Lightspeed Attenuator a new passive preamp

[tinitus]

George, seems like you have removed 100R on one LDR ?

 

[georgehifi]

Oops!!! Thanks! Just seeing if you guys are on the ball

Cheers George

 

[Blues]

Oops!!! Thanks!

Cheers George

Looks familiar....

 

[DRONE7]

Maybe slightly bigger resistors before LDR

Tried that, 280R, 560R then 1k no change.

I begin to think that I could wire in a beetle, a diamond, and a poem without making any appreciable difference .

Thank you George for the circuit and reminder. I have ordered some parts and will rebuild my LSA to your layout.

Don't know what it is like over the ditch but here in N.Z even a bog standard 100k pot is getting hard to source.
Duck Smith don't have 'em and the nearest Jaycar is a 70 minute round trip.
Their online stores charge an arm and a leg for freight to a rural address so it is often just as fast and same cost to order from the U.K or U.S. (end rant)

Thanks for all your help.

 

[georgehifi]

Tried that, 280R, 560R then 1k no change.

I begin to think that I could wire in a beetle, a diamond, and a poem without making any appreciable difference .

Thank you George for the circuit and reminder. I have ordered some parts and will rebuild my LSA to your layout.

Don't know what it is like over the ditch but here in N.Z even a bog standard 100k pot is getting hard to source.
Duck Smith don't have 'em and the nearest Jaycar is a 70 minute round trip.
Their online stores charge an arm and a leg for freight to a rural address so it is often just as fast and same cost to order from the U.K or U.S. (end rant)

Thanks for all your help.

Jaycar have them.CAT. NO. RP3762
Cheers George

 

[DRONE7]

Not much of a cheese shop is it ?

Jaycar have them.CAT. NO. RP3762

Thanks George.
I had an order in for a couple of these (and some other components) with the Jaycar online store.

The courier arrived with my parcel 3 hours ago and guess what ??.

No 100k log pots!!

Out of stock and back-ordered.

So, here in N.Z, an otherwise modern first world country, one cannot buy such a simple thing as a 100k pot. end rant.

Still there was a 100k dual linear pot so I've put that in and, whilst the range is dreadful of course, the improvement to sonics and especially low frequencies is astonishing !.

I wouldn't have believed it would make such a difference going from a 500k single pot to a 100k dual

So now I am awaiting Jaycar to make good on its delivery and will fire off a couple of fast and furious e-mails explaining to them the concept of 'bait advertising' and how it is illegal here.

 

[AndrewT]

I wouldn't have believed it would make such a difference going from a 500k single pot to a 100k dual

sounds like there is an impedance mismatch.

Changing from 500k single to 100k dual has the effect of increasing the LED currents which in turn will decrease the LDR resistances.
The decreased resistances has a direct effect on the Zin and Zout of the attenuators.

Decreasing Zin will put more loading on the source. This is unlikely to be heard if it did not previously give a problem.
Decreasing Zout will drive the interconnects better. This could have a profound effect on the sound coming out of the next stage.

I suspect you have not given sufficient thought to how you are using/connecting the Lightspeed into your audio system.

 

[DRONE7]

sounds like there is an impedance mismatch.
I suspect you have not given sufficient thought to how you are using/connecting the Lightspeed into your audio system.

Thanks Andrew,
quite possible as I am not technically minded and have little test equipment so tend to 'try it and see (listen )'.

Though I have to report that levels are more than adequate and that the cables to and from the LSA are each under 200mm (yes mm) in length. Running from Philips cd to Plinius power amp.

Seems to me that the LSA is an ideal adventure as there is not much that can go horribly wrong.
Its simplicity is its strength.

Since stumbling upon this thread 3 months ago and building the LSA I have been blessed with the most musical improvement to my listening enjoyment in the last two decades.

cheers, Bob.

 

[tinitus]

I no understand
Me thought pot was completely out of signal

Also thought it was stated single pot not good, at all
That dual pot work different ways
Not that any could explain

btw, do not high impedant mean higher noise

 

[georgehifi]

I no understand
Me thought pot was completely out of signal

I think he means the volume control curve characterisics are dreadful in the way the the range operates.
With a 100K linear everything comes on way too quick at the begining of the travel.
Cheers George

 

[coloradosound]

Allied has these:
PerkinElmer Optoelectronics

datasheet:
http://www.alliedelec.com/images/products/datasheets/bm/perkinelmer/980-0064.pdf

are these similar to original part?

 

[DRONE7]

I think he means the volume control curve characteristics are dreadful in the way the the range operates.
With a 100K linear everything comes on way too quick at the beginning of the travel.
Cheers George

That is exactly what I mean.

 

[tinitus]

Ah,yes thanks, lienar pot no good, I know thats DRONs problem

I was more wondering about Andrews post about load impedance issues
Why I said thought pot had no say in this
Maybe I just dont understand what Andrew is saying

 

[DRONE7]

maybe just a little cheese ?

So, here in N.Z, an otherwise modern first world country, one cannot buy such a simple thing as a 100k pot.

I think I've found one, just had an e-mail from a supplier who has (hopefully) one left in stock !!

New Zealand, gem of the Pacific. 3 Islands, 3 Million inhabitants, 23 Million sheep, and one 100k dual log pot.!

And it's mine d'yhear, mine, all mine........... (maniacal laughter.....exit stage left..)


EDIT... so here I am posting this and the courier sounds his horn.
Race out to the gate and there is my back-order from Jaycar.
2x 100k log pots. Thanks Jaycar!!
Boy oh boy a Lincoln toy.........exits stage left with soldering iron..

 

[cedricb]

Hi guys,

I'm just wondering if we can use LDRs to convert speaker output (4/8 ohms from a tube power amp) to headphone impedance?

HeadWize - Headphone FAQs


Regards,
Ced.

 

[dvb projekt]

Professional Lightspeed Attenuator PCB in Production

Hi to all,

for those who want to have a optical and technical perfect solution for the Lightspeed Attenuator, i have made a real nice PCB.
It is a 2-Layer Design to seaprate the Audio-Lines (Bottom Layer) from the Electrical-Lines (Top-Layer).
The regulated 5V PSU is included. Furthermore i made the Audio-Lines extra wide (1mm) and choose 70µm copper to get minimal loss.
At the moment the first units are in production.

The PCB has the following data:

Material: FR4 - 2mm
Layers: 2
Board size: 87x54 mm
Surface finish: Immersion Gold
Copper weight: 70µm
Soldermask: Both sides - blue
Silkscreen: Legend on top


The price will be as followed:

Professional 2-Layer PCB: $15
Worldwide shipping: $ 4
paypal fee: 3,9%

For those who are interested, i have add the BOM-List for the PCB-Parts.
There you can see, where to order the necessary parts and the PCB as a line-drawing.
I will add some picture, after the first PCB´s arrived!


Best regards to the community,
dvb-projekt

 

[bequerel]

Great! Keep us updated!

 

[AlanElsdon]

Hi to all,

for those who want to have a optical and technical perfect solution for the Lightspeed Attenuator, i have made a real nice PCB.
It is a 2-Layer Design to seaprate the Audio-Lines (Bottom Layer) from the Electrical-Lines (Top-Layer).
The regulated 5V PSU is included. Furthermore i made the Audio-Lines extra wide (1mm) and choose 70µm copper to get minimal loss.
At the moment the first units are in production.

Best regards to the community,
dvb-projekt

Hi - I have not fully checked the board but it looks as though the 100K pot is wired incorrectly - I will have another look this evening by which time some others (Uriah??) will have checked it out.

Otherwise it looks great - I like the separation of the Audio and Supply lines.

I will certainly have some of these.

Alan

 

[dvb projekt]

Hi - I have not fully checked the board but it looks as though the 100K pot is wired incorrectly - I will have another look this evening by which time some others (Uriah??) will have checked it out.

Otherwise it looks great - I like the separation of the Audio and Supply lines.

I will certainly have some of these.

Alan

Hi Alan,

you are right! The connections on the second Pot are mirrored.
I have corrected this. I will hope i could stop the production of the first PCB order...

In the attachment is the new, corrected layout.


Regards,
Oliver

 

[Puffin]

Hi - I have not fully checked the board but it looks as though the 100K pot is wired incorrectly - I will have another look this evening by which time some others (Uriah??) will have checked it out.

Otherwise it looks great - I like the separation of the Audio and Supply lines.

I will certainly have some of these.

Alan

Me too please