A question/thought about ATT

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A question/thought about ATT

Postby captaincowhouse » 19:39, 19 February 2011

I'm not really knowledgable when it comes to electronics (although that doesn't stop me from trying), and I had a thought about mod-ing the ATT switch.

At the moment, it's quite a big volume difference when you turn it on/off. I was wondering if by changing the resistor (?), you could lessen that gap. I don't like volume boosting with the volume control for a solo, because when it comes to the end of the solo, I've got to think about changing patch, getting the volume quickly and accurately back to the rhythm level, and also sometimes using both hands to play with.

My plan is to see if by altering the electrics in the ATT, and moving the switch to somewhere more accessible (such as by the D-beam), I can have an easier access to volume change, and can then concentrate more on the performance.

Anyone got any ideas?
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Re: A question/thought about ATT

Postby Karmafied » 21:23, 19 February 2011

Why to modify the ATT switch when you can just go to your ax-synth editor and modify your lead/solo sounds to have a boost on volume this way when you do program changes you will get the proper volumes at any time.
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Re: A question/thought about ATT

Postby captaincowhouse » 03:08, 22 February 2011

That does make sense, but a lot of the time, I want to boost for a piano solo or organ solo, and I don't want to have the same patch saved twice, one for rhythm playing and one for solo. And generally, even with a solo sound that already had a boost on, I still have a volume boost aswell.
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Re: A question/thought about ATT

Postby Arjan » 12:16, 22 February 2011

captaincowhouse wrote:That does make sense, but a lot of the time, I want to boost for a piano solo or organ solo, and I don't want to have the same patch saved twice, one for rhythm playing and one for solo. And generally, even with a solo sound that already had a boost on, I still have a volume boost aswell.


I second the motion for programming your patches for their respective roles, but it you want to be able to do sponanteous solos or stuff like that I think you might be better off with some kind of pedal rather than butchering your Ax:

http://www.muzique.com/boost.htm

Of course these are all probably mono and meant for guitar but in principle there's no reason why you couldn't use a pedal like that if all it does is provide a clean signal boost.

You could also buy some cheap stomp box and modify it internally to do signal boosting or attenuation.

http://www.diystompboxes.com/wpress/?page_id=2
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Re: A question/thought about ATT

Postby captaincowhouse » 14:30, 22 February 2011

I did think about that and do some research, but the problem with that solution is, I use a wireless pack and like to go roaming, and want to be able to switch volume wherever I am.

I thought about getting them and putting them into the ax-synth, but they're all powered by 9v, and i'm already charging 10 AAs a week!

I looked into passive circuits but then realised that it would surely be easier to mod the attenuator circuit already in the keyboard.
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Re: A question/thought about ATT

Postby Arjan » 16:01, 22 February 2011

captaincowhouse wrote:I looked into passive circuits but then realised that it would surely be easier to mod the attenuator circuit already in the keyboard.


It could indeed be as simple as changing a resistor. Anyone happen to have the service manual for the AX Synth?

Actually, if you're going to move the ATT knob to the neck, you might as well leave it where it is and create an additional 'solo boost' switch on the neck in series with the ATT knob. Or perhaps you can hi-jack, say, the 'Hold' button so you don't have to butcher the body of your Ax. That will take some additional circuitry though.
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Re: A question/thought about ATT

Postby captaincowhouse » 16:35, 22 February 2011

That's a genius idea! Might take out the portamento switch, cos' I never use it.

I think from having opened up the synth before, it's a two resistor jobby, nothing fancy. Just need to find out which resistors they are, and which one I need to put in for less of a volume gap.
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Re: A question/thought about ATT

Postby Arjan » 17:10, 22 February 2011

captaincowhouse wrote:That's a genius idea! Might take out the portamento switch, cos' I never use it.


Keep in mind that these are buttons, not switches: they have a single make/break contact which only creates a connection while pressed (momentary switch). The LED is controlled by the CPU in the Ax, it is not tied directly to the 'state' of the button.

That's why I said you'll need some extra circuitry to make this work because you'll want to convert this momentary switch 'signal' to a toggle switch which can route your audio signals (stereo!) through one of two different routes. Unless you don't mind having to hold the button while playing your solo part but then you can't really use the ribbon and modulation bar.

Mmmm... Why does my post look like it was written completely in bold typeface?
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Re: A question/thought about ATT

Postby captaincowhouse » 13:06, 2 April 2011

Ok, so I had to open my synth up the other day for some minor repairs, and I took a pic of the att set-up.:

Image

Can anyone shed some light on what resistor I might need in order to have less of a boost?

Another thing I was thinking about, is having a box that I can velcro onto the synth, which i'd plug a jack lead into (coming out of the synth) have an Attenuator circut in there with a switch, and then a jack output for my wirless unit or whatever.

Is that do-able?
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Re: A question/thought about ATT

Postby captaincowhouse » 13:07, 2 April 2011

Wow, that pic didn't really work! Here's a link:

http://i40.photobucket.com/albums/e215/captaincowhouse/IMAG0157.jpg
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Re: A question/thought about ATT

Postby Arjan » 14:50, 4 April 2011

I cannot determine how the attenuation works based on just this picture. I might be able to take a look at the circuitry when I open my AX Synth to install those straplocks but some schematics would be nice. In principle you could order a Service Manual from Roland.
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Re: A question/thought about ATT

Postby Arjan » 14:15, 24 May 2011

Hey captaincowhouse,

Don't know if you're still interested in doing this mod but I know a bit more about the attenuation circuit now. Basically all it does is connect a 330 ohm resistor between the line output and ground. The actual attenuation is then a function of the ratio between that 330 ohm resistor and the actual output resistance of the output circuit proper. If the switch is in the 'open' position it passes the original voltage, if it is in the 'closed' position the 330 ohm resistor together with the output circuitry preceeding it becomes a voltage divider.

Bottom line: you need to replace those resistors with a larger value to reduce the amount of attenuation achieved by the ATT switch.

Since the output resistance of the preceeding circuit is unknown and since Roland does not specify the ammount of attenuation achieved by the ATT switch it's not really possible to determine how much attenuation will result from a given change in resistance for R1 and R2. Apart from that I don't think this is something you'd want to calculate anyway.

A simple way to do this mod is desolder one side of resistors R1 and R2 and connect a stereo POT between them and the other terminal on the PCB (by putting the pot in series with the resistor you can be sure that you are not going to short-circuit the actual output circuit). You'll have to switch on the power after this and play around with the pot setting and toggle the ATT switch until you get the desired difference in volume. Then remove the pot, measure it's actual resistance, add 330 and you will know what size resistor to use in place of the originals.

Of course you could also measure the actual attenuation achieved by the ATT switch if you output a single constant 440Hz sine wave from the AX and measure the output on a dB meter with and without the ATT switch engaged. This should allow you to calculate the output impedance of the output circuit. Next use the fader on your mixing desk to determine how much attenuation you want to achieve, put all those numbers in a math blender and calculate the resistor values to achieve the desired amount of attenuation :-) In theory this should work but I think the pot approach is a lot more straightforward.

In principle you can also implement your own separate attenation circuit parallel to the existing circuit. You could even put a stereo pot (in series with a 330 ohm resistor for L and R) in the neck along with a switch so you are not limited to one fixed amount of attenuation.

Have fun,
Arjan
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