I have installed 3 different SPC controls in my, I guess you can say, "home made" Lone Star Strat. I took my MIM strat and loaded it with the Seymour Duncan Pearly Gates Plus bridge, and Texas Specials in the neck/middle positions. After lots of research into the differences between the Clapton mid boost and the SPC, I want to go with the SPC for these reasons. It's smaller, less gain boost, supposed to do the same thing ie mid boost, and if you lose your battery you can still play. Dont get me wrong, I LOVE Clapton's tone and what his guitars do.

Now..... after I installed this SPC unit, I got this unGodly whistle that would change in pitch as I rotated tone or volume controls. It did this with 3 different units. EMG couoldnt even come up with an explanation. I've been wiring guitars and what not for over 20 years. I know what microphonic feedback is, and these pickups are not microphonic. They're pretty quite. Its not feedback of any kind. Just a whistle that changes pitch when the tone control is turned. It stops when the volume control is rolled back to around 5, or when the SPC is rolled off completely. I rewired the entire guitar with all new components. same thing. Installed the SPC in my Les Paul.... same thing. Installed in my old Kramer.... same thing. The only thing I can think of is that my Les Paul and Kramer both have Seymour Duncan pickups installed. According to EMG, this unit should work with any type, name brand, passive or active pickups. I'm at my wits end and have no clue what to do now. Bought the unit from Sam Ash, they wont take it back since its been installed and say that EMG dont want it back if it defective. EMG has said otherwise and is going to help get me my money back. EMG has amazing customer support and tech support and have bent over backward to help me. I just want to find out why this SPC control is doing what its doing. Does ANYONE have any clue as to why this may be doing this cause if I can keep this unit I would like to.

Try a different guitar cable, maybe it´s your amp (do you use a tube amp?).

Cheers,
Robin

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yes its a tube amp. the cable is fine. its something to do with the SPC itsself because if the cable was bad, or the amp, it would make some kind of noise all the time. Its not 60 cycle hum. The amp is set across the room on low volume, so theres no way its feedback.

Some tube amps can oscillate by adding a gain stage (the SPC). The 1st tube in your amp is getting all kind of signals (guitar cable acts like an antenna) and amplifies them.
Maybe you can check by using another amplifier, just to be sure it´s not the amp oscillating but the SPC.

Cheers,
Robin

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Ok based on my fitting of Clapton midboost circuits, it sounds like you've too much resistance in the circuit. The Clapton boost howls wildly if you try using a 250k volume pot with it, you're ok up to about 100k. Especialy between 3-8.
Without looking I suspect the EMG thingy is mounted on one of the pots. If so it could be that the pot has gone bad. It could be due to a mismatch between the pickups and some part of the circuit. It's pretty hard to tell without getting hands on.

Put a multimeter round the circuit and see how much resistance your pots are giving. Then measure the pickups in circuit, not at the pickup. Thats negative of the multimeter to the ground at the jack socket, positive to the hot side of the pickups as you go through the switch one by one.

These things are designed to work with the manufacturers pickups. Thats why EMG are not interested in giving you a answer. If you were using their pickups you'd probably be fine. Unless of course it is a bad pot.

Can a cold solder increase resistance? That may be worth looking into. I honsetly don't know the answer.

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Adding the SPC permanently changes your circuit from high impedance to low impedance where the OEM volume pot value then becomes way too high. Consequently, the highest resistance you'd be able to get away with on the volume pot is like 50K or you'll get that aforesaid shrieking and howling and the guitar overall would sound like fecal matter.

Note too that as the battery fades, so does the integrity of your signal.

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You dig?

well, EMG told me that I dont have to change out the pots with 25k or 50 k, they told me no. said they are designed to work with any active or passive pickups, and will work with any value pot. I rewired the whole thing a half dozen times with new pots, same result. Actually used 3 different SPC units all with the same results. Asked EMG if the amp would have anything to do with it, they asked me what kind of amp and everything, told me it couldnt be the amp. Its a brand new amp, set across the room at low volume. Dont think it would make that howl at such a low volume, but ya never know. Not gonna trade a killer amp just for a lil active mid boost. LOL But to answer your question, yes I tried 3 amps. My sons lil Marshall MG 10, and my BIG Marshall half stack, wired it in 3 different guitars and it did the same thing no matter what I played it through. Thats why I'm at witts end with it. My guess is that with regular pickups, not noiseless, it dont like them. Then again, the Pearly Gates Plus is noiseless seeing how its a humbucker and that was the pickup that made the worst noise. Bypassed all the pots, pickup switch, wired each pickup straight to the unit itsself, you name it. same result no matter what I did. Its just plumb crazy. Hopefully the clapton kit will work. Gonna get some Seympour Duncan stk s4 pickups for the neck and middle, and do some comparisons before I send it back.

EMG are wrong, you need low impedance pots.

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No no and no

What he said!

Note that the Clapton circuit also comes with a 50K volume pot for the same reason we've been telling you all along.

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You dig?

well what could I do? EMG tells me what theyre own product is supposed to work with. you'd think that their main tech would know. I was told that the unit was installed with passive pickups with regular 250k pots like any other strat at their shop and it supposedly worked. I wasnt there so I dont know. Its not like they were trying to get me to keep something that wasnt working. They bent over backward to help. So I sent it back. I do still have the one EMG sent me to try. So, I get a 50K volume pot, wire it in and see if it works? sounds like a plan.

I do appreciate the input folks. Just odd that regular folks know more about stuff than the master techs at the manufacturer does. kinda funny dontcha think?

Well, they want to sell.

Robin

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And there you have it!

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You dig?

if they wanted to sell it that bad they'd know to tell someone they need to change out a pot. if thats all it takes, they'd have had a sell, but, I sent it back and am getting my money back. they didnt want to sell it too bad or they'd have told me what I needed to know. lol

By putting in the SPC control you've sent the guitar active. It is no longer passive, whether you use active pickups or passive, that is the same.
It's the same if you put the Clapton circuit in a guitar with Vintage Noiseless or Lace Golds. Or if you put the circuit in a guitar with a dummy coil ala the Powerhouse strat. Either of those guitars is passive until the circuit goes in. Once in, the guitar is active. It has a seperate powersource, other than the string motion over the pickup causing a minimal amount of current.
You've done exactly the same thing but instead of using a Clapton circuit, you've used a EMG circuit. The components on the circuit don't matter. It doesn't matter that the circuits are completely different. The nature of the powersource does, thats really what determines whether a circuit is passive or active.

Now EMG despite being thoroughly nice helpful people (I've dealt with em and found em exactly as you say). Want you to give up on the other brand passive pickups you're using and decide that the only way to do the job is by using their pickups.
They would be fools not act from that standpoint, they are not fools.

So you need a 25 or 50k pot, like they tell you to use with their pickups when you buy them.
I guarantee, buy a set of their pickups and see the recommendation for a 25k volume pot on the wiring instructions for the pickups. Costing you about £160.
Or take our advice spend £3.50 on a 25/50k pot and see it work out ok.

When you find out we're right, we'll gladly accept gifts for saving you money.

Seriously for £3 it's worth it, just to chance that we are right. Best of luck with it all anyhow. Whatever you decide.

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No no and no

+1 on Martian and the Ninjas posts (here and in general!)

My very first post on this forum was about what would happen if I used a 250k pot with the Clapton mid-boost instead of the recommended 50k. Martian replied to me as he has to you here.

I took his advice and I have a stonking guitar for it, BUT I just had to see what all the fuss is about the 50k pot. So I wired up my other parts-caster with a boost kit and a 250 vol pot.... and it was pretty much unusable. I got the same howling you described.

I'd be very surprised if a 50k pot wouldn't solve all your issues.

Andy

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Pending Greatness