Sovtek MIG-50 help

[insanezp]

hello everyone i'm a newbie so forgive my ignorance.

have just bought a MIG-50 with a matching Sovtek 2X10 cab. The cab is 8ohms.

I have the opportunity to purchase another matching 2X10 at a great price. So my question is is it possible to connect two 2X10's to the MIG-50.

Sorry for sounding dumb. I've never had a head/cab...always combo's.

Do I just hook one cab to the other and the head to one of the cabs? If they are both 8ohms does the load now become 16?

Hope someone can help clear this up for me.

This thing is a monster and I don't want to burn it up by connecting it wrong.

I'm anal about mismatching otherwise I'd get a Marshall cab. Besides the Sovtek cabs are very compact and fit my space perfectly.

[Dave Curtis, dB AudioTech]

hello everyone i'm a newbie so forgive my ignorance.

have just bought a MIG-50 with a matching Sovtek 2X10 cab. The cab is 8ohms.

I have the opportunity to purchase another matching 2X10 at a great price. So my question is is it possible to connect two 2X10's to the MIG-50.

Sorry for sounding dumb. I've never had a head/cab...always combo's.

Do I just hook one cab to the other and the head to one of the cabs? If they are both 8ohms does the load now become 16?

4 ohms (parallel). If you wire them in series, they're 16 ohms. It's best to run both cabs to the head, but you can daisy-chain, since you have one jack for each impedance, IIRC.

-DC

[Amp Kat]

I agree with Dave that IMO 4 ohms sounds better but amp manufacturors will tell you to series them and run them at 16 ohms to keep the tubes from pulling more current and perhaps messing up their MTBF numbers. If you have two speaker jacks and run each cab into a jack flip the selector switch to 4 ohms. Switching it to 8 ohms will diminish the volume and 16 ohms even more. I'd wire the two cabs in parallel for 4 and use one speaker wire to the speaker jack and set the selector to 4 ohms and that's where IMO it will sound the best.
http://www.colomar.com/Shavano/speaker.html

[Dave Curtis, dB AudioTech]

I agree with Dave that IMO 4 ohms sounds better but amp manufacturors will tell you to series them and run them at 16 ohms to keep the tubes from pulling more current and perhaps messing up their MTBF numbers.

Well, I haven't heard that from amp manufacturers, but the prevailing theory I've heard elsewhere is that the 16 ohm tap (normally) uses all of the secondary and should sound better, be easier on the amp, etc.

If you have two speaker jacks and run each cab into a jack flip the selector switch to 4 ohms.

IIRC, there's one for each impedance 4,8 & 16.

Switching it to 8 ohms will diminish the volume and 16 ohms even more. I'd wire the two cabs in parallel for 4 and use one speaker wire to the speaker jack and set the selector to 4 ohms and that's where IMO it will sound the best.
http://www.colomar.com/Shavano/speaker.html

Thanks for the link update, I'd wondered where that page went.

-DC

[flyingtele]

I actually own a MIG-50, absolutely great amp. In theory, as already stated, the 16Ω tap should be louder and sound better than the 8Ω or 4Ω tap, as it does indeed use the whole secondary of the output transformer. If you wanted to take that path then wire the two speakers in series.

I would wire them in parallel for 4Ω and then in series for 16Ω and use whatever sounded better. As long as each impedance tap is used correctly it will not be harder on the amp, because that is how its designed. And valve amps are different to solid state amps, in that with solid state you can use the rated impedance or higher, whereas valve amps typically you should use the right impedance, but lower than rated is better than higher than rated.

Hope this helps

[soundmasterg]

From Kevin O'Connor's FAQ on his website www.londonpower.com .

Q: An "expert" suggested that I change my speakers to ones that match the highest impedance tap on my amp. How do I do this and still have the option of using a second cabinet when I play out? I think I would need three cabinets to achieve this.

A: Yes, and what a waste of your money.

Not too surprisingly, this is the same expert as in the tube-pulling/power reduction question. He really should stop talking about transformers.

Rest assured, the impedance taps on your amp are there for your convenience, to use as you will. Connecting the rated cabinet impedance to the identical rated tap selection will get you the rated power bandwidth of your amp into that load. As stated above, any "mismatch" reduces power and bandwidth, and that is all.

If you are using your 4-ohm cabinet and the 4-ohm tap, does it matter if the 16-ohm tap is being unused? Of course not. This subject is explained in detail in TUT3, as the "Myth of Encompassment" - a myth created purely to sell speakers and transformers. To unsuspecting players and readers of the "expert's" column, it is no more than a scare tactic.

Transformer designers take into account the loads to be connected to the device. There is limited space in the winding window for each lamination size, and the designer wants the space to be fully utilized. The percentage of space used is the "build". Ideally, all windings are used all the time, to keep parasitic effects to a minimum. When there is a tapped secondary, some of the secondary may not be loaded under certain conditions, so those "free" parts of the winding can potentially upset the parasitic balance. The amount of upset is usually so small as to be insignificant, even in hi-fi where such a thing might matter. In MI, there is no concern whatsoever.

In most amps, you can set the impedance selector to whatever sounds best. The one caveat is: NOT in English amps. Having replaced more Marshall OTs than anything else, I would advise that the impedance selector always be set to the rated load, or less.


Bottom line, use whichever tap matches your speaker load. If you want to use some other tap with the same given speaker load, then it changes power and bandwidth as you go one way or the other, and in extreme cases, can damage the amp, but tubes are quite forgiving. Its actually potentially worse to mismatch down than up because it is "that" much closer to a dead short and can cause arcing inside the output transformer, but again, we're talking extreme cases here. I ran my brother's Silvertone 1484 full up for years into an 8 ohm load with the 4 ohm tap. It is still fine now even though I modded the amp and am running even more power than before into a greatly undersized output transformer. THe tone was great for leads when mismatched that way, very compressed and distorted, but as if the highs and lows were scrunched up. The power level was much less also when running that way. Its easier on the tubes because they run cooler, whereas if you have a 4 ohm tap and run it into a 2 ohm speaker locad, that is harder on the tubes and can result in arcing inside the transformer. Its best to match your loads up for power and tone.

Greg

[Roy Blankenship]

I agree with Kevin's assessment, I want to add to the explanation. For people who want to run multiple cabinets on occasion, you are better off to wire your two 8 ohm speakers in series for 16 ohms, then you can add another like cabinet (16 ohms) and use the 8 ohm selector on your amp. If you wire in parallel for 4 ohms, you have no further extension cab options.

The evidence for running 16 ohms (or the highest impedance tap on an amp) is anecdotal at best. My personal experience with "using the whole transformer" originated in Hifi mythology. A local player where I grew up (OK, I never REALLY grew up) did a lot of sonic testing and decided that a Marshall through a 4 x 12 wired for 16 ohms through the 16 ohm tap sounded better to him than the same cab wired in parallel for 4 ohms on the 4 ohm tap. This is purely a subjective analysis and a personal opinion. It is a reality that an amp running 16 ohms will have more swing from 0 to full output, whether this is audible is a subject on which I would like to hear other's opinions.

Roy