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September 27, 2021, 07:23:19 AM

Author Topic: Measuring voltages while playing a 60 Hz sine wave. [resolved]  (Read 1082 times)

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Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #15 on: July 23, 2021, 04:14:27 PM »
Thanks! This is with the 60 Hz wave playing.

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

Offline Paul Birkeland

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #16 on: July 23, 2021, 04:20:11 PM »
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?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #17 on: July 23, 2021, 04:34:36 PM »
RCA left = 99.3 k ohms
RCA right = 99.4 k ohms

Nothing was plugged in.
Ross

Offline Paul Birkeland

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #18 on: July 24, 2021, 05:23:50 AM »
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.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #19 on: July 24, 2021, 06:29:45 AM »
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.
Ross

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #20 on: July 24, 2021, 09:12:24 AM »
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
Ross

Offline Paul Birkeland

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #21 on: July 24, 2021, 10:04:27 AM »
Time to junk that old cable.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #22 on: July 24, 2021, 11:17:41 AM »
Definitely haha. I'll listen for the rest of the day with the new cable, and I'll see if anything sounds off.
Ross

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave.
« Reply #23 on: July 26, 2021, 02:34:51 PM »
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!
Ross

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave. [resolved]
« Reply #24 on: August 04, 2021, 06:43:23 AM »
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
Ross

Offline Paul Birkeland

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Re: Measuring voltages while playing a 60 Hz sine wave. [resolved]
« Reply #25 on: August 04, 2021, 06:53:40 AM »
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.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave. [resolved]
« Reply #26 on: August 04, 2021, 06:58:25 AM »
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.
Ross

Offline Paul Birkeland

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Re: Measuring voltages while playing a 60 Hz sine wave. [resolved]
« Reply #27 on: August 04, 2021, 07:00:07 AM »
DC resistance.  You can use your meter to measure the resistance of each driver, though at 60Hz that measurement may not be so useful.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Colonl_Charisma

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Re: Measuring voltages while playing a 60 Hz sine wave. [resolved]
« Reply #28 on: August 04, 2021, 07:02:47 AM »
I can take the measurement now. Do I need to disassemble my HD600 to get to the driver?
Ross

Offline Paul Birkeland

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Re: Measuring voltages while playing a 60 Hz sine wave. [resolved]
« Reply #29 on: August 04, 2021, 07:05:04 AM »
No, you can measure across the headphone plug.  The tip is L+, the ring is R+, and the sleeve is common.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man