I do not wish to do the matching myself, and have been lead to believe nobody sells matched sets anymore. I wish they did, but apparently no. In that case, I would entertain something. If you'd like, PM me so as not to derail the thread.
Look at my very first post (No. 5) of this thread on how to match them yourself.
http://www.diyaudio.com/forums/anal...attenuator-new-passive-preamp.html#post924390
Administrators have allowed a rehash of the first post, so all can easily find and do one for themselves.
Cheers George
$2.42 at Silonex - NSL-32SR2S - Optoelectronics & Lighting - Optocouplers/Optoisolators - Allied Electronics is the best price I found now. If buying 100.
Hopefully I won't need 100 to get a matched set
I am seriously considering going through the trouble if need be, as the LDR seems to get a fair deal of praise.
Like I've said in the 1st post,
http://www.diyaudio.com/forums/anal...attenuator-new-passive-preamp.html#post924390
you'll only need around 15 x NS32SR2S to get 2 matched quad sets so go halves with a buddy get 20, a quad set each and then maybe a third set you could sell here.
Cheers George
http://www.diyaudio.com/forums/anal...attenuator-new-passive-preamp.html#post924390
you'll only need around 15 x NS32SR2S to get 2 matched quad sets so go halves with a buddy get 20, a quad set each and then maybe a third set you could sell here.
Cheers George
Thanks George,
Would a tester like this suffice?
Good Handy 2 150mA LED Bulb Light Lamp Tester Test Meter Box Tool for Arduino | eBay
I am quite tempted to order 15 and give it a go. I cant find anyone local to split with but still feel like it will be a good investment. Currently just reading through posts from members who matched their own to see how their attempts have panned out.
Would a tester like this suffice?
Good Handy 2 150mA LED Bulb Light Lamp Tester Test Meter Box Tool for Arduino | eBay
I am quite tempted to order 15 and give it a go. I cant find anyone local to split with but still feel like it will be a good investment. Currently just reading through posts from members who matched their own to see how their attempts have panned out.
I would go either of these as they go lower than 2mA
LED Tester Check THE Function Brightness Colour Polarity | eBay
Kemo M087N Light Emiting Diode Tester LED Tester Made IN Germany | eBay
Cheers George
I did a cheap-and-dirty LDR regulator. Bought 5 non-selected ones. 2 in series are with constant voltage and 2 shunt regulated. Matched shunt ones for my real loudness needs.
Serial ones are set for 9,6 kOm and shunt ones work mostly somewhere between 200 ohm and 2 kOm, but they are actually good match up to 10 kOm.
Had black Alps before, with LDR-s sound in so much better, I didn't think that upgrade can be soo big.
Serial ones are set for 9,6 kOm and shunt ones work mostly somewhere between 200 ohm and 2 kOm, but they are actually good match up to 10 kOm.
Had black Alps before, with LDR-s sound in so much better, I didn't think that upgrade can be soo big.
Thanks. I will keep my eyes open for one that goes that low. No shipping to Canada on that cheaper one. There are plenty of reasons I wish I was an Aussie... This is one of those times
The cost of this is starting to run away from me, and want to save what I can where I can. Not looking like this will be the place haha.
Thanks. I will keep my eyes open for one that goes that low. No shipping to Canada on that cheaper one. There are plenty of reasons I wish I was an Aussie... This is one of those times
Morton look at the ready made one at $490aud shipped (that's $466cad) and it's pug and play, and saves 1 days labour as well.
Cheers George
I jumped in head first and built the lightspeed. 1st impressions are really nice. I've been using a stepped attenuator. The SE has a flat dry sound to it.
I purchased 25 optos from Digikey and spent the weekend collecting data. I was able to find 4 of them that matched well enough so a trim pot isn't needed.
I'm driving my own version of a AD815 line amp which I need to drive multiple filters boards for my active crossovers. The line amp has a fet front end so loading is not an issue.
The gain of the AD815 is too high so I need to change it and listen again.
I added a 20k resistor in series with the series opto to lower the signal. It works but the circuit was picking up too much noise. I think it's just from having the LS on a breadboard and all the wiring being clip leads, power supply wires being 2 feet long, etc. Great way to cause problems.....
I ordered a 200k pot to try too. For $1.50 why not. Worst I can be is wrong.
Impression so far; I like this. A lot. There is a musicality to it that is easy to listen to and I did not expect this. Like the difference in sound between a AD1862 and a TDA1541. the AD is nicely detailed but the TDA is musical in a way that says I gotta get some of this. I'm not sure how else to describe it.
I'm figuring this is just a small amount of 2nd order being added. OK. So be it.
I have much work to do to dial this in for my system, At least 3 weeks.
Will post the details.
Mike
I purchased 25 optos from Digikey and spent the weekend collecting data. I was able to find 4 of them that matched well enough so a trim pot isn't needed.
I'm driving my own version of a AD815 line amp which I need to drive multiple filters boards for my active crossovers. The line amp has a fet front end so loading is not an issue.
The gain of the AD815 is too high so I need to change it and listen again.
I added a 20k resistor in series with the series opto to lower the signal. It works but the circuit was picking up too much noise. I think it's just from having the LS on a breadboard and all the wiring being clip leads, power supply wires being 2 feet long, etc. Great way to cause problems.....
I ordered a 200k pot to try too. For $1.50 why not. Worst I can be is wrong.
Impression so far; I like this. A lot. There is a musicality to it that is easy to listen to and I did not expect this. Like the difference in sound between a AD1862 and a TDA1541. the AD is nicely detailed but the TDA is musical in a way that says I gotta get some of this. I'm not sure how else to describe it.
I'm figuring this is just a small amount of 2nd order being added. OK. So be it.
I have much work to do to dial this in for my system, At least 3 weeks.
Will post the details.
Mike
The power supply has been discussed here on numerous occasions but I feel there is some useful input to be had from my experiences. I tried unsuccessfully on two occasions to purchase the “recommended” power supply and quite frankly I just do not understand how the company do any sales at all. Enough said! However I decided to give this one a try as it is reasonable in price!
Hifi linear power DC-1 USB/amp/DAC/external power supply with digital display-SN | eBay
It was despatched quickly as promised and worked very well. But what I discovered when opening it up (we all do) that it was not earthed, so I drilled a hole and fitted a 4mm binding post and added a short cable to the earth on the iec connector. I did think that the sound is slightly better with this unit, some will say that it should not matter etc etc but what I did next was added a replacement mains filter in place of the standard iec, I ordered a 6A model, I always get a higher rating than required then just fitted 4A fuses. This is where the sound really opened up, better bass, sweeter treble etc, much improvement all round! I could go on, but I know some will say that it is possible that my mains is full of mush to start with or else it would not make this amount of difference. I just thought I should let you know!
FN9260-6/06 - SCHAFFNER - FILTER, 6A 2 FUSE | CPC UK
Hifi linear power DC-1 USB/amp/DAC/external power supply with digital display-SN | eBay
It was despatched quickly as promised and worked very well. But what I discovered when opening it up (we all do) that it was not earthed, so I drilled a hole and fitted a 4mm binding post and added a short cable to the earth on the iec connector. I did think that the sound is slightly better with this unit, some will say that it should not matter etc etc but what I did next was added a replacement mains filter in place of the standard iec, I ordered a 6A model, I always get a higher rating than required then just fitted 4A fuses. This is where the sound really opened up, better bass, sweeter treble etc, much improvement all round! I could go on, but I know some will say that it is possible that my mains is full of mush to start with or else it would not make this amount of difference. I just thought I should let you know!
FN9260-6/06 - SCHAFFNER - FILTER, 6A 2 FUSE | CPC UK
Might not have the fancy digital readout, but this has the goods inside for close to half the price, quality components, like Panasonic FM Gold Caps, ei encased transformers and the rest don't look to shabby either, and you get a 5v USB power output for computer stuff thrown in.
TeraDak U9VA Linear Low noise Power Supply
Cheers George
TeraDak U9VA Linear Low noise Power Supply
Cheers George
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I didn't of hear of any purchase problems.
Lots of my customers have them. Some say they can detect a difference going from a standard 300mA linear wall wart, some say no difference whatsoever.
But then you can almost power the Lightspeed by rubbing to sticks together.
The LDR's are so slow to react to the led brightness via the voltage change of the volume pot, they are self damped, and almost immune to slight voltage variations.
But they don't like SMP power, their HF rubbish get's through the ground plane into the output, and that can be measured.
Cheers George
Thanks for that, it would be interesting to know if any UK users have either tried to or are using the Teradac unit. I see them on the internet from other suppliers but are costed at £44 + and not $. So I have some suspicions as to them supplying to the UK! But I don't want to waste too much time on this issue as the lightspeed is now singing away as never before!!!
What a fantastic pre amp it is!
What a fantastic pre amp it is!
LDR resistance too low with 100K pot
Hi,
I am testing if a LSA is something for my DCB1 buffer, just to get a feel with the LDR's.
I tested 10 32SR2s LDR's in the LSA advised 5V circuit with an 100K simulation pot (10 step ladder) and a MM to measure the LDR resistance.
The LDR resistance goes from 20R to 2600...3500R if the pot goes from 0 to 100K.
If I change the pot from 100K to 200K I measure an LDR resistance of 11K.
This are the Rled's from 10 pieces at 100K
4660, 3531 , 3331, 3231, 3017, 3017, 2785, 2724, 2699, 2628
As the DCB1 normally has a pot of 15...20K, I am at 3.5K with the LDR's on the advised 100K pot, or 11K with the 200K pot.
Anyhow the load resistance of 3.5K does seem far lower than 15...20K, not optimal for the sources, I guess....
Am I missing a point? Should I increase the pot to 200K/250K to increase total LSA input resistance (series + shunt)?
Are the LDR's OK?
Albert
Hi,
I am testing if a LSA is something for my DCB1 buffer, just to get a feel with the LDR's.
I tested 10 32SR2s LDR's in the LSA advised 5V circuit with an 100K simulation pot (10 step ladder) and a MM to measure the LDR resistance.
The LDR resistance goes from 20R to 2600...3500R if the pot goes from 0 to 100K.
If I change the pot from 100K to 200K I measure an LDR resistance of 11K.
This are the Rled's from 10 pieces at 100K
4660, 3531 , 3331, 3231, 3017, 3017, 2785, 2724, 2699, 2628
As the DCB1 normally has a pot of 15...20K, I am at 3.5K with the LDR's on the advised 100K pot, or 11K with the 200K pot.
Anyhow the load resistance of 3.5K does seem far lower than 15...20K, not optimal for the sources, I guess....
Am I missing a point? Should I increase the pot to 200K/250K to increase total LSA input resistance (series + shunt)?
Are the LDR's OK?
Albert
Hello George and forum members...
I've been doing a stack of reading about passive attenuators for audio applications in the last few weeks...it's amazing how much online real-estate is devoted to the topic. In "light" of this, I am aware of how late to this thread and discussion the following thoughts are...no doubt I am treading across very trampled ground...
Anyway...
My application straddles between home hi-fi listening for pleasure, and perhaps a more technically "stringent" scenario whereby I will use my 2-channel h-ifi playback chain as my monitoring chain for recording, mixing, and mastering my own original music. I'm thinking about going with a passive solution to front a solid-state power amp, and I've been looking long and hard at the Slagle/Intact auto-former solutions, and resistive solutions.
Three questions/thoughts about your optical attenuator...
1) Can the channel balance ever be as good as a carefully spec'd switched resistor network?
2) It seems the main advantage you claim for the optical device - as compared to switched stepped resistive-ladders (L-topology) attenuators - revolves primarily around the elimination of the switch. Let's just say one accepts this and puts it to one side for the moment, what I don't see mentioned is the actual sonic quality of the resistive element itself. It seems to me that although with a switched resistor network one does incur the liability of switched contacts, one also benefits from having the freedom to spec the quality of the the resistors themselves.
By way of example, lets look at the following: Lets say we attenuate to a comfortable level on your optical device, and then we make a note of the arrived at series and shunt values, and then we solder up the equivalent L-pad using say - the well known Vishay bulk foil resistors. Now, at least for this single attenuation setting, we can connect up in the same way as to the optical device without any switch in the signal path and we can compare apples with apples. Shouldn't the advantage then go to the Vishay L-pad? Further, won't channel matching be easier to nail with Vishays?
3) Further, there are some incredibly high-spec hermetically-sealed gas filled military grade switches out their if one wants to spend the bucks. Surely there are some which make good contact...no? And further, given we'd then have the opportunity to win back whatever minor sonic ground is lost in the switch using L-pad Vishay arrangements and superb channel matching, and we'd not require any support electronics or DC powered control circuitry, aren't we better off?
All I am saying is, when one thinks it through considering all of the above, it seems like a lot of trouble to build an optical device - particularly with all of the fine-tuning and matching work that goes into it, when the same care and attention to detail thrown at the conventional approach could be very good indeed.
I'm not for a moment suggesting the final results of the optical approach are not good, I'm simply saying that with the use of the best military grade hermetically-sealed switches, and the choice of the most transparent resistors on the planet, it seems the window of possible improvement is very small, if it is even open at all...
I've been doing a stack of reading about passive attenuators for audio applications in the last few weeks...it's amazing how much online real-estate is devoted to the topic. In "light" of this
, I am aware of how late to this thread and discussion the following thoughts are...no doubt I am treading across very trampled ground...Anyway...
My application straddles between home hi-fi listening for pleasure, and perhaps a more technically "stringent" scenario whereby I will use my 2-channel h-ifi playback chain as my monitoring chain for recording, mixing, and mastering my own original music. I'm thinking about going with a passive solution to front a solid-state power amp, and I've been looking long and hard at the Slagle/Intact auto-former solutions, and resistive solutions.
Three questions/thoughts about your optical attenuator...
1) Can the channel balance ever be as good as a carefully spec'd switched resistor network?
2) It seems the main advantage you claim for the optical device - as compared to switched stepped resistive-ladders (L-topology) attenuators - revolves primarily around the elimination of the switch. Let's just say one accepts this and puts it to one side for the moment, what I don't see mentioned is the actual sonic quality of the resistive element itself. It seems to me that although with a switched resistor network one does incur the liability of switched contacts, one also benefits from having the freedom to spec the quality of the the resistors themselves.
By way of example, lets look at the following: Lets say we attenuate to a comfortable level on your optical device, and then we make a note of the arrived at series and shunt values, and then we solder up the equivalent L-pad using say - the well known Vishay bulk foil resistors. Now, at least for this single attenuation setting, we can connect up in the same way as to the optical device without any switch in the signal path and we can compare apples with apples. Shouldn't the advantage then go to the Vishay L-pad? Further, won't channel matching be easier to nail with Vishays?
3) Further, there are some incredibly high-spec hermetically-sealed gas filled military grade switches out their if one wants to spend the bucks. Surely there are some which make good contact...no? And further, given we'd then have the opportunity to win back whatever minor sonic ground is lost in the switch using L-pad Vishay arrangements and superb channel matching, and we'd not require any support electronics or DC powered control circuitry, aren't we better off?
All I am saying is, when one thinks it through considering all of the above, it seems like a lot of trouble to build an optical device - particularly with all of the fine-tuning and matching work that goes into it, when the same care and attention to detail thrown at the conventional approach could be very good indeed.
I'm not for a moment suggesting the final results of the optical approach are not good, I'm simply saying that with the use of the best military grade hermetically-sealed switches, and the choice of the most transparent resistors on the planet, it seems the window of possible improvement is very small, if it is even open at all...
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