Fixed attenuator for balance control?

[Paul Birkeland]

The maximum input impedance of the Mainline is 39.6K and the minimum input impedance is 20K. 

[phatfish]

Is it as simple as calcing for 30k then between the two?

[Paul Birkeland]

PJ tends to be able to simplify situations like these with a minimal amount of head scratching.  It is worth considering that if you leave the fine control up all the way, then you have a constant input impedance of 39.6K, which might be an acceptable compromise.  I'd have to mull over whether it might be better to adjust one resistor value in the attenuator setup itself to achieve what you're looking for. 

[phatfish]

Well, I've officially purchased a mainline today.  

Any more thoughts on a good solution for the fixed balance adjustment?  Are there better options within the Eros2 or between the turntable and Eros2? 

I definitely wouldn't want to leave the fine control in one position...  Assuming it wouldn't be totally dumb or not work, I'm inclined to put a balance pot in front of the attenuators in the mainline (perhaps just for one of the selectable inputs) similar to what I did in the crack (over getting a preamp just for balance). 

But I'd love to build a simple rca adaptor that I can easily remove or change if that's possible...  Is the issue that the amount of attenuation would change significantly between 20k and 39.6k?

[hmbscott]

Congrats on the Mainline. Hopefully you will find this helpful.

Shooting for a 1.50dB Lpad a 29.8K midpoint impedance for the Mainline, using the Speaker Lpad calculator, the R1 & R2 resistor pair it calculates (selecting the closest .01% resistor values available) are 4.75K and 158K. They yield 1.51 dB attenuation at that 29.8K impedance point.

At the impedance extremes for the Mainline, that same resistor pair produces 1.21dB attenuation at 39.6K impedance and 2.06dB attenuation at 20K impedance. That's essentially 1.5dB +/- 0.5 dB, which isn't too bad. Half a dB change in volume is very hard to hear. I don't think I can actually.

[phatfish]

Thank you hmbscott and PB!  That is a reasonable range and well worth trying.  I see how you're getting the numbers and I might play around with the values to hover a bit lower in attenuation.

Anyone know a good male to female rca coupler offhand to use for this?