Aro bias investigations

Was playing lp’s this morning, on the 3rd or 4th side I thought ‘wow, this is sounding even more amazing than usual (usual being pretty blooming amazing), on getting up to change sides, I noticed that the bias hanger weight had slipped from the first inner slot to the third. I set the bias a la Mark Dunn, bias hanger on first slot and increasing the weight with black tac. I had calculated the required amount of extra weight for the VTF set and had left it at that. This episode got me thinking that an increase in bias weight might improve SQ. I reset the hanger to the first slot and over the course of the rest of the day, added very small pieces of black tac and noting any changes. Well blow me, every time I added a very small amount, the SQ got better! I had added quite a bit extra, in very small amounts over the course of 3 to 4 hours, each time the SQ getting better. At the last addition, suddenly the sound got worse, a sort of deadening and lifelessness, whereas before, each addition seemed to bring more life to the music. On removing this last piece of added black tac, the SQ sprang back to life again, so I guess I’ve hit some kind of sweet spot. Obviously, even though it sounded bloody good to me, I hadn’t got the bias setting anywhere near right, despite carefully calculating and weighing the extra. Anybody else experienced anything like this with the Aro?

Just using the stock weight, there was always one notch that sounded best but it was never the last one.
I was given a few heavier brass weights to try. These allowed me to try different angles for the hanger arm, always ensuring the line ran horizontal to it, bending the arm if necessary. Conversely to what I’d expected, best performance came with the stock weight and the line running parallel to the arm by the end of the side thus increasing bias towards the centre of the record.

I played with bias so much when I had the Aro
Tried more weight / less weight / different angles of the hanger …and after many weeks I decided that they all sounded great…on the right album
There did not seem to be a one solution fits all for me
If you Google Aro bias mods…or similar…you will find quite a few threads on the subject

Pinkfish is good for info too

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