Re: Speaker impedance question


"Jim" <jim@xxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:5oednWWzvv7NBqTXnZ2dnUVZ_u-dnZ2d@xxxxxxxxxxxxxxxxxxxxx
Pollwan wrote:
I hope that this is the right newsgroup so I'll ask away.

I have a Fender Blues Junior that I am going to run an extension speaker
cab off. This will be another speaker running as well as the existing
speaker. Both are 8 ohm. I have been trying to find out if its possible
to run this cab with the existing transformer that's in the Blues Junior.
The tech says that as it is effectively a 4 ohm load with the two of them
then its not good to run these from the existing transformer that is I
imagine geared up for 8 ohm. Yet I bought a mod kit from Bill Machrone
(http://home.comcast.net/~machrone/bluesjunior.htm) and he maintains that
the existing transformer should be fine. To further complicate things
(for me at least) I bought some replacement transformers from Mercury
Magnetics but when I did I wasn't aware of this issue and I got an
upgrade output transformer for the Blues Junior that is 8 ohm without a
tap for 4 ohm. They have backed up the tech by saying that an 8 ohm
transformer should not run a 4 ohm load and that what is needed is a
transformer with the 4 ohm tap.

So is there a definitive answer to this as there seems to be differing
points of view.

Thanks if anyone replies.

Didn't you get a definitive answer when Mercury Magnetics told you not to
run their transformer at 4 ohms?

If you do it anyway, it's for sure that it won't sound the same, you'll
eat up the power tubes faster, and it'll produce less power. Whether
it'll cause other problems, I can't say. I wouldn't do it.

Take your pick. Combo speaker OR just the extension.

Or buy two 16 ohm speakers. Or a new OPT.

To be fair to Mercury, they just said that their recommendation was for a
4/8 ohm tapped TF for this setup. I have ordered this one and they will
take the other (straight 8 ohm TF) back and credit me. Its unused and still
packaged so its no drama. I'm not so sure about BillM. Makes you wonder.

With regard to techs. I would never go into this and do it myself. Guitars
yes, amps never (except for the odd fuse or pilot light!!). Good techs are
never expensive. The purchase of the incorrect TF in the first place was my
fault. Mercury have been great to deal with. I'm not sure if the purchase
of a new output and power transformer will make all that much difference its
something I've never done before but have read about. I bought the Blues
Jnr to have a bit of muck around although it will end being a million dollar
amp by the time I'm finished (considering I just bought a road case for it
yesterday as well!). My pride and joy amp is my 1969 Deluxe Reverb. I
don't think my tech would even let me modify that one!

Thanks heaps guys, this is great info. The other side is that a friend was
also going to go down the same TF path as me but baulked at the price. He
is doing the extension cab like me and I have copied these replies to him so
he will inevitably have to buy a new output TF I'd say.




.

Relevant Pages

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