Turntable / Phono Preamp Distortion

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OK-- this thing has been driving me totally forking bananas for about a month now. I have a pair of Bottlehead Paramours and a Foreplay preamp (I know-- not real DIY] hooked up to a Hagerman Bugle SUPER SUPER CHEAPO preamp (but I really like it) and a Music Hall MMF 2.1 turntable (I know, not real hi-fi).

When I play jazz records that hit a certain frequency range (Monk's piano in Bemsha Swing, for example) I get this crackling on one channel for the duration of the tone. Its only in one channel and this happened when this particular TT and phono pre were hooked up to a GainClone, so I feel confident that its not the amps or the line stage.

Some records just sound great, while others hit this frequency rather hard and I JUST GO CUUURRAAZZEEEE when I hear this distortion. You know, I just had this idea that Miles Davis shoudn't make you want to kill indescriminantly-- that's what Micheal Bolton is for.

Anyway, before I take my preamp apart and start re-soldering, are there any of you geniuses out there who would like to play "Find and Fix Kofi's Distortion Problem" for a shot at a hand-knitted hat, scarf or mittens (your choice!) from Mrs. Annan?

Help me. For the sake of my marriage, help me.

Kofi
 
From your problem description you probably have a stylus mistracking problem where the crackling is a symptom of the stylus bouncing in the groove. This can cause groove damage after repeated playings, with the crackling being permanently engraved into the groove.

You can increase the tracking force up to the maximum in grams recommended by the cartridge manufacturer while listening for improvement.

If the crackling is in the right channel only this may be corrected if your tonearm has antiskating adjustment, refer to the owner's manual for your tonearm or turntable for adjustment instructions. This is because as the disc rotates and the groove spirals from outer to inner disc area, more force is applied to the inner portion of the groove, which contains the left channel, and less is applied to the outer portion which contains the right channel. Mistracking occurs if too little force is applied to the right channel, antiskating adjustment applies a force towards the outer edge to compensate.

If the cartridge is incorrectly aligned I would expect both channels to have more distortion, and not a sudden increase in crackle in one channel. I notice a more grainy and gritty sound with bad overhang adjustment, about equal in both channels, but no gross mistracking.

You might even have a damaged cartridge, stylus or cantilever, particularly if the stylus has been dropped or scraped across the platter mat or platter edge. If this has happened, you may damage your records with repeated playing.

I think your preamp is the least likely cause of the problem, try swapping left and right channel on preamp inputs and outputs, if the problem moves to the left channel then something is wrong with the preamp.
 
Since I don't see too many TT post, let me interrupt this thread by asking a quick question. Hopefully someone has a quick answer ...

Assuming everything is working properly, if I want MORE bass, should I push the weight located at the back of the tonearm forward (towards the front of the TT) or push it backward (towards the rear of the TT)?

I understand that I have to change in it small increment to find the "sweet" spot - that I will experiment myself. I just wanted to make sure that I'm moving the tonearm weight in the right direction.
 
diyAudio Senior Member
Joined 2002
Hi,

Koffi,

You could have a badly set anti-skating force pulling the stylus tip too much inwards.

Sometimes a combination of this + too little tracking force can do this as well.
The distortion is there all the time though, it's just you hear it more clearly on difficult to track material such as jazz piano (especially Mr. Thelonius Monk, ...kidding)....

fcel,

You don't adjust frequency repsonse by changing the tracking force, it should be well within the recommended settings of the cart manufacturer or you'll damage both record and stylus.

To increase tracking force move the counterweight forward, the assembly works like a lever.
Set the weight accordingly and if you're looking to set VTA for best imaging vary the tracking force by very small increments.

Cheers, ;)
 
fdegrove (Frank?),

I forget to mention that I have set the tracking force per manufacturer recommendation and I'm not looking to improve imaging.

Based on your answer, adjusting tracking force is not the correct way to adjust bass response. What is the one single adjustment that I can make to adjust bass response - in my case, I want a little more bass? Thanks.
 
diyAudio Senior Member
Joined 2002
Hi,

fdegrove (Frank?),

Yup...

Based on your answer, adjusting tracking force is not the correct way to adjust bass response.

Correct.

What is the one single adjustment that I can make to adjust bass response - in my case, I want a little more bass? Thanks.

MM cartridges' frequency response can be adjusted a little by capacitive loading of the phono input. This should be done at the preamp input side and should involve a pair of caps of say 100-250 pF shunted across the standard (50K but you'll likely find a 47K resistor)) input impedance.
The manufacturer should state the recommended capacitive loading, this varies from cartridge to cartridge.
Don't expect a world of difference; if your current setup is seriously lacking in bass output the problem's quite likely elsewhere.

MC cartridges should be loaded with a resistive load, again according to the manufacturer's recommendation but response to loading will go from less controlled bass response to splashy highs. Whichever direction you go neither way will alter bass response much.

All in all it could well be your problem is not the cartridge nor it's loading but perhaps a deviating RIAA curve.
Please verify you have connected the armleads to the correct preamp input.
On older preamps you sometimes find phono inputs for ceramic cartridges which aren't meant to be fitted with MM or Moving Iron carts for instance.
If needed check with the preamp's manual.

Cheers, ;)
 
Not trying to OT, but. . .

As I am a 2 week newbie to vinyl, some clarification might help both Kofi and myself. I have the Music Hall MMF-5, similar to the 2.1, I assume.

On my TT, the counterweight is adjusted via rotation bringing the weight closer or farther from the pivot (pretty standard, I assume) and have set the force, not by the graduations on the dial, but using a digital gram scale (also for speaker measurment. . . ) at platter height. This seems a feasible solution using tools at hand.

However, the anti-skating force was just set via the manual. There is (on my TT) a weight suspended by fishing line and a notched lever on the tone arm. There were only 3 positions and the manual stated put the weight in notch 2 for the supplied Goldridge cartridge.

I don't note any problems, however, I would like to know more about these settings. Any comments about the proper way to set things up and troubleshooting by ear when problems may be occurring would be great. I searched for TT FAQ which yielded nothing, so I apologise if this is a common question.

I really am more interested in not damaging my equipment/media right now and hope to learn more so I can intelligently upgrade over time. I'm thinking next would be a Pass Pearl Phono kit to replace the receiver phono pre-amp I'm using now.

Thanks for all comments.

Sandy.
 
Frank,

Thanks for the response. I was looking more into the one mechanical adjustment. I guess there isn't any - you have provided a electrical solution.

Again, there isn't really anything wrong with my TT. It's just that I have bought a new TT recently, did not own one since my teenage years, I'm curious and I've got questions ..... I will probably have more questions as I get more involved in the vinyl adventure. I'll start a new thread next time.

Now, back to regular programming ....
 
Sandy,

I just saw your post. I'm a newbie too. I got my MMF 2.1 about 4 weeks ago. The owner's manual did not really discuss in depth why things are set the way they are and thus I have all these questions.

Yes, as you said it, I would also like to learn how to set and troubleshoot by ear when problem arises.
 
diyAudio Senior Member
Joined 2002
NOTHING'S EVER PERFECT...

Hi,

"The term "skating" refers to the vector force created as a tonearm with an offset headshell traces a record groove. This force, which continously changes across the surface of a record, tends to pull the arm towards the record's center. Many tonearms incorporate devices which attempt to counteract this force. Unfortunately, the best these devices can do is approximate the force required to counteract the ever-changing skating force. Worse yet, the materials used to implement most anti-skating devices vibrate and are, therefore, a source of noise."

A snippet from VPI's site announcing doom and gloom....
Unfortunately the statement is quite correct, there is no ideal one setting that solves it all in one go.

Any comments about the proper way to set things up and troubleshooting by ear when problems may be occurring would be great.

When AS is set so there's too little compensation the left hand channel information will be emphasized as the stylus is pulled against the sidewall of the groove and the stereo image will tend to shift towards that channel.
Conversely, too high an outward pull, indicative of too much correction will make the balance shift to the right hand channel.
Needless to say, a few plays with incorrect settings will have permanently done away with the better part of the high frequencies of the vinyl groove....

The manufacturer of the tonearm will have chosen a particular system to compensate for this according to a series of cartridge weights and knowing the inward pivotal friction caused by the tonearm's wire dressing, as such it will leave the user with little choice but to accept this preset countermeasure.
The more sophisticated tonearms will likely allow more freedom of adjustment but the users will need to spend more time to adjust for this centripetal force.
Without proper tools this can be quite time consuming...

Hope this helps, ;)
 
Stylus chatter!

I'm not sure what cartridge/stylus you are using, but some are ultra sensitive to stylus pressure and resonances. The simplest test I know is to vary the stylus pressur in 1/4 gram increments from about 1 up to 2.25 and see what happens. If the nasty sound changes you have pretty good evidence that it is a cartridge related problem like alignment. If the offending sound goes away, be happy and use that setting.

Shure had a test LP they called the "Audio Obstacle Course" (long out of print). If you can find someone with a clean copy of that (like me) who is willing to lend it to you (maybe), it will also help you diagnose your problem.
 
Whoa! You go to Geneva for a couple of days for a conference on the Najaf cease fire and when you come back, this happens!

Thanks for all the great information-- it looks like some others had similar questions.

Fcel-- I really enjoy my MMF 2.1. OK, its hi-fi for lo-do, but I still like it.

Maybe I'm hearing things, but it appears to me that the distortion gets worse as the record plays. That is, could there be a correlation between the increased distortion and the stylus' proximity to the record's center?

Also, I may be ready to upgrade my TT soon. Any recommendations on a sub $500 TT? (These responses ought to be interesting). I'm not afraid to buy used or assemble a kit.

Kofi
 
Hi all!

Maybe I'm hearing things, but it appears to me that the distortion gets worse as the record plays. That is, could there be a correlation between the increased distortion and the stylus' proximity to the record's center?

Most probably your cartridge is longitudinally misaligned. In other words, the so-called "overhang" (that is, the imaginary distance between the stylus and the platter's pivot if we imagine to place the tonearm in such a way that it passe over the pivot itself) is wrong.

Usually, given a TT/arm combination, there is an optimum value for this "overhang", which minimises the distortion over the entire record, nulling it at two precise point. This distortion arises from the fact that the cartridge, due to the pivoting nature of the tonearm, is not parallel ("tangential") to the groove, except at those two points I mentioned above. This tangential error (which is, actually, an angular deviation from the ideal condition of parallelism) leads to distortion. It can be minimised over the entire record surface by carefully choosing the longitudinal position of the cartridge. There are some simple tools to adjust this parameters, I guess your TT came with such a tool.

Cheers,

Bruno
 
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