Lightspeed Attenuator a new passive preamp - Page 61 - diyAudio
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Old 17th April 2007, 04:39 PM   #601
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Default One of each

I have a passive and an active with LDR volume control. I think maybe the passive is better, but the passive is a 10K control and the one on the AD815 is a 22 - 25K.
The active is set up with a gain of 2. Also, I am not sure about using a passive on an amp with a 27K input. All mine have 100K, that works great with the passive.
I am pulling it apart tonight, maybe post pics of the fancy filtering on the LDR's.

George
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Old 19th April 2007, 02:20 AM   #602
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Default Try for Pics

Pulled my active, AD815 apart and did a little tuning. Adjustedf the reg back to 5 volts and diddled with it a little.
The pics of it in the chassis, do not show much. Here are the boards out. This is a close up of the LDR's and wiring.
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Old 19th April 2007, 02:23 AM   #603
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Default Top of Lightspeed clone

This shows the boards as the middle of the unit. They are stacked inside, LS on bottom, the AD on top
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Old 19th April 2007, 02:25 AM   #604
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Default Bottom of Lightspeed

Shows those caps added across LDR's, also top of AD board
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Old 23rd April 2007, 07:46 AM   #605
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Default Impressions

Thought I'd post some initial notes in my set-up:

Theta Data III
Theta Gen Va DAC with mods
AD815 pre with LDR (substituted a DACT pot)
Greg Ball's Simple Killer Amp (GB150)
Royd doublet speakers

The LDR's have a very open and neutral presentation. Clarity is fantastic across the frequency spectrum. Yet, despite the clean clear sound, I do not notice any harshness/sharpness, which in my experience has tended to accompany "open" presentations in the past. There is no "etching" of the sound, yet everything is remarkably present/clean.

Things I will still do include the use of capacitors across the LDR's.
Note that I am using ultra low noise power supplies (Andy Weekes super regs)

A VERY worthwhile upgrade, even to a DACT pot (a highly regarded stepped attenuator) running in shunt mode.

Ryan
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Old 24th April 2007, 09:13 PM   #606
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Hi Ryan, I had the same impressions of the Lightspeed ... very clear, not harsh, neutral, well resolved, smooth, etc. No complaints yet! I also use ultra low noise supplies.
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Old 25th April 2007, 05:59 AM   #607
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Default A further improvement....

Based on recent posts, I fitted a 47uF, 6.3V Murata ceramic cap to the LED leads on the LDR. It seems that this has brought a further improvement in the performance of the pot.

Listening last night revealed a key ingredient of the magic of this pot: Low level background info is produced with greater clarity than ever before. Whereas with other pots there was a degree of masking or a sense of loss of the immediacy of the background info, the LDR pot seems to manage to keep the detail and volume of this info.

Another aspect which is hugely impressive is the pinpoint resolution and placement of instruments-In the past the "position of instruments" in the soundstage was discernable, but reasonably broad. The LDR has created the impression of "exact location", which, for me anyway, substantially heightens the sense of realism of the performance.

Sometimes it is easy to just listen to music and forget that there are human beings involved in the creation of the soundscape. The LDR pot pinpoint sharpness coupled with distinct low level information paints a much more vivid image of the performance and I find that this lends to a greater enjoyment of the display of musical skill-each song becomes more of an "event" than just "another song".

Finally, the greater availability of previously low level nuances (subtle changes in tone, timing, breathing etc) heightens the experience of the performance.

This is a relatively easy mod and in my 10 plus years of hifi diy'ing, the best bang for buck and single biggest step change (using diy) that I've had in my system. (FWIW, the AD815 counts as second, Greg Ball's GB150 as 3rd).

George, thanks for sharing the concept and parts info. Who knows, maybe sometime in the future, LDR's will be the only acceptable signal attenuators across the music industry. We'll all benefit if that turns out to be the case.

Ryan
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Old 25th April 2007, 06:28 AM   #608
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Default Re: A further improvement....

Quote:
Originally posted by Dr.H
George, thanks for sharing the concept and parts info. Who knows, maybe sometime in the future, LDR's will be the only acceptable signal attenuators across the music industry. We'll all benefit if that turns out to be the case. Ryan

Ryan, I already believe that to be the case, if I can be that bold without being chastised.

Cheers George

ps like my new avatar, that's an Aussie Mick Doohan @ 160kph hanging the rear out power sliding with opposite lock, poetry in motion.
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Old 26th April 2007, 12:43 AM   #609
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Default Magic in the pot

Ryan,
If you are hearing all that there is magic inthe pot.


George
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Old 26th April 2007, 05:46 AM   #610
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Default Magic?

Hello all,

Yeah, I am hearing background details that were much less present before. It helps to have the Data III in combination with the Gen Va (both modded-mostly power supplies and ultra low noise regulators). Not to mention the AD815 using Jung-type super regs (i.e. the pre is not passive) and of course the fantastic resolution provided by the GB150's!

The impact of background detail is interesting-much like adding small "true to life" details to a painting can greatly aid the illusion of it being a photo/real rather than just a painting.

With recordings, it is sometimes hard to discern the human element-could be machine playing the guitar/clarinet/violin/bass etc. But add subtle details like the sound of the soloists sharp intake of air (the classical music fans will understand) and suddenly VOILA, a performance unfolds before your eyes/ears!
Of course if the info was not there to start off with (lets say a rock band going hell for leather on stage, it does not suddenly appear, but where is is present, it makes a huge contribution to the illusion of live musicians playing

The 47uF mod is worthwhile by the way...

Panelhead/others, what have been your experiences? Less resolution?

Ryan
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