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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  VOX V847 Wah AC jack mod 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: VOX V847 Wah AC jack mod  (Read 2155 times)
Johnny Lemonhead
Posts: 31


VOX V847 Wah AC jack mod
« on: June 05, 2010, 06:41:31 AM »

Hi,

After adding an AC jack to the v847, I encountered the dreaded motorboat hum. After sifting through several posts regarding the subject, I couldn't find a definite conclusion on how to go about solving this.
Is the power supply the only culprit or is there something else that can be added to the circuit in order to filter the noise?

I'm thinking about trying a Visual Sound 1Spot -  does anyone have any experience with it as far as hum goes?

Thanks.
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paulyy
Posts: 282



Re: VOX V847 Wah AC jack mod
« Reply #1 on: June 05, 2010, 07:06:39 AM »

Iv notice with some cheap power supplies  that this could happen. I own a 1spot and they are worth the money and are made to filter out any unwanted noise. You can try that but I'm not sure about the ac jack.
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petemoore
Posts: 18793


As Yet Unrated


Re: VOX V847 Wah AC jack mod
« Reply #2 on: June 05, 2010, 07:52:49 AM »

  DC Jack.
  No need to run AC into a wah case.
  Try a voltage regulator for the wah supply, subtract 2 or so volts from what is your supply voltage, which is needed for the regulator to work, reducing supply by 2v.
  Usually this is not a problem since 9v powersupplies often put out 15 or so volts without a substantial load on them.
  I bought another 7812, it will give me exactly 12.00 VDC, ripple free = noise free.
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Convention creates following, following creates convention.
Paul Marossy
Posts: 12527


Just Another Guitarhead


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Re: VOX V847 Wah AC jack mod
« Reply #3 on: June 05, 2010, 08:46:18 PM »

Try adding a 220uF cap across the power supply. And use a regulated power supply. Cheapo wall warts are typically very poorly filtered and can cause a lot of 120Hz buzzing when you use them.
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_/\_/\_PJM_/\_/\_

www.diyguitarist.com
www.soundcloud.com/Paul-Marossy

"Tone is in the fingers."
zombiwoof
Posts: 1096

Alan T.


Re: VOX V847 Wah AC jack mod
« Reply #4 on: June 06, 2010, 04:22:40 PM »

I'm always amazed when I see people using cheap Radio-Shack adaptors or ones that came with their phone answering system or such (not saying the OP is doing this).  A good regulated 9 volt adaptor that doesn't cost a lot is the Danelectro "Zero-Hum" adaptor, it only costs about $8-9 and works great with all of the pedals I have.

Al
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Paul Marossy
Posts: 12527


Just Another Guitarhead


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Re: VOX V847 Wah AC jack mod
« Reply #5 on: June 06, 2010, 07:07:09 PM »

I'm always amazed when I see people using cheap Radio-Shack adaptors or ones that came with their phone answering system or such (not saying the OP is doing this).  

Yeah, that is probably the problem 90% of the time.
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_/\_/\_PJM_/\_/\_

www.diyguitarist.com
www.soundcloud.com/Paul-Marossy

"Tone is in the fingers."
Johnny Lemonhead
Posts: 31


Re: VOX V847 Wah AC jack mod
« Reply #6 on: June 06, 2010, 08:48:27 PM »

Thanks to everyone for helping out. I really appreciate you taking the time to answer.

I'll try to get a regulated PS and a 220uf cap and post the results.
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Johnny Lemonhead
Posts: 31


Re: VOX V847 Wah AC jack mod
« Reply #7 on: June 06, 2010, 11:10:14 PM »

Well, I stumbled across a 2200uf cap and gave it a go. Although the hum might have been reduced, the wah is still unusable when powered from the wall.
I just connected the negative and positive leads of the pot to their corresponding leads on the DC jack. Is that correct or should I wire it differently?

Next  - a regulated PS.
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Paul Marossy
Posts: 12527


Just Another Guitarhead


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Re: VOX V847 Wah AC jack mod
« Reply #8 on: June 07, 2010, 09:28:11 AM »

Well, I stumbled across a 2200uf cap and gave it a go. Although the hum might have been reduced, the wah is still unusable when powered from the wall.
I just connected the negative and positive leads of the pot to their corresponding leads on the DC jack. Is that correct or should I wire it differently?

Next  - a regulated PS.

Yes, that is correct way to connect capacitor. Regulated power supply might fix problem.

I hadn't thought of this before now: A word of caution, if you put a wall wart right next to a wah pedal that has an inductor in it, the inductor will pick up EMI from the wall wart just like a single coil pickup would. Especially so with a high gain distortion pedal. That will make it massively worse. The cure for that is to put the wall wart as far away from the wah pedal as possible. I had this happen to me once and it was driving me nuts until I figured out that the wall wart being too close to the wah pedal was the problem.
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_/\_/\_PJM_/\_/\_

www.diyguitarist.com
www.soundcloud.com/Paul-Marossy

"Tone is in the fingers."
zombiwoof
Posts: 1096

Alan T.


Re: VOX V847 Wah AC jack mod
« Reply #9 on: June 07, 2010, 02:31:00 PM »

I think a regulated adaptor is required with a wah, try it and see.  That Danelectro adaptor I mentioned is a great low cost one.  I got one because Bob Sweet mentioned it as an acceptable one for the MojoVibe, and I've used it with many other pedals with no problems.  No need to pay $20 for an adaptor, they are all made in China these days and the Dano is a good one.  And you can get them just about anywhere.

Al
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Johnny Lemonhead
Posts: 31


Re: VOX V847 Wah AC jack mod
« Reply #10 on: June 07, 2010, 04:52:43 PM »

Thanks for the recommendation, zombiwoof. The problem is I don't live in the states and we use 220V. I'll just have to find something here or order the 1spot (it supports 120V-240V).
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Johnny Lemonhead
Posts: 31


Re: VOX V847 Wah AC jack mod
« Reply #11 on: June 10, 2010, 11:02:19 AM »

I finally found a 1Amp regulated PS made by a local company and it's a whole different ball game. I had no idea it made that much of a difference because all of my other pedals are pretty quiet. It solved the wah problem completely and with the tonebender it removed the hum, but introduced a high pitched shriek I have yet to research on the forum. That's for another thread.

Thanks for the help, everyone.
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zombiwoof
Posts: 1096

Alan T.


Re: VOX V847 Wah AC jack mod
« Reply #12 on: June 10, 2010, 11:12:50 AM »

I finally found a 1Amp regulated PS made by a local company and it's a whole different ball game. I had no idea it made that much of a difference because all of my other pedals are pretty quiet. It solved the wah problem completely and with the tonebender it removed the hum, but introduced a high pitched shriek I have yet to research on the forum. That's for another thread.

Thanks for the help, everyone.

I thought the regulated adaptor would help with the wah, but I have no idea what to say about the "shriek" with the Tonebender.  Is it a commercial Tonebender, or one you built?.  Is the polarity correct?

Al
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Johnny Lemonhead
Posts: 31


Re: VOX V847 Wah AC jack mod
« Reply #13 on: June 10, 2010, 12:25:10 PM »

Is it a commercial Tonebender, or one you built?.  Is the polarity correct?

Al

It's homemade and not quite done. I still need to add in a circuit to make it work with a shared negative supply. This is getting off-topic, so I'll continue to post here:

http://www.diystompboxes.com/smfforum/index.php?topic=84942.0

Thanks!
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Paul Marossy
Posts: 12527


Just Another Guitarhead


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Re: VOX V847 Wah AC jack mod
« Reply #14 on: June 10, 2010, 03:16:24 PM »

I finally found a 1Amp regulated PS made by a local company and it's a whole different ball game. I had no idea it made that much of a difference because all of my other pedals are pretty quiet. It solved the wah problem completely and with the tonebender it removed the hum, but introduced a high pitched shriek I have yet to research on the forum. That's for another thread.

Thanks for the help, everyone.

Cool, that's good news.  icon_cool
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www.diyguitarist.com
www.soundcloud.com/Paul-Marossy

"Tone is in the fingers."
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