Mark IV and speaker jacks

[disassembled]

You can do the 8 ohm and 4 ohm speakers. The two 4 ohm outputs are wired in parallel and are meant for one '4' ohm or two '8' ohm speakers.

You could daisy chain two 16 ohm cabs in parallel and then add one 8 ohm cab hooking into the 4 ohm jacks but I don't think the mark would be suited for powering more than 8 12" speakers at a time. It will work but each speaker is going to see less and less voltage/wattage the more you add.

Greg

 

[psychodave]

try replacing all 4 6L6's. It is better to be safe than sorry 8)

 

[JOEY B.]

apparently there is no correct match when using 8ohm jack and one 4ohm jack simultaneously...

How right you are . Also, the 4 ohm jacks are hardwired together (parallel) inside the amp. Thus connecting two 4 ohm cabs to these jacks will result in the amp seeing a 2 ohm load. Looking at it again, example #7 on page 15 may be a little easier to understand, for using the combo speaker in conjunction with the G-flex. Same load though.

 

[Aart]

I just ordered 4x6L6GC and 2xKT77 from eurotubes. I explained to Bob the situation so we'll see what his reply is.

So should I go ahead and throw away the Mesa 6L6GC's that were in the amp from yesterday? Like a tire going bad, replace 2 or all 4?

I usually don't have tube issues (lucky I guess, never had with Marshalls, mostly JJ's), so plz forgive the newbie questions...

and check this quote out from Tom Mitchell's How to Service Your Own Tube Amp book:

pg. 144-145:

Matching the impedance of your speakers to the output impedance of your amplifier is a critical adjustment. Some people have the misguided notion that putting an 8 ohm load on an amp with the impedance selector set to 16 ohms somehow "magically" increases the output power, or that running a 16 ohm load with the selector at 4 ohms gives you a "good" sound at lower volume. Regardless of the myths, one thing that doing these things will do is to cause the power tubes to work too hard (due to the impedance mismatch) resulting in premature tube failure and possibly output transformer damage as well.

OK. So this guy and Mesa obviously disagree about the "safe mismatch" concept...

No, that part is about speakerload that is smaller than the amps outputload.

Safe mismatch = bigger speakerload than your amps output load. As stated in the Mk 4 manual.

 

[phyrexia]

Boogiebabies said you can do 8ohm in the 8 ohm output, two 8 ohms in the 4 ohm outputs, but I'm not about to try it...

edit: ok, i tried it, and had no problems. 8)

 

[Russ]

WHOOOOAA!!!!!

Nasty Ice.... J/K

You can put a 16 ohm load into the 8 ohm jack. It just sounds a little darker than usual. I was doing this with my 1960AX cabinet. Mesa suggested that I just take it easy because my Greenbacks were at risk. Had they been V30's they could have been turned up. I forgot to try that with my 65's before they went bubbye...

Drink another Natty and fathom this:
They also told me that I could run a 16 ohm load into the 8 ohm jack and run an 8 ohm load into a 4 ohm jack at the same time. Deductively I would think that you could run 3 16 ohm cabinets then in the three jacks (one in the 8 ohm and one each in the 4 ohm jacks)? I am not telling you this is safe but it seems to be what is suggested by saying that as long as you double your ohm load per jack keeping in mind that the 4 ohm jacks as a pair are looking for 4 ohm load together. This points to the 8 ohm jack wanting a 16 ohm load and there being an 8 ohm load being put on the two 4 ohm jacks (pair of 16 ohm cabinets) if all jacks are being used. I am not accepting any liability for any damages arising from this. I am just pondering aloud. Feel free to chime in if you know differently.


BTW did they pop pretty loud in that ziplock? I always wondered if a vacuum being broken in a ziplock would make as much noise. I also wondered if the bag would slightly collapse from the vacuum suction. I guess I could try it with some of my vintage preamp tubes.... :idea: :shock: :roll: :wink:

 

[Russ]

O......E........

You didn't have to go there.... :lol:

Ice beers are cool. I used to work for Anheuser Busch. We called Natural anything Natty or Nasty, ie. Natrual Ice= Nasty Ice.

I was cool with Heineken but I actually prefer Becks over Heineken.

 

[devilrob1979]

I'm running two 8 ohm cabinets daisy chained into one 4 ohm jack. This is the correct setup is it not? 2x8 ohm= 4ohm correct?

 

[Russ]

That sounds fine to me. How does it sound to you?