Quick question... I haven't had any problems with my internally modded Technics 1200 turntables and my TTM-57, but I had a question.

I did the mod per online instruction, TT ground cable to one of the RCA's signal grounds.

So each RCA cable has a signal wire and signal ground. I tied the turntables chassis ground into the rca's signal ground, which grounds at the mixer's rca input.

Does this have any negative effect on the mixer? As I said, it works perfectly, but I don't want to do any harm to my mixer.

Thanks.

Shit mate, that aint a quick question.

I dont fully understand what you've done here, but any ground problems will make themselves noticeable straight away. If not, should be fine.

you have a link for this procedure you have done??

Sorry for any confusion. Check out this link.
www.gigacrate.com

You'll notice that each RCA wire has 2 connections to the board, making a total of 4 connections.
The red wire has a signal wire and signal ground, same with the white. I basically tied into one of those grounds.

the mixer works fine with the internal ground..

i did my tables and it works with no problem... a club i dj in has one table grounded internally and the other one is still external.. mixer still works fine...

I started doing this back in 1993 and from what I remember about this mod is that, as long as the device you have the turntable connected to has a universal/centralized ground, then you should be fine. I discovered this by accident one night by trying to hook up my 1200 directly to my Mackie mixer and I couldn't figure out how to ground it properly. I accidently let the ground wire touch the ring on the 1/4" input jack and noticed that the buzzing stopped. I ended up slipping the ground wire underneath the insulation on the rca connector while connected to the mixer and it worked. I didn't know anything about preamps (equalization) back then. I called Mackie and asked them about it and the tech I spoke to on the phone told me back then that although he didn't advise doing that (and explained RIAA phono preamps), the reason that it worked in their mixer is because the mixer had a common ground (all the grounds throughout the mixer are connected). He also told me that it should work in any other device that shares a common ground (I haven't seen a mixer yet that doesn't).

This doesn't mean that you won't EVER have a problem, but most gear that you'll be connecting your turntable to will have a common ground.

I was so confident when I did mine, I cut my ground wires off my tables and never looked back. Besides, you can always redo them if need be. You really don't even need to do them both, but if you ever have your cables go bad on you (common on frequently mobile turntables) then that's when you'll be glad that both of them were grounded.

i grounded one channel, but also left the ground wire on my tables just in case i had a problem.. i read a while ago that this didn't work on 1 specific mixer but i haven't come across it.. i dont remember what mixer it was either...

Yeah I remember hearing of rare products back in the day. I doubt that mixer is even in use anymore. The only thing that kept me skeptical at first was, why didn't the manufacturer ground them internally from the factory? Then when I thought about all of the different preamps and home receivers that were used over the years, it made sense because some of the more exotic stuff had separate grounding points. I have a Carver preamp that has a ground lift installed on it but I've never connected my 1200 directly to it to see if it matters. Maybe I'll do it today just to see.

I'll let you know...

dELfONiK

in my area the majority of djs use TTs and most of them at this point, especially in the clubs, have been internally grounded. also, most places i play have their own 57. so far in the 2 years i have been playing on them i have come across no issue with internally grounded TTs or the 57...

i haven't pulled a 57 apart to see what the grounds are attached tho.
simply grounding thru an rca to the mixer shouldn't do anything.
personally i have NEVER seen an issue with this in any the decks/mixers i have played on.

you will proabably do more damage thru wear and tear than in the long run than anything an internal ground will possibly do.

Internally grounding, grounding the ground-cable to the audio ground is not a good idea I was told...!

nik39 I think it depends on the circumstances. The whole reason that this ground mod became so popular is that countless DJ's were either tired of always having to fool with the ground cable, or they were tired of trying to connect ones that were worn out/damaged from constant use. Then of course there are those times that you use another DJ's setup only to find that either that terminal at the end is damaged and just barely holding on, then it slips off during a set and you end up with a sound effect that you didn't want. :) When this mod became know to the DJ community, a lot of people weighed out the pros and cons of doing such a permanent fix to their tables and I know for me it was worth the risk. Each situation is different but, I always use my own tables and mixer so I know what works and what doesn't. At first I very nervous about doing it because I figured that there had to be a reason why this wasn't done by the designers or a the factory when it was built. What really kind of gave me peace of mind is when I got some insight a tech support rep at Mackie about WHY it works, and situations when it won't. After that for me, I had no reservations whatsoever about doing it and I even started converting my all my RCA cables over with heavier duty gold cable ends. I started doing it on other DJ's tables who were known to really known to abuse a pair of 1200's. Like I said earlier I started doing this back in 1993 and I'm still using those same decks and none of the tables I modded have ever had problems (at least that I know of).

The main downside to doing this mod was because there may be some devices without a common ground. I test a piece of gear for this by using my multimeter to test a device for a common ground if I'm unsure, and I haven't run into a mixer or preamp yet that doesn't have this configuration. I'm not saying that my method is the best, but it had served me well all these years so, I keep using it. Now keep in mind that I'm not hooking my 1200's up to $2000 audiophile phono preamps or anything so if there's anyone who can speak to that, I'd be curious to know if anyone has found a situation where this would be a problem.

For all of my applications (so far) it has worked...

I don't think it's a problem, if it were I don't think the SL 3 would work properly.
With the SL 3 you have the choice of grounding either to the box or to your mixer and both work, I pretty sure the reason both work is because the grounding posts are also internally grounded with the RCAs.

Are you talking about the SL3 now or turntables?

I'll let you know what I find out.

the SL 3

Combining a turntable's (motor) ground wire into the audio RCA "ground" is a very bad idea. There's a reason the ground wire is an independent conductor. And while it may be true it works much of the time, in my opinion, it's not worth chancing it for the one very bad time that it does not work. If you consider yourself a "professional," keep the ground wire independent.

The TT ground wire connects the motor control board in the turntable to an earth ground (or at a minimum, the conductive surface acting as an earth ground for the audio system*). As you know, electric motors are notoriously noisy things, electrically. To reduce and keep the motor noise out of the low voltage phono-level audio signal, it is earth grounded through an independent wire. This wire is also specifically NOT wrapped near or adjacent to the unbalanced audio signal cables. The earth ground wire is not wrapped in or near the audio cable to keep the capacitance low between the noisy motor ground currents in the wire and the RCA audio currents. Placing these nearer each other increases the capacitance between them and greatly increases the noise pick up that adds motor noise to the audio (and also adds audio "noise" to the motor housing - but no one should care about that ;).

The idea of sending the noise currents down the audio cable is like finding a hungry fox (noise currents) and letting it in the nice safe, full hen house (audio cables), then locking the fox inside and going out for a pint.** Technically this would be called common impedance coupling - where two currents intended to be separated from one another to avoid noise and interference between them, share at least some length of common conductive current flow. When the ground wire is independently run to a grounding post, the motor's noise current flows far away from the audio currents since they are separate cables. Further, the noise current from the motor flows on the outside of the (hopefully) metal chassis of the mixer (or device containing the phono stage). This noise current flows directly (using the lowest impedance path available) to the third prong of the line cord (or other electrical path so the noise current can return to its motor power supply's source). Thus, the noise current never shares a common path ("impedance") with an electrical conductor that is also carrying audio current.

While it's clear many people have gotten away with this since it's more "convenient," I think it's asking for very serious trouble and probably when you least expect it. And when you encounter the trouble, there will be no fast fix except to undo the earth wire in the 1200. I don't know about you, but when I do gigs, I don't travel with a soldering iron and extra TT ground wires - nor would I want to be performing such an operation in front of a paying client or DJ crowd.

Steve


* What I'm hinting at here is the idea that airplanes, for example, are electrical devices these days and they fly just fine with no "earth" connection. It's the metal exterior of planes that is used to "ground" all the plane's electrical systems to a "charge reservoir" - which is a conductor in the electrical system that contains the most "free" electrons. This idea has been around since probably the 1930s (most famously by author & noise/grounding guru, Henry Ott). In many audio systems (especially 100% unbalanced consumer audio systems - e.g., when all devices involved have only a two prong AC line cord) the device with the biggest metal chassis acts as the "earth ground." It's the mixer (or SL 3) or hopefully metal device which contains the phono input circuitry that the motor must be connected to.

** copyright 1995 Neil Muncy (the "locking the fox in the hen house" analogy)

Steve,
I've never quite understood turntable ground wires. Why are they not simply connected to an electrical ground?

They are connected to an electrical ground. The important part is, to connect them to an electrical ground through a path that is not shared with audio signals.

Alright. I THINK I understood all that. They must pay you a lot. No wonder Rane's gear is so expensive. Thanks for the info Steve, but I'm gonna ride it out for now since my stuff stays in the house and for the streets I use either my CD players or the VCI-300 that I ordered today. That does answer the question that I used to have as to why turntables were wire like that. What about the ones that have line level outputs on them. Do they have ground wires or is it all done inside the unit.
I think as long as I'm using Rane's gear, then I shouldn't run into any problems (fingers crossed).

oooo k, wait a second...

so steve, if i read that correctly you are saying that the ground wire is somehow associated with the (motor). assuming we are talking about the industry standard technics turntable that typically connects to a mixer, it is in no way associated with the motor.

"The TT ground wire connects the motor control board in the turntable"... that is not true with what we are talking about. the tone arm and ground wire are COMPLETELY separate than from the motor system in a 1200. they work completely separate from each other and in no way are ever connected to each other.


the ground wire associated with the tone arm is not connected to anything electrical within the technics 1200.

and btw westell54, if done properly the internally grounded mod for a 1200 is not permanent.

The way I do mine they are, unless I open them back up. I cut and remove the original and do 2 short jumpers on the tone arm board. To reverse that I'd have to open them back up, cut the jumpers and reattach/solder the ground wire back in. That's the only reason I say "permanent".

The turntable ground cable prevents the magic smoke from being released from the electronic circuits, you must have them connected to the DJ mixer or SL3 box (SL3 box has a USB 2.0 magic smoke inhibitor that's why the USB port is organge, the SL1 didn't have a magic smoke inhibitor because it wasn't supported in the USB 1.0 protocol) .

That's all you need to know and that's what you tell others.

A lot of people like magic smoke like puff the djdragon....

Okay but seriously I've had my tables internally grounded for YEARS and I play on multiple systems 4-5 days a week. What are the circumstances that something could go wrong? In plain mans terms? Using a certain kind of mixer or something?

My point exactly J-Fresh. Mine have been grounded since 1993 and I've never had issues either, so I'm sticking with it. I've heard it depends on the component that the turntable is hooked up to. Steve M gave a much more technical explanation of it, but for my purposes, all I need to know is that it works for me and anyone considering doing the mod needs to be aware of the pros and cons of doing it. As with anything you buy, if it's something that the manufacturer did not design the product to do, you attempt it at your own risk.

Honestly, I've had a lot less issues with mine than I have with messed up ground wires at clubs.....

Mine have been ZERO! How about you?

Boooooo, like i've never heard that one before LOL

i don't have too read much further than this line in Steve M's post to know he is COMPLETELY WRONG.


the 1200 ground wire and the motor control or anything electrical in a technics are totally and completely independent.
they work totally separately and not connected by any wires at all.

they are in no way connected
the ground hum you get is NOT electrical.


i don't even know why this post is still here.
Steve M is very misinformed.
research the subject, take a TT apart or work on them, you will see.

i have personally internally grounded many turntables and repaired well over 300.
unless the work was shotty, i have never had an issue or heard of anyone having an issue with an internal ground ever.

Have you actually taken a DMM and measured the resistance between the 1200 ground wire and the ground on the pcb of the techs?

yep

So, if they are completely isolated you wouldn't want to connect the two grounds together.

what 2 grounds??

you definitely do NOT want to ground the tonearm internally to anything electrical or the motor or any other ground not associated with the arm.
there's no reason to do that. the electronics and the tonearm are independent units. don't connect them.

i've been internally grounded for 7 years.... never have had an issue.

Now you're confusing me. :-/

oh, just take a 1200 apart and you will see.

it's easier than you think, just do it.

Ha! I have opened a few 1210s in the past ;)