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Mr Anderton, please advise


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Hello Craig,

 

Back in the early 80's, I bought your book 'Guitar Electronics for Musicians'. I built the Ring Modulator. I still have it. I have one issue with it. There is a drone/null freq that is in the output of it. It can be adjusted to match the 'key' of the song however (a new device ????) I checked it over a bunch of times but never could figure out what was incorrect. Was the schematic OK? I have since lost the book and schematic. Please advise. Thanks!

 

PS I miss your column in GP!

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Have you played with the little nulling trimpot?

 

there are also a couple of sensitive values in there

 

 

carrier bleedthrough is not uncommon in ringmods...one thing to consider as well is that a noisy modulator (hiss from the "guitar side", etc) will translate into what sounds like carrier bleedthrough (the modultor noise is "feeding" the ringmod, so it has something besides silence to act upon)..some designs actually use a noise gate to prevent just that

 

 

I figured I'd throw that out b/c while I certainly thing the question itself is valid - I fear that we could slide down into asking Mr Anderton for tech support...tech support on designs a quarter of a century old...tech support for units he didn't build

and I'd hate to see us igo too far down that road

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Hey, glad to help whenever I can.

 

Yes, there is a nulling trimpot that is very sensitive. You can't null past about -55dB but that should be enough unless the RM is being followed by a real high gain stage. If the null point does't fall toward the middle of the trim pot, you may need to adjust the resistance values on either side of it...in other words, if the nulling gets better and better but then the pot rotation won't go any further, you'll need to lower or raise the total resistance so that the null point falls within the trimpot's range.

 

The power supply voltage is crucial, by the way, to create good nulling. Use the power supply voltage mentioned in the book for best results.

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Hello,

 

Thanks for the reply. The null pot is mounted on the outside and yes, it does vary the 'strength' of the freq, however, I cannot adjust it out completely. I will try to vari the resistance on either side of the pot. I have it running off battery, what type of DCV did the book say to use? (i lost the book due to lending it out) Thanks again.

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hey Richard, hope I didn't come off wrong in that last post ( I realize the tone of that post might have come off a little wrong and my concerns weren't pointed at you. more just the danger of a social trend..which hasn't appeared, so maybe I should just shut up ;) )

 

 

we good?

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Originally posted by Richard Guy

Hello,


Thanks for the reply. The null pot is mounted on the outside and yes, it does vary the 'strength' of the freq, however, I cannot adjust it out completely. I will try to vari the resistance on either side of the pot. I have it running off battery, what type of DCV did the book say to use? (i lost the book due to lending it out) Thanks again.

 

 

The book says that it has a power consumption of +or - 11mA, and his power supply unit listed in the book list it as having + or - 200 mA. I would say if you have you box setup with the proper jack, you could use a Boss PSA-120. You can 200 mA of of it.

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I thought most of those projects required bipolar supply, but that's from the crusty old mem

 

One concern I'd have is that many supplies aren't actually regulated ('m not familiar with the Poss supply, so maybe it's not an issue with that), so your actual voltage might float around a bit, causing instability in trimming stuff out (how robust this design is to that...I'm not sure)

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Originally posted by MorePaul

I thought most of those projects required bipolar supply, but that's from the crusty old mem


One concern I'd have is that many supplies aren't actually regulated ('m not familiar with the Poss supply, so maybe it's not an issue with that), so your actual voltage might float around a bit, causing instability in trimming stuff out (how robust this design is to that...I'm not sure)

 

 

I didn't think about the bipolar deal.

 

The Boss PSA is regulated. The ASA isn't.

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Yeah, batteries are a problem. I suggest using a regulated power supply if you don't want to keep adjusting the trimpot -- it's the voltage that matters, not the current drain. I believe the power supply was set to supply slightly under 9V...the book hasn't been unpacked yet :( And yes, it's a bipolar supply.

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