Since the lightspeed was introduced, a few new versions have been made, specifically with a buffered output, typically based on the B1 buffer of Nelson Pass.
Has anyone compared the unbuffered vs the buffered LDR preamps. I have a Krell KSA80 B which has about 47k input impedance
Has anyone compared the unbuffered vs the buffered LDR preamps. I have a Krell KSA80 B which has about 47k input impedance
I built both George's original Lightspeed and Nelson's buffered versions. On the buffered version I put the buffer at the input to help match my source. They both were a great improvement in my system. I did not hear any obvious drawbacks to the buffered version so that's what I use.
Rick
Rick
Rick,
1) What source is that that you need a buffer for? What output impedance?
2) What happened if you used just George's version, with no buffer?
Carlos
1) What source is that that you need a buffer for? What output impedance?
2) What happened if you used just George's version, with no buffer?
Carlos
Calmart,
My CD player has a Zout of about 150 Ohm and my Pearl phono stage is quite a bit higher if I'm not mistaken. George was recommending 50 Ohm input to the Lightspeed so I put the buffer in front. The frequency range seems more extended with the buffer. No testing other than my ears.
Rick
My CD player has a Zout of about 150 Ohm and my Pearl phono stage is quite a bit higher if I'm not mistaken. George was recommending 50 Ohm input to the Lightspeed so I put the buffer in front. The frequency range seems more extended with the buffer. No testing other than my ears.
Rick
Hi Uriah,
I did try that. I also had both input and output buffers but ended up with too much dc and didn't want coupling caps so the input buffer won out in my system. It is definitely worth exploring all options, though.
Rick
I did try that. I also had both input and output buffers but ended up with too much dc and didn't want coupling caps so the input buffer won out in my system. It is definitely worth exploring all options, though.
Rick
I think ill try it. I have a ifi itube with buffer or pre amp mode.
ill eventually get a lightspeed attenuator and compare with and without buffer at the output.
ill eventually get a lightspeed attenuator and compare with and without buffer at the output.
Zum is being told he has his Buffer in the wrong place.
Don't make the same mistake.
A Buffer is required where a Source is not capable of driving the cable and load properly.
Don't make the same mistake.
A Buffer is required where a Source is not capable of driving the cable and load properly.
Huh? There is no mistake.
I need the buffer at the input and that's where it has happily been for 5 years. As I said I tried the buffer at the front and back ends. For me it worked best a the front. youknowyou can try both as I did and whatever he finds works the best he can use, without making a mistake.
I need the buffer at the input and that's where it has happily been for 5 years. As I said I tried the buffer at the front and back ends. For me it worked best a the front. youknowyou can try both as I did and whatever he finds works the best he can use, without making a mistake.
For good impedance drive so long as the output impedance and input are at least 1-10 ratio all will be matched with or without buffers.
As far as the driving interconnect cable hysteria goes, most good quality cables these days are <100pf per foot and even lower, bad interconnects can be higher.
If your output impedance of your source or preamp (passive or active) is very high eg ( 3kohm) with a cable capacitance of 100pf per foot and you have 1mt this is around 328pf, with the unusually high output impedance 3kohm this equates to a -3db roll off at 162khz!!!! and 2mts is still -3db at 80khz
As you can see driving cable capacitance is a furphy, started by active preamp manufacturers so they can sell their products. And cable resistance doesn't even come into it, it's that low.
Cheers George
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Georgehifi, your logic has completely missed "a Source is not capable of driving the cable and load properly."
The output current capability of the Source must be able to charge and discharge the capacitances one attaches to the source.
This is not solely about frequency response, it is about current.
The output current capability of the Source must be able to charge and discharge the capacitances one attaches to the source.
This is not solely about frequency response, it is about current.
Well then eg: with a typical output impedance of most (non tube) below 50ohms and more like 10ohms and able to give around 80mA current, at what pF figure of capacitance would that output not be able to cope and how is it disadvantaged???
Cheers George
Cheers George
Apply your question to your LED/LDR volume control and show your readers where it can source "80mA current" (peak, or average, or transient?) and how your volume control has achieved more like "10ohms" output impedance.
OK Andrew, here is an average typical Lightspeed, scenario. (I've added the worst 2.7kohm possible output position on the Lightspeed)
10-50ohm>>>200pf >>>10kin/2.7kout>>>200pf>>>50k-100kohm/in
Source >>>>>Cable>>>>>Lightspeed >>>>Cable>>>> amp
Cheers George
10-50ohm>>>200pf >>>10kin/2.7kout>>>200pf>>>50k-100kohm/in
Source >>>>>Cable>>>>>Lightspeed >>>>Cable>>>> amp
Cheers George
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Your the one who bought my Lightspeed into it not me.
How about you giving the detriment to the typical above scenario it's used in with an 80mA source current, in post 16
Cheers George
How about you giving the detriment to the typical above scenario it's used in with an 80mA source current, in post 16
Cheers George
I never mentioned your "Lightspeed"
I said a "Source" without specifying what type it is, or needed to be.
You came up with a scenario and I asked you to apply it to your attenuator.
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Is there my ex wife in you, maybe your are her under an alias.
As I said because your the aggressor here, you prove it, in the typical LDR scenario I posted.
Cheers George
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