Orange Amps Forum

Ok. Had my custom shop ad50 for about a year now with my ppc212 ob and my les paul. I have just changed back to the 30 watt setting which I think brought the amp more alive. From what I have read it seems the 30 watt setting is cathode biase (bias automatically) and the 50 watt setting is fixed bias. I have a feeling that the 50 watt setting is biased a bit cold and soon I will take it to a tech who can bias it hotter for more bark and bite.

I changed the orange ecc83 preamp tube in v1 with an old stock rca 5781 with a gain factor of 70 %. This made the amp more alive and less muddy. Even more than two old stock phillips ecc83 (supposedly similar to mullards). It breaks up later and nicer. I kept the original orange ecc83 in v2. Better lows, mids and highs all together now. I have tried to play with the volume knob but must admit this does not seem to be for me. Basically I am not that fond of this amps distortion when you use the gain knob. Therefor I have it very very low (a bit more than 8 o´clock) just so it has a little tiny bit of dirt when I play clean.
The volume I have around 2 o´clock, presence at 12, treble at 1 and bass at 1.30. When I step on my t-rex dr. swamp distortion it really rocks. Anyone out there who have any experiences with this amp ?

You are probably right. My AD50 came quite cold. I think I recall it was set to about 50%. This is very common, not only by Orange, to set the bias cold to make the tube last very long.
The cathode bias is quite the opposite though. The old Philips data sheet states 130 ohm for cathode bias. That was OK for those old tubes considering they were meant never to distort. Pushing todays tubes like we do today with such bias isn't a good idea IMO. I've lowered mine to 250 ohms for better tube life span.

I agree that an ECC83 is a little too much for V1. I actually run a ECC81 and think it works great.

I have experienced with my amp quite a bit. Been trying a lot of different values here and there for minor tweaks. All these mods are very easy to do as the amp is handwired. If you want to know more, PM me.

A single 150 ohm cathode resistor shared by both EL34s seems to be a very low value and would run the tubes very hot.

Orphin - I can't find the cathode resistor value you are referring to in the Philips datasheet I have found.
However, the Mullard EL34 datasheet here : http://frank.pocnet.net/sheets/129/e/EL34.pdf" onclick="window.open(this.href);return false; suggests when using 2 EL34s cathode bias with a plate voltage of 450V to use a 465 Ohm cathode resistor per valve (it is on page 4).

The Rocker runs two EL34's in Cathode bias with parallel 270 ohm and 330ohm resistors which gives 148.5ohms. The plate voltage is around 450v.

Here's the data sheet I was refering to:
http://www.hifitubes.nl/weblog/wp-conte ... s-el34.pdf" onclick="window.open(this.href);return false;
Page 4

I have an AD50 and love it. I too prefer the 30w setting but I tend to run the gain a lot higher; at least 12 o'clock but more usually 2 o'clock. I really like this as a thick base tone that I then boost with an overdrive or booster. I run two greenbacks and I love the sound.

I'm sorry but I can't comment at all on the biasing or how hot it runs. A bit beyond my limited technical knowledge. I have bought some replacement 12AX7s but to be honest I haven't felt the need to replace the existing ones, or even take the time to just swap them out and hear the differences. I suppose that's testament to me just being really happy with it at the moment as it is.

The only other thing I will add though, as I read someone else saying over on the community discussion, these amps really come into their own when the master is turned up and the amp is really working.

Incidently, a quick question; if the 30w setting is self-biasing, does that mean I can change the power amp valves like I can in my AD15 or did in my AD30, without getting it re-biased by a tech?

Ade

Hi Ade and thanks for your reply. From what I understand from different posts you dó not need to check bias when replacing power AMP tubes when in 30 watt mode. What are your settings treble, bas and presence ? Dó you play humbucker Pick ups

Ade wrote:I have an AD50 and love it. I too prefer the 30w setting but I tend to run the gain a lot higher; at least 12 o'clock but more usually 2 o'clock. I really like this as a thick base tone that I then boost with an overdrive or booster. I run two greenbacks and I love the sound.

I'm sorry but I can't comment at all on the biasing or how hot it runs. A bit beyond my limited technical knowledge. I have bought some replacement 12AX7s but to be honest I haven't felt the need to replace the existing ones, or even take the time to just swap them out and hear the differences. I suppose that's testament to me just being really happy with it at the moment as it is.

The only other thing I will add though, as I read someone else saying over on the community discussion, these amps really come into their own when the master is turned up and the amp is really working.

Incidently, a quick question; if the 30w setting is self-biasing, does that mean I can change the power amp valves like I can in my AD15 or did in my AD30, without getting it re-biased by a tech?

Ade

You can, but just remember your 50 watt setting will or may need biasing.

Jondog wrote:You can, but just remember your 50 watt setting will or may need biasing.

Thanks Jondog. So as long as I continue to use it on the class A/30w setting I can just whack another pair of EL34s in?

Out of interest, what would be the ramifications if I did change them without re-biasing and then flicked over to the 50w setting? Will it damage the amp? The valves? I'm not really familiar with the actual purpose of biasing. Thanks.

Ade

Ade wrote: Out of interest, what would be the ramifications if I did change them without re-biasing and then flicked over to the 50w setting? Will it damage the amp? The valves? I'm not really familiar with the actual purpose of biasing. Thanks.

Ade

Biasing is the act of setting the idle current through the power tubes. Each tube is a little different, with some being very different from others. We install tubes that are matched. Matching tubes is nothing more than some dude going through a bunch of tubes and picking out the ones that are electrically similar. Although the new set is matched, and the old set is matched...set A and set B aren't necessarily electrically similar to one another.

We set the bias with any new set of tubes to ensure they are running within safe parameters. You don't want them drawing too much current, or they could overheat and fail. This will hopefully blow a fuse within the amp, but it will often take out some resistors with it and can arc over a tube socket (making the socket bad). It can even lead to a situation where one tube fails and continuing to operate the amp with the remaining tube damages the output transformer.

These are extreme cases. But they are reasons why it's prudent to bias the amp when installing new tubes. Another good reason would be the tone. Tubes sound best when they're running properly.

-Nick

So basically, to summarize: Always(!) use matched power tubes. A fresh pair can be used without bias adjustment when run in cathode bias mode (labeled 30-watt). With a new pair of tubes in fixed bias mode (labeled 50-watt), bias adjustment is highly recommended.


And Karsten. Don't get hung up on magic sounding EQ settings. That's not what the EQ is all about. Even if you would find a sweatspot where the amp sounds absolutely the best, it won't sound the same in a different venue. An EQ setting that someone recommends might sound crap, even to this person, when playing your amp where you are located.
EQ is short for equalizer. Its function was originally intended for bass loss due to the proximity effect when micing actors from a distance when making movies. Sometimes, at some venues you'll hear that the room for instance eats up all bass or dampens the highs etc.. Now you use the EQ to "equalize" for these acoustic (d)effects.
However, there is no rule that doesn't allow you to use the EQ for dialing a specific tone. Experiment freely, especially with this amp as pretty much any settings will sound good on the AD50. But trust your ears, not someone elses words.

Thanks fiveightandten and Orphin for the info regarding biasing and the 30/50w settings.

The only thing I'd add about EQ is firstly, what sounds "good" or where a sweet spot is may differ from guitar to guitar and from cab to cab. What settings I use with my P90 SG and greenback cab don't necessarily work with a Les Paul standard and a V30 quad. Secondly, the best advice I got here when I first got my AD50 was to use the EQ controls to limit as much as boost frequencies and to appreciate that they're quite interactive with each other. Oh and thirdly, I've found with the AD50 at least, the EQ is more responsive the lower the gain and the higher the master (even though I like quite a high gain setting on this amp in general).

Ade

kars0747 wrote:Hi Ade and thanks for your reply. From what I understand from different posts you dó not need to check bias when replacing power AMP tubes when in 30 watt mode. What are your settings treble, bas and presence ? Dó you play humbucker Pick ups

kars0747, sorry mate, I completely missed your question. I mainly play P90s as mentioned, though have been playing a bit with a humbucker equipped Flying V of late. For what it's worth, with my P90 SG and the greenback loaded Hiwatt cab, these are my usual setting settings. They work for me...



The V is clearly in that pic, but I usually tweek the EQ a bit for humbuckers or different cabs.

But as Orphin said, trust your ears rather than my words (or pic ).

Ade

kars0747 wrote:I have a feeling that the 50 watt setting is biased a bit cold and soon I will take it to a tech who can bias it hotter for more bark and bite.

Common mis-conception IMO. Hotter bias (usually) sounds warmer, more fuzzy, less dynamic than running cooler. (Or is that what you meant?)

I generally prefer a cooler end bias on most amps (talking fixed bias here, not the cathode bias setting on your amp!). As long as you don't go too far that is and start getting crossover distortion. Gets you more defined, more dynamic and plain livelier sounds which is the way I prefer to go.

Also a cooler bias doesn't limit the power output in the way many people seem to think these days. In fact it will tend to increase clean headroom.

All depends what you really want sound wise...



Andy.

FOod for thought. I have allways thought a colder bias made an AMP Sounded more dead and dull