#1
Can you guys give me a crash course? I know my Marshall has an unshielded 1/4", but that's about it. What's good, what's bad, and why? Thanks! \\o
#2
connect the heads speaker out into the cabinets input...it really doesnt get much easier than that. just make sure you match up the impedance...do you know how many ohms your head and cabinet is?
Quote by evening_crow
As far as i know the only liquor that should not be stored after opened is wine, and even then it's mainly the french one. American wine usually has conservatives in it to stop this.
#3
Match impedances...and USE A SPEAKER CABLE! Instrument cables will ruin your head over time if you use them to connect a head to a cab.
#4
My head's like 4 ohms... I guess the cab's about the same. What I really mean is: does shielded or unshielded make a difference? Instrument cables or speaker cables? What about stereo??? That sort of thing.
#5
Quote by eyebanez333
Match impedances...and USE A SPEAKER CABLE! Instrument cables will ruin your head over time if you use them to connect a head to a cab.

That's what I was talking about. How would I find the impedance of the cable and the head?
#6
First rule is to always use a speaker cable. Instrument cables are not properly insulated and can't handle the load being transferred from the head to the cab - most times they will physically melt before any damage is caused, but using an instrument cable can damage the head, the cab, or both.


Second, always match impedance the best you can. Make sure the cab you're plugging into has an equal or greater impedance rating than the output of the head. Be aware, though, that if the cab is rated higher than the head you will notice a slight loss of volume and tone.

NEVER connect a head to a cab with a smaller impedance rating. There won't be enough resistance for the head and you will cause serious damage (mainly to the output transformer, if its a tube head).


Third, always make sure that the cab can handle the load being delivered from the head. While a speaker can generally handle approximately 1.5x its handling rating, its not a very safe practice to use a head with a higher wattage rating than the cab is rated to handle.
#7
What amp and cabs are in question here? Most are labeled as far as ohms, wattage for stereo/mono operation, etc.

EDIT: your profile says you have an MG head. The MG100HDFX has two speaker outputs. Both are 8ohm. Unfortunately you can't change the ohms on that amp, so you're cab (s) must be 8ohm. If you're running one cabinet, make sure its 8ohm, and can handle 100 watts. Using a speaker cable, go from the left speaker output on the head to the input jack on the cabinet. If you're running two cabinets, use both speaker jacks...and do the same thing with the right jack on the head going to the 2nd cabinet.. This will put a 4ohm load on the amp, which is as low as it can handle.
Last edited by eyebanez333 at Oct 29, 2009,
#8
Well, my stack is a Marshall MG (shut up, I like it) and the cab is the MG412 (I like it too). But my friend is borrowing another dude's Randall stack, but didn't give him a cable to connect with. Both are solid state.
#9
So you're just running the MG412 with the MG100HDFX and thats it? (see my EDIT above).
#10
Quote by eyebanez333
What amp and cabs are in question here? Most are labeled as far as ohms, wattage for stereo/mono operation, etc.

EDIT: your profile says you have an MG head. The MG100HDFX has two speaker outputs. Both are 8ohm. Unfortunately you can't change the ohms on that amp, so you're cab (s) must be 8ohm. If you're running one cabinet, make sure its 8ohm, and can handle 100 watts. If you're running two cabinets, use both speaker jacks...same parameters for the cabs. This will put a 4ohm load on the amp, which is as low as it can handle.


He could use a 16 ohm cab.
#11
Quote by eyebanez333
So you're just running the MG412 with the MG100HDFX and thats it? (see my EDIT above).

Yes, that's what I'm doing. But I'm more interested in my friend's stack (the Randall).
#12
Quote by i_am_metalhead
He could use a 16 ohm cab.


Yeah you could do what's called a safe mismatch. Running a higher ohm cabinet (i.e. 8ohm head to a 16ohm cab). This isn't a great habit to get into though, because this will fry a tube amp. And it doesn't work the other way...(i.e. running a 4ohm cabinet with an 8ohm head).

Quote by Saminator
Yes, that's what I'm doing. But I'm more interested in my friend's stack (the Randall).


What do you need to know about it?
Last edited by eyebanez333 at Oct 29, 2009,
#13
Quote by eyebanez333
Yeah you could do what's called a safe mismatch. Running a higher ohm cabinet (i.e. 8ohm head to a 16ohm cab). This isn't a great habit to get into though, because this will fry a tube amp. And it doesn't work the other way...(i.e. running a 4ohm cabinet with an 8ohm head).


That is a complete and total myth. I've talked to several amp techs and read several columns written by techs who have said that its perfectly safe to mix-match impedance with any tube amp as long as the cab is rated higher.

Also, my brother has a masters in electrical engineering and I passed it by him one day, as well. He said it wouldn't damage anything as long as the resistance of the cab is equal to or greater than that of the head.


I'll admit it is always the best practice to make sure everything matches up correctly, you're not going to hurt the head if you connect to a cab with a higher impedance, tube or SS.
#14
The usual rule for tube amps is you can double the impedance, i.e. 8 ohm head into 16 ohm cab. Some amps (fenders, usually) can handle a halving as well (8 ohm amp into 4 ohm cab) but that's not something to make a habit of if you're not sure of your amp. With Marshalls, try to match exactly if at all possible since they have awfully sensitive transformers.
With SS heads, it doesn't matter. Any cab is fine.
#15
So do "speaker cables" generally have enough impedance to handle the source load? Does this also mean heads generally have a certain impedance level?

Also, would having two cabs (like in the case of my Marshall) run in parallel be louder (aside from the freaking obvious fact that I'd now have two cabs) because of the lower impedance?
#16
Quote by i_am_metalhead
That is a complete and total myth.


I will have to say there are many, many people who will disagree. I was browsing forums a few months ago looking for a similar answer because I modded an Epiphone valve jr. but it was the combo chassis so it only had one 4ohm output. I knew about safe mismatches, but wasn't sure about tube amps. I asked around if it would be safe to run it through my 112 cab that has an 8 ohm speaker in it and everybody I asked said it would eventually kill the power section of the amp. I will try to dig up a thread that dicusses it in further detail. Don't want to argue...because arguing on the net is pointless...but I just thought I'd point that out.

On topic:
Quote by Saminator
So do "speaker cables" generally have enough impedance to handle the source load? Does this also mean heads generally have a certain impedance level?

Also, would having two cabs (like in the case of my Marshall) run in parallel be louder (aside from the freaking obvious fact that I'd now have two cabs) because of the lower impedance?


Yes speaker cables are built to handle the impedance load between a head and a cab. Two cabs won't be louder in terms of dB...because the amp is still 100 watts peak wattage regardless of whether thats into one 8ohm load, or into two 4 ohm loads. But it will sound fuller, and have better bass response, which some people may perceive as an increase in overall volume.
Last edited by eyebanez333 at Oct 29, 2009,
#17
Quote by Roc8995
The usual rule for tube amps is you can double the impedance, i.e. 8 ohm head into 16 ohm cab. Some amps (fenders, usually) can handle a halving as well (8 ohm amp into 4 ohm cab) but that's not something to make a habit of if you're not sure of your amp. With Marshalls, try to match exactly if at all possible since they have awfully sensitive transformers.
With SS heads, it doesn't matter. Any cab is fine.



I'm not trying to argue with you, Colin, because you clearly know more about this kind of stuff than me.

But I clearly remember reading a response to an e-mail by Matt Bruck (former guitar tech for EVH) where the sender was asking about mixmatching impedance with his Marshall head. Matt responded by saying that "you can safely mix-match impedance with any tube head as long as the cab is rated higher than the output of the head."
#18
Quote by eyebanez333
I will have to say there are many, many people who will disagree. I was browsing forums a few months ago looking for a similar answer because I modded an Epiphone valve jr. but it was the combo chassis so it only had one 4ohm output. I knew about safe mismatches, but wasn't sure about tube amps. I asked around if it would be safe to run it through my 112 cab that has an 8 ohm speaker in it and everybody I asked said it would eventually kill the power section of the amp. I will try to dig up a thread that dicusses it in further detail. Don't want to argue...because arguing on the net is pointless...but I just thought I'd point that out.



I'm not trying to argue with anyone either, because I'm not a master on this subject. But the things that I do know I have learned from people who have worked as techs for several years for professional guitarists and from people who know the science behind it all.