Quick amp & cabinet ohms matching question / fingers itching to play it!

[albatross]

Is it safe to run a 4 ohm only valve junior amp into 16 ohm cab?
or should i put my hand in my pocket an purchase a new output transformer with a 16 ohm tap?

The valve junior does have a 8 ohm tap hidden.

Would the higher ohms of the cab make this OK, but if it(the Cab) were lower than 4ohms it would be bad?

[Hanglow]

Doesn't the VJ also have a 16 ohm output? at least the head does.

What version do you have? If its V1 or V2 then get a new OT anyway, along with a few more mods it makes a world of difference. Hammond make some good ones for $30/£35 depending where you are

[albatross]

Hi yeah I'm in the UK, i was thinking of getting a Hammond 125ESE, but as far as i can see only 1 place in the UK sells them, thats www.bluebellaudio.com

They are £30 before tax i think. Im a little skint for now after buying the cab, so im hoping its ok to run it like it is until i replace the output transformer.

The combo version is identical to the head version but the output transformer has one 4ohm output and a 8 ohm tap hidden, also the board has the 2 spare spaces on the pcb for mounting the additional jacks.

I did just read this article and it appears to be ok for now, you just lose clean output power. ---> http://www.premierguitar.com/education/200603_educationcenter_askbudda.asp

I just dont really want to open a brandnew expensive 4x12 to rewire it.

[Hanglow]

I used tube town http://www.tube-town.net/ttstore/index.php/cat/c18_Hammond-SE.html for all my parts. They gave good service and are reasonably cheap.

I am no expert but I have also read that you can get away with running speakers of a higher impedance. It's only if you run speakers of a lower impedance that you run into trouble.

[birt]

I am no expert but I have also read that you can get away with running speakers of a higher impedance. It's only if you run speakers of a lower impedance that you run into trouble.

wrong.

a tube amp likes to see a matching load or a LOWER load. in a lot of amps you can get away with higher because the transformers are big enough but i wouldn't recommend it. open circuit is a very big load, this means you OT gets all the power. in most cases you can actually hear the guitar signal vibrating the OT. very bad.

an SS amp likes to see a matching load or a BIGGER load. with a lower load the transistor/chip tries to give more power and overheats. if the load is bigger the chip/transistor gives less power. open circuit means no power. no problem.

[Hanglow]

 

see I said I was no expert. Although that premier guitar article says different

I did know the thing about having no speaker attached is very bad for a tube amp. Didn't realise that was not the case for SS amps

[R.G.]

There is a Tube Amp FAQ at GEO that covers most tube amp issues.

Tube amps don't like open outputs, SS amps don't like shorted outputs.

It is rare that a tube amp will give trouble of any kind with a 2:1 mismatch up or down. 4:1 down I would not hesitate at all. 4:1 up  (i.e. 4ohms to a 16 cab) I would try and see if I liked. I do not think any problem will come from it, especially in a low power amp.