Orange Amps Forum

I've picked up this great sounding OR80, but I'm quite interested in finding out how old this thing could be??
I can see in this forum that the serial number not always is enough to date it.

I've uploaded some pics.-I know the know the big knobs is not original.

Mads - Denmark

Wow! Nice amp! Welcome to the forum!

Around 72-74- check it out here....
http://users.telenet.be/orangefg/" onclick="window.open(this.href);return false;

Awesome amp!! Welcome to the forum!

Hi hetoft2. Yes, welcome to the forum!

Beautiful old amp!

I see it has the output impedances labelled as 4/8/16 ohms. You might want to read through these threads:
viewtopic.php?t=2945" onclick="window.open(this.href);return false;
viewtopic.php?t=21823" onclick="window.open(this.href);return false;

Basically Orange used identical output transformers with the OR120 and OR80 amps. Because the OR80 only uses 2 output valves though that changes the effective output impedances. With those labelled like yours unless they have been converted the chances are the impedances are actually wrong and you need to bump things down one setting for correct impedance matching. Meaning running a 16 ohm cab with the amp set to 8 ohms.

Just so you know!


Andy.

Hi guys!
What a helpfull forum. Thanks!!!
From what I can see at the '72 pics they look a lot like mine, but the logo (upper right corner) is with the black background and not white as it is on bclaire's link.

Thanks for info about the impedance! Nice to know. I will not kill my cab by switching to 8ohm connectet to a 16 ohm cab?

I have to ask Andy... You're talking about 2 output valves, but mine has got 4 valves from what I can see.

Anyway, thanks for helping me out!

Mads

hetoft2 wrote:Hi guys!
What a helpfull forum. Thanks!!!
From what I can see at the '72 pics they look a lot like mine, but the logo (upper right corner) is with the black background and not white as it is on bclaire's link.

Thanks for info about the impedance! Nice to know. I will not kill my cab by switching to 8ohm connectet to a 16 ohm cab?

I have to ask Andy... You're talking about 2 output valves, but mine has got 4 valves from what I can see.

Anyway, thanks for helping me out!

Mads

Glad to help Mads.

If it has four of the big EL34 power valves than someone has converted it to an OR120. In which case there should be no impedance issues. It should also have two (very occasionally three) of the smaller preamp valves in addition to that.

The two amps (80 and 120) were identical in every respect apart from the number of output valves, so wiring in a couple of extra power valve sockets is an easy conversion.

If it only has two than no, you'd not harm the cab doing what I suggested. The only thing which could be harmed is the amp, by running an impedance mismatch. Unfortunately many OR80s, having been mislabelled, were unknowingly run into the wrong impedances and did have problems with blown output transformers. Though that was much commoner with the '90s reissues as they used different transformers which weren't so able to handle mismatching as the original '70s ones. The mislabelling of (some) OR80s - original AND reissue - was a really basic stupid fault from Orange...

In fact you can easily run any OR120 as an OR80 by simply removing two power valves (one from each side leaving one of the left pair, one of the right) and dropping the output impedance as I suggested. Just have to remember to reset the impedance selector to the correct position if running 4 valves again.


Andy.

Cool thanks...
I've been told that you'd need to adjust your amp if you remove any of the valves. Adjustment will make sure that the valves won't be overloaded by to much voltage. - so the valves will get equal "quantity" of voltage (or however you say)??

I'm new to valves so thanks again.

Mads

hetoft2 wrote:Cool thanks...
I've been told that you'd need to adjust your amp if you remove any of the valves. Adjustment will make sure that the valves won't be overloaded by to much voltage. - so the valves will get equal "quantity" of voltage (or however you say)??

I'm new to valves so thanks again.

Mads

If they are talking about the same thing that isn't great advice. (Though to be fair they may be talking about something slightly different.)

It has NOTHING to do with overloading the valves, everything to do with not damaging the output transformer which is both the 'heart' of a valve amp and (along with the power transformer) its most expensive component. The easiest way to damage the OT is by impedance mismatching too far, especially in the wrong direction.

You won't have to change the bias with these amps if that is what they were maybe talking about. That might be a factor with some. Also it isn't safe to pull valves like that with all amps, only ones which have so called 'fixed' biasing. Never try it with 'cathode biased' amps, things like Vox AC30s, Orange AD30s, Matchless DC30s, all those sort of beasts.



Andy.