Measuring voltages while playing a 60 Hz sine wave. [resolved]

[Colonl_Charisma]

Thanks for your help, PB! I am unable to post pictures (site not allowing it). Do I measure across the plugs that connect to the left and right sides of the HD600 while the headphone is plugged into the Crack with the 60hz sine wave playing?

[Paul Birkeland]

No, you unplug the headphones from the Crack and measure across the plug on the headphones.

[Colonl_Charisma]

My bad haha. Got those measurements for you!

L headphone DCR = 0.303 K ohms
R headphone DCR= 0.302 K ohms

[Paul Birkeland]

Yeah, I think you could try some different tube combinations to tighten up the channel balance.

[Colonl_Charisma]

Thanks, will do! The channel imbalance does seem less noticeable when using a 12AU7 tube compared to a 6SN7. I have a new problem now though haha. I opened up a new thread.

[Doc B.]

That's half a dB, which is audible but not horrible

It's audible by a few with a lot of ear training, but not many.

[Paul Birkeland]

Doc brings up a good point, I'm not sure I would readily pick up on half a dB myself!

[Colonl_Charisma]

Right on! Doc B and Paul, it could easily be my mind playing tricks on me haha.

[Colonl_Charisma]

That's half a dB, which is audible but not horrible.  What is the DCR of each headphone driver? 

You may find that tube rolling could yield more equal balance, or you could fit a balance control if you prefer.

PB, you mentioned that I could try fitting a balance control. I am all about modding my Crack. How much space would be required to add one? I believe space to be my limiting factor.

[Paul Birkeland]

You'd need to fit the 100K linear version of the volume pot we supply, and you'd want it close to the volume pot itself.

[Colonl_Charisma]

Cool! Do you have the dimensions by any chance? I can take a look at my amp to see if it would be worth the trouble. It would be a fun addition to my build.

[Paul Birkeland]

You have the dimensions, it's exactly the same as the stock pot but just has a different part number.

[Colonl_Charisma]

Oh haha. I'll look into this on my end, and see if I can implement this into my amp.

[Colonl_Charisma]

Hi, PB! So, after looking at my amp, I think I will be able to install another potentiometer for balance control. Can I  order the pot off of DigiKey or Mouser?

[Paul Birkeland]

Mouser has it.  We provide RV24BF-10-15R1-B100K-LA as a balance pot with our kits.  You'd need a pair of 33K resistors as well.