Volume adjustment with high sensitivity headphone

[Edhead]

Hello,

I just finished my S.E.X. 3.0 kit a couple weeks ago and I am loving it.

However, when I am using it with a high sensitivity headphone (Hifiman Ananda) it gets very loud even with a very small turn in the volume knob. It's uses only about 5% of the knob's full range and it's already very loud. This makes it hard to make small adjustments.

I would like to seek some advice on how I can reduce the signal strength so I can make volume adjustments easier with my Ananda.

I noticed in the Crack's FAQ (https://forum.bottlehead.com/index.php?topic=4295.0), it has instructions and a diagram on how to do it.

1. Can I apply the same idea to the S.E.X. 3.0? For instance, instead of the red and white wires, it will become the orange/white and blue/white wires?

If this is the case, how about the resistors? The suggested ones for the Crack are 75K for the signals and 33K between the lugs.

Any rough estimation on how much of the signal in percentage will be reduced?

2. I also noticed in this thread (https://forum.bottlehead.com/index.php?topic=13451.0) it mentioned the use of an inline attenuator. Is it true that the inline attenuator method is essentially the same as adding the resistors in the circuit, but it's just using a potentiometer to reduce the signal coming into the amp? I guess the attenuator method will be more versatile since it can provide the original power for the speaker output if needed.

Thanks in advance!
Ed

[Paul Birkeland]

The inline attenuator has a much, much lower resistance than the pot modification does, so they will make the input impedance of your amp 10K instead of 100K.

The Crack mod would be what I would use, and it is a -12dB pre-attenuator. 

[Edhead]

Thanks Paul for the prompt reply!

I am not familiar with electronic components at all. For the resistors, should I get metal film or other types?

Thanks!

[Paul Joppa]

Metal film 1% is an excellent choice. Carbon films are usually pretty good sounding but rarely available in  better than 5% precision. The precision helps keep the channel balance.

We usually us Dale RN series; 1/4 watt , 1/2 watt, or 1 watt - it really doesn't matter, this is a very low power application.

[Edhead]

Awesome, thanks again!