I have a Beogram 1800 with a rebuilt MMC5 (Alex did it). On some of my records, the loudest parts of vocals are distorted. Any thoughts on a possible cause?

could be your turntable overloading your amp... what is your beogram 1800 connected to? 

Andrew

I don't think that's the problem, but maybe I'm wrong. The Beogram 1800 is connected to a Musical Fidelity V-LPS phono stage, which in turn is connected to an Anthem TLP-1 preamp and a B&K ST-140 power amp.

Thoughts:

Is the tracking weight OK?

Is the loading on your pre-amp correct? Should be 47Kohm (I seem to remember!) and the capacitance is also important - I'll have to look that up at home!)

I'll check the loading and capacitance on the pre-amp. Not sure if the tracking weight is ok. After having the MM5 rebuilt by Alex, it's now something of a different animal than a regular MM5. I'll check the weight I have it set at and report back.

Still having this problem: distortion at the loudest parts of (mostly) female vocals. The tracking is set correctly for a MMC5 at 1.5g. As for the loading and capacitance of the phono-stage, here are the specs:

• Input impedance: MM 47K ohm; MC 100 ohm
• Input sensitivity: MM 3.5 mV; MC 450 uV for 300 mV out
• Total harmonic distortion: MM 0.01%; MC 0.01% @1kHz, 300 mV out
• Signal / noise ratio: MM >80 dB; MC >70dB "A" weighted
• Input overload margin: MM 15 dB; MC 22 dB

Anyone have any more thoughts on the above?

Peter -- Do you have any suggestions for what I might try to correct this?

Not sure how/why this would be an intermittent problem, but once again I have distortion on the loudest parts of vocals. Only difference between the last time I posted about this and now is that it also happens with a rebuilt MMC2! Help?

The usual problem is going to be wear. Obviously not the case with your new MMC2. Axel suggests his cartridges track at a slightly heavier weight - my MMC5000s track best at about 1.3g. In the first event, I would increase the weight. Have you checked that the scale on the tone arm is accurate?

Hi,

Does the problem worsen near the end of the records?

Hello, the problem normally gets worse when the stylus is getting closer to the center of the record. I have had the same problem with a rebuillt MMC2 from Axel, simply increasing the tracking weight from the normal 1g to 1,3g helped a lot.

Actually no, it's just as bad at the beginning of a record as it is toward the end.

Ok, I'll try increasing the weight a little.

As for checking that the scale on the tone arm is accurate, how do I go about doing that?

I would advise that you should use a specialized tracking force weight(the cheapest being the "fulcrum balance"-type). This can be far more accurate than the weight measuring ring on the 1800 arm, if it needs calibration. There is some way of calibrating the scale, but I don't know how to on the radial decks.

-Søren

With the cartridge in place, turn the counterwight CCW until the arm is balancing, hold the counterweight tight and turn the plastic dial to "0", set your tracking force. For MMC 5 some 1.5 gr.

By tracking force weight, do you mean use a stylus force gauge, such as the digital type? If so, can anyone recommend a brand they like?

http://www.hi-fi-accessories-1.com/digital-stylus-force-gauge.htm

I just keep it simple with an Ortofon Fulcrum force gauge, they are cheapest

I also use the original B&O one I had along with my MMC20 EN cartridge!

chartz:

http://www.hi-fi-accessories-1.com/digital-stylus-force-gauge.htm

They state, in relation to jewlers scales from ebay...

In reality these scales gave large errors such as reading 2.1 grams for tracking force when the actual measurement was only 1.4 grams. We can vouch that the scales we are offering are accurate and have received excellent feedback from users

That is not what I found! I use some ebay scales that cost me about £12. I have tested with coins etc. of known weight and they appear accurate and repeatable every time down to about 1/10 of a gram - they are NOT fussy where the contact force is applied either! Only problem is you need to remove the platter to account for the thickness and have the stylus at record-level..

I'm not familiar with stuff that is sold as "jeweller's scales", but many of them seem exactly the same as those sold as powder scales for cartridge reloading. And I can assure those work correctly, as gross errors as the one mentioned above would be outright dangerous and possibly risk blowing the gun in your face! When used correctly, they are accurate to 10 mg or so.

The problem with them is just what you say Step1, they are usually too thick for measurements at the record level. The shown weight might be something else than truth when the arm is pointing at the ceiling. As with most engineering, you need to know how to measure and what other phenomena might affect the reading, in addition to having the instrument...

So the distortion didn't disappear until I pushed the tracking force up to 1.6 g for my MMC2. There's still some inner groove distortion in the last song on each side, but that's to be expected.