Switchcraft Headphone Jack Question ? [resolved]

[Mucker]

Hi all,

I have been using my Crack with speed-ball since 2015 and can't express how happy I've been with it. Paired with Beyerdynamic DT-1990 Pro it's an absolute dream. I also use a Woo Audio WA2 (also from 2015) which is fantastic but I'll have to say, the Crack holds it own in spades and gets equal or more playtime for me. I am waiting for a sale on the Crackatwoa, money is already in the bank to buy it!

That being said, I have a question on changing the stock jack to a Switchcraft phone jack (152B).

I understand the stock jack is switching, so when the phones are unplugged, the tip, ring, and sleeve are all grounded (if the jack mod has been done on the older units like mine). When the phones are plugged in, the ring and tip grounds are lifted and just the sleeve is grounded. Please correct me if I am wrong.

If a non-switching Switchcraft jack is used, are the ground resistors not used? Do you just wire the red, white, and black in directly and then when using the phones wait to plug them in after turning the amp ON and then unplug them before turning the amp OFF? Thank you.

Greg

[Paul Birkeland]

You are correct that the stock jack grounds the tip and ring to the sleeve when nothing is plugged in.  If you do not have the switching function, then the 2.49K resistors are absolutely critical, otherwise the output side of the coupling caps will not be held to 0V potential DC and when you plug your headphones in, you'll get a huge pop and shock and probably a broken pair of headphones. 

The big problem with the 152B is that the sleeve will be forced to touch the chassis unless you install some kind of insulator to keep the jack from touching the chassis.  If you don't, then you'll allow signal current to flow through both the audio ground and the chassis ground, and this will inhibit the performance of the amplifier.  Based on these issues, I would recommend not using that jack. 

If you have to use it, you will need to get a step bit and drill out the hole in the chassis to be much larger, then mount the 152B on a piece of plastic that mounts underneath the new larger hole. 

[Mucker]

Awesome info. Thank you Paul. I think I'll pass on the change; the stock jack is working great.

I am also looking at increasing the volume range of the pot. 9 to 10 is very loud. I have the 75K and 33K resistors but they are the smaller blue film ones (1/4W). The ones you pictured are larger brown ones. Will the small ones be OK with the smaller gauge wire? Thank you.

[Paul Birkeland]

Yes, the resistor size isn't super critical there.

[Mucker]

Great. Thank ya much!

[Mucker]

I messed up an Alps pot (broken ground pin) about a week ago and just put an identical replacement in last night. This time, however, I used a circuit board and it worked beautifully. The wire runs are much cleaner, and now with the resistors installed, I have better range on the pot. Can't go past 2 o'clock or it gets very loud (perfect!)

I just got a 10 pack of these boards from Amazon for $13, Alps pot from US seller for $17, so $30 total and awesome performance!

https://www.amazon.com/gp/product/B083XX92V2/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

The boards I received are a bit different in layout (see attached photos). It looks like they separated the signal wires farther apart by placing the grounds together in the center. I bridged the grounds on both the IN and OUT of the board because apparently they are separated to reduce cross-talk as per ad description (but not applicable to Crack???). I made the diagram after figuring out how I wanted the wiring to go. All I can say is this board works excellently to cleanly pass everything.

EDIT: I should have checked the board with a meter before bridging the grounds. They do not need to be bridged. All of the grounds on the board are tied together, therefore I removed the bridges.

Edit2: I ended up taking the resistors out. The range of the pot can go up to 60% max (sometimes) and everything sounds really good, so all is well here ..... Also in the photos, I ran out of white wire so if colors look wrong, that is why.