Lightspeed Attenuator a new passive preamp - Page 383 - diyAudio
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Old 7th December 2010, 05:49 PM   #3821
SY is offline SY  United States
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That assumes input stage Johnson noise is dominant. In many designs (e.g., Joachim's or syn08's), one can reduce input stage noise to below the intrinsic Johnson noise of the source, so the 3dB penalty is moot. In other designs (like mine), those analyses are not valid.
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Old 7th December 2010, 07:12 PM   #3822
ondesx is offline ondesx  France
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May be an important precision must be recalled here... We are speaking of two different things. The balanced nature of the cartridges AND the use of the current mode instead of the voltage ! Even there are some "current preamp" on the market (for example 47Labs, the various Dynavectors, the ESE Nibiru, Jean Hiraga's DIY) the balanced version of this current preamp is rare !...

Then, most of the drawbacks of the balanced voltage preamp don't apply to the current mode preamp. The amplification in current mode, for example, does not require any impedance matching.
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Old 7th December 2010, 09:22 PM   #3823
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Quote:
Originally Posted by georgehifi View Post

And then there is dacs/cdp's with so called balanced outputs, very few are balance all the way from the dac chips outputs right through to the xlr connectors usually they are single ended from the dac chips through the I/V stage then through 2 opamps to give the balanced output where the same but single ended output goes through 1 opamp after the I/V stage

Cheers George
This would not be the case.

Nearly all high performance DAC chips these days are balanced OP. They do
this specifically to get very low distortion figures through cancellation of
(some of) the even order components.

WRT all of those opamps, one of the best upgrades you can do to most fully
balanced voltage OP DAC's is throw away the whole back end and use a
VHQ line OP transformer such as Jensen or Cinemag.

Then you get a true galvanically isolated, bal or unbal OP - just like in
studios in the old days when they made great sounding recordings

Terry
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Old 8th December 2010, 01:09 PM   #3824
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No good idea put a DMM on the cartridge!!
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Old 11th December 2010, 04:35 PM   #3825
kerux is offline kerux  United States
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Thumbs up I finally got my lightspeed working

I finally got my lightspeed working and it sounds amazing. I used Quanghao's pcb of Salas's Low Voltage Shunt Regulator circuit to power it.

My wife is also amazed at how good my stereo sounds now.

Thank you George, Salas and Quanqhao for providing these circuits and pcb.
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Old 11th December 2010, 06:34 PM   #3826
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Oh great - a Lightspeed post at last !!

It's been all about cartridges, balanced stuff and pro audio recently.

Nice one Kerux - congratulations.
I'm recently a convert too and I'm still delighted with mine.
It's a big upgrade.
Your power supply sounds interesting - I'll check that out

Andrew
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Old 12th December 2010, 06:41 PM   #3827
Marra is offline Marra  United Kingdom
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Quote:
Originally Posted by AndrewGM View Post
Oh great - a Lightspeed post at last !!

It's been all about cartridges, balanced stuff and pro audio recently.

Nice one Kerux - congratulations.
I'm recently a convert too and I'm still delighted with mine.
It's a big upgrade.
Your power supply sounds interesting - I'll check that out

Andrew
Andrew;
Check out dvb-projekt's Salas shunt regulated boards for powering the Lightspeed
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Old 13th December 2010, 12:18 AM   #3828
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How hard would it be to make a balanced version of an LDR attenuator?
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Old 13th December 2010, 12:26 AM   #3829
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Quote:
Originally Posted by TheShaman View Post
How hard would it be to make a balanced version of an LDR attenuator?

Wish you luck on the matching, and have some Valium handy.

Cheers George
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Old 13th December 2010, 08:52 AM   #3830
markusA is offline markusA  Sweden
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I bought my matched ldrs from a friendly person on this board. costs are a premium but it saved me many grey hairs.
I actually have the case now and most of the small bits and pieces. As soon as I manage to free up some time I'll start assembly.
(Three projects running in parallell and my classes at the local techical university keep me quite busy.)
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