DP3T switch confusion

[hylaphone]

Hi folks, I am building an SVT preamp, I believe the original Ultra Low and Mid select switches are DP3T. Is it possible to connect a 4PDT On-On-On switch to do the same thing? I'm having a hard time visualizing this.Here is the schematic, thank you!

[HotBluePlates]

If you're willing to use a slide-switch rather than a rocker-switch, you could just grab this from Digikey.

Pretend the upper 4 boxes on the Bass Select switch are labeled 1 through 4; the lower 4 boxes would be 5 through 8.
   - The schematic is drawn with the switch in 1st position, with Box 1 connected to Box 2.  In a separate circuit, Box 5 is connected to Box 6.
   - In 2nd position the two contacts slide one box to the right:  Box 2 is connected to Box 3, and Box 6 is connected to Box 7.
   - In 3rd position the two contacts slide to the right again: Box 3 is connected to Box 4, and Box 7 is connected to Box 8.

The Mid Range Select switch functions exactly the same way, but is drawn vertically.

If you grab the slide switch I noted, you can wire it visually exactly as the schematic is drawn & not have to mentally re-map the switch lugs.

[hylaphone]

Thank you for the response, that's intuitive of course but I'm already committed to 1/4" panel hole, and am trying to use a miniature toggle. I couldn't find DP3T so I'm trying to get these 4PDT to do the job.

If you're willing to use a slide-switch rather than a rocker-switch, you could just grab this from Digikey.
Pretend the upper 4 boxes on the Bass Select switch are labeled 1 through 4; the lower 4 boxes would be 5 through 8.
   - The schematic is drawn with the switch in 1st position, with Box 1 connected to Box 2.  In a separate circuit, Box 5 is connected to Box 6.
   - In 2nd position the two contacts slide one box to the right:  Box 2 is connected to Box 3, and Box 6 is connected to Box 7.
   - In 3rd position the two contacts slide to the right again: Box 3 is connected to Box 4, and Box 7 is connected to Box 8.

The Mid Range Select switch functions exactly the same way, but is drawn vertically.

If you grab the slide switch I noted, you can wire it visually exactly as the schematic is drawn & not have to mentally re-map the switch lugs.

[scstill]

I've used this switch before,
https://www.amazon.com/dp/B07XJ99JKD?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_3&th=1

In my application, it was as an experiment switching in different NFB resistors when the OT speaker impedance is switched. Didn't notice a great difference in the NFB approach. But the switch was quality.
https://stillampd.com/philco-champ

Here is an on/on/on version
https://lovemyswitches.com/taiway-4pdt-on-on-on-switch-solder-lug-long-shaft/

[hylaphone]

Thanks to HotBluePlate's simple explanation, I believe I've successfully mapped this out.Don't know why I find switching so challenging!Does this look right?

[hylaphone]

Oops sorry position 3 is wrong. I need to stare at this for another few hours haha

[elams1894]

The Mid Select (SW5) looks to be needlessly overcomplicated. I think it only needs to be a SP3T. SW3 Looks to be a DPDT. See attached for my suggestion for schematic of switching. Double checking is of course advised as switching can be head-wrecking.

[DummyLoad]

My take on this uses a 4PDT on-off-on switch. Schematic attached, switch is shown with rear view pin numbering.

Refer to the  SVT schematic attached in initial post for component reference designators.


In BASS CUT - nothing connected to the slide switch is connected.
In OFF - C2 + C6 + C4 +C5 + R10 are all connected.
In Ultra Low - R10 is shorted | R9 is connected to C6.


Boolean: There are 5 wires connected from external sources to the slide switch
Node C2,R8,C4 is A
Node C6,C5 is B
Node C4,R10,C5 is C
Node R9 is D
Node R10,R11 is E

BASS CUT - Nothing connected - Center off position.
OFF - A*B*C connected together - Down position.
ULTRA LOW - B*D connected | C*E connected - Up position.

*= AND

I *think* this correct, please check, no one is infallible. :p 


**EDIT** Made an error with B*D switching - Corrected and attached r2..

--Pete

[elams1894]

@Hylaphone. If you could clarify which switches you are referring to, that would help (SW1, SW2, SW3.. etc). Covering many of the switch geometries already, so that is good. Cheers.

[shooter]

Boolean

He was my favorite math teacher 

[hylaphone]

Good call, it's SW1 and SW5 I'm up against. Thanks for the Mid Select schem, I'll have a think on that.

@Hylaphone. If you could clarify which switches you are referring to, that would help (SW1, SW2, SW3.. etc). Covering many of the switch geometries already, so that is good. Cheers.

[hylaphone]

Can this be done with On-On-On?Here is an NKK datasheet showing how to add jumpers to make XPDT On-On-On switches into XP3T, but I'm still confusedIf not, I'll order some On-Off-On like Dummyload suggestsThanks --

[elams1894]

Thanks for clarification. I think it can be done by the looks of it. I'll work on it.

[elams1894]

I think this will work. The external connection on the switch is different to that outlayed by NKK. However if the centre position switch poles (5 and 11) latch in the way the NKK switch schematic indicate, then the external connections outlined in my attachment should work no problem. It is possible to draw the schematic in a way that fits the external connections provided by NKK if neccessary, and initially I thought I had, until I realised that I had my switch back to front.

However I do not think it matters as long as the switch latches in the way the schematic displays. Good luck with it, and of course always double check as my eyes are a bit too glazed over to give a 100% guarantee.

[hylaphone]

Thanks for working that out!Everything makes sense except the Bass Cut position, I don't think B and C should be connected?

I think this will work. The external connection on the switch is different to that outlayed by NKK. However if the centre position switch poles (5 and 11) latch in the way the NKK switch schematic indicate, then the external connections outlined in my attachment should work no problem. It is possible to draw the schematic in a way that fits the external connections provided by NKK if neccessary, and initially I thought I had, until I realised that I had my switch back to front.

However I do not think it matters as long as the switch latches in the way the schematic displays. Good luck with it, and of course always double check as my eyes are a bit too glazed over to give a 100% guarantee.

[elams1894]

Thanks for working that out!Everything makes sense except the Bass Cut position, I don't think B and C should be connected?

From what I can see on the original schematic, B and C are connected at the bottom position via the cross connection seen in red.

[hylaphone]

What am I missing? The diagonal line doesn't connect to B, which remains "floating" in the Bass Cut position, according to the Ampeg schem. Also referencing Dummyload's version above, which shows no connections made in the Bass Cut position.

From what I can see on the original schematic, B and C are connected at the bottom position via the cross connection seen in red.

[DummyLoad]

What am I missing? The diagonal line doesn't connect to B, which remains "floating" in the Bass Cut position, according to the Ampeg schem. Also referencing Dummyload's version above, which shows no connections made in the Bass Cut position.

From what I can see on the original schematic, B and C are connected at the bottom position via the cross connection seen in red.

Perhaps the attached will help with visualization. Shown are the three positions of the slide switch.


Nothing that is connected to S1 is connected together in the BASS CUT position. The line between the contacts in that Ampeg schematic just means that they are mechanically connected to together, if that's where the confusion stems from.   

Regards,

--Pete

[elams1894]

Thanks DummyLoad and hylaphone for clarification. The schem didn't make sense. Shame on me for believing that a connection on a schematic means a connection. What a whack way to draw a schem. However now of course it makes way more sense, and also way less complicated. It was good practise for my brain though. I find switching problems better than Sudoku

I have amended the switch schem. Hopefully now it should all work out. It will need eyes on it, for checking purposes, of course.

[hylaphone]

I have amended the switch schem. Hopefully now it should all work out. It will need eyes on it, for checking purposes, of course.

Thanks again guys. I think the Ultra Low position is incorrect, we want connections B-D and C-E, *not* B-C, D-E

[elams1894]

So true! What have I done? I'm losing it in my old age. This time perhaps. This could be it, fingers crossed.

[hylaphone]

Far as I can tell, this is it! I'm gonna tack it together and follow up here.Can't thank you enough, this was way more confusing than I anticipated.

So true! What have I done? I'm losing it in my old age. This time perhaps. This could be it, fingers crossed.

[hylaphone]

elams1894's last draft works perfectly, hope this saves some head scratching for future builders. Thanks again!

[elams1894]

Thats great news! Glad it works. I am going to use this switch in my builds as well. The middle position will open extra doors that I was previously unaware especially in high gain preamps with many stages.