Well, I did a little bit of research...................and the information about adjustable impedance is in documents on the Tortuga website.
This is quite a unique offering. But since all seems so well at the present, I intend to leave things be as is.
And lastly, the reason I got curious about the LDR module is that I am going to build out my volume controller to be fully balanced. This requires an additional e-Pot controller. Mort no longer offers the resistor module, so the fully balanced controller will have the LDR modules. So I wanted to know how the LDR modules sounded. Worked out quite well.
This is quite a unique offering. But since all seems so well at the present, I intend to leave things be as is.
And lastly, the reason I got curious about the LDR module is that I am going to build out my volume controller to be fully balanced. This requires an additional e-Pot controller. Mort no longer offers the resistor module, so the fully balanced controller will have the LDR modules. So I wanted to know how the LDR modules sounded. Worked out quite well.
Well, with a 100K input impedance power amp I guess you can get away with a 6K pot but that won't do with a relatively low impedance solid-state power amp.
My experience has been that with an impedance mismatch the sound seems 'compressed' or maybe 'lifeless,' the 'air' is gone. If I actually get around to refreshing my LDR controller (BTFSystems) again I'll use it with a buffer.
One last observation.....
I have noticed in these past 3-4 weeks, since I changed the modules in the e-Pot that I no longer listen to music loud, or ever feel the desire to turn the volume level up. This is in stark contrast to music with the stepped attenuator, the resistor module in the e-Pot, or the original Tortuga unit. Previous to now, I always tended to listen with as little attenuation as possible. Now I seem to be able to hear everything, even at moderate levels. It is a very noticeable difference.
This is only an observation. It could very well be just current system synergy. But the difference did occur when I changed modules in the e-Pot.
I have noticed in these past 3-4 weeks, since I changed the modules in the e-Pot that I no longer listen to music loud, or ever feel the desire to turn the volume level up. This is in stark contrast to music with the stepped attenuator, the resistor module in the e-Pot, or the original Tortuga unit. Previous to now, I always tended to listen with as little attenuation as possible. Now I seem to be able to hear everything, even at moderate levels. It is a very noticeable difference.
This is only an observation. It could very well be just current system synergy. But the difference did occur when I changed modules in the e-Pot.
This post has done two very important things for me. The first was that I learned about the adjustable impedance feature that I was previously unaware of. The second was that I recently did much as Bilbo did in changing from a 20k impedance to 10k. This was a monstrous change in all aspects. I had always thought 20k to be the minimum level for impedance, so never considered going lower. Now that 10k has magic, I may try to tweak it a little bit.
When I designed the BTFSystems LDR volume control I had to choose an impedance to use. Since I'm (mostly) a solid-state guy with lower power amp input impedances I elected to go with 10k ohms. I could have gotten a bigger attenuation range with 20k but I felt that made the system sound somehow 'constrained.' The sound of 10k works for me, but I only got about 45dB attenuation out of the control because I chose 40R as the lowest resistance. If I were to do it now, I'd do a little more software magic and increase maximum current from the (then) 10mA to 15mA and probably get maybe 25R out of the LDRs. What is the minimum R that the Tortuga delivers?
Here is a further update.
I have some slight corrections to make about my previous posts.
While I did get a big sound improvement when I changed the attenuation module from resistors to LDR's, the reason was most likely due to the impedance change from 60k (resistor) to 20k (LDR).
I am now running a balanced controller. My 10k impedance setting, where I get the best sound, correlates to 20k impedance in single ended, due to the two controllers each at 10k.
Another issue that has recently come up is how to do an impedance recalibration. Trial and error have shown that one needs to do the recalibration twice, and then do a power cycle. This has given me perfect results.
I have some slight corrections to make about my previous posts.
While I did get a big sound improvement when I changed the attenuation module from resistors to LDR's, the reason was most likely due to the impedance change from 60k (resistor) to 20k (LDR).
I am now running a balanced controller. My 10k impedance setting, where I get the best sound, correlates to 20k impedance in single ended, due to the two controllers each at 10k.
Another issue that has recently come up is how to do an impedance recalibration. Trial and error have shown that one needs to do the recalibration twice, and then do a power cycle. This has given me perfect results.
There are 2 controller boards. The impedance is set on the primary board, which then slaves that to the secondary board.
If I have occasion to take the unit out of the system again, I will then measure as you mention.
To me the actual setting does not really matter. It is the sound quality that matters. The sound is much better at lower impedance settings than it is at higher impedance settings.
If I have occasion to take the unit out of the system again, I will then measure as you mention.
To me the actual setting does not really matter. It is the sound quality that matters. The sound is much better at lower impedance settings than it is at higher impedance settings.