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Azimuth meter

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Fatmangolf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2013 at 8:55pm

The finished unit. The meters are Left separation, phase difference, and Right separation. The switches are on/off and the Left +6dB/neutral/+6dB right.


I used a Farnell 14 pin adaptor board and realised I could get the 22uF caps and the links between pins 9/10 and 12/13. I built it quickly and took it off the breadboard and into the box with fast point to point wiring.

It works and the preset pots on the L/R meters allowed me to balance FSD on the signal meters. I miss the precision of a DMM on the 2V scale and will add terminals for this.

Edited by Fatmangolf - 02 May 2013 at 9:43pm
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Fatmangolf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2013 at 10:19pm
Use of the device:

Azimuth adjustment means altering the angle of the stylus/cantilever and coils or magnets, trying to get the cartridge vertical in the groove. Unfortunately the mechanical and electrical parts may not be perfectly aligned.

Look at the cartridge straight on and imagine rotating it clockwise or anti-clockwise. If you headshell or arm fitting allows this then you can experiment with the azimuth.

The standard azimuth test is to put a mirror under the cartridge and check the cartridge and its reflection match. Or make sure the turntable plinth is level then put small spirit level on top of the headshell, adjust the azimuth for level.

Beyond that you can adjust for the best sound, listening for width of the soundstage and clarity of instruments across it. Or use a multimeter on your preamp outputs (or the speakers - use earplugs as M.Fremer suggests) and play a test record with left signal only and right signal only tracks.

On the Left only track there will be some spillage onto the Right side or crosstalk, and vice-versa. Measure the Left to ground and Right to ground level for both tracks, It's the relative levels or separation that you're measuring but be aware that not all cartridge are perfectly balanced so one channel may be louder whatever you do. This also means that adjusting azimuth so the left and right only signals are the same level may not give perfect azimuth (or anti-skate setting).

If you're still reading you can use the voltmeter measurement of separation and then listen for the clearest sound.

My experiment with phasemeter was about the phase of the dominant left channel to the crosstalk on the right. I have read that minimising the L-R (and R-L on Right only track) phase difference sounds best. My setup showed the lowest and similar phase differences at the same azimuth as the maximum separation, which also matched. Inevitably it was really close the vertical position I found with spirit level earlier.

You'll need to draw a table where you write channel level and phase difference on the Left only and Right only tracks. Take these measurements for each incremental step on azimuth. I took a shortcut and measured the level headshell followed by slightly ACW and slightly CW. You could run through a series of steps.

If you want to experiment and make it repeatable you will need a tubular spirit level so you can roughly measure and note the azimuth angle between headshell angle and level. I used one of the keyring levels Maplin sell for £1. It works but is imprecise. I considered a more sophisticated version with a longer tube sourced on the Internet but the sun came out...

Obscure point: the offset angle on most arms means that rotating the arm at the pivot to adjust the azimuth also alters the cartridge alignment slightly. Like arc alignment, VTA/SRA and VTF, it's all linked. Not much to be fair.

Like the standard height/arc/downforce/bias settings your sound will improve if you get the azimuth right, but it may be fine tuning IMO.

In conclusion if it sounds good it probably is good.
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jul 2013 at 10:37pm
It has moved forward a bit. I've disconnected the panel meters and fitted 2mm sockets for Vmag, Vphase and 0V. I am trying a -15dB attenuator at the moment which will move Vmag for typical cartridges into the flatter part of the IC's curve.

My overall approach remains the same. The optimal electrical azimuth should be where the inter-channel crosstalk is minimised and equal and the phase differences are equal. Ideal if the cantilever/stylus are aligned with the electromagnetic system.
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 10 Jul 2013 at 10:03pm
The Vmag starts at around 900mV for an equal L and R signal input, then the deflection is 30mV per decibel. Up to 1.9V (it overshoots!) for left channel only and down to about 20mV for right channel only. Vph is easier as it drops by 10mV per degree of phase difference from about 1.8V with no phase difference between left and right.
Jon

Open mind and ears, whilst owning GSP Genera, Accession, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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