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I’m sorry for the lack of posting recently, but I’ve been working a lot as well as having bit of a writer’s block. I’ll soon be posting the first of what I hope will be an extended series on amplifier design topics. Here are a few things I’ve collected over the last few weeks:

The Lossless Audio Blog has switched from blogger to WordPress (the same software used here). Their new URL is http://www.losslessaudioblog.com/

Speaking of lossless compression, the Philadelphia Orchestra is offering performance recordings for sale online in both MP3 and FLAC format. The prices for most works are $4.99 for MP3 and $5.99 for FLAC, although Beethoven’s Symphony #9 goes for $9.99/$11.99. These prices are for the entire piece, so range from $0.37/minute for Britten’s Sea Interludes from Peter Grimes to $.11/minute for Schubert’s Ninth Symphony for the FLAC version (these were two I bought). Not really cheap but not bad for 16-bit 44.1KHz lossless files.

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Morgan Jones, the British writer on high-quality audio and author of Valve Amplifiers was reviewing my comments on unipivot tonearms (see the introductory part of “Mackris on cartridge set-up“) and sent me the following comments regarding his experience with these arms. He has plenty - he has been building these since he was 15 years old! There are significant ideas here that I haven’t seen described before. Here is Morgan Jones:

All “uni-pivot” arms plus many conventional arms have the center of mass of the counterweight below the pivot point, and will have the effect of making the effective VTA very sensitive to arm angle. The tracking force has an even greater effect on the angle of the stylus to the groove as the stylus swings up and down.

A unipivot only needs to have its center of gravity fractionally below the pivot point, yet most arms have it way below the pivot point in a misguided belief that it’s more stable. It isn’t. The center of gravity should be fractionally below the pivot point so as to minimise the length of the pendulum and maximise its resonant frequency. A higher resonant frequency allows damping to be applied more effectively. Further, most unipivots apply their damping poorly. You need least damping for normal up and down motion following warps, a little more to follow record eccentricity (which is slower) and most to damp torsional movement of the arm. The other important point ignored by most unipivots is that the pivot height ought to be at the same height as the stylus tip. Again, it’s a misguided belief about stability. Naturally I’m biased, but here’s the arm I made that uses all of these design features (see pictures in this posting - J.A.). It looks as though the center of gravity is very low but that’s because the pivot height is at stylus/record height, not 3/4″ above as is common.

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Thom Mackris recently sent the following observations on cartridge set-up to his friends, and asked me to put them up on the blog. These observations back up something I learned in one of Wally Malewicz’s talks at the Rocky Mountain Audio Fest: that tonearms with under-hung counter-weights will change the effective VTA (Vertical Tracking Angle) quite a bit, depending on the height of the cartridge. All “uni-pivot” arms plus many conventional arms have the center of mass of the counterweight below the pivot point, and will have this effect. The tracking force has an even greater effect on the angle of the stylus to the groove as the stylus swings up and down. Here are Thom’s observations:

Recently, I’ve seen several references to extremely high tracking force recommendations for the Dynavector XV-1s cartridge - forces as high as 2.5 to 2.6 grams which is considerably above the 1.8 to 2.2 grams specified by the manufacturer.

Comments made on various audio forums also referred to Harry Pearson recommending that the XV-1s be set up in this manner. My experiences with the XV-1s is not in agreement with these observations. My results show the low side of the recommended range to work with the two samples I have been running in - even during the early stages of break-in when the cartridge’s suspension is the least compliant.

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