanks George.
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Old 16th August 2011, 02:23 AM   #4216
soongsc is offline soongsc  Taiwan
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Quote:
Originally Posted by georgehifi View Post
Here are some updated distortion measurments for those interested from Silonex and then AP ones done by a member here.

Cheers George
I noticed its the NSL32SR3 instead of the NSL32SR2 used in the Lightspeed. Why was the NSL32SR3 not used in the Lightspeed? Matching issues?
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Old 16th August 2011, 03:36 AM   #4217
georgehifi is offline georgehifi  Australia
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I found that the impedance spread on the SR3 too great at 60ohm to 25megohm to get quad matching, compared to the much tighter SR2s at 40ohms to 5megohms which will give you much tighter quad matching which also gives a better logarrithmic feel to the volume control because of that quad matching.
The SR2s also goes lower in impedance which give a closer to zero volume than the SR3 can.

Cheers George
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Old 16th August 2011, 04:52 AM   #4218
soongsc is offline soongsc  Taiwan
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It seems that these devices vary in resistance with signal amplitude, which could be a good thing. I still need to do some more testing though.
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Old 16th August 2011, 04:57 AM   #4219
georgehifi is offline georgehifi  Australia
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Quote:
Originally Posted by soongsc View Post
It seems that these devices vary in resistance with signal amplitude.
?????? I suppose they might if overdriven with 10v or more which may change their internal temperatures, but at normal source levels .5-2v they do not.

Cheers George
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Old 16th August 2011, 06:15 AM   #4220
soongsc is offline soongsc  Taiwan
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I ran a quick test last week, driving signal was less than 5V peak-peak, adjusted the output from 10%~90% at 20% increments, the impedance curves looked flat, but the value changed with level in a fixed manner. As I mentioned, I still need to do more testing with the right setup.
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