OT Impedance and speaker load question

[markmalin]

Ok..I'm sure this has been asked a bizzilian times, so feel free to just point me to a thread. 

Can someone explain to me, if I have an output trans with an 4 Ohm secondary, what are the effects if I hook up to an 8 Ohm speaker?  I'm wondering electronically how it effects the circuit, and whether it negatively effects the amp/output tubes, etc.  I understand that the reflected impedence to the tubes will double (right?).  Is that hard on the amp?

...for what it's worth, I'm asking this because they want to use isolation cabinets where I typically gig and they are all 8 Ohms.  I have a 4 Ohm tranny in my favorite amp :(...

[duke of earl]

The speaker load can have a higher impedance than the OT. The tone may be a little darker but by all means try it and see if you like the tone. Tube lilfe is extended with this combination I do believe.

[jojokeo]

Can someone explain to me, if I have an output trans with an 4 Ohm secondary, what are the effects if I hook up to an 8 Ohm speaker? I understand that the reflected impedence to the tubes will double (right?).  Is that hard on the amp?

1) Yes, it doubles the pri Z the relected impedance of tubes, i.e. - w/ a 5k:4 ohm tranny it becomes 10k:8 ohm (w/ the 8 ohm speaker)
2) No, it's not hard on the amp in the slightest

...for what it's worth, I'm asking this because they want to use isolation cabinets where I typically gig and they are all 8 Ohms.  I have a 4 Ohm tranny in my favorite amp :(...

You may not even notice any percieved difference in sound or output power - when going 1 step above or below the recommended speaker output impedance.

[markmalin]

Thanks, guys!

Mark.

[Ritchie200]

OK, for the sake of discussion - lets say he has a combo amp and it has a 4 ohm speaker.  He then also plugs into the 8 ohm iso cabinet from his ext speaker jack.  Both are being fed at the same time.  What now?

Jim

[jeff]

He has a 2.6 ohm load.

[phsyconoodler]

Quote:"no, it's not hard on the amp in the slightest"

Not true.A mismatched load,up or down can introduce flyback voltages that can kill output tubes and/or output transformers.Most OT's an handle the mis-match but some are poorly built and cannot.It usually is just fine unless you dime the amp all the time or use an attenuator at really low volumes.
  a mismatch will find the weakest spot and exploit it.It happens most with amps with big bottle tubes where lots of current is present.Like a Marshall 100 watt/50 watt or similar 100 watt amp.I find EL34's don't like to be cranked with any attenuators for very long.
  If you are not in the habit of cranking your amp to 10 or use something like a Ho attenuator to get bedroom volumes from you amp then you likely just fine.
   

[Willabe]

or use something like a Ho attenuator to get bedroom volumes

What is a "Ho" attenuator?


     Thanks,    Brad     

[Tone Junkie]

Its when you set the "Ho" to a lower volume, oh i better not finish I might get the boot (LOL)

 

[Willabe]

OK, I missed that.  Never mind.


       Brad             I think I need a new light bulb.

[Tone Junkie]

Sorry Brad I should have finished anyway not many lady,s on here to offend and yes school boy humer (its when you set the ho to a lower volume so she wont wake the neighbors) the thought somehow seemed funny yesterday, today not so much <G> Bill

[Willabe]

No need to apologize Bill.

I thought it was some company/brand name I had never heard of. Went right over my head.

I still think I might need a new light bulb.       


           Brad       
           

[Tone Junkie]

Brad he probably was talking about a product of some kind I was just adding bad humer to the situation. i can blame my father for his childish sence of humer (LOL)

[Willabe]

Bill,

I would'nt worry about it.

Everybody knows your a nice guy.   


        Brad                  ( sorry I like this little guy)