Welcome to Audiocircle. Your product looks very nice, well thought out, and a good value. Congratulations.
Some questions if you don't mind...
Are those little silver dots on the front source LED indicators or source switching buttons?
Thanks Rich and Happy New Year everyone! The dots are LED indicators. There are 7 on the LDR6 of which 6 indicate which input is selected and the 7th is a status indicator. The LDR1 only has the single status indicator LED. All control actions are possible via both the rotary encoder knob and the infrared remote.
Is there a visual volume level indicator?
No. The current models do not have a visual volume indicator. The next revision of these models will likely have a graphical volume bar & dB read out along with other status information. The balanced version of the LDRx will probably be the first to have a graphical info display when it come out later in the 1st quarter.
What's the big flat black circle on the left front panel?
It's an optical grade polymer infrared filter that only lets in infrared control signals. An IR receiver sits right behind it. The IR command reception if very robust. I've even see it work at a near 90 degree angle to the remote 30+ feet away.
Is there a remote control? IR or RF? What functions?
Yes, there's an IR remote. Functions include: power on/off, raise/lower volume, mute, select/confirm, balance mode enable, balance reset, balance adjust left/right, and for the LDR6 only, individual input select buttons for each of the 6 inputs.
What is the input impedance, is it constant across all attenuation levels?
The LDRx models emulate a ~100k ohm potentiometer/attenuator (L-pad) and thus have variable impedance accordingly.
Will your buffer be discreet or IC?
Current plans call for using highly regarded audio grade op amps (ICs) with a high quality regulated linear power supply.
Will the balanced version still be LDR only signal path? So using XLR>SE adapters will not affect SQ?
As things stand now, yes.
How is variable LDR attenuation superior to Vishay S102 resistors as used in Placette Passive Preamp, or autoformer as used in Bent Audio TAP-X? Prices of these RC passive preamps are roughly comparable to yours.
We became convinced of the sonic superiority of LDRs through early prototype work comparing performance to conventional resistive devices/materials (pots & metal film resistors). I don't have an explanation for this other than to point out that LDRs utilize a light dependent cadmium based semiconductor resistive material which is very different from that used in any pot or resistor. The best way I have to describe it is LDRs get out of the way of music rather than participate in it. In one of the early tests we had a manual bypass switch that allowed bypassing the LDR preamp altogether. Using a relatively low gain amp (loud but not too at full volume) we ran the LDR at full volume and flipped the bypass switch on and off. I personally could not tell any difference in the audio quality with the LDR vs. direct path between a DAC and a solid state amp (did not try this with a tube amp but wouldn't expect different results). In my mind, this further confirmed my perception that LDRs are pure volume attenuators with remarkable clarity and lack of coloration....or if you will, superior conductors of music!
I personally have not compared our LDR pre vs. any transformer based attenuator. What I can say is one of our customers was once an owner/user of a Bent Audio Slagle auto-former pre-amp and traded that for a LDR based unit and never looked back. He later upgraded to a Tortuga Audio LDR1 because he wanted the ability to fine tune the left/right channel balance.
