Volume pot resistors - suggestions

Ty89m · 408

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Offline Ty89m

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on: November 12, 2019, 02:25:22 PM
Hey all!

Finally finished my first Bottlehead kit over the weekend - Loving the Crack thus far, might wait a bit before I install my Speedball kit - as I'm worried I'll mess up a perfectly functioning amp ha! 

Side note, kit was smooth sailing, instructions were GREAT.  Fortunately I have a fair bit of experience with a soldering iron at this point, so found it fairly relaxing.  Few melted ends of insulation trying to maneuver the iron into tight places, but nothing to concern myself with.  Did get a bit trigger happy soldering the diodes before instructed - managed to get them unsoldered without roasting them ha!

Anyway, I digress..

Like several others, I'm finding my HD650's getting very loud at about 7:30-8:00 on dial (I have my knob set so volume off is directly at 6:00) and noticed the FAQ mentions soldering some resistors on RCA lines/pot. 

I was on mouser looking at different parts, and I see there's more options than just wattage and ohm rating.. I'm a complete noob when it comes to this, so hoping some of you who've done this mod could recommend some options? 

Those who've added the resistors, how much volume is required after install to get to your baseline listening level?  Half way on pot? 

Anyway, great kit, looking forward to the Speedball (probably next weekend if I find the time/courage)!

Any input greatly appreciated!



Ty Peres


Offline Paul Birkeland

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Reply #1 on: November 12, 2019, 03:03:50 PM
You'll probably be happiest just going with the RN55D resistors at Mouser.  The values of 33K and 75K are not set in stone.  If there's an RN55K that is within 10% of each of those values, that's certainly close enough.

The listening level required depends a whole lot on the source voltage that you have available.  If you have a DAC with a 2V output and someone else is using the headphone jack of their cellphone, there will be almost a 16dB of difference just coming from the source. 


Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Ty89m

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Reply #2 on: November 12, 2019, 04:06:55 PM
Thanks Paul,

My sources all sit at 2.0v and up, Airist R2R is a bit hotter I believe.

So these part numbers would suffice per your suggestion?

RN55D7502FRE6 for the 75k

RN55D3302FRE6 for the 33k

Thanks again for the quick response!

Ty Peres


Offline Paul Birkeland

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Reply #3 on: November 12, 2019, 05:20:09 PM
Yes, those will work nicely.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man