[mike1127]

Has anyone here delved into the interior of a Hifiman EF5? I am planning to replace the pot and I want to know what pot value to order so I can do that ahead of shipping the EF5 to my tech guy.
 
Mike
 
EDIT: I'd like to add a question about choosing the pot, in particular a stepped attenuator versus "normal" continuous pot. I use the EF5 on its high gain setting because it sounds best, but that means I get very little useful volume range with my headphones (LCD2.2 and HD650).
 
If you divide the clock face into minutes (and the full-down position is at 45 minutes), "too quiet to be practical" is at around 49 minutes and "too loud to be safe" is at 52 minutes. My entire listening schema has to fit by sliding ever-so-gently within these three minutes. How does that affect stepped attenuators? I would guess I need to divide those three minutes into 6 levels at least, so I need one that steps in half-minutes or amost 120 steps.
 
Another option might be customizing a stepped attenuator so that I has more precision at the bottom of its range, I suppose.

 

[qusp]

Quote:

Another option might be customizing a stepped attenuator so that I has more precision at the bottom of its range, I suppose.

^^ this is the best way forward
 
without a schematic or pics its impossible for anyone but the designer or someone else who has internal knowledge of the ef5 to help you with any details. seems very strange that you have such a steep logarithmic slope

 

[mike1127]

Yes, I'm hoping for someone here who has a schematic or pics or direct experience replacing the pot.
 
I have also contacted Hifiman, but I don't know how easy it will be to get a response. I have tried to ask questions before (about substituting a tube type, which safety of depends on the heater current draw) and all I got back was "Hifiman recommends you use the tube that came with the amp and only get replacement tubes from Hifiman."
 
I'm trying to avoid opening the case myself because I am a klutz, and this EF5 is already modded and has capacitors shoehorned into the box all over the place. I hire a guy to do all the mods, I don't have the physical skill to work with small things. Kind of sad that I am missing out on learning to do it myself, but I get good results by hiring the guy.
 
Mike
 
EDIT-- I looked at the specs on the TKD pots, as given at Michael Percy's website, and they have a much higher taper at the low end. At the low end 15 degrees is about 10 dB of change, while at the high end 15 degrees is about 2 dB. I may need this amp someday for less efficient 'phones so I don't want to change too much the way the volume control works. If I can get a quality pot that doesn't have channel imbalances at the low end and functions as a good quality resistive component at the low end, then I think I will be fine with an ordinary type of taper, such as this TKD pot. I'll still have most of my usable range in a few minutes of angle, but as long as it sounds good, that's fine.