Morch DP-8 arm on a Helix Two turntable
@dover at some point I may try the Morch on the Garrard, I would have to get a 12” wand to fit my plinth. I’ve already made arrangements to trade in the DP-6 for a DP-8 so I’m really looking forward to it. This video may be helpful in setting up the Morch DP-8. https://youtu.be/BDk-NlBtkwY |
| Post removed |
@lewm , what is the argument for a high horizontal effective mass? Cartridge manufacturers do not specify a vertical and lateral compliance for cartridges. Are they the same? From my experience they are very close. The arm I have been using for years has a slightly higher horizontal effective mass than vertical. With a host of cartridges the lateral resonance frequency is always a little lower than the vertical resonance frequency. On top of this you have the moment of inertia which determines how much torque is required to move the tonearm in a given direction. This is generally higher for higher mass tonearms and again there are both horizontal and vertical moments of inertia. In any arm the lower the moment of inertia the easier it is for the cartridge following the groove to move the tonearm. Raising the horizontal effective mass is going to lower the horizontal resonance frequency and raise the moment of inertia. This can and does result in a low frequency horizontal wiggle that can be seen on an oscilloscope. I have seen it in air bearing tangential trackers. Because the DV501 and 505 are pivoted the horizontal effective mass would not be as high as an air bearing arm even though the DV's look massive. It would be interesting to check both vertical and horizontal resonance frequencies to see what you have. My instinct has always been to have the horizontal effective mass slightly higher than the vertical to spread out and lower the resonance peak but close enough to keep the resonance frequencies between 8 and 12 Hz preferably under 10 Hz. This has always worked well in my tables and ones that I have set up. I did own a Transcriptor's Vestigial arm once, sort of a light weight version of your DVs. It was an awful arm because it's vertical mass was just too light. It took me 6 months to realize there was no way I was going to get that arm to work well. |
The problem cleverly addressed by the DP-8 is that frequencies below around 150 Hz are recorded in mono. It is simply not physically possible to separate these signals into 45° left and 45° right and maintain the correct amplitude at all dynamic levels. In effect this means that the bass is only cut laterally (horisontally). By placing the lateral f-res as low as possible the frequency and phase response of the bass becomes more linear (= a good thing). Here is the lateral f-res of my DP8/Blue Precision armtube/Ortofon Royal N. https://vintagehifi.dk/forum/download/file.php?id=25271&mode=view Here is the vertical f-res plot of the same https://vintagehifi.dk/forum/download/file.php?id=25272&mode=view How does it sound? in a word "excellent". Is it an improvement on the DP 6? Yes. |
