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Old 10th January 2011, 12:38 AM   #3911
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Sorry Mike didn't mean you were naive, but it will attract them.
As for the NLS32RS2S (selected) they have a batch letter R2C and the number of 208 on my last batch, and I've also noticed they have much thicker legs on both sides, than the NSL23RS2 that I have had which had the number 401C on them with thinner legs. I think the ones in the EVA 2 could be something else again from Silonex. As for the relays, there are 3 of them with 3 transistor drivers one each and which look to be DPDT double pole double throw, unless they used one for each input?
Cheers George

Cheers George
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Old 10th January 2011, 01:45 AM   #3912
udailey is online now udailey  United States
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Silonex has changed their manufacturing. You will soon see ALL the LDRs having thinner resistor side legs. LED legs are the same.
309 has been on SR2 for a few years now, when purchased from Allied. I get other numbers on the side but that one shows up often. I bought 1000 LDRs this fall and they all had the thin legs and a 4 digit number on the side, all SR2. This last batch I bought over Christmas has the 309 again, well half of them do. Forget whats on the other half right now.
They put a 3 page announcement from Silonex on this last purchase (oddly it wasnt on the previous one) saying how they were changing manufacturing facilities and the leads would be a bit thinner we could all alter our through hole size apparently. Still sounds the same
Uriah
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Old 10th January 2011, 01:52 AM   #3913
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The last batch of NSL32SR2S I recieved I had to wait for from Silonex to be delivered 4 weeks ago still had the thicker legs.

Cheers George
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Old 17th January 2011, 07:13 AM   #3914
Alexiss is offline Alexiss  Sweden
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Default Another Lightspeed review?

Hi everyone.

I ve been very interested in hearing a Lightspeed in my own system for a long time, and reading the rave reviews about it everywhere on the net fueled my enthusiasm even more.

I would like to thank Mr George who has been kind enough to share his ideas and design with the rest of the community. This in turn has given rise to countless permutations of the original, where the extra efforts have mostly been focused on the PSU and noise improvements.

A friend of mine who is knowledgeable in electronics decided a while back to build the latest version of the original Lightspeed. He finished it a few days ago, and after measurements and checking and rechecking and optimizing the PSU, we finally sat down yesterday for some critical listening. I would like to point out that we compared the unit against a pure resistive divider.

This might not be the right place to post these comments but I have to tell you that my initial impression was less than enthusiastic.

I would like to know if there are any others who have had similar experiences with this obviously very intriguing and wonderful design.

Here is what i heard:

Low frequencies sounded slightly cluttered and imprecise. I experienced an artificial roundness in the bass that was quite obvious after spinning many familiar discs.

Midrange was much warmer and slightly grainier compared to the resistive divider and once again percieved as artificial.
However, this did not seem to effect the soundstage in which the midrange frequencies were recreated -- strange.

I perceived highs as being rolled off and slightly congested. This inevitably lead to a perceived loss of detail in the music.

As previously mentioned, the soundstage was - astonishingly - completely intact compared to the purely resistive divider.

My friend measured the frequency response with and without the Lightspeed in the signal path and could not find any discrepancies.

Have you had any similar experiences? if not, what do you think the problem might be?

Thanks.

System parameters:

Amplifier input impedance: 1 Mega ohms
CD output impedance: 50 ohms


cheers
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Old 17th January 2011, 08:47 AM   #3915
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Strange, can I ask what were the specs of interconnects from cdp to Lightspeed and from Lightspeed to poweramp
1: Lengths?
2: Capacitance per foot?
3: What was the volume position on the Lightspeed for normal good level listening?
4: Does the CDP have an output dc offset blocking capacitor, and what size is it?
5: The pure resistive divider you used was just simple soldered in voltage divider at a set volume? consisting of a soldered series resistor and soldered shunt resistor, if so it would be interesting to know the values of the series and shunt resistor?

Cheers George
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Old 17th January 2011, 09:21 AM   #3916
Alexiss is offline Alexiss  Sweden
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The interconnects used are 0.5 meters of Supra Interconnect EFF-1
from CD Player to the Lightspeed unit, and the same running from the Lightspeed unit to the amplifier.

# Resistance: 0.038 Ohms/m
# Capacitance: 77 pF/meter
# Nominal impedance: 75 Ohms @ 1 Mhz
# Propagation velocity: 0.66c

Supra Cables

CD Player is a Pioneer pd-95 modified a few years back with the zapfilter installed:
L C Audio Technology / ZAPfilter 2

Amplifier is lcaudio's Zapsolute class A 50W modified for 1 Mega ohms input ( I wanted to be able to connect it to valve preamps ).

The position of the volume control was mostly 8 to 9:30 since the power amp posesses high gain. I am not sure what resistance values this interval corresponds to, but my engineer-friend measured the total resistance of the lightspeed unit to be exactly 10 kohms.

The resistors used in the purely resistive divider was a 5600 ohms in series, with various values for the shunt resistor, all being under 1000 ohms. We simply connected the DC Coupled output of the CD Player to this very divider, and by changing the value of the several paralleled shunt resistors, we changed the volume setting. The argument behind this very awkward setup was proposed by my friend as to create the most neutral "volume control" that can be made to function as a reference.

Have you ever, under any circumstances experienced anything remotely similar? possibly due to some malfunction or a bad connection?

Thanks

Last edited by Alexiss; 17th January 2011 at 09:35 AM.
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Old 17th January 2011, 10:25 AM   #3917
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All seems good to me, I am a big fan of the Zapfilter, did a lot of cdp mods using this, I did have quite a few rejects though with big dc offset problems (50-200mV), but they were all replaced sometimes twice and three times before I got reliable ones, you should check the dc offset regularly.
The only thing I have a question over is the amp is it a "class D (PWM) amplifier" as they seem to have stoped production of this, never been a big fan of them (PWM), and from what I've seen not successful at getting them to behave well with input impedances over 20kohm.

Cheers George
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Old 17th January 2011, 11:25 AM   #3918
Alexiss is offline Alexiss  Sweden
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Yes Mr George. The Zapfilter was a revelation.
I was shocked at the level of improvement once it was installed in my already top-of-the-line CD Player many years back.

I have not experienced any problems with the DC offset. It measures (five minutes ago) 18 mV at the left output and 24mV at the right output.

The power amplifier is a Zapsoulte mk4 pure class A design, producing approximately 40 Watts of class A music while producing HUGE amounts of heat. The production of this underestimated jewel was sadly discontinued, as its magical creator, Mr Clausen of LC Audio decided soon after, that it was time to move on, and sold the company.

My amp was a factory-assembled unit ( with a slight modification installed at the factory that produced higher impedance ), and I have been using it since 2005 with great pleasure.

I totally agree with you on the class D amplifiers. Their sonic goal is far from what hi fidelity aims to achieve. I have listened to many ultra expensive, commmersially available class D designs, and many passionately-assembled diy efforts. None of them in mho managed to paint anything more than a gray, lifeless and congested picture of the musical event.

I know many people use them to power their subwoofers. I would not consider using them even for that!

Back to the Lightspeed, I honestly do not know what might be wrong with our assembly. Since I do not know anything about electronics, I have contacted my engineer-friend ( who built the kit, actually two ) and he informed me that he is going to recheck all the connections and voltages once more, and change the matched LDR's with the new matched ones bought last week.

It is however a puzzle to me, as the design is wonderfully straight forward, logical -- and according to everyone -- a sonic ace.

He told me that the PSU is built extactly according to your recommendations of the original Lightspeed:

1. Normal transformer-based, regulated battery eliminators 12 VDC out @ 300mA
2. Onboard chip regulator called LM7805
3. RC filtered 10 ohms 4700uF feeding the LDR's on the pcb via the dual volume control
4. LDR's mounted carefully on the pcb and soldered quickly at low heat.

Do you think there is anything we might have forgotten? any mistakes or mismatches?

thanks for your help

Last edited by Alexiss; 17th January 2011 at 11:43 AM.
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Old 17th January 2011, 12:08 PM   #3919
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Quote:
Originally Posted by Alexiss View Post

I have not experienced any problems with the DC offset. It measures (five minutes ago) 18 mV at the left output and 24mV at the right output.


Do you think there is anything we might have forgotten? any mistakes or mismatches?

thanks for your help
18mV & 24mV is quite high dvc offset for source equiptment. When working properly the Zapfilter are suppose to fluctuate between 1-5mV because they are dc servo'ed

As for the ldr's I have no more answers for you, I have seen the series ldr's cooked with high inputs from high levels of ac or dc esspecially when the output has been loaded down, one customer feed in 10v 1k sine wave while the output was close to shorted with a 100ohm load and this cooked the series ldr's so they only had a range of 50ohms to around 1k.
Cheers George
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Old 17th January 2011, 12:32 PM   #3920
Alexiss is offline Alexiss  Sweden
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Quote:
Originally Posted by georgehifi View Post
18mV & 24mV is quite high dvc offset for source equiptment. When working properly the Zapfilter are suppose to fluctuate between 1-5mV because they are dc servo'ed
I believe the possible reason as to why I have not had any problems with the DC on the output of CD Player is that it is probably further reduced by the voltage-dividing volume control. The power amplifier itself is DCservoed, thus compensating for any DCs present at the input.

As far as the Lightspeed goes I thank you for your help and as stated earlier, we will try to look at the rest of the circuit to find a possible explanation to this strange behavior.

Thank you
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