Rega, AT33PTG/II, Guns N' Roses and IGD

Hi everybody.

 

I recently bought the Audio Technica AT33PTG/II cartridge for my Rega RP3 (with an RB-303 arm), and I've been having some problems with inner groove distortion, mostly on the two Guns N' Roses' "Use your Illusion" albums.

 

I have included sound clips at the end of this post. I have recorded most of the changes that I've tried.

 

I haven't used the cart much yet, so I've only managed to find a few more albums with inner groove distortion, one of which I've included as a sound clip (although it might just sound muffled as opposed to distorted).

 

 

Before I go into details I will state the objective of this thread:

 

The (online) seller has said that they could send me another unit to see if that would fix the problem, but if I can figure out a fix on my own (if the cart is not the problem), then I might as well save both me and the seller the hassle (and the postage costs).

 

So my question is: Can any of you suggest a fix that I haven't already tried yet (outlined below)? Maybe there's something I just didn't think of.

 

I've been going crazy over this for a couple of weeks now - as you can see there are a lot of details to report!

 

 

What is a bit odd about all this is that I downloaded Pbthal's rips of the two Guns N' Roses albums, and despite different equipment, the beginning of the album, "Right Next Door to Hell", sounds identical (as you will hear in the sound clips), but especially the last song on side 1 of "Illusion I", "Perfect Crime", is heavily distorted on my setup. On Pbthal's rip, there's only a slight bit of distortion. It's a loud, aggressive song, so distortion should be expected. I also downloaded a different rip done with a Zyx cartridge on a Pioneer, and that also only has very slight inner groove distortion.

 

The distortion is most noticeable in the part of "Perfect crime" that starts after 48 seconds.

 

However, on the song "My world" on "Illusion II", which is also a loud and aggressive song at the end of the side, my recording sounds the same as on Pbthal's. "So fine", also at the end of a side, also sounds identical, but that is a more mellow song. And then "Breakdown", also at the end of the side, sounds a bit more distorted, or at least muffled, on my setup. These are included in the sound clips as well.

 

 

My gut instinct tells me that the problem would be one of the following things:

 

* The cart is faulty.

 

* The alignment is off.

 

* The records, although looking to be in practically perfect condition, have been played with a bad cartridge, and therefore it's simply just the records that are at fault, and I can't fix it. I did try to clean the record though, with no effect.

 

* My tonearm (RB-303) simply can't track the inner grooves properly.

 

* The azimuth is off.

 

 

 

Before I go into further details, I should probably mention that I'm the sceptic type. I've considered buying the Mint Protractor, but despite all the glowing reviews I still haven't seen a single before/after sound clip being posted, and then the stories are essentially no different than the glowing reviews of a $5000 power cord. I have, however, found that alignment does indeed matter, and I've passed blind tests between different alignments, also blind tests of different VTA settings, on two different cartridges. On some cartridges alignment makes more difference than on others in my experience. So this is why I'm still considering buying the Mint Protractor. But I would like to see/hear more proof than just stories :-).

 

 

 

So here's what I have tried to adjust so far:

 

 

* Alignment: I have used a magnifying glass and light to get this right, and I also bought a jeweler's loupe. I have used the printable protractors from Vinyl Engine by Seb and the Conrad Hoffman printable protractors as well. I've tried Baerwald and Stevenson by Seb and Loefgren A and B by Conrad Hoffman. One thing I found out is that Stevenson by Seb actually corresponds to Loefgren A by Conrad Hoffman, and Baerwald by Seb corresponds to Loefgren B! I also found that the angle of the cartridge/cantilever on the two different protractors were markedly different. All this was quite surprising. After printing I checked both with two different rulers. But it's possible that something has gone horribly wrong while printing.

 

I have also tried pushing the cart all the way forward, pull it much further back, angling it a little towards the label, angling it a little more, angling it a little less, putting it completely straight in the tonearm, angling it to match the protractors, angling it a bit more or a bit less than the protractors. And lastly, I found a close-up picture of someone with an RP-8 who used the same cart, so I tried aligning the cart the same way as in that picture.

None of this seemed to change anything.

 

* Anti-skating: I've tried pulling it all the way out, pushing it all the way in, and many positions in-between. No effect.

 

* Tracking force: The recommended tracking force is 1,8 to 2,2 grams. I've tried going from around 1,3 to around 2,6 grams. No change.

 

* Azimuth: When looking at the cantilever it seems straight, but it's difficult to tell (I've seen bent cantilevers before). I did, however, notice that the cantilever bends a little to one side when it touches down on the record. The only way I could get it not to bend was to put a lot of paper washers on top of the cartridge on one side or under one of the screws that attaches the arm to the plinth. But it looked completely crazy. So, I think this makes it more likely that the cart is the culprit rather than the azimuth. I increased the numbers of paper washers gradually and then listened. I tried this on both sides of the cart. I also tried putting the paper washers under each of the three screws between the arm and the plinth. I also used a bubble level on top of the headshell as well as on the plinth and platter, and the level was completely perfect.

 

Here's a picture that I took while playing that actual GN'R record:

https://i.imgur.com/MIKpW1C.jpg

 

 

* VTA: I've tried raising the arm with thin metal washers and bolts (around 1, 2, 3 and 6 mm), and I've "lowered" the arm by putting another record or two under the record mat. My experience tells me that VTA gives more more or less treble, so it wouldn't affect distortion, and not surprisingly it didn't get rid of the distortion.

 

* As for my tonearm, this could be a possibility, although the arm has a great reputation. It should be noted that Pbthal uses a linear arm, which should lower IGD. However, the rip with the Zyx cartridge was done on a Pioneer PL-7L, which also has a pivoted arm.

Last year I tried out a different cart, which didn't sound like I expected (lack of treble), and I then put it on an acquaintance's old Thorens TD-321 with a Mørch DP-6 arm. It sounded more or less identical on that one, but slightly better on my setup (I made a recording). Also, this cart was actually an older model, and the shop let me do recordings of the new model on their setup (and they set it up), and I liked the newer model even less (even greater lack of treble). They said that the new model sounded exactly like it was supposed to.

So I think my tonearm is okay :-).

 

 

 

And finally, here's a link to the sound clips:

 

https://mega.nz/#!RQhQyAga!TuBjTzX-WQlu3A6z7iioVWumj90ce6V_xkx-XpK6S4Y

 

 

All suggestions are welcome :-)!

 

Thanks!