Mission 774 Arm

[karma67]

4 tins of baked beans gets the turntable up in the air with room to work underneath

[walpurgis]

4 tins of baked beans gets the turntable up in the air with room to work underneath

Spaghetti Hoops sound better!

[tomb]

Forgot to give you guys an update... got the cake really well secured with some carefully positioned cable ties (around various points on the chassis of the deck).

Had some fun and games with alignments, especially due to the ease of screwing up the azimuth when adjusting the wand length etc...we had it dialled in ok when I dropped it off a few weeks back, but my brother reckons he’s got a really good Stevenson alignment on it now... he’s confounded as to why it can’t get Baerwald but afaik it’s because the offset angle is fixed at 21 degrees or so...

What do you guys use on your 774s? Perhaps this is worthy of a new thread on its own...?

[Barry]

Do Mission quote the offset angle for their 774 arm? I have had a look at vinylengine.com but it only states the effective length to be 229mm and the overhang as 13.6mm. Are these figures correct?

Armed with this information and assuming IEC figures for the maximum and minimum groove radii, we can calculate the overhang and offset angle for the Baerwald alignment to be 18.14mm and 24.1 degree respectively. If DIN figures for the maximum and minimum groove radii are used, the overhang and offset angle becomes 17.1mm and 23.5 degree.

If we look at the Stevenson alignment prescription, the calculated overhang and offset angle are 15.9mm and 22.7 degree.

None of these figures tally with figures of 13.6mm and "21 degrees or so", but are closer to Stevenson than Baerwald. I would imagine your friend was able to set up his arm the follow the Stevenson alignment because he was able to alter the effective length of the arm far enough to set the overhang to 15.9mm.

[Barry]

According to http://www.edsstuff.org/docs/tonearm_specifications.htm,

the relevant values for the Mission 774 arm are as follows:

Effective length: 229mm
Overhang: 13.6mm
Offset angle: 20.5º
Pivot to TT spigot distance: 215.4mm.

Given these figures we can calculate the radii for the two null-points to be 60.5mm and 99.9mm. These are the points that need to be marked on the alignment protractor.

(Compared to the null-points following the Baerwald geometry of 66mm and 121mm.)

http://theartofsound.net/forum/showt...earm-alignment

[Martyn Miles]

I am seriously thinking about selling my 774 arm.
Please message if you're interested.

MGM.

[mikeyb]

I am seriously thinking about selling my 774 arm.
Please message if you're interested.

MGM.

If this is for tomb, he bought my one