Minimising the signal path
Hi George,
I am almost there but unfortunately the real world places limits on what you can leave out.
The Altmann DAC, that I am currently using, has a current to voltage converter followed by a unity gain output stage buffer. I am planning on deleting the on-board buffer and re-jigging the current to voltage conversion stage when time allows. This will simplify the path from the DAC chip current output nodes.
I feed the DAC, or my phono stage if I chose to listen to vinyl, straight into a “Lightspeed” MKII then into ONE high power, DC coupled IXYS IXTH 20N50D depletion mosfet, in the source follower configuration, operating in class A. The source follower is current source loaded, with another IXTH 20N50D, on split rail supplies to allow DC coupling to the loudspeaker load. The mosfet source follower drives my parallel-wired, open baffle line source arrays, which have an efficiency of 105 dB per watt at one metre.
Because the eight Visaton B200 line source array drivers in each array are wired in parallel, for a 0.75 ohm load, very little voltage swing is required to go very loud. I like to listen at realistic volume levels, when the mood takes me, and the arrays are basically just idling at these programme levels and their distortion contribution is very low. The IXYS depletion mosfet provides all the current required to motivate the line arrays in my listening room. This is a very transparent minimalist arrangement that complements the musical abilities of the “Lightspeed” very well, and crucially, it sounds good at all listening levels.
Regards
Paul
Hi George,
I am almost there but unfortunately the real world places limits on what you can leave out.
The Altmann DAC, that I am currently using, has a current to voltage converter followed by a unity gain output stage buffer. I am planning on deleting the on-board buffer and re-jigging the current to voltage conversion stage when time allows. This will simplify the path from the DAC chip current output nodes.
I feed the DAC, or my phono stage if I chose to listen to vinyl, straight into a “Lightspeed” MKII then into ONE high power, DC coupled IXYS IXTH 20N50D depletion mosfet, in the source follower configuration, operating in class A. The source follower is current source loaded, with another IXTH 20N50D, on split rail supplies to allow DC coupling to the loudspeaker load. The mosfet source follower drives my parallel-wired, open baffle line source arrays, which have an efficiency of 105 dB per watt at one metre.
Because the eight Visaton B200 line source array drivers in each array are wired in parallel, for a 0.75 ohm load, very little voltage swing is required to go very loud. I like to listen at realistic volume levels, when the mood takes me, and the arrays are basically just idling at these programme levels and their distortion contribution is very low. The IXYS depletion mosfet provides all the current required to motivate the line arrays in my listening room. This is a very transparent minimalist arrangement that complements the musical abilities of the “Lightspeed” very well, and crucially, it sounds good at all listening levels.
Regards
Paul
Paul,
I love the simplicity of what you are doing - it was one of the reasons I was attracted to Susan Parkers Zeus but unfortunately it requires some transformers to realise this design.
I have just searched & found your thread on Audiocircles about this circuit so rather than asking any questions here (& possibly repeating what was asked over there) I will ask my Qs there.
Thanks Paul
One other use for odd LDRs might be their use as a high quality resistor in the feedback role of GFB circuits (also allows adjusting & varying the feedback)?
I love the simplicity of what you are doing - it was one of the reasons I was attracted to Susan Parkers Zeus but unfortunately it requires some transformers to realise this design.
I have just searched & found your thread on Audiocircles about this circuit so rather than asking any questions here (& possibly repeating what was asked over there) I will ask my Qs there.
Thanks Paul
One other use for odd LDRs might be their use as a high quality resistor in the feedback role of GFB circuits (also allows adjusting & varying the feedback)?
For those who are interested in the "comparison" of different LS flavours...
First, as stated several times by GeorgeHiFi, the MKII version won all comparison with both MKI and MK1.5. Whatever the resistors used the worse are SMC.
I couldn't measure impedance values easily and the only achievable data was the resistor value for series before inserting the module in the audio system.
All the parameters are better with the MKII version, sound stage, transparency, resolution, harmonic structure of the instruments and voices, etc...
I definitely don't explain why, but in my system the MKII version was the large winner.
For the P&S LS OPC271, I asked to these guys several months ago and the answered that they used LDRs in series and shunt, then it's also a... MkII version ! After my request, they offered both single-ended and balanced versions. The price falls slowly and I hope it will be available at a decent price in a couple of months... If everybody send a mail to ask a better price, this will probably boost the fall...
First, as stated several times by GeorgeHiFi, the MKII version won all comparison with both MKI and MK1.5. Whatever the resistors used the worse are SMC.
I couldn't measure impedance values easily and the only achievable data was the resistor value for series before inserting the module in the audio system.
All the parameters are better with the MKII version, sound stage, transparency, resolution, harmonic structure of the instruments and voices, etc...
I definitely don't explain why, but in my system the MKII version was the large winner.
For the P&S LS OPC271, I asked to these guys several months ago and the answered that they used LDRs in series and shunt, then it's also a... MkII version ! After my request, they offered both single-ended and balanced versions. The price falls slowly and I hope it will be available at a decent price in a couple of months... If everybody send a mail to ask a better price, this will probably boost the fall...
Lightspeed remote control
Hi folks,
It is taking me longer to get the website revision sorted than I thought. Never enough time in the day. However I am nearly there and the Lightspeed remote control application notes will be included when I post the updated website.
I found a problem with the transmitter board when I began assembling my own unit. The PCB manufacturer cut them to the wrong width and this means a very sloppy fit in the extrusion I designed the board for. They are sending replacements, correctly cut, by the end of the week. I will be sending all the boards out as soon as the replacements arrive so you should get them around the time the application notes are on line. I will be starting the module build and getting these out as well.
Regards
Paul
Hi folks,
It is taking me longer to get the website revision sorted than I thought. Never enough time in the day. However I am nearly there and the Lightspeed remote control application notes will be included when I post the updated website.
I found a problem with the transmitter board when I began assembling my own unit. The PCB manufacturer cut them to the wrong width and this means a very sloppy fit in the extrusion I designed the board for. They are sending replacements, correctly cut, by the end of the week. I will be sending all the boards out as soon as the replacements arrive so you should get them around the time the application notes are on line. I will be starting the module build and getting these out as well.
Regards
Paul
Texas Instruments resistors, specially made for audio, very expensive, apparently makes Vishays look like Rat Shack carbons.
http://www.texascomponents.com/pdf/tx2352.pdf
http://www.texascomponents.com/pdf/tx2575.pdf
Cheers George
http://www.texascomponents.com/pdf/tx2352.pdf
http://www.texascomponents.com/pdf/tx2575.pdf
Cheers George
Yep, Mikelm,
This would be good news all round if the LDR resistors sound better than the bulk foils - good for the pocket & good for sonics.
Only way to find out is do the corollary of the above experiment - replace a bulk foil R with a LDR set to give the same R & listen.
Who's volunteering? Mikelm, I think you have some of these bulk foils in specific places in a SKA amp, no? Do you have any spare Optivols? Would it be difficult to do this test?
This would be good news all round if the LDR resistors sound better than the bulk foils - good for the pocket & good for sonics.
Only way to find out is do the corollary of the above experiment - replace a bulk foil R with a LDR set to give the same R & listen.
Who's volunteering? Mikelm, I think you have some of these bulk foils in specific places in a SKA amp, no? Do you have any spare Optivols? Would it be difficult to do this test?
Hi George, agreed MkII seems to be the winner soundwise for vol control.
What I'm talking about is using an LDR in another place in a circuit where high quality resistor is a bonus, such as feedback resistor. So replacing an existing bulk foil R with a LDR in this position & reporting on sound.
The opposite of what Ondesx did!
What I'm talking about is using an LDR in another place in a circuit where high quality resistor is a bonus, such as feedback resistor. So replacing an existing bulk foil R with a LDR in this position & reporting on sound.
The opposite of what Ondesx did!