Using 2 different output taps at the same time

[Rlw59]

Participating on a thread on a Marshall forum, pointlessly arguing whether a 2:1 or 1:2 mismatch is safer.

And a couple of guys are saying it's perfectly ok to plug an 8 ohm cab into the 8 ohm tap and a 16 ohm cab into the 16 ohm tap at the same time. Even suggesting rewiring amps that have impedance selector switches -- hardwire the taps to the jacks so you can do that.

Do I have Alzheimer's? Mandela effect? That ain't right, is it?

[Rlw59]

Google is not my friend.

Half the results say "sure, no prob".
The other half say "NO, don't do that".

[Rlw59]

Hmmm. According to a Marshall engineer if you have 8 and 16 ohm cabs, you can use the 4 and 8 ohm taps simultaneously.

And if you have three 16 ohm cabs you can daisy chain two into the 4 ohm tap and one into the 8 ohm tap.

Moot for Orange since Orange doesn't do 4/8/16 transformers.

[Gladmarr]

I’ve always been told you cannot do this. This would only match impedance correctly if each speaker was on a separate WINDING. In the proposed scenario(s), the speakers would just be on different TAPS of the SAME winding. I wouldn’t recommend doing this.

[Rlw59]

Yeah, I've always been told not to, and I don't plan on ever trying.

Just relaying that the designer of the JVM series says it's ok with any amp that has separate jacks for 4 and 8 ohms.

(Also claims it results in equal power distribution between the cabs.)

[Rlw59]

8+16 cabs = 5.3 ohms total.

Supposedly, the reflected voltages are such that using the 4+8 ohm taps gives a virtual 5.3 ohm tap, and because of the different lengths of wire and geometry of the secondary coil it'll split the power equally.

Sounds like witchcraft to me...

[bclaire]

Price the cost of a replacement output transformer and see if you still want to do that....

[Rlw59]

No, like I said I have no need, urge, or desire to do so.

And the claim is that you have to have both a 4 ohm and and 8 ohm jack, so the standard advice to not do that with an.Orange amp is correct.

[Rlw59]

If you have a 16 ohm cab and an 8 ohm 212 or 412, you could rewire the 8 ohm cab to be 32 ohms. Then plug the 32 ohm cab into the amp's 16 ohm jack and the 16 ohm cab into the 8 ohm jack

Sorry. This concept and that some people advocate it just really twisted my brain.

Plenty of cabs out there. Weber Z-Matcher. No reason for anyone to ever do weird things. A good output transformer, tubes, and a trip to a tech cost more than a cab.

[Gladmarr]

Yeah, I've always been told not to, and I don't plan on ever trying.

Just relaying that the designer of the JVM series says it's ok with any amp that has separate jacks for 4 and 8 ohms.

(Also claims it results in equal power distribution between the cabs.)

This definitely surprises me. I’ll run this by some people smarter than me, but it sounds risky for the health of your output transformer.

[Rlw59]

He did say that using the 8 and 16 ohm taps for an 8 and a 16 ohm cab would be very hard on the transformer and might well destroy it.

[Gladmarr]

He did say that using the 8 and 16 ohm taps for an 8 and a 16 ohm cab would be very hard on the transformer and might well destroy it.

Well, that IS an important caveat.

[Rlw59]

I had to keep re-reading the Marshall post that described this, because I thought "4 and 8 ohm jacks" for "8ohm cab + 16ohm cab" had to be a typo. But that poster referenced the engineer who suggested it, so I searched the engineer's posts. He explained it far more clearly and technically than I can.

What's the etiquette on this forum about linking to other forums?

[Gladmarr]

I don’t think there’s any restriction on linking to other forums. I’ve done it and no one has kicked me out yet.

[Rlw59]

Here's one thread that also has links to other confirming threads.

The engineer is "santiall" - Santiago Alvarez.

http://www.marshallforum.com/threads/af ... cab.94638/