Dropping the voltage on a 401.

[Paul Dimaline]

Been meaning to try this for a while but never got round to it. The cheap way is to wire a lightbulb (parallel or in series I cant remember) but today I managed to pick up a nice variac. Its a big bugger, 5-10 amps the guy in the shop reckons so its a bit overkill but it will come in handy i'm sure.
Got it running at 170v at the moment and this allows the eddy current brake to be almost fully wound off, and at this voltage the neon still works which is handy.
Listening test to come later tonight but a quick play with a stethescope most definatly reveals less motor noise with the reduced voltage.
This has got me thinking however, do the Loricraft power supplies reduce the voltage? From reading the website it would seem not as it says you can run other components from them, so are they just a filtered supply?
Right, off for a listen now, will report back later.


Paul.

 

[Peter Stockwell]

The light bulb works, has to be in series IIRC, I didn't really notice much difference when I tried it.

Lowering the voltage and having the eddy brake off is a 'good' thing. Garrard lore has it that the more voltage into the motor the more vibration in the motor.

The on deck strobe is only as useful as the accuracy of the mains frequency.

 

[Paul Dimaline]

Well, had a good listen last night and.......not a lot of differance to be fair. I think the music lost a bit of impact and there was slightly less sibilance, but the effects were subtle and could easily have been imagined.
As I am using a £22 cartridge and very old Kef Coda's driven by 20 year old unserviced amps perhaps the system is not capable of revealing subtle differances. This is more than likely if i'm honest!
What cant be denied however is the reduction in mechanical noise from the motor unit when the voltage is reduced. This is clearly audible by ear, but the stethescope threw up a (pleasant) surprise. Listening to top plate it is quite obvious when the voltage is reduced, but if you place the stethescope on the (decoupled) arm board this is a lot less noticable. The noise that I had assumed to be a worn idler bearing has all but dissapeared. This can only be good news surely?
When I built the plinth I had concern's over mounting the delicate arm and cartridge on the same board as that massive motor, hence I decoupled the armboard with a rubber gasket. Last night convinced me that I am on the right line of thinking, even if I have not yet taken the idea as far as I could.
I will have a go at varying the voltage tonight, although I am no longer expecting to hear much differance.
For referance, from what I have been able to determine, (info is very scarce on the web) the Dr. Bastin's power supply outputs around 200v, although that is secondhand info.