AD 15/12 - Master Volume Mod?

Orange Amps Technical Q&A's

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grgurich
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Post by grgurich » Mon Mar 06, 2006 8:51 pm

Anyone ever attempt to turn their AD 15/12 into a non-master volume amp? Is it even possible, it being of PCB manufacture?

If I’m trying to get the most vintage sound possible out of this thing, I know that I can dime the master, then use GAIN as a volume knob, but I was wondering how close this really came to the whole non-master volume thing.

I anticipate someone saying: “Hey, that ain’t what this thing is. If that’s what you want, then go get a Princeton reissue.â€
John

irish_admiral
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Post by irish_admiral » Mon Mar 06, 2006 9:38 pm

If you're looking for that sound, might want to try one of the older OR series. Otherwise it's like getting an automatic car and wondering how to turn it into a manual one.
Joe

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acorkos
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Post by acorkos » Mon Mar 06, 2006 9:45 pm

if you know where the master connects on the pcb, it would probably be simple to bypass the master volume pot and associated capacitors with a pair of alligator-clip-ended leads....leave 'em in place while you try it out....take 'em off to hear the difference. if you like it better with the master bypassed, just solder in a couple of wires and you're done. you know about discharging caps, right?

acorkos
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Post by acorkos » Mon Mar 06, 2006 9:46 pm

or a more hip trick is to replace the MV pot with a pull-switch pot of the same value....leave it pushed engages the MV, pulling it up defeats the master....slick

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Post by bclaire » Mon Mar 06, 2006 11:41 pm

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by acorkos</i>
<br /> you know about discharging caps, right?
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

This is my new favorite post....

grgurich
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Post by grgurich » Tue Mar 07, 2006 12:58 am

That's funny.

Two part answer. Yes, I know that discharging caps needs to be done. No, I don't know how to do it. But I would certainly find out before attempting such an adventure.

The big question though. Is there any appreciable difference to me just doing what I said up top, i.e., maxing the master and using the gain as a volume knob? You know what I'm saying? Can you hear any difference between the two?

That push-pull pot thing is an interesting idea. How would that work? Would my MV pull up and down?
John

irish_admiral
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Post by irish_admiral » Tue Mar 07, 2006 9:32 pm

Bit less circuitry in the way... also the way the amp responds to just the one dial might be different!

Discharging caps - generally don't use your amp for a few days to let residual charge drain off. However, some can still remain. You should be able to discharge any remaining charge by getting some well insulated pliers and touching it to the Cap's +ve a bunch of times. Alternately, you can get some insulated wire with croc clips on either end, attach one to the cap +ve, and touch the other to the metal chassis several times. If there's charge left, you'll get a nice bang and maybe a flash too if you're lucky...
Joe

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Andy H.
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Post by Andy H. » Wed Mar 08, 2006 9:02 am

From:The safety info document instuctions at:
http://www.ax84.com
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">DISCHARGING CAPACITORS - the filter capacitors in an amp will retain a charge for quite some time after the amp is shut off and unplugged. It is a good idea to make sure your amp is safe to work on. My personal preference is to take a wire with an INSULATED alligator clip on each end. Clip one end to a good ground point, and the other to one of the plate leads for the first stage preamp tube. Another method would be to put a 100k, 5 or more watt resistor in line of these 2 clips and put one end first to ground, then the other to the filter caps themselves. NEVER SHORT THEM OUT DIRECTLY!<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">It really is best to drain them more gently by making yourself a discharge probe with a resistor.

The exact value of the resistor isn't critical, but a 100Kohm 5watt resistor will allow full discharge in under a second. This will avoid damage to the cap. And to whatever you use to discharge it. (A big cap contains enough energy that the spark could micro-weld a screwdriver to the contact point...) [:0]

For more background see also:
http://www.thegearpage.net/board/showthread.php?t=74283

<b>"Be careful out there, and do it to them before they do it to you!"</b> ;)

Andy.
Only dimly aware of existence, a dimly existing awareness...

You get a wonderful view from the point of no return.

Ade Emsley
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Post by Ade Emsley » Wed Mar 08, 2006 10:15 am

The AD15 has a dual gang 100k pot instead of the two resistors in a vee found in a non master volume amp.
Simply put, this means that when the master is dimed on an AD15, it is a non master volume amp!:D

irish_admiral
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Post by irish_admiral » Wed Mar 08, 2006 10:43 am

Well well... there you have it!

I'm going to have to make a discharge or two myself in the next week or so, as i've got that new OT to put in.
Joe

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grgurich
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Post by grgurich » Wed Mar 08, 2006 6:34 pm

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Ade Emsley</i>
<br />The AD15 has a dual gang 100k pot instead of the two resistors in a vee found in a non master volume amp.
Simply put, this means that when the master is dimed on an AD15, it is a non master volume amp!:D

<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Wow. The word of the designer. That pretty much settles it for me. No mod necessary. Great. What an amp. It's the best of both worlds.

Ade, thanks for chiming in, and for making such a great amp. I probably wouldn't have done anything anyway. Hate to mess with a man's handiwork.

Thanks to everyone else as well. And it's probably just as well that I didn't get into discharging caps, what with not having a will, who would this brilliant little amp have gone to had things gone tragically wrong?
John

Amoun
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Post by Amoun » Wed Mar 08, 2006 9:50 pm

bit late to butt in on this post seems done and dusted

someone told me once it is a good idea to clip some 100k resistors across the filter caps just to be sure, but remember to take them off before you fire it up.

i have always understood that putting a master on full and using the other control as volume makes it a non mv amp, the mv should serve only to get the cranked sound at lower volume, although with some manufacurers the mv also has its own effect on the tone.

irish_admiral
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Post by irish_admiral » Thu Mar 09, 2006 12:45 pm

Amoun,

That's right about the caps... you can vary the value of resistor to discharge faster or slower.

Ade - would an EQ-defeat mod, such as you have on the custom shop amps be possible on an AD30 also, or does turning the EQ onto full essentially have the same effect?
Joe

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Ade Emsley
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Post by Ade Emsley » Fri Mar 10, 2006 10:02 am

No, maxing the EQ wont do it! However, EQ defeat is possible on an AD30!
Probably the best way is to change the mid pot from 25k LIN to 250k LOG. The mid will then work as normal from 0 to 4 but 4 will be mid on max on a standard amp. Anything over 4 will start lifting the whole EQ out of the circuit with 10 being totally bypassed giving you quite a bit more gain.
The other way is to wire a 220k resistor in between where the standard 25k LIN pot goes to ground. You then short this resistor back to ground via a footswitch. This does the same thing but is footswitchable.
You will need to use the same ground point and coax cable going to an extra jack. The footswitch cable should also be shelded!8)

irish_admiral
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Post by irish_admiral » Fri Mar 10, 2006 12:32 pm

Might be an idea!
Joe

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