Aria Line-Stage

A short history so far:

Started back in 2009, the Aria Line Stage was shelved because of the lack of facilities to properly audition it here.

Since then we had the new workshop built (2010) which has sufficient space (only just) to be able to audition using speakers. However, we didn't have the right amplification or speakers.

Since the start of 2011 the Proprius twin monoblocs have been developed (now being productionized) and we have two sets of speakers, completing a system that's mercilessly revealing.

To remote control or not?

Initially, the Aria, a "desktop" line preamp stage, one of its uses being desk top, was not going to have remote volume control.

However, "the trade" didn't like that. So over the past few weeks I've been researching remote control.

I have looked at both solid state and semi-mechanical solutions.

The solid state solutions include a number of types of transconductance "op-amps", either encapsulated "discrete" or integrated on one chip. The transconductance devices vary from lo-fi to studio console quality. All of them require a considerable amount of logic and precision integrators to function correctly.

Forget optical volume control along the lines of the "Lightspeed" or similar: RoHS (now virtually world-wide) forbids light dependent resistor usage because the substances used are classed as hazardous, and, 5 years since RoHS came in, no manufacturer has come up with a non-hazardous solution.

The semi-mechanical solution is basically a motor driven (wait for it!...) Alps RK271 dual potentiometer (hyped up as being "blue velvet" or "blue beauty"). That's the easy bit. The remote transmitter and receiver is a bit more difficult but not beyond me.

Separate power supplies?

The problem in using a motor driven pot, and the remote control circuit itself, is interference, and that's why I didn't want one in the first place!

However, needs must, so we're looking at a circuit that's going to draw near on 200 mA (0.2 Amps) average just to save us getting off the settee...

(the Alps pot uses between 100 and 150mA. The decoder and logic getting close on 100mA)

That is 200 mA of "dirty current" you don't want mixing up with the audio power supply current. I don't like having the power supply in the stage so I do external power supplies.

Due to different countries having different rules, to make it possible to sell our products world-wide, we stick to one of two approved power supplies: the PSU1 and the switchmode ("green" - now a silenced version).

The only way we can power the remote control is off a separate power supply to the audio one (either a PSU1 or "green"), so the Aria will end up having two power supplies: one for the audio and one for the remote.

At least the purist will easily be able to disable the remote control completely, simply by not using its power supply.

I trust would-be purchasers would be happy with this?

We will be including the Aria (and Proprius) in the loaner program.

tg wrote: I assume from reading this that the motorised pot would also have a knob and with its motor drive not powered on would still be usable as a manual control ?

Quite correct.

It would conceivably also be possible to completely remove the remote control board and replace the motorised pot with a non-motorised pot.

I do use an LFD MkIII amplifier > no remote > purity of design (take a look inside) .

Hi Graham (and everyone else!), I remember reading about the tone control you had developed for this and being very interested. I hadn't considered the volume control aspect but would agree with pay more for the RC if that helps.