socks on, try it yourself. easy to see it has good merit for audio circuits being transistors, emulating semiconductor diodes.I recall receiving much praise for the improvement they provided.
The idea saw surface mount transistors mounted on Brown Dog adapters, with usually AD825 op amps AD825 Datasheet and Product Info | Analog Devices
I recall making some for you what was it 11 years ago - how did they go ?
The idea saw surface mount transistors mounted on Brown Dog adapters, with usually AD825 op amps AD825 Datasheet and Product Info | Analog Devices
I recall making some for you what was it 11 years ago - how did they go ?
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You obviously enjoyed them immensely , but are IMO Kafkaesque in your comments.
I agree he was a great writer , but no need to see every moment, as he also saw things.
Franz Kafka: Chronicler of Darkness - YouTube
I agree he was a great writer , but no need to see every moment, as he also saw things.
Franz Kafka: Chronicler of Darkness - YouTube
Being the OP, I ask the Mods to leave it where it is thanks, and just remove the last 16 posts, as he always does someone has polluted a thread with his own BS.
Thanks George
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The LDR datasheets and app notes are there for anyone to read and make up their own minds where the BS is. LDR's are optically isolated devices it it safe to say there is zero reciprocity between the resistive elements and the LED's.
Until you try.... Noting the cathode is in poor designs at exactly the same potential as signal ground.
Whilst there is little if any, reverse bias leakage current in a DC sense, the same may not be said for signal AC.
However when the cathode is not directly grounded, the better possibility arises of using the cathode current effectively, akin to current drive.
The attribute of having both anode, and cathode current available presents many new opportunities, which relates to the semiconductor devices used to sense both.
Whilst there is little if any, reverse bias leakage current in a DC sense, the same may not be said for signal AC.
However when the cathode is not directly grounded, the better possibility arises of using the cathode current effectively, akin to current drive.
The attribute of having both anode, and cathode current available presents many new opportunities, which relates to the semiconductor devices used to sense both.
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Sorry Steve I thought it was the Lightspeed DiY thread. But glad you think the same.
Cheers George
I have some new things to post in this long dormant thread that I started back in December 2015.
From the initial postings and discussions, I learned quite a lot. I learned that LDR’s are terrible abominations and totally unfit for most anything, let alone audio volume controlling. And I learned that while some of the defects of LDR’s could be corrected, they added a harmonic distortion component to the sound of the audio system. Yet I persisted in the use of my LDR volume controller.
In 2021 I got curious about what I might really be missing by not using my stepped attenuator and the no harmonic distortion sound. So. I installed the stepped attenuator back in the system to give it a go once again. And I really liked it. I could tell the difference it made in the sound. I could hear the lack of harmonic distortion-lack of any rich and warmth component.
However, the actual controlling of the volume with the attenuator was not so good. The steps were large, as in 2 decibels. And the very first step down was a full 5 decibels. And it just so happened that so much of my music really wanted to be listened to in that first 0-5 decibel step. I had no choice but to get used to having the music play a little less optimally in volume. The LDR unit had 0.5 decibel steps for every single step. There were never any issues with finding the optimal volume level.
So, I looked at my choices. One was to design a new attenuator with more usable steps in the most used regions of the switch. For my needs, that pretty much meant a 47-step switch rather than the more common and affordable 23-step switch. And the cost of a 47-step attenuator is not cheap.
So, then my attention turned to the new unit from Tortuga that offered a module with discrete smd resistors for controlling the volume. This was like a dream come true. It had lots of control and no harmonic distortion. It was also cheaper than any of the 47-step attenuator options.
So that is what I did. I retired the stepped attenuator and swapped control units in the volume control box and went with the new Tortuga controller and resistor module. It was so good that I thought about posting about it here in this thread. But it wasn’t an LDR volume controller anymore, so I did not post.
And then 2 years went by listening to music with my wonderful no harmonic distortion volume controller. In the meantime, I changed amplifiers from a Class AB to a very low distortion Class D GanFet amplifier from Orchard Audio. I had virtually no harmonic distortion in the audio system, or something like that.
And then recently I got curious about LDR’s again. I also had the LDR module for the controller, but I had not used it at all other than for a brief test listening to make sure it worked. I just wondered about it. So, I swapped out the modules and gave the LDR module a go.
I was stunned by what I heard. I could barely believe what I heard. I listen to music on my audio system for 4-5 hours most every day. This is so called “serious listening” as I just listen to the music. The music is mostly classical and jazz.
It is easy to hear a difference when something changes in the system. Often there is no difference. That is also easy to hear. The music now seemed to flow with virtually no signal voltage attenuation, as happened with the resistor module and the stepped attenuator. Yet I had full loudness control. And I did not notice any harmonic distortion component in the sound, no added little bit of rich and warmth. I expected to hear some rich and warmth in the sound especially as I now have the Class D amplifier. But no, I did not hear it. I only heard wonderful music constantly flowing out of the speakers and into the room.
Sorry for the flowery language above. But I could not help it. And I well know that this is all one off anecdotal whatever. I tend to think it is also in large part system synergy at work. Nonetheless, the music listening is nice.
From the initial postings and discussions, I learned quite a lot. I learned that LDR’s are terrible abominations and totally unfit for most anything, let alone audio volume controlling. And I learned that while some of the defects of LDR’s could be corrected, they added a harmonic distortion component to the sound of the audio system. Yet I persisted in the use of my LDR volume controller.
In 2021 I got curious about what I might really be missing by not using my stepped attenuator and the no harmonic distortion sound. So. I installed the stepped attenuator back in the system to give it a go once again. And I really liked it. I could tell the difference it made in the sound. I could hear the lack of harmonic distortion-lack of any rich and warmth component.
However, the actual controlling of the volume with the attenuator was not so good. The steps were large, as in 2 decibels. And the very first step down was a full 5 decibels. And it just so happened that so much of my music really wanted to be listened to in that first 0-5 decibel step. I had no choice but to get used to having the music play a little less optimally in volume. The LDR unit had 0.5 decibel steps for every single step. There were never any issues with finding the optimal volume level.
So, I looked at my choices. One was to design a new attenuator with more usable steps in the most used regions of the switch. For my needs, that pretty much meant a 47-step switch rather than the more common and affordable 23-step switch. And the cost of a 47-step attenuator is not cheap.
So, then my attention turned to the new unit from Tortuga that offered a module with discrete smd resistors for controlling the volume. This was like a dream come true. It had lots of control and no harmonic distortion. It was also cheaper than any of the 47-step attenuator options.
So that is what I did. I retired the stepped attenuator and swapped control units in the volume control box and went with the new Tortuga controller and resistor module. It was so good that I thought about posting about it here in this thread. But it wasn’t an LDR volume controller anymore, so I did not post.
And then 2 years went by listening to music with my wonderful no harmonic distortion volume controller. In the meantime, I changed amplifiers from a Class AB to a very low distortion Class D GanFet amplifier from Orchard Audio. I had virtually no harmonic distortion in the audio system, or something like that.
And then recently I got curious about LDR’s again. I also had the LDR module for the controller, but I had not used it at all other than for a brief test listening to make sure it worked. I just wondered about it. So, I swapped out the modules and gave the LDR module a go.
I was stunned by what I heard. I could barely believe what I heard. I listen to music on my audio system for 4-5 hours most every day. This is so called “serious listening” as I just listen to the music. The music is mostly classical and jazz.
It is easy to hear a difference when something changes in the system. Often there is no difference. That is also easy to hear. The music now seemed to flow with virtually no signal voltage attenuation, as happened with the resistor module and the stepped attenuator. Yet I had full loudness control. And I did not notice any harmonic distortion component in the sound, no added little bit of rich and warmth. I expected to hear some rich and warmth in the sound especially as I now have the Class D amplifier. But no, I did not hear it. I only heard wonderful music constantly flowing out of the speakers and into the room.
Sorry for the flowery language above. But I could not help it. And I well know that this is all one off anecdotal whatever. I tend to think it is also in large part system synergy at work. Nonetheless, the music listening is nice.
I am wondering whether the benefits you note with the return to the Tortuga following a change of power amp is due to a better impedance match between the two units. When you had the previous power amp did you play around with the impedance settings on the Tortuga? I have found these settings to be quite critical to getting the best sound from my amps.
Yup, I remember when I first listened to my LDR volume control, it was quite a stunning revelation.
Originally, I made mine a 10K pot driving the power amp directly and limited the current to a maximum of 10mA so the result was a 45dB control, not quite enough. I haven't used it in years but I'm thinking about rewriting the code to make it a 20K pot and instead of fixing the lower resistance at 40 ohms per the original, actually measuring the minimum resistance of each shunt LDR at 15mA during calibration and setting the lower resistance for both channels at whichever resistance is the higher. The lower resistance should then vary between about 28 ohms and 38 ohms and with a greater range between upper and lower resistance I'll have a much wider attenuation range.
A question -- do you use your LDR control with an output buffer/preamp or do you drive your power amp directly? And if the latter, what's the input impedance of your power amp?
Originally, I made mine a 10K pot driving the power amp directly and limited the current to a maximum of 10mA so the result was a 45dB control, not quite enough. I haven't used it in years but I'm thinking about rewriting the code to make it a 20K pot and instead of fixing the lower resistance at 40 ohms per the original, actually measuring the minimum resistance of each shunt LDR at 15mA during calibration and setting the lower resistance for both channels at whichever resistance is the higher. The lower resistance should then vary between about 28 ohms and 38 ohms and with a greater range between upper and lower resistance I'll have a much wider attenuation range.
A question -- do you use your LDR control with an output buffer/preamp or do you drive your power amp directly? And if the latter, what's the input impedance of your power amp?
If following the Lightspeed diy circuit, you can easily come down to 33kohm for the input impedance of your amp/s. Your source should be 1kohm output impedance or lower.
https://www.diyaudio.com/community/threads/lightspeed-attenuator-a-new-passive-preamp.80194/
Cheers George
I drive the amp directly from the volume control. There is an RCA to XLR converter directly after the amp and then balanced cables to the amp. The specified input impedance of the Starkrimson Ultra balanced input is 44k Ohms.
In my long and winding post................................
Let me clarify.
I have always used a Tortuga volume controller since October 2015, other than the 2 months in 2021 when I was using the shunt type stepped attenuator.
October 2015 to May 2021 - I used 3 different Class AB amplifiers, all of my own construction and by the same designer, with the Tortuga LDR volume controller.
May 2021 to August 2021 - same Class AB amp as last one above with 20k stepped attenuator. Volume here was at the same level as with the LDR controller.
August 2021 to November 2021 same Class AB amp but now with 60k resistor module in new e-Pot Tortuga controller. Volume level the same as before.
During this time I used the 20k LDR module for one day in a trial. I noted that it played louder at same controller setting. Did not any real other difference.
November 2021 - changed amps to Orchard Audio Starkrimson Ultra.
November 2021 to June 2023 - Starkrimson and 60k resistor module in e-Pot. Volume level same as before.
June 2023 - changed to 20k LDR module in e-Pot. Noted volume level much louder at same setting as previously noted. However, also noted sound differences as noted in my post.
So, in answer to your question, I didn't really play around with impedance settings on the Tortuga other than noted. And I don't think Mort offers different impedance modules now. But if you can follow my above timeline - 20k stepped attenuator and 60K resistor module were same volume level and were same as original Tortuga controller. The difference is with the e-Pot and the 20k LDR module.
I'm a bit confused but as I understand it the ePot.V3 has configurable output impedance via the ARM microcontroller just like the V2.5 module I use. I found the default 20K setting not very good and use mine with a 6K setting. If I change to 5K or 7K I can clearly hear a difference and 6K is the sweet spot. My power amp (Sanders Magtech) has an input impedance of 100K.
HI Bilbo,
Interesting.............. I don't know about any configurable impedance. That would be beyond me.
We all have our sweet spots, and I now have mine.
After thinking about this some.....................
Your comments are most interesting.
As I mentioned in my new post earlier, perhaps it is all system synergy.
What I have now is easy effortless like music, as if I had high efficiency speakers and some low power amp.
It is just that I have the exact opposite.
Interesting.............. I don't know about any configurable impedance. That would be beyond me.
We all have our sweet spots, and I now have mine.
After thinking about this some.....................
Your comments are most interesting.
As I mentioned in my new post earlier, perhaps it is all system synergy.
What I have now is easy effortless like music, as if I had high efficiency speakers and some low power amp.
It is just that I have the exact opposite.
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