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In Reply to: RE: Atma-Sphere MP-1 Mk 3.3 interior photo posted by Brian Walsh on October 27, 2015 at 19:20:52
is a thing of beauty. IMO, one of the unappreciated bargains in commercial audio. Looks like they've gone to ladder type attenuators, motor-driven. Is that so?
-was replaced by a Shallco part similar to what you see in the photo with the introduction of the MkII (about 1997).
I'm guessing you must have a Mk1 to be asking that question (I know your preamp is modified but it must have started life as a Mk1).
Both controls are built along the same lines; the Mk1 employed a custom Electro-Switch part (similar to what you see in a Convergent preamp, but more decks). The Shallco part of the MkII and later sounds a little better purely on account of its construction.
With the Mk3.1, the taper of the control was changed to reduce Miller effects mid-band in the control and to make the use of digital products easier. The Mk3.2 took this a step further; in the Mk3.3 the Gain Trim controls were changed to a shunt-style system making them secondary volume controls in their own right so now you can set up the gain structure however you want.
This was important because in the Mk3.3 the phono gain is so much higher that with most LOMC cartridges the output is about the same as you see from digital sources. If you had speakers with more than about 95 db 1 watt/1 meter or an amplifier with over 30db of gain, you might have had troubles with the main control not having enough notches at the bottom end of its range. With the Gain Trim system thus updated this problem is eliminated without a down side.
Yes, my unit is a Mark I and has the Electroswitch volume control, but more important than the brand, mine has (or had) a series type attenuator, and I was asking whether the Shallco attenuator is a ladder type. About a year or two ago, I replaced the Electroswitch attenuator with a stereo balanced shunt type, using nude Vishay resistors. That was quite a worthwhile upgrade.
As you know, on the old PCB, there just is no room for a stereo balanced ladder type attenuator, because the tubes interfere. Thus I concocted a shunt type, which fits nicely.
Yes, that is what you get with the remote volume control option.
So much music, so little time!
That IS a thing of beauty.
Where should I list my MP-1 mk3.2 "for sale"?
How much should I ask for it?
The update for a MkIII, 3.1 or 3.2 is involving mostly the preamp section and some minor power supply work.
Thank you Ralph
I'll let you know when it's on it's way.
Euphoria Speaker Design
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