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

Colonl_Charisma · 3211

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Offline Colonl_Charisma

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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?

Ross


Offline Paul Birkeland

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

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Colonl_Charisma

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My bad haha. Got those measurements for you!

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

Ross


Offline Paul Birkeland

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

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Colonl_Charisma

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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.

Ross


Offline Doc B.

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Quote
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.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Paul Birkeland

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

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Colonl_Charisma

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

Ross


Offline Colonl_Charisma

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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.

Ross


Offline Paul Birkeland

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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.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Colonl_Charisma

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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.

Ross


Offline Paul Birkeland

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

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Colonl_Charisma

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

Ross


Offline Colonl_Charisma

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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?

Ross


Offline Paul Birkeland

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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.
« Last Edit: August 18, 2021, 09:22:38 AM by Paul Birkeland »

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man