#1
ok myfriends crate bvh-120 (wich is for sale ) had the head running at 8 ohms and the cab at 16 ohms. I fixed it when i saw it but, would this have caused any damage? would it have been affecting the sound.
#2
yeah it would of possibly burnt out the wiring and caused some damage to the head.
might not of though, but get it checked out by a tech
#3
It will make it sound worse, but it shouldn't cause damage if it is only run like that for a short time.
#4
it's always safer to run out to more ohms so the head doesnt build up and fry.
but any mismatch can be a problem.

seems like it didnt this time, so smack his hand and tell him not to do that again.
Jenneh

Quote by TNfootballfan62
Jenny needs to sow her wild oats with random Gibsons and Taylors she picks up in bars before she settles down with a PRS.


Set up Questions? ...Q & A Thread

Recognised by the Official EG/GG&A/GB&C WTLT Lists 2011
#6
Quote by jj1565
it's always safer to run out to more ohms so the head doesnt build up and fry.
but any mismatch can be a problem.


A mismatch will be equally damaging either way, up or down, there is no 'better' mismatch.
#8
I guess if you're (or your friend is) about to sell it, it might be good to make sure it's not broken/damaged.
#9
Quote by mr_hankey
A mismatch will be equally damaging either way, up or down, there is no 'better' mismatch.



it's safer to run out to a higher ohm'd cab than the head is putting out. and is probably why the head didnt fry.

would i do it, probably not. but if u ask any tech they will tell u the same thing.

trust me if i saw u had posted i wouldnt have bothered. i dont like getting quoted and explaining my posts.
Jenneh

Quote by TNfootballfan62
Jenny needs to sow her wild oats with random Gibsons and Taylors she picks up in bars before she settles down with a PRS.


Set up Questions? ...Q & A Thread

Recognised by the Official EG/GG&A/GB&C WTLT Lists 2011
#10
Quote by mr_hankey
A mismatch will be equally damaging either way, up or down, there is no 'better' mismatch.

actually, a mismatch with greater load impedance than the amp is expecting pushes less current, with the transformer running cooler. It's considered a "safe mismatch". There is still a power drop in either direction, but the transformer pushes more current if it sees a lower impedance than it was expecting, which can damage the transformer or tubes.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
amp clips
amp vids
#12
Quote by Erock503
actually, a mismatch with greater load impedance than the amp is expecting pushes less current, with the transformer running cooler. It's considered a "safe mismatch". There is still a power drop in either direction, but the transformer pushes more current if it sees a lower impedance than it was expecting, which can damage the transformer or tubes.


"running into too high-impedance a load causes high 'flyback' voltages which can arc through the insulation... dead transformer.

Generally, keep within half or double either way and you're OK. Just be careful with anything older and potentially more fragile (and less replaceable). Matching is always safest, and IMO sounds the best too."

http://www.thegearpage.net/board/showthread.php?s=&threadid=77567

"What happens when I mismatch output impedances in my tube amp?

* Lower impedance will _generally_ stress the power tubes gradually more and more as the volume goes up.

* Higher impedance will _generally_ stress the power tubes less as the volume goes up until the powertubes cut off at high volume levels. This will create voltage spikes on the plates of the power tubes called flyback. "

http://aga.rru.com/FAQs/technical.html#imp-1




Ok, I was wrong, it's better to run an amp into a lower impedance speaker/cabinet.
#13
^im telling u, it depends on the amp. i know for a fact i can run my blues junior at 4 ohms. even tho it's rated at 8.

i can also run it at 16 ohms. if u know ur amp there are plenty of "safer" ways to mismatch.

it doesnt always fry. you need to know ur specific amp.
Jenneh

Quote by TNfootballfan62
Jenny needs to sow her wild oats with random Gibsons and Taylors she picks up in bars before she settles down with a PRS.


Set up Questions? ...Q & A Thread

Recognised by the Official EG/GG&A/GB&C WTLT Lists 2011
#14
Quote by jj1565
^im telling u, it depends on the amp. i know for a fact i can run my blues junior at 4 ohms. even tho it's rated at 8.

i can also run it at 16 ohms. if u know ur amp there are plenty of "safer" ways to mismatch.

it doesnt always fry. you need to know ur specific amp.


It depends on the quality of the OT. More than 2x either way will almost certainly damage it.
#15
idealy you want them to match. You never want the amp to be at more ohms than the cabinet. It's alright though for the amp to be a step down from the cabinet (for example; amp @ 4 ohms, cab @ 8ohms... or amp @ 8 ohms and cab @ 16 ohms).
#16
Quote by Gutch220
idealy you want them to match. You never want the amp to be at more ohms than the cabinet. It's alright though for the amp to be a step down from the cabinet (for example; amp @ 4 ohms, cab @ 8ohms... or amp @ 8 ohms and cab @ 16 ohms).


Please read my post. ^^^
#17
Yeah, I agree more than one step should be avoided in either direction. I have heard of the flyback problem with severe mismatches, although I don't know much about it. I always recommend matching when possible also, even one step mismatches can be shaky if it's a weak tranny from what I've read. However, like JJ said, it depends on the amp. My Mesa manual has 4ohm to 8ohm, or 8ohm to 16ohm listed as "safe mismatches" for my Mark IV. The tone changes with the mismatch as a result of the tranny running cooler according to the manual, which is caused by less current being drawn. It explicitly says not to run a lower impedance cab, as do most amp manuals. Those links looked like he knows what he's talking about, but he didn't mention anything about the effect on the tranny with a low impedance mismatch, where the cab is drawing more current than the tranny was designed for so it's running hot.
"The fool doth think he is wise, but the wiseman knows himself to be a fool." - W.S.
amp clips
amp vids
#18
Quote by mr_hankey
Please read my post. ^^^


i'm too lazy, i just read the first post usually unless it's the "pictures of hot chicks" thread


but you mentioned it's alright to go up or down one step and it's alright. That's not true. If your amp is at more ohms than the cabinet you WILL do damage to your amp
#19
Quote by Gutch220
i'm too lazy, i just read the first post usually unless it's the "pictures of hot chicks" thread


but you mentioned it's alright to go up or down one step and it's alright. That's not true. If your amp is at more ohms than the cabinet you WILL do damage to your amp


Dude, just read my post. The one with the two links in it.
#20
Quote by mr_hankey


Generally, keep within half or double either way and you're OK.



.....
#21
Quote by Gutch220
.....


Quote by mr_hankey
"running into too high-impedance a load causes high 'flyback' voltages which can arc through the insulation... dead transformer.

Generally, keep within half or double either way and you're OK. Just be careful with anything older and potentially more fragile (and less replaceable). Matching is always safest, and IMO sounds the best too."

http://www.thegearpage.net/board/showthread.php?s=&threadid=77567

"What happens when I mismatch output impedances in my tube amp?

* Lower impedance will _generally_ stress the power tubes gradually more and more as the volume goes up.

* Higher impedance will _generally_ stress the power tubes less as the volume goes up until the powertubes cut off at high volume levels. This will create voltage spikes on the plates of the power tubes called flyback. "

http://aga.rru.com/FAQs/technical.html#imp-1




Ok, I was wrong, it's better to run an amp into a lower impedance speaker/cabinet.



.......
#22
Look at the sentence starting with "Generally"

If your amp is double the ohms as the cab, you will f*ck your amp up