The Saga continues with the Technics SL-1200....................................

Wayner · « **on:** 23 Feb 2008, 06:12 pm »

Today, I was looking at the VPI table (with Audioquest PT-6 tonearm) and noticed the cartridge hook up wires were twisted together, red with green and blue with white.

So, gears in the head started moving again. What would happen if I twisted my cartridge wires together in the Technics? Well, the existing wires were too fat to do that so it was time to plug in the soldering iron and make my own. I have successfully used computer connectors (with 1/16"dia. shrink tube on the outside) as an excellent cartridge connector, so I made a new set of wires. I use computer wire, perhaps it has 5 stands in it, guessing the gauge is in the 30's. The insulation has to be Teflon as it is a bitch to cut (forget stripping the insulation with your teeth...too tuff).

I twisted the pairs together and installed them onto the cartridge and head pins. The hum has almost completely disappeared and I have now reconnected the ground wire of the table. I used to get hum with it connected before finding that connecting the (-) of both channels was a better cure hum. All that has changed now. This table is starting to sound incredible.

I'm playing Kraftwerk, Computer World (a really stupid album, with stupid songs but great sound effects) and zowie!!!!!

3D sound in abundance thru the AVA electronics.

As a on the side experiment, I have re-arranged the mat set-up. I have not been real happy with the Faraday shield so I went out to the garage and got my 10" fine tooth tablesaw blade and put that on top of the die-cast platter, then the mat. This has almost completely killed all hum proving that the source is truly the motor magnet of the direct drive mechanism. I'm going to try and find a blacksmith shop around here and have him circle-shear me a disc to fit the platter better. I would like to use some 16ga galvanized steel if possible.

Wayner

low.pfile · « **Reply #1 on:** 24 Feb 2008, 01:21 am »

Wayner
I read this post very early this morning and was envisioning you carrying the TT to your shop bench and i dunno.... performing hari kari! Now I see you just used your saw blade as an additional "mat" - I guess I would call it an isolating disc. Well that seems reasonable since the SDS isoplatmat is essentially a metal-polymer-metal sandwich and is does a great job on the 1200-I use one. Of course it is not cheap. Hope your DIY works out. I wonder if you could spray it with some plastic type paint for a little dampening? ...sort of a reverse isoplatmat.

cheers, ed

Airborn · « **Reply #2 on:** 24 Feb 2008, 06:20 am »

So, Wayner, you've got me worried with all this hum talk.

My next move was going to be a KAB Technics SL-1200 MKII w/fluid damper on the tonearm. (I was supposed to get one for X-mas, but that's a different story). It would replace my old Dual 601 belt drive w/ AT 440 MLa cart. While old and w/some speed stability problems, it has no hum w/my 6SN7 based MAD Ultra 4 SE preamp. As for cartridge, I am going to continue to use the AT 440 MLa unless something better comes along for a similar price.

However, I am now worried about hum. Do you think the Cardas tonearm rewire by KAB would cure the hum you are experiencing? Anyway, I don't think I can afford both the Cardas tonearm rewire and the fluid damper, which should I go with ( I still think fluid damper would be more significant sonically, but I'm not sure now)? Is the SL-1200 worth it or is the hum that significant an issue?

Wayner · « **Reply #3 on:** 24 Feb 2008, 12:57 pm »

The hum level I'm talking about is hum starting to show up at the 12 o'clock position, relative to the volume control. I don't think most people would listen to vinyl at that level, but my Empire 598 II and VPI are dead quite at that volume position (they also have the AT440MLa). I'm kind of a perfectionist, I guess and a few people have told me that the hum was thru the poor interconnects. I kind of believe that and kind of don't as it seems to come from both ends.

The Technics hum problem is elusive. I can change its intensity by moving the interconnect cables, adding or removing chassis ground, re-arranging cartridge wires and of course, making mat sandwiches. What drives me to continue on is the fact that the SL-1200 is capable of digging out some incredible grooves and with the AT440MLa, has become a stellar performer. I'm just that little bit away. I have decided that the AT is susceptible to hum in direct drives, but I am sure I can get it to almost zero if I keep fiddling.

richidoo · « **Reply #4 on:** 24 Feb 2008, 03:41 pm »

I'm having same problem with SL-Q2, I'll try some of your ideas. Thanks Wayner.

lcrim · « **Reply #5 on:** 24 Feb 2008, 04:14 pm »

I've run a KAB modded Technics 1200 MKII for years with no hum issues whatsoever. I had the tonearm rewire done ove a year ago and have used many different cartridges w/o hum issues. I would point out that its history as a favored rig for DJ's is a testament to its reliability and freedom from such issues in general. I have to crank the volume to 4:00 o'clock before any niose intrudes and at that point tube rush not hum can be heard faintly, this in all tube system. In addition I have been using much lower output cartridges than the AT moving magnets cartridges and therefore should be more susceptible to electrical interference but still no hum. The issues described are not common and I honestly don't think one should be concerned about hum in purchasing this TT.
I do hope on the other hand that the two members solve their hum issues.

TheChairGuy · « **Reply #6 on:** 24 Feb 2008, 04:59 pm »

My 1200 has an aftermarket arm on it....and I experience no hum issues with it.

However, my JVC DD has captive wiring and leads on it and there is perceptible noise (hum, if you will) as you turn the volume up.

Wayner - I'm pretty surprised merely twisting headshell wires/leads would cure any large degree of hum....I think the nature of the problem with any of the stock/captive tonearms is that the final several feet of wire terminating in rca's isn't shielded.

With line level outputs, depending on where you live in proximity to radio and TV transmissions and where you gear is located in proximity to one another....you can often do without shielding on interconnects quite fine. But, with super low level phono signals (particularly before they have been amplified by your phono stage), generous shielding of the interconnect leads seems almost a must.

The KAB re-wire termiates after the tonearm with either rca or DIN connector...so you can plug in your own shielded or balanced interconnects from table to phono stage. A good thing in all ways I'd think

One day I'll either re-wire the leads from my JVC with well-shielded OFC cable or add HighWire All-Clears wraps on the captive leads to add a large degree of shielding that is needed. The JVC sounds pretty dang good as is with the Grado/shibata....less noise can only be more beneficial to it

It's just one more interaction one must minimize to enjoy vinyl....yet another reason why so many give up on it even tho it is a superior music source to CD/Redbook

John

Wayner · « **Reply #7 on:** 24 Feb 2008, 05:02 pm »

Off hand, I'll say that the AT440MLa isn't the most perfect match for this table. However, it's sonic virtues make it a worthy attempt at defeating the evil hum bug. If I were to drop the stylus at my 12 o'clock position, it would be incredibly loud. This morning, I stripped back the stock interconnect cables and braided them together with the ground wire, then wrapped that in Mylar foil which has dropped the hum level a bit more.

The hum is a tale of 2 sources, obviously 1 from the electronics of the direct drive circuitry, the other from the permanent magnets of the drive mechanism. The other interesting factor is that I'm testing the hum level with the tonearm on the arm rest. If I move the tonearm over the outside edge of the record, it all but disappears, and that is where it counts. Personally, with 30 years of production on this table, I don't think the designers have done all of their homework, as I have fairly easily manipulated the machines hum output. The obvious improvement is shielding the magnet assembly better. There isn't really any type of shielding in this regard. The other issue is the that the tonearm is not grounded. I get zero continuity to ground lug from any point on the arm, however, I do from the pivot points and frame. And also, the interconnects blow.

Wayner

Wayner · « **Reply #8 on:** 24 Feb 2008, 05:11 pm »

John,

Twisting the leads together did make an improvement, but as yesterday went on the degree of improvement lessened. I have to blame the interconnects for this as just moving them around seems to produce noticable effects. I am considering chopping all but 3 inches off and wiring on some female RCA's and then use some better ICs. However, that is one more connection that really isn't necessary. That maybe next weekends project.

W

TheChairGuy · « **Reply #9 on:** 24 Feb 2008, 06:49 pm »

Extra connections may add as much 'noise' to the overall system as the cheapo/unsheilded leads themselves...in general, not a good way to go is adding rca connections to low level phono voltages.

KAB re-wires the entire arm for $160 I think...I remarkably fair price given the work involved. I think rca connections generally a lousy sounding connection overall...I'd have KAB terminate it in 5 pin DIN connectors and add a good, shielded DIN-to-RCA phono cable from deck to phono stage.

End of hum issue entirely this way I'd think

The other option is adding Highwire All-Clears Wraps to the existing captive IC's...the spiral (non-ferrite) element is an impressive rejecter of RFI. They are just a smaller version of Power Wraps used on power cords.

In a lot of ways, they are actually better than shielding. Shielded cables have a tendency to make a system sound forced or etched and unnatural I've found. The Highwire All-Clears - they're $21.95 at Michael Percy Audio for a pair.

Quote from: Power Wraps

Power Wraps also benefit audio and video interconnect cables. They improve the performance of low- and medium-priced cables for less
than one would spend on a more expensive cable. They are especially helpful on non-shielded cables. The All Clear version of Power
Wraps has a smaller diameter, which is more suited to interconnects.

John

Toka · « **Reply #10 on:** 24 Feb 2008, 07:27 pm »

Airborn,

One thing to keep in mind is that you can always add the tonearm damper by yourself at a later time when the funds become available...the tonearm rewire, not so easy. Food for thought.

And I've never had hum issues with the '1200 at all, ever, either...don't run one at the moment (still hoping to change that soon...) but have been around them for years at various levels and it just never happened (that is, no hum that could be sourced to the 'table). Wayner, if it is the 'table itself, maybe something is amiss with the power supply? IIRC you purchased it used...maybe it was knocked around a lot in a prior life?

low.pfile · « **Reply #11 on:** 24 Feb 2008, 07:30 pm »

Quote from: Airborn on 24 Feb 2008, 06:20 am

So, Wayner, you've got me worried with all this hum talk. ...............Anyway, I don't think I can afford both the Cardas tonearm rewire and the fluid damper, which should I go with ( I still think fluid damper would be more significant sonically, but I'm not sure now)? Is the SL-1200 worth it or is the hum that significant an issue?

@airborn
I have a SL-1210 using a AT 150MLX MM cartridge. I have never heard a hum. my 1210 has both KAB fluid damper and rewire and rear RCA plate. I would suggest the fluid damper it would have the most impact on sound.

good luck

TheChairGuy · « **Reply #12 on:** 24 Feb 2008, 09:18 pm »

Toka - Wayner's SL-1200 was bought new (mine was beaten to hell used)

John

Toka · « **Reply #13 on:** 25 Feb 2008, 02:39 am »

Quote from: TheChairGuy on 24 Feb 2008, 09:18 pm

Toka - Wayner's SL-1200 was bought new (mine was beaten to hell used)

Ah, must've gotten a wire crossed.

Thanks!

Wayner · « **Reply #14 on:** 25 Feb 2008, 07:05 pm »

I found a shop to make me a couple of Faraday shields out of 16ga. galvanized steel. I will make a mat sandwhich tonight when I get home. I'm thinking this will do the trick. I paid $23 for the 2 discs including material, labor and sales tax. Not to bad. The other disc is for the Technics SL-Q2.

Wayner aa

Wayner · « **Reply #15 on:** 25 Feb 2008, 10:50 pm »

The hum is all but gone. The new mat sandwhich did it.

Chassis ground is still not connected. Buzzes when it is. The (-) of cart terminals connected together.

Sandwich ingredients:

1) .09"thk. EPDM closed cell sponge, 50 durometer.
2) 16ga. galvanized steel
3) .09"thk. EPDM closed cell sponge, 50 durometer.

Now your Technics table will work with virtually any cartridge made, IMHO.

Wayner

mcgsxr · « **Reply #16 on:** 25 Feb 2008, 10:56 pm »

I am with lcrim on this one, the T1200 is a long standing DJ standard, I spun on a set of these decks many moons ago, and it is basically indestructible. When I eventually get into vinyl, I will likely start with one of these work horses, and it is great to see that a lot of the mod research is getting done while I toil away at my mortgage, and lay in wait!

low.pfile · « **Reply #17 on:** 26 Feb 2008, 07:18 am »

Quote from: Wayner on 25 Feb 2008, 10:50 pm

The hum is all but gone. The new mat sandwhich did it..........
Wayner

That is awesome Wayner! Nice DIY!

What did you listen to after the mod?

'ed

low.pfile · « **Reply #18 on:** 26 Feb 2008, 08:13 am »

Wayner,

Again, a sweet DIY you did.

I thought it might be a good idea to show that SoundDeadSteel (aka. non DIY) mat on a Technics so I just took a few quick snaps of my set up.
the SDS is a aluminum/polymer/Aluminum sandwich, powder coated in black, but costs $100US

my SDS isoplatmat on a KAB - SL1210

more of my quick pics tonight (in the dark) with the Herbies mat on top of the SDS isoplatmat .... http://s150.photobucket.com/albums/s113/bpmandfps/technics_mat/?albumview=slideshow

enjoy your music
ed

[that's a ubiquitous AT 150MLX MM cartridge in my pics]

Wayner · « **Reply #19 on:** 26 Feb 2008, 12:37 pm »

low.pfile,

I was about to head down that path of purchasing that mat, but then I found this company in the yellow pages. They made the 2 parts by noon. I was quite pleased with the outcome. Your mat looks sweet too. I will paint my steel portion this weekend and glue the whole thing together. The steel "Faraday" shield is the cats meow for suspect cartridges going onto DD tables. The saw blade experiment this weekend proved it but I new I needed a larger diameter, which paid off on spades.

Wayner aa