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Spider II HD 150 on Crate GX412XS (1997)
by MrTheEdgeSTB on 2010-06-09 14:24:19.7210


Been playing with a certain guitar setup for some time, and decided to make a switch.  Only AFTER I bought the new head unit though did I understand my *possible* mistake.  Therein lies the problem - I find conflicting articles, some that would suggest my setup will be OK, others that suggest doom and disaster.

Here's my current setup:

  • Digitech GSP2101 Studio mono/stereo tube effects preamp
  • Marshall Valvestate 8004 40wX40x Power Amp, 8 ohms each channel
  • Crate GX412XS 4x12 cab (1997) 120w RMS, x2 8 ohm jacks in the back.

Now when I bought this rig, the dude at Sluggo music told me to run one patch cable from the Digitech Left (mono) Out -> Marshall Channel B (mono) In -> and from the Marshall Channel B (mono) out -> Crate Left jack.  This has worked fine, but I always wondered why not run both lines (is it because the cab isn't stereo?  Just 4x12 mono?  Or is it because one of the jacks isn't active?)

So, I scored a Spider II HD 150 the other day on eBay, intending to simply replace the Digitech/Marshall combo; however, only later did I learn the the HD150's really need to run in stereo (as opposed to the HD75's which I pretty much ignored on eBay - my bad!).

The concern is that I find conflicting evidence on the Web as to whether the GX412XS is mono or stereo?  Or does it even matter?  (IE can both jacks on the Crate be active @ 8 ohms each, but just not wired in a stereo configuration?  I don't understand the electronics aspect enough to know the difference.)

If I read the FAQ's here correctly, plugging in only one of the Out Channels from the HD 150 will almost surely blow the head.  However, if I plug both channels into each of the jacks on the Crate, am I going to blow my cab instead?  (Not too worried about the disparity in wattage, as I don't ordinarily run that hot, and again, if I read everything right, the ohms match and that seems to be the killer.)

Any thoughts?  Advice?

Oh - and kindly refrain from the "dude just buy a new cab" type-comments.  That really isn't helpful.  If the information provided here suggests that I'm going to have an absolute incompatibility with my existing equipment, I can come to the "buy new cab" conclusion all by myself, thanks.  If cash weren't an issue, I wouldn't even bother asking this question (and hope that this would be obvious).  Trying to find solutions with what I already have.

And I know the Spider can run direct as an alternative...that was part of why I bought it.

Thanks lads!  Cheers!

Re: Spider II HD 150 on Crate GX412XS (1997)
by MrTheEdgeSTB on 2010-06-17 19:46:07.3340

Wow!  What a shame that I cannot get a response here.  Even the Line 6 service center that I called locally, when posed with the question, said get a second cab and run one channel to each.

So, after much research, I shall answer my own question, and share my findings to others with a similar curiosity or dilemma.

The short answer is - no, you cannot run the Spider II HD 150 on the 1997 Crate GX412XS cabinet as is - the cabinet must be modified.  I found a really useful site that discusses in great detail the diffrerences in 4x12 cab setups, wiring diagrams, how to go from mono to stereo, etc.  Great articles!

Combine that with my own efforts - pulled the back off my cab and had a look - took a bit to sort out the wiring of my speakers with the diagrams I found (I'm no electrician, so it's all a bit arcane to me), but with perseverence was able to sort it out.  Based on this link (first of many that I will post here):

...and comparing the wiring and actual speaker components in my cab, mine is 4 - 8ohm speakers in Series-Parallel, giving a mono 8 ohm load across any one channel.  In fact, further research indicates that (barring a very specialized setup - I'd love to see how the Spider Cabs are configured) it's impossible with 4 8ohm speakers to get a stereo 8 ohm load (8 ohms in each channel).  You can get 4 ohm load (2 speakers in parallel wiring) or 16 ohm load (2 speakers in series wiring) - that's it!

Now based on this link ( the latter configuration would work, but with a perceptable loss of volume, which would only matter really depending on the style of music you're after.  As my own playing is more of an ambient/rhythm style, this is insignifcant.

So - I can reconfigure the Crate GX412XS cab to a stereo/16ohm setup and run the Spider II HD 150; but then I can't run my old Digitech/Marshall setup unless I start running that in stereo as well - vote's not in on that one yet.  Or, I can get a DPDT switch and turn it into a switched 8ohm/mono // 16ohm/stereo cab.  All for fairly cheap.

And maybe someday I'll scrape up enough again to swipe a Spider IV Cab - we'll see.

It is a shame that a novice like myself would have to find all this out the hard way, but hopefully this will be of assistance to other poor souls looking to not ruin their music gear investments.


Other links, just for kicks - it's really a great site! (nice commentary on the rationale for a stereo single-unit setup, and frankly one that resonates with me)

Re: Spider II HD 150 on Crate GX412XS (1997)
by rockn-rich on 2012-06-29 19:18:29.0230

Thanks for posting this, you have helped me. I just bought a spider II HD 150, and a crate GX412XS cab today at a pawn shop. Not because I needed another amp, but because it was so dirt cheap. They were giving it away basically because it had been there too long. I got the head for $75, and the 4x12 cab for $60. That's out the door, no tax.

When I tried it at the pawn shop, they just ran one channel into the cabinet and it worked fine. Of course no stereo that way, but it sounded good. Also, with a solid state amp, it doesn't hurt it to run with nothing hooked to the output jacks, like it does with tube amps. The two are totally opposite in that regard.

The links will come in handy....thanks!

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