Help an idiot with an amp ?

Jake · September 23, 2012, 07:57:21 PM

Listen, not to shit right in the middle of an internet graph fight, but having experience with nearly the same exact problem you seem to have with your Orange, I thought I could at least tell you what I did to "expand" the cabinet options for my amplifier.

The problem:
Your amp is the same as my Thunderverb 50: Three output jacks – ONE jack for a single 16ohm cabinet and TWO other jacks, one for using a single 8ohm cab or both for using two 16ohm cabs together – yielding an amplifier minimum 8ohm load. Yes, these amps can not operate below 8ohms. Lame.

The solution:
I built a DIY Series Cable which enabled me to run two 8ohm cabs together at a 16ohm resistance. The loads are simply "added" together using this device, so 8+8=16ohms. I'm posting a diagram below (cable on bottom left). It's very cheap and a very simple build.

The caveat:
In your case, the load would be 4+8=12ohms, so you'd need to run it from your 8ohm output to keep from harming your amp. This mismatch is definitely not ideal for either the amp nor the speakers, but I'm fairly confident that you will not be irreparably harming your Orange if you choose this route. The experts are sure to chime in and confirm or deny this. But...will it sound good? I dunno. That's totally up to you, your ears, and your ability to interpret the graphs in this thread.

Mr. Foxen · September 23, 2012, 08:01:58 PM

With a valve amp, you want a lower load than the tap if you are mismatching. If you check the jacks, they are shorting if unplugged, because a shorted output (low/no impedance) doesn't harm valve amps. The issue to consider is that the power distribution between different impedance cabs is uneven, so for example, its better to use a 8 ohm 4x12 and a 16 ohm 2x12 because each individual driver will get the same power (assuming all drivers are same impedance), rather than 8ohm 4x12 and 8ohm 2x12, where the smaller cab is receiving double power.

Hemisaurus · September 23, 2012, 08:08:00 PM

Nice graphic

I did kind of allude to this, but being chicken wouldn't say 12 ohm was absolutely safe

Quote from: Mr. Foxen on September 23, 2012, 07:53:43 PM
The important bit being, that the volume output will be significantly cut in the scenario with mismatched cabs at the high impedance frequency, as already described.

No, I think the important bit is you telling someone their amp would blow up. If you said you might get a lumpy frequency response that would have been truthful, note the might. It might sound awesome too, you never know.

Yeah, Jake makes it clearer, there is no cab you can safely add to this rig, without making the special cable first, 8 ohm is your minimum limit.

Jake · September 23, 2012, 08:10:11 PM

PS: Stupid me did not see the big red DO NOT mix cab impedances in series! Ex: 8 + 4, etc. on the diagram I posted, so you may want to ignore my meddling altogether in your current scenario.

BUT, since you already have an 8ohm cabinet, and seem to be interested in adding another cabinet to your setup, make sure to keep the diagram I posted in mind if you end up finding another 8ohm cab that you want to run with it someday.

Hemisaurus · September 23, 2012, 08:11:05 PM

Quote from: Mr. Foxen on September 23, 2012, 08:01:58 PM
With a valve amp, you want a lower load than the tap if you are mismatching. If you check the jacks, they are shorting if unplugged, because a shorted output (low/no impedance) doesn't harm valve amps. The issue to consider is that the power distribution between different impedance cabs is uneven, so for example, its better to use a 8 ohm 4x12 and a 16 ohm 2x12 because each individual driver will get the same power (assuming all drivers are same impedance), rather than 8ohm 4x12 and 8ohm 2x12, where the smaller cab is receiving double power.

What he's saying is if you do it, use the 16 ohm tap, and make sure the 2x12 can handle at least 2/3 of the piwer that it is already handling

Mr. Foxen · September 23, 2012, 08:12:20 PM

Quote from: Hemisaurus on September 23, 2012, 08:08:00 PM
No, I think the important bit is you telling someone their amp would blow up. If you said you might get a lumpy frequency response that would have been truthful, note the might. It might sound awesome too, you never know.

Were is that bit?

Lumpy frequency response in the room might sound awesome in one place, but it won't sound like that in another place, that's quite a lot of the point. That not knowing is why to avoid it, recommendations should be based on stuff that is known.

Hemisaurus · September 23, 2012, 08:27:23 PM

Quote from: Mr. Foxen on September 23, 2012, 06:01:55 PMThere is plenty of possibility of blowing your shit up right there. Running cabs off different heads negates the impedance problem. Running mismatched cabs from the same head is a whole bunch of potential trouble, both for sound, and amp safety.

Sam Hain · September 23, 2012, 08:52:13 PM

I missed out on that Ampeg anyway....turns out the jackass sold it last week and never pulled the ad. He even said in the ad "dont email me and ask if I still have it, if the ads up I still have it."

I don't know why I'm looking anyway. I dig my tone a lot, no real need to change it but I'm always trying different shit.

Interesting stuff in this thread, way over my head though.

dunwichamps · September 23, 2012, 08:59:13 PM

just important thing to remember:

If you run a mismatch. Always run a the larger impedance tap into a small impedance load. For example, if you do series the cabs and get 12 ohms then run it from the 16 ohm tap since this produces a better mismatch. The reason for this is due to reflected impedance back on the primary, where running a smaller impedance tap into a larger impedance load results in flyback voltage on the primary (ie running 12 ohms off the 8 ohm tap) which can spike the output tubes with high voltage causing death.

The easiest thing is to buy a impedance converter from Weber or build 1 using their autotransformers.

VOLVO))) · September 23, 2012, 11:01:29 PM

Wow, what a clusterfuck of a thread this is. Lolololol

clockwork green · September 24, 2012, 01:41:59 AM

Even if the impedances matched the bass cab would probably be far quieter and supremely shitty sounding which mixed with the 2x12. Does this bass cab have a tweeter? Can you turn it off or unplug it because otherwise it'll sound even worse. Back when I thought I was brilliant for coming up with "bass cabs can really handle a lot of low end so they must sound great for drop tuned doom riffs" I tried running a 100-watt tube guitar amp into a 4x12 Marshall and a 1000-watt solid state amp into a Mesa 4x10 bass cab. By itself I thought the bass cab kinda sounded cool..insanely scooped mids though. When I matched it with the guitar amp it just disappeared...except for turning the guitar amp nearly off could I even notice the bass cab and amp even when dimed. Add another guitar player and it just got stupid. If you're a two-piece and you want to lug around a ton of shit then go for it. You might come up with some novel sounds but there's a slim to none chance of any your all time favorite recorded guitar tones were made this way and it's not because you thought of it first.

Sam Hain · September 29, 2012, 10:04:54 AM

Rather than start a new thread about my lack of amp knowledge I figure I would just post here again..

This has to do with slave amp setup. I know nothing about them.

For instance take Dixie's bass setup from Weedeater. I believe he runs his bass into a 200w Sunn Concert Concert lead ,with a concert lead slave and 2, 215 cabs. Not sure what type of fuzz he runs.

Anyway...how do you setup this up? Does his signal get split before the amps? Or does he run signal into the amp then into the slave?

Hemisaurus · September 29, 2012, 10:42:18 AM

Quote from: Sam Hain on September 29, 2012, 10:04:54 AM
Rather than start a new thread about my lack of amp knowledge I figure I would just post here again..

This has to do with slave amp setup. I know nothing about them.

For instance take Dixie's bass setup from Weedeater. I believe he runs his bass into a 200w Sunn Concert Concert lead ,with a concert lead slave and 2, 215 cabs. Not sure what type of fuzz he runs.

Anyway...how do you setup this up? Does his signal get split before the amps? Or does he run signal into the amp then into the slave?

The latter, the slave takes a line out from the main amp.

Read this thread it talks all about, especially important for people using tube amps.

http://riffrocklives.com/forum/index.php?topic=925.0

Sam Hain · September 29, 2012, 05:14:45 PM

Quote from: Hemisaurus on September 29, 2012, 10:42:18 AM
Quote from: Sam Hain on September 29, 2012, 10:04:54 AM
Rather than start a new thread about my lack of amp knowledge I figure I would just post here again..

This has to do with slave amp setup. I know nothing about them.

For instance take Dixie's bass setup from Weedeater. I believe he runs his bass into a 200w Sunn Concert Concert lead ,with a concert lead slave and 2, 215 cabs. Not sure what type of fuzz he runs.

Anyway...how do you setup this up? Does his signal get split before the amps? Or does he run signal into the amp then into the slave?

The latter, the slave takes a line out from the main amp.

Read this thread it talks all about, especially important for people using tube amps.

http://riffrocklives.com/forum/index.php?topic=925.0

Cool...thanks!