OR120 Help

Post by **bclaire** » Fri Aug 08, 2008 10:49 pm

By the way, where are you located?

buxtonsarethieves · Post by **buxtonsarethieves** » Fri Aug 08, 2008 11:35 pm

I am in Westmont, New Jersey, right outside of Philadelphia.

Simon Wicks · Post by **Simon Wicks** » Sat Aug 09, 2008 8:08 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by bclaire
 I've heard plenty of horror stories about amp techs that think an Orange is just a colorful Marshall and start replacing stuff, screwing up the amp in the process.

I'd get it back from him- find a REAL tech- and have them go through it and fix what has been messed with. If the current tech replaced any parts, tell him you want the old parts. Then tell him you want the money back if the new guy finds it was hacked...
<hr height="1" noshade id="quote"></blockquote id="quote">
I've heard tales like that too. The Orange amp is unlike any guitar amp save the Matamps it was derived from. Good luck with that. If nessacary download a schematic and give it to a tech so they can see the amp's architecture.

Gladmarr · Post by **Gladmarr** » Sun Aug 10, 2008 4:54 pm

One would think any amp tech worth a damn would have already done that! If that tech didn't consult a schematic, I'd say a lynching is in order!

Simon Wicks · Post by **Simon Wicks** » Sun Aug 10, 2008 11:01 pm

Some just assume they know it all and go right ahead. There was a guy in the UK who knackered my OR120 like that....

Andy H. · Post by **Andy H.** » Mon Aug 11, 2008 2:30 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Simon Wicks
 Some just assume they know it all and go right ahead. There was a guy in the UK who knackered my OR120 like that....
<hr height="1" noshade id="quote"></blockquote id="quote">Yeah, I've also heard plenty of tales of 'great techs' who just assumed Oranges were basically 'just about pretty much like Marshalls' and got things way wrong. Because they ain't just funny coloured Marshalls...

Anyone unfamiliar with the amp and trying to get it to work right needs to grab a schematic and not just guess component values and voltges etc. Otherwise chances are they'll guess wrong! [:0]

For starters even biasing up an OR is a pretty different story from standard Marshalls. And they'll need great power valves if you want them to survive long when it is properly biased up. Bung in most modern cheap to standard EL34 types and the amp will spit the fried remains back at you pretty quickly. Good quality sets of valves can last well though and are basically needed, not just optional.

Ade Emsley, current Orange designer:
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Ade Emsley
(http://forum.orangeamps.com/viewtopic.php?t=7296)

 OR120`s need to be biased on the hot side to sound right because of the type of phase inverter used in those amps. The crossover notch will not clear up untill the output tubes are taken to around 70%. You need a really great set of tubes to make the amp reliable!
Another tube that works well for bass in an OR120 is a 6L6. Those tubes will bias up in that amp just from turning the bias pot (with no resistor change) and they are fine at 500+ plate and 500+ screen. You will get the most out of them if you change the screen resistors to 470 ohm but this must be changed back to 1000 ohm if you put EL34`s back into the amp!<hr height="1" noshade id="quote"></blockquote id="quote">
Normally speaking in most amps 70% idling plate dissipation is about the upper end limit of where you'd set biasing. (Usually between 50 - 70, and often preferably at the cooler end for reliability and valve life unless it actually sounds significantly better hotter!) But with an OR120 70% is about the lower limit, so these are very hot running amps! This is the sort of stuff a tech needs to know to set these amps up right.

It is worth getting it right though. When maintained right and running 'A1' these are truly monster amps - just awesome!

And actually generally very reliable too. Just ask DAVESOUNDS about the sort of workload some of his amps have handled...

Andy.

evergud · Post by **evergud** » Mon Aug 11, 2008 11:02 pm

Very interesting info about the biasing, Andy H. Thank you. However, I do not have a bias pot in my '72 OR 120, so the question is: What valves would work for me? Or is it really a good idea to modify the amp to have a bias pot?

Gladmarr · Post by **Gladmarr** » Tue Aug 12, 2008 5:49 am

If you really want to be able to run that amp optimally and safely, you should really have a bias pot added in there....

Simon Wicks · Post by **Simon Wicks** » Tue Aug 12, 2008 6:40 pm

Get yourself some RFT EL34s. They're still cheap enough and will handle the high plate voltages found in those amps.

Gladmarr · Post by **Gladmarr** » Tue Aug 12, 2008 10:53 pm

Simon, do you get a commission off every pair of NOS RFTs sold? You must really love those tubes!

Andy H. · Post by **Andy H.** » Wed Aug 13, 2008 10:49 am

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Gladmarr
 Simon, do you get a commission off every pair of NOS RFTs sold? You must really love those tubes!<hr height="1" noshade id="quote"></blockquote id="quote">Who cares. Means more NOS Teslas for the rest of us... [:p]

Andy.

Simon Wicks · Post by **Simon Wicks** » Wed Aug 13, 2008 6:56 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Gladmarr
 Simon, do you get a commission off every pair of NOS RFTs sold? You must really love those tubes!

<hr height="1" noshade id="quote"></blockquote id="quote">
No mate but they're the cheapest NOS glass kicking about at the moment

If you can get hold of Teslas then thise are the ones to have (or Mullard xf2). Trouble is the Teslas are getting more and more pricey. People have cottoned onto them and they are going up in price.

buxtonsarethieves · Post by **buxtonsarethieves** » Fri Aug 15, 2008 1:40 am

Ok so I got the amp back yesterday, works great. My only concern is that the amp sounds really harsh and brittle, when I play up on any string higher than the D, it's like an icepick to the ear. Not very musical at all. Would this have anything to do with: a. the Fender Stratocaster I'm using or b. the Marshall 1960a cab I'm using?

Simon Wicks · Post by **Simon Wicks** » Fri Aug 15, 2008 9:40 pm

What speakers are in the cab? Also, what tubes do you have in there?

chrismathewsjr · Post by **chrismathewsjr** » Fri Aug 15, 2008 10:34 pm

I think the stock Marshall 1960A cabs come stock with G12-T75s don't they?

Never tried them myself, but they get pretty poor reviews when used with Marshall's.

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