Lightspeed Attenuator a new passive preamp

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#1,863
ondesx said:
Thank you James. I did a try before going to bed yesterday night with a very simple operational amplifier mounted in follower mode (a couple of LME 49720) and the observed phenomenon at low level remain... I concluded that there isn't an impedance issue !

Moreover, the impact and intensity of the lows are just amazing, that wouldn't be the case with an impedance mismatch, or this mismatch just appears for low levels ?

Perhaps somebody knows what happens if one use a too high or a too low power supply ? Anyone tried batteries instead ? With a charger, it'll be perhaps the best solution isn't ?

I'll try with different PSU now and we'll see...

For an enough high level, all is pretty good, the sound is just incredible, better than with my third opus of auto-transformer (which still reached a very very good audio quality indeed, much better than most active preamps, even some swiss made costly gear...). We have more presence, transparency, the sound stage is very large, the voices are more natural, with a very good stability for high frequency at high levels, the dark side is the mixing errors are more evident too !...😉

Enclosed a picture of my first balanced LS opus !
Click to expand...

That's neat. How do you wire up balanced inputs/ outputs?
 
#1,868
jackinnj said:
Reading the review in Stereophile of the new Boulder integrated amp (tens of kilobucks) -- it appears that we have yet another high-end device which uses a "light activated attenuator".
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Well,the evidence of our ears would suggest that they(and Dartzeel) are not mistaken in their attempts to utilise a light activated attenuator.
 
#1,869
jackinnj said:
Reading the review in Stereophile of the new Boulder integrated amp (tens of kilobucks) -- it appears that we have yet another high-end device which uses a "light activated attenuator".
Click to expand...


I read the article and I am still scratching my head tying to figure out how you deduced that it uses an optical volume from the 4 words printed.

Just curious.... 😀
 
#1,870
There is no need for an external control microprocessor. Why complicate the issue un-necessarily. Also I do not need an LCD readout to tell me how loud the music is, just my ears.
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I think it is absolute necessary to have even a LCD for volume or to have a stepped attenuator. How could you compare things, if you cannot do it with the abolute same volume or the volume you have found out to be the right for the compared parts...? 🙁

Btw: Would someone be so gentle to make a little conclusion about this thread? Only about the things, which are worked out up to now. Yesterday I started to read from the beginning and there is no end -> about 1900 posts ... I saw that after Georges solution and input there were Uriah and Paul going on ... But for me it is not clear what are the differences ... or the advantages to Georges solution (I still saw the remote control in Pauls solution).

I am very interested in a way to switch between a balanced and a unbalanced version. The balanced version in Georges way will need a 4 x 100k poti, which I think could only be solid built with a stepped att. by its own. With LCD and balanced, but with other resistors from here: Jos v. Eijndhoven - unbalanced or the balanced version (without the pre): Jos v. Eijndhoven - balanced . The unbalanced built version is also found at Tentlabs . This would be also very practical, but only with 4x10k: Thel .

So like I said: Forgive me .. because I am not up to date 🙂
 
#1,871
georgehifi said:
I've already sent a while back the US/European Patent offices proof that I started it (MkI) over 30 years ago
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I'm pretty sure I've got references of cadumim sulphide cells used for audio amplitude control dating back to the 50's.
The earliest I can find at the moment is the Teletronix LA-2A compressor amplifier of 1965:
 

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#1,872
Well I wont rehash the whole thread but I tell most people this:
Read the first 4 pages. Build it. The rest of the thread is conjecture, very little arguing which is nice 🙂, congratulations and thanks to George (well deserved), talk about matching, talk about disbelief, talk about power supplies and thats about it.
The sound is truly phenomenal at any volume.
Balanced might be great but most people that have asked me about balanced dont get how it operates. If you have a CDP with RCA outputs or an amp with RCA inputs what can you gain from a cord that is designed for balanced but either doesnt have a balanced line transceiver or a balanced line receiver? Balanced line isnt really something that is inherent to the cords you use or the fact that you use inverted, uninverterd and a common line. You have to have a receiver and transceiver. If you happen to have both then I see the point. Balanced line is also for 25ft or longer runs that pass over lots of other wires, are in high RFI EMI situations and probably pass over huming power supplies as well. If you have short runs, keep your cables neatly sorted and ground properly you will probably have no need for balanced. If you have RCA ANYWHERE in your line then stick the Lightspeed directly after the RCA and try that. However, as George has said, getting balanced LDRs is near impossible. I got a few balanced sets out of 350 of them. Makes me doubt I would have got one balanced set with 100. Maybe maybe just maybe but I doubt it.
I think Zen Mod might still be selling LDRs and I am not sure but I think he had some balanced. I have a few as well. I still would rather use these single ended as balanced will just be to fiddly.
Uriah
 
#1,874
Lightspeed remote control

Hi folks,

I have built and tested the VCCS board and it works fine, so I did not make any electrical errors on the revised layout. Now that the VCCS board is verified I can complete the application note. I did notice an error on the component ident and I will correct this in the application note. This may take a day or two as I will have to do this in my spare time. I'm just too busy at work at the moment to fit it in during the day.

Once the application note is finished I will begin shipping boards unless you ordered the IR boards as well. If all goes according to plan I will have the IR boards sorted by mid next week as long as the boards arrive this week.

Here are a few pics of the VCCS test module :-

VCCS1A1.jpg


VCCS1A2.jpg


VCCS1A3.jpg


Regards
Paul
 
#1,875
Lightspeed remote control

Hi TJF,

I don't need an LCD display. If you feel the need for one there are options around that may be adaptable. The DS1802 has a 3 wire serial control port that allows read and write functionality. I have left the option to use this on the board. I am no expert when it comes to programming. Maybe someone in this field can contribute a solution for those who require a readout. We have turned this project into a group buy, lets continue and turn it into a progressive group design to find solutions to more complicated applications.

The VCCS module can be addapted to provide a balanced volume control provided you can find a matched set of four LDRs for the series LDRs and a matched set of four LDRs for the shunt LDRs.

Regards
Paul
 
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