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

[Colonl_Charisma]

Thanks! This is with the 60 Hz wave playing.

Left channel RCA plug: 1.488 V
Right channel RCA plug: 1.487 V

[Paul Birkeland]

OK, this is helpful information.  That's 0.005dB.

What DC resistance do you get from center pin to shell on each RCA jack on your Crack with nothing plugged in?

[Colonl_Charisma]

RCA left = 99.3 k ohms
RCA right = 99.4 k ohms

Nothing was plugged in.

[Paul Birkeland]

Something isn't adding up.  To get an imbalance when you plug in your RCA cables, you'd need to load down the DAC, which would show as low impedance across the RCA jacks.  Consequently I would question the measured AC voltages.

[Colonl_Charisma]

When I get home, I’ll re-measure everything. I’ll also bend the RCA cables in the angle that they are plugged in at. I have had some issue with this RCA cable in the past with the right channel.

[Colonl_Charisma]

Quick update! I picked up a new RCA cable, and I took two new readings with a 60 Hz wave playing.

Old RCA cable measurements:
RCA left center pin = 1.487 V
RCA right center pin = 1.368 V

New RCA cable measurements:
RCA left center pin = 1.489 V
RCA right center pin = 1.488 V

[Paul Birkeland]

Time to junk that old cable.

[Colonl_Charisma]

Definitely haha. I'll listen for the rest of the day with the new cable, and I'll see if anything sounds off.

[Colonl_Charisma]

Hi, PB! I think you can mark this thread as resolved. I've been listening to my Crack for awhile now since switching out RCA cables, and I do not perceive any channel imbalance. What I was experiencing was pretty distinct.

Thanks for your help!

[Colonl_Charisma]

I'm back with some new measurements. Turns out my channel imbalance seems to still be present. My headphones sound balanced when just plugging them straight into my computer, but the right channel sounds quieter than my left channel when plugged into my Crack.

I followed the measurement instructions on this thread https://forum.bottlehead.com/index.php?topic=7788.15

My RCA jack measurements, middle lugs on potentiometer, and A2 and A7 were more or less equal. However, I seem to have a discrepancy when measuring AC voltage on terminals 1 and 5.

AC voltage with amp on and volume pot turned all the way up.
Terminal 1: 6.51
Terminal 5: 6.92

[Paul Birkeland]

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.

[Colonl_Charisma]

I agree. It isn't as bad as what I was experiencing with the bad RCA cable, but I still notice it.

What does DCR mean? I am unfamiliar with the acronym haha.

[Paul Birkeland]

DC resistance.  You can use your meter to measure the resistance of each driver, though at 60Hz that measurement may not be so useful.

[Colonl_Charisma]

I can take the measurement now. Do I need to disassemble my HD600 to get to the driver?

[Paul Birkeland]

No, you can measure across the headphone plug.  The tip is L+, the ring is R+, and the sleeve is common.