Fixed attenuator for balance control?

[phatfish]

I have a bit weaker hearing in my left ear and was happy to add a balance control to my crack.
https://forum.bottlehead.com/index.php?topic=15470.0

Well, I've got the upgrade bug and I'm planning on a mainline.  I'm looking for the best way to attenuate the right channel a fixed 1 - 1.5db between my EROS2 and future mainline.  I'd prefer not to add a balance pot to the mix with the assumption that'll defeat the benefits of the stepped attenuators.  My thought was that I could add a bit of fixed attenuation via an RCA adaptor.  Something like this:
https://www.parts-express.com/RCA-Line-Level-Attenuator-1-dB-266-230?quantity=1

I haven't been able to find something like this in stock anywhere (only much larger values).  I assume it's just a resistor in there and is something I could create myself, but I have no idea what value I would need.  Any advice on the best way to accomplish this?  I'm also curious the ideal place in the audio stream for something like this: Turntable > Phono Preamp > Amp > Headphones?

Thanks for reading.

[hmbscott]

It contains a very simple circuit called an LPad, that consists of two resistors. One connects signal to ground (R2) and the other connects inline in the signal path (R1).

The trick is to figure out what two resistor values to use, which is complicated by the fact that the LPad R values depend to a degree on the impedances of both the source and driven components (driven impedance typically is the most important).

It's possible to buy the RCA shell and add your own R1 & R2 resistors wired as described to make your own LPad attenuator with the attenuation you want.

Assuming the impedance your driving is 50kOhm. A pair of resistors that will preserve that 50KOhm impedance while introducing approximately 1.5dB of attenuation is R1 = 23.2kOhm and R2 = 124kOhm. I believe both values should be available as 1% tolerance resistors. If anyone would care to double check my numbers, I'd appreciate it. However, I think if you build one using close to those values, it should be about the right attenuation.

[Paul Joppa]

The problem with that kind of attenuator is that the impedances are important but never provided by the maker. (I think that's because the explanation it thought to be too complicated for the average customer.)

I have some 12dB Harrison Labs units with 10K input impedance, which is pretty low for Eros. One person, somewhere on the Web, has measured a Rothwell - I think it was a 10dB unit - at 100K which is good for Eros, but it's output impedance would be around 30K, which means it would likely change the attenuation of the switched controls.

Technically, you are better off rolling your own.

[phatfish]

I'm good with rolling my own.  It sounds like an LPad would be more appropriate than a single resistor?

I did find a calculator, but it seems geared towards speakers:
https://sengpielaudio.com/calculator-Lpad.htm

Using 50,000 Ohm and 1.5 db came up with pretty different numbers than hmbscott.
R1 = 7930.24
R2 = 265248.86

How would I go about calculating this for the EROS2 > Mainline?  Sounds like the mainline impedance is variable due to the attenuators I assume "25Kohms minimum" from the product page.  Is 50K more typical or was that just an example?

[2wo]

How about adding a pot in place of L-pad to the desired channel and dial it in.