“Plug and Play” speaker jack plate, wiring

[beans-on-toast]

Try it and see, with some cabs it can clear up muddiness in the lower mids. Lining the back is the starting point.

 

[Ringhammer]

Thanks for that info, it helps for sure! Nice to understand what the effect is, I never considered that it could clear up muddiness, my assumption would be that it would deaden it, so as usual, I'm glad I asked!

 

[Ringhammer]

Another question somewhat related:
Is there a good way to use an 8ohm cabinet with an early '70's SVT? I think using the B25B with a certain cabinet (8 ohm?) was achieved by plugging the cab in the main speaker out and a dummy load in the other. Would plugging an 8 ohm in the main speaker out and an 8 ohm dummy in the extension speaker out give the head a 4 ohm load correctly?

Also, with the old SVT, when using two 4 ohm cabs, is running a speaker cable from the main speaker out to the 1st 4 ohm cab, and then, through the parallel connection on the back, to the 2nd 4 ohm cab actually incorrect? Does the extension speaker out need to be used when using 2 cabinets in order for the transformer taps to be connect to correctly (I'm out of my knowledge of amp tech type stuff with that last statement I think).

 

[coreyfyfe]

The dummy plug (note: not a dummy load, just an open 1/4" plug) trick works on the B25 because the switching jack selects between 8 and 16 ohm windings in the OT. The stock main output is 16 ohms, with a plug inserted into the extension output the jack switches to the 8 ohm tap with the two outputs in parallel. If you did the same on an old SVT you'd have the 2 ohm secondary selected.

An 8 ohm load is not advised for an SVT. Though plenty of people do it with an SVT, and Bill Hughes himself has said it would probably be fine, I wouldn't want to test it on a vintage output transformer. If you want to run two 8 ohm loads on a vintage SVT connect them in parallel off the main speaker out. If you want to run two 4 ohm loads the best way is one cab to each jack because of the switching output previously mentioned. If you plan to run using a parallel connection on the cab use the dummy plug trick mentioned for the B25B.

 

[Ringhammer]

The dummy plug (note: not a dummy load, just an open 1/4" plug) trick works on the B25 because the switching jack selects between 8 and 16 ohm windings in the OT. The stock main output is 16 ohms, with a plug inserted into the extension output the jack switches to the 8 ohm tap with the two outputs in parallel. If you did the same on an old SVT you'd have the 2 ohm secondary selected.

It's funny that a B25B cabinet is built with a 16ohm / 4ohm switch, but I guess that would mean that the cab switched to 16ohm works to the B25B head when simply plugged into the main speaker out and with nothing plugged into the other output?

So there is no good way to run one 8 ohm cab with an old SVT, no way to trick the head into running at 4ohms? I suppose even if there was, there would be no way to get the full power to the one 8 ohm cab.

This is just all out of curiosity, and trying to be sure I fully understand what my old amps are capable of and what is best for them. I have plenty of 4 ohm options for my SVT's, so not being able to use this 4x12 V4 cab with my SVT is no big deal. Just looking forward to hearing it with the V4 head and hoping it's going to be exceptional sounding.

 

[Ringhammer]

I noticed something on the jack plate I used for this cabinet, it seems like a printing error:

How can
1+ = POS (+) and
1+ = NEG (-)


I did test the Speakon connectors with a Speakon to 1/4 cable, and through the circuit board, to the connector on the other side of the plate, and the white wire was Tip, the blue wire was Ring (sleeve), same as with the 1/4" jacks.

Also confirmed a reading of about 5-6 ohms when cabinet is perfectly still so I'm confident my series parallel wiring connections are solid and it is an 8 ohm cab.

 

[agedhorse]

Yes, that has to be a printing error. The bottom line should say 1-

 

[beans-on-toast]

It also looks like is says PCS instead of POS.

Normally these sort of things are reviewed at multiple levels. Rubber stamping reviews doesn't work well.

 

[Sixjam]

View attachment 4788481

View attachment 4788483

Has anyone used one of these, seems like the same thing the newer SVT810's do.

In my case I'll be using 4 x 8ohm 12's, so my config will be more like 4 ohm left, 4 ohm right, 2 ohm mono(?), and 8 ohm mono. I think. However I'm hoping someone knows how I need to wire this for sure. I don't know who makes this thing.

I think I am supposed to wire the left two 8 ohm speakers in parallel to one pair (red/white?) and the right two 8 ohm speakers in parallel to the other pair (black/green), and then if I plug one speaker cable ONLY into the jack marked "4 ohm mono", I will actually be at 2 ohms, OR if I plug one speaker cable ONLY into the jack marked "16 ohm mono" I will actually be at 8 ohms, OR if I plug one speaker cable into the jack marked "8 ohm left" AND one speaker cable into the jack marked "8 ohm right" I can bi-amp with an amp that has two 4 ohm rated outputs, or two separate amps with 4 ohm outs, since the left and rights will be 4 ohm, not 8 as marked. (I'll be breaking out the label maker for sure)

Likely will only use the jack that is marked 16 ohm mono, which will be 8 ohm for me, but could be fun to have the bi-amp option, making left and right actually be top and bottom.

Hoping for confirmation on my logic from someone with experience, thanks in advance.

I am trying to get this config too. 8ohm Mono, 4ohm stereo . I have 4 8ohm greenbacks. Any luck??

 

[Sixjam]

View attachment 4788481

View attachment 4788483

Has anyone used one of these, seems like the same thing the newer SVT810's do.

In my case I'll be using 4 x 8ohm 12's, so my config will be more like 4 ohm left, 4 ohm right, 2 ohm mono(?), and 8 ohm mono. I think. However I'm hoping someone knows how I need to wire this for sure. I don't know who makes this thing.

I think I am supposed to wire the left two 8 ohm speakers in parallel to one pair (red/white?) and the right two 8 ohm speakers in parallel to the other pair (black/green), and then if I plug one speaker cable ONLY into the jack marked "4 ohm mono", I will actually be at 2 ohms, OR if I plug one speaker cable ONLY into the jack marked "16 ohm mono" I will actually be at 8 ohms, OR if I plug one speaker cable into the jack marked "8 ohm left" AND one speaker cable into the jack marked "8 ohm right" I can bi-amp with an amp that has two 4 ohm rated outputs, or two separate amps with 4 ohm outs, since the left and rights will be 4 ohm, not 8 as marked. (I'll be breaking out the label maker for sure)

Likely will only use the jack that is marked 16 ohm mono, which will be 8 ohm for me, but could be fun to have the bi-amp option, making left and right actually be top and bottom.

Hoping for confirmation on my logic from someone with experience, thanks in advance.

I am trying to get this config too. 8ohm Mono, 4ohm stereo . I have 4 8ohm greenbacks. Any luck??

 

[Ringhammer]

This was over three years ago, so I think forgot. Best recollection I have is I just wired the cab mono, using the SVT jack plate pictured.

 

[Redbrangus]

I have 4 8ohm greenbacks.

Unless you're trying to build a gee-tar cab, I wouldn't bother. Especially if you want to power it with any more than about 100-120 watts.

 

[agedhorse]

The Greenbacks won't last long with bass guitar at more than 25 watts/driver.