Aria Line-Stage

On the subject of stereo balance control, I too agree that the extreme "max/off" isn't for me.

However, think about it? A narrow range of adjustment can result in the control being at or near its extremes. When so many are configured so a slight offset of the control gives a noticeable shift of stereo image, there may be a natural aversion to a more range specific control?

I've done it myself. I've built balance controls with something like +/-3dB to find with some albums the control is parked near to its extreme one direction or the other. I've been a bit worried about doing that on a production product. Customers could think it a fault? "Why is your balance control so different to my XYZ Graham?"

Apart from that user worry, such a balance control is easier to implement IMO. It would be a simple gain pot with one gang wired the reverse of the other - a linear control.

However, as any potentiometer manufacturer, including Alps, will tell you, it is impossible to get both gangs of a pot to match perfectly over its entire range. Even the AC30 so loved by all and sundry (IMO hype) isn't gain matched. Therefore any preamp will be biased in level toward one channel or the other, unless on-board gain trimmers are included and channels balanced on test during production. Those tests cannot be automated because they require an amount of human reasoning because gain matching varies with a pot's position. This is just another thing you wouldn't know.

Whilst on the subject of pots, you may not know that the larger UK and European competing manufacturers dictate to the importers of a certain (hype) potentiometer on who is allowed to buy what. Do you find that shocking? Yes, I did too! The pots in question would sell to these manufacturers for around £4 each, that's motorised... take a look on Rapid, you'll find them for over £20 including VAT. Such is the hype level applied by the importers, or maybe the manufacturer itself...

These pots are carbon track at the end of the day. Conductive polymer or as it used to be called: conductive plastic, is far more superior - is still made to this day in the UK (and also the US) - and isn't made by cheap labour as is the carbon elements used by the Japanese manufacturer being talked about here.

I have stocks of motorized pots made by one of the element subcontractors, but they don't carry the "famous name". Do you think the average audiophile would accept "such rubbish" even though it's the same "rubbish" that's perfectly OK because it carries the name?

For those who are willing to accept manual adjustment I will try to use the superior British made conductive polymer pots.

Apologies to those who because of life's mishaps must have remote controlled volume. I have popped the question to the British manufacturer about adding a motor.


Edited by Graham Slee - 11 Jan 2013 at 6:19am

The next part of the Aria preamp development I'm revisiting is the remote control.

I've not been happy with the conventional remote control arrangements. The motorised volume control is the way to go. Variable gain amplifiers are not to be trusted - their characteristics change with every change in volume control setting.

The problem with motorised pots is they are not without noise, and the power has to come from somewhere. It's bad enough making sure every amp stage is happy with its power never mind the noise from a DC motor getting shunted back up it's Kelvin/Kirchhoff current return.

I want the "pure" power of a PSU1 supplying this preamp. I feel 125mA (stall current) is a waste of PSU1 quality.

So what's the answer? Rechargeable batteries!

"Build in rechargeable batteries Graham!" I said, but to comply with the EU, make them removable so they can be replaced after umpteen years so the preamp lasts "forever".

A trickle charge of the PSU1 won't muck up the supply to the audio circuits. And whilst we're at it why not have a recharging point to recharge the handset?

So that's the next stage of development being thrashed out. There are many matters to iron out before the PCB can be drafted - most of it is waiting for suppliers...

I personally don't need remote. Maybe another poll is in order? Or maybe there are already too many cooks in the kitchen.

I don't know how much room there will be inside the case,,,   but did you consider stepped attenuators for the volume control? The switching mechanism is expensive, and the labor to wire the resistors adds to the cost, but it's another way to get good matching and you can pick your flavor of resistor.

Just a thought.