Impedence switch boards

[Paul Joppa]

The jack that switched the speakers off in the SEX amp was only in production kits for a short while. We can't get a suitable jack at this time. The current jack still cuts the speakers, but no longer has the 120 ohm resistance to equalize the level across different impedance headphones.

The impedance switch board has three outputs - Pos, Neg, and Ground. The tip-ring-shield jack goes to Pos and Ground, the balanced outs get their signal from Pos and Neg.

Yes it took me some time to figure all that out!

 

[jrebman]

Ok sorry, I'm confused here -- do the currently shipping headphone jacks on the 2.1 cut the speakers when the phones are plugged in?  It appears this is what Josh is saying, but it appears that PJ is saying the opposite.

A clarification would be great, and then perhaps an update to the product page?

-- Jim

 

[fullheadofnothing]

I hate to disagree with you Paul, but the current jack (marked "new" in the pic) does cut the signal to the speakers when a TRS is plugged in. I'm actually listening to my cans right now though such a jack and the speakers aren't making a peep.

My understanding of the choice for the "old" jack was to utilize the 120Ω resistors and still have the shorting feature. Since those resistors ended up being eliminated, the new jack could be used for the S.E.X. 2.1.

Todd, how many outputs are you planning on having? As far as I know, these boards have only been used as the TRS/XLR in Smack and TRS/Speaker-binding-posts in the S.E.X. TRS/XLR hasn't been attempted in a S.E.X. (but I don't see why it wouldn't work) but TRS/XLR/Speaker-binding-posts might be more complicated than I can wrap my feeble mind around. I think wiring as Paul suggests will make the BAL/UNBAL switch a selector between your TRS and XLR and my guess is you may have to choose which configuration you want your speakers in when you wire the binding posts (if you are indeed wiring the binding posts).

Please take my wiring comments with the very large grain of salt that I don't necessarily know everything that's going on here and my electrical knowledge falls pretty squarely in the average (or a bit below) of most Bottleheads.

 

[Paul Joppa]

Josh, you're right, and I have edited my post. I remember the disappearance of the good switching jack, but mis-remembered the choice that was made of what to do about it.

 

[Todd R]

Todd, how many outputs are you planning on having? As far as I know, these boards have only been used as the TRS/XLR in Smack and TRS/Speaker-binding-posts in the S.E.X. TRS/XLR hasn't been attempted in a S.E.X. (but I don't see why it wouldn't work) but TRS/XLR/Speaker-binding-posts might be more complicated than I can wrap my feeble mind around. I think wiring as Paul suggests will make the BAL/UNBAL switch a selector between your TRS and XLR and my guess is you may have to choose which configuration you want your speakers in when you wire the binding posts (if you are indeed wiring the binding posts)

I'm not using the speaker terminals so it will just be the TRS & XLR (provided there is enough room to make a new hole)

 

[Doc B]

I'd just like to say that I really enjoy having so many smart guys working with Bottlehead now. With so many kits and projects going at any one time I just can't keep up with all of the questions anymore, and PJ, PB, Shawn and Josh have been amazing when it comes to stepping in to answer everyone's questions. Thanks guys!

 

[jrebman]

Thanks Josh and PJ for the clarification.

-- Jim

 

[Todd R]

$14.83 shipping on the impedance boards??
That can't be right.
Can you check your shopping cart settings before I order Doc?
Thanks

 

[jrebman]

Todd,

There is a note about this in the stickeys at the top of the general discussion forum.  Basically, they know this is a problem and will credit your card/paypal after the purchase.

-- Jim

 

[jrebman]

Paul, is this a good time to remind you about the wiring description for these boards?  I won't be building the smack right now but will be building a s.e.x. dedicated to headphone use and want to do the same thing with a set of 3 exposed switches on the top plate -- or maybe even just two.

Thanks,

Jim

 

[Oberst Oswald]

$14.83 shipping on the impedance boards??
That can't be right.
Can you check your shopping cart settings before I order Doc?
Thanks

I just received my credit card bill and was charged $14.95 for shipping.

 

[Todd R]

Hi everybody,
I got my kit today and am looking over the instructions.

I do not have the speaker terminals hooked up and don't intend to ever use them.

I have the newer style headphone jack.

My plot is to install a 4 pin balanced XLR (somewhere) to use with my headphones that are re-cabled in that manner as well as keep the TRS jack for the phones that are conventionally wired. 

Looking at the instructions, I'm not sure if I have my potential wiring correct in my head, but tell me if I do:

Pos & Neg will go to pos & neg terminals of the 4 pin XLR, and ground will go to the safety ground. The switch will be on BAL when using the balanced phones.
Correct so far?

Now to wire the TRS jack: I jumper from the 4 pin XLR, the pos wire for each channel, then.......I get stuck. What do I connect to the ground terminal of the TRS? Is it still the ground?

 

[jrebman]

Todd,

I'm goig to be interested what the answer to this is as well.  Hopefully it will get me one step closer to understanding the switching scheme.

-- Jim

 

[Paul Birkeland]

The POS of each switching board need to go to the appropriate terminals on the 1/4" jack (the tip and the ring).  Th e sleeve connects to the ground of the amplifier.

When the toggle switch is set to UNBAL, the negative and ground are wired together, when the toggle switch is set to BAL, this connection is lifted and replaced by a pair of resistors, one between ground and neg and the other between ground pos.

 

[Todd R]

The POS of each switching board need to go to the appropriate terminals on the 1/4" jack (the tip and the ring).  Th e sleeve connects to the ground of the amplifier.

When the toggle switch is set to UNBAL, the negative and ground are wired together, when the toggle switch is set to BAL, this connection is lifted and replaced by a pair of resistors, one between ground and neg and the other between ground pos.

Thanks Paul, that helps me understand how it works.
So (in my application) the ground wire from each board will go to the ground on the TRS, and the neg wires from each board will go to the appropriate terminal on the 4 pin XLR, correct?

 

[Paul Birkeland]

Thanks Paul, that helps me understand how it works.
So (in my application) the ground wire from each board will go to the ground on the TRS, and the neg wires from each board will go to the appropriate terminal on the 4 pin XLR, correct?

Perfect.

 

[Todd R]

Installed the boards today and all went smoothly with the exception of a couple of the transformer wires needed to be longer (sorry, I should have noted which ones).
I got real brave & drilled big holes in my top plate and was able to fit a Neutrik locking 1/4 jack and a 4 pin XLR jack in that area. (Pictures later)

Now I need that C4S upgrade!

Come on Doc, I'm ready!

 

[Oberst Oswald]

Now I need that C4S upgrade!

Come on Doc, I'm ready!

Me too

 

[Noskipallwd]

Got the boards the other day as well and got them populated, still waiting on my Amp kit. I'll worry about the C4S a little later.

Cheers,
Shawn

 

[Todd R]

Got my boards in as well and a couple of Neutrik locking jacks. See, there is room (just barely)