shar-vell Dan
Well-known member
My apoligies.
Is it safe to use an 8 Ohm cab with a 16 Ohm output on amp?
conanthewarrior
Member
No need to apologise mate, I do realise I may come across strangely and that is my issue, you wasn't to know.
I mainly joined here for help with the amp but also people to talk too, which may be one reason I have replied so much with different ideas, just so I can speak to people in the responses.
rushcentrale
Well-known member
I bought one of these for this exact situation. https://www.tedweber.com/z-matcher/
It'll match any mismatched cab to any head. It's not cheap, but it might be useful here and there for years to come.
It'll match any mismatched cab to any head. It's not cheap, but it might be useful here and there for years to come.
conanthewarrior
Member
That is so cool, thank you for sharing it!
Only one question, it says in the description it can match 2.6 and 5.3 Ohms, do some amplifiers output at this resistance then? As that is something new to me
rushcentrale
Well-known member
I think that's to cover amps that are in between and may be mislabeling what their true ohms output is. I've never seen it personally but I think some vintage Orange amps are like that.
conanthewarrior
Member
Oh I see, so its not actually a standard but sometimes for example a manufacturer could have labeled a 5.3 Ohm amp as 8 Ohms, or even potentially a 2.6 Ohm output as 4? I never knew some old Orange amps did this, thanks for the info!
thegame
Well-known member
You've come to the right place then. Welcome
conanthewarrior
Member
Thank you- I take it that was a genuine welcome and also a joke that other members are also a bit strange too haha?
thegame
Well-known member
Yes and yes
rushcentrale
Well-known member
No I've never seen anything like that. I'm saying an amp might be labeled as 4 ohms but it's really putting out 4.25 or something slightly off like that.
conanthewarrior
Member
Oh I see, I gathered where the Z matcher had those impedance choices it was likely what had happened, my mistake.
SQUAREHEAD
Well-known member
Just reading through this, maybe you have already tried this, but I had an amplifier that I bought once and only the 8ohm speaker Jack had been used for years and years.
(The 16 ohm speaker output was never used).
The 16 ohm speaker jack did not work, so I just took the speaker cable and vigourously
rammed it in and out quite a few times, and voilà, the 16ohm output came alive, and works perfect for years.
Obviously, contact cleaner works best, but if you’re in a pinch, the ‘ram it’ method has worked for me more than a few times in the past.
(The 16 ohm speaker output was never used).
The 16 ohm speaker jack did not work, so I just took the speaker cable and vigourously
rammed it in and out quite a few times, and voilà, the 16ohm output came alive, and works perfect for years.
Obviously, contact cleaner works best, but if you’re in a pinch, the ‘ram it’ method has worked for me more than a few times in the past.
shar-vell Dan
Well-known member
Lets see i stuck a bobbypin in an outlet once at 5 years old. The arc blew the bobbypin out my hand. I thought it was so cool i did it again getting bit by 120v. Don't recommend that.
I accidentally grounded out 460v 3 phase working electrical maintenance. 40 years ago. Don't recommend that either.
I once burned out the 8 ohm tap of a 50 watt Marshall using the wrong wattage speaker 40 yrs ago. Sounded fantastic right before it died. Don't do that either.
And also 40 years ago i had used an instrument cable for a speaker cable. Also not recommended.
Had many other brushes with greatness to numerous to mention.
SQUAREHEAD
Well-known member
Lets see i stuck a bobbypin in an outlet once at 5 years old. The arc blew the bobbypin out my hand. I thought it was so cool i did it again getting bit by 120v. Don't recommend that.
I accidentally grounded out 460v 3 phase working electrical maintenance. 40 years ago. Don't recommend that either.
I once burned out the 8 ohm tap of a 50 watt Marshall using the wrong wattage speaker 40 yrs ago. Sounded fantastic right before it died. Don't do that either.
And also 40 years ago i had used an instrument cable for a speaker cable. Also not recommended.
Had many other brushes with greatness to numerous to mention.
Ok,
So, this explains your condition, Dan
JK
thegame
Well-known member
I don't know what to think about Weber speaker's opinion on this:
"Here are the straight facts on impedance mismatches, and hopefully it will explain why there are contradictory reports:
ON A TUBE AMP
It is okay to run a LOWER impedance cabinet or speaker than the amp’s output impedance. Usually a mismatch of 2:1 is okay. (i.e. amp at 16 ohms, cab at 8 ohms.) It is dangerous to run a HIGHER impedance cabinet or speaker, as there is a potential for flyback currents that could either cause a catastrophic failure, or the stress over time can cause long-term failure eventually. (although with a tube amp, it’s really best that you keep the impedance matched.) Amp power is not affected by mismatching.
ON A SOLID STATE AMP
It is okay to run a HIGHER impedance cabinet or speaker than the amp’s output impedance. (i.e. amp at 4 ohms, cab at 8 ohms.) It is dangerous to run a LOWER impedance cabinet or speaker. Amp power output is reduced, the higher the impedance.
"Here are the straight facts on impedance mismatches, and hopefully it will explain why there are contradictory reports:
ON A TUBE AMP
It is okay to run a LOWER impedance cabinet or speaker than the amp’s output impedance. Usually a mismatch of 2:1 is okay. (i.e. amp at 16 ohms, cab at 8 ohms.) It is dangerous to run a HIGHER impedance cabinet or speaker, as there is a potential for flyback currents that could either cause a catastrophic failure, or the stress over time can cause long-term failure eventually. (although with a tube amp, it’s really best that you keep the impedance matched.) Amp power is not affected by mismatching.
ON A SOLID STATE AMP
It is okay to run a HIGHER impedance cabinet or speaker than the amp’s output impedance. (i.e. amp at 4 ohms, cab at 8 ohms.) It is dangerous to run a LOWER impedance cabinet or speaker. Amp power output is reduced, the higher the impedance.
Bottom line: match it."
conanthewarrior
Member
I didn't think of the ram it technique, I am going to try that literally right now.
I can think of a few times in my life a different "ram it" method has worked though....
SQUAREHEAD
Well-known member
Yes, for me it was just the fact that the one speaker output Jack was never used and probably clogged with dirt and dust, etc.…
When I shoved the speaker cable in and out quite a few times it finally made contact where it needed to.
shar-vell Dan
Well-known member
Simon Dorn
Well-known member
Check this out:
https://hughes-and-kettner.com/news/ohm-cooking/
https://hughes-and-kettner.com/news/ohm-cooking/
conanthewarrior
Member
Yeah I imagine not being used for years had let all sorts build up inside the jack connection, I'm glad it worked for you though.Yes, for me it was just the fact that the one speaker output Jack was never used and probably clogged with dirt and dust, etc.…
When I shoved the speaker cable in and out quite a few times it finally made contact where it needed to.
Unfortunately the ram it method didn't work for me, and the amp is also now doing the same thing on one of the 16 Ohm outputs, so it didn't fix it like I thought.
I will still get some more contact cleaner though to give everything a good clean, then decide wether to take it to an amp tech or save the money for a new amp head.
Thank you! I never imagined using a 4 Ohm cab with a 16 Ohm output to be safe where it is such a difference, but reading the article it seems to follow what they call the 25% rule and is OK, at least to Hughes and Kettner. I didn't realise it was the opposite, using a higher impedance cab with a lower impedance output that could potentially damage things by increasing voltage in the tubes for it to work.
The only thing I would be a bit worried about is that using a lower impedance cab increases the current, could this potentially stress the output transformer or would it be the transformer trying to put out more volts that is the issue?
At least they also say they have never even been able to put a tube amp out of its comfort zone, let alone leave one broken! I guess it would be a lot worse to run an amp with no load as this is when things can break.