Crack Upgrade Questions

[mSummers]

I have two questions on crack upgrades:

1)  Does is make sense to upgrade the headphone jack?  I see a lot of people upgrading to the Neutrik locking jacks, but I don't see a need for a locking jack on my amp.  Is there a replacement for the stock jack that is more durable or has better materials that makes a sonic difference, or is it not worth replacing?

2)  Which resistors are good candidates for upgrades to Kiwame or KOA?  I saw a thread that mentioned the R1 Resistor in the Speedball was a good choice.  Are there any others?

Thanks!

[Doc B.]

The stock jack is good quality. The Neutrik locking jack is a two edged sword. We use it on the Mainline because customers seem to think it's hip, it goes functionally and visually with the 4pin XLR jack that is behind it,  and it seems the expectation on an amp in that price range. It's well made, but find it a bit cumbersome to plug and unplug myself.

[mSummers]

Thanks Doc!

[Paul Birkeland]

I have two questions on crack upgrades:

1)  Does is make sense to upgrade the headphone jack?  I see a lot of people upgrading to the Neutrik locking jacks, but I don't see a need for a locking jack on my amp.  Is there a replacement for the stock jack that is more durable or has better materials that makes a sonic difference, or is it not worth replacing?

2)  Which resistors are good candidates for upgrades to Kiwame or KOA?  I saw a thread that mentioned the R1 Resistor in the Speedball was a good choice.  Are there any others?

If you want a jack that is hands down better than the stock jack, get this one. 

The Kiwame resistor idea is kind of funny, R1 on the C4S board needs to dissipate very little power, and those Kiwame resistors are giant.  The PRP 240R/0.25W would probably work a little better, or simply a Dale RN55D.

As always, build everything stock first so you know it's working properly before changing out parts.

-PB

[adamct]

The stock jack is good quality. The Neutrik locking jack is a two edged sword. We use it on the Mainline because customers seem to think it's hip, it goes functionally and visually with the 4pin XLR jack that is behind it,  and it seems the expectation on an amp in that price range. It's well made, but find it a bit cumbersome to plug and unplug myself.

I couldn't agree more. I find locking jacks to be a royal pain in the ass:

(1) I've never had a plug accidentally fall out of a jack.
(2) In just about any scenario you can think of where a locking jack would make a difference, I would rather have a non-locking, rather than a locking jack. If you trip over your headphone cable, would you rather the jack gets unplugged, or would you rather pull your amp off the table/rack/whatever and have it crash onto the floor?
(3) Unplugging headphones becomes and awkward affair that generally requires two hands. I hate it!

[mSummers]

Paul, the jack you linked to is mono.  Don't I need a stereo jack?

[adamct]

Try 152B.

[Paul Birkeland]

Paul, the jack you linked to is mono.  Don't I need a stereo jack?

You can check the datasheet here.

Switchcraft lists all those jacks besides the 151 as being stereo.  If you're using these as TRS balanced jacks, then a 3-conductor jack would be considered a mono jack.

-PB

[mSummers]

Thanks Paul!  I didn't think to check the manufacturer's page.

[mSummers]

Quick follow up question.  The Switchcraft 153X-ND isn't switched, but the stock jack is.  Would I need to do anything differently to use the 153 since it isn't switched?  In case it matters, I plan to leave the headphones plugged in all the time.

[Paul Birkeland]

The switching function isn't used in the Crack circuit (though you can check the "Oops Moment" sticky for using that functionality).

Switching headphone jacks are unfortunately not all that common.

-PB

[mSummers]

Ok.  Since the switching is only used to force a ground when nothing is plugged in to the jack and I intend to keep the headphones plugged in, would it be a good idea to use a switch to force a ground at the headphone jack to prevent the headphones from seeing the startup voltage?  Maybe put a DPST after the jack and tie it to the ground?  Or am I worrying about a voltage that won't do any damage to the headphones? 

[Paul Birkeland]

The voltage is somewhat high when just the 2.49K resistors are used, hence the switching mod to bleed that off quickly if no headphones are plugged in.

With headphones plugged in, that resistance goes way, way down.  With 600 Ohm headphones, the startup spike will be a couple of volts very briefly, with lower impedance headphones this voltage drops even lower.

A great many commercial headphone amps have this startup spike.

-PB

[physicsmajor]

Hey, I just finished building my Crack from the Massdrop buy - fantastic experience, looks exactly like the photos, and sounds great!

I decided to register and stop lurking to ask a couple of questions. The first:

Earlier in this thread, both the Switchcraft 153X-ND and the 152B were recommended. These appear extremely similar in parts, metallic composition, etc. yet the 152B is only 40% of the cost of the 153. The ground pin appears a bit different, as does the plate mount (knurled vs. a big flat-head) but these are entirely cosmetic.

Am I missing something? I'd like to get the 152B and put the savings toward a stepped attenuator of some sort, but feel that kind of a differential has to be justified.

[Doc B.]

Looks like the 153 is for mounting through wood, like a guitar cab. Also Switchcraft notes that it has gold plated springs. Reads like the 152 might be a better fit for the alu panel, but I did not look at any DXFs.