ART MPA Gold - Starved Plate or Tube!!??
« on: November 12, 2008, 03:02:04 AM »
I recently bought an ART MPA gold preamp because I thought it was a tube preamp but there has since been various threads debating it's claims to be a tube preamp!?

http://forum.cakewalk.com/tm.asp?m=1543560&mpage=2&key=

Most people say that swapping the tube makes a big difference to the sound of the MPA Gold but a small number of people say it makes no difference at all!?

I would really value your thoughts and expertise on this whole debate!


elektrovolt

Re: ART MPA Gold - Starved Plate or Tube!!??
« Reply #1 on: November 12, 2008, 10:15:25 AM »
I have one, it has a switch for high and low plate voltage. the high setting sounds a little more natural, more high end. swapping tubes to JJ ecc803s did a good job, less dull and better details.
it is not that much of a difference though. the tube is between two opamp stages, no it is not a true tube circuit.

Denyle Guitars

Re: ART MPA Gold - Starved Plate or Tube!!?? New
« Reply #2 on: November 12, 2008, 03:44:25 PM »
I measured about 220v on the ax7s with the tubes removed. I thought mine sounded grainy and did away with it without trying any other tubes.
« Last Edit: November 13, 2008, 10:01:25 AM by Denyle Guitars »

stanz

Re: ART MPA Gold - Starved Plate or Tube!!??
« Reply #3 on: November 12, 2008, 06:49:39 PM »
I had an ART TPS II, when I opened it up and saw the Red LED behind the tube, I was pretty bummed. Had several issues and had sent it back, and even after that, the metering wouldn't switch between input/output. Knowing what I now now, let's see, one 12ax7 for two channels, hmmmm.

Mylithra

Re: ART MPA Gold - Starved Plate or Tube!!??
« Reply #4 on: November 13, 2008, 01:43:35 AM »
Starved Plate would be less than 100v at the tube. (more likely something around 50 or so volts.. if that) The MPA Gold has at least 180v at the tube. The switch on the front says 300v for the high plate voltage but I found that to be inaccurate. It ends up being around 200v. While maybe not the High voltage some other preamps use, ( speaking of those with 400v +) its far from starved.

gyraf

Re: ART MPA Gold - Starved Plate or Tube!!??
« Reply #5 on: November 13, 2008, 03:59:38 AM »
..but no in- and out transformers that i can see. This is probably the most important problem for the sonic imprint of the unit...

Jakob E.
..note to self: don't let Harman run your company..

Mylithra

Re: ART MPA Gold - Starved Plate or Tube!!??
« Reply #6 on: November 13, 2008, 05:14:07 AM »
No.. no signal path trannies here. Ive not done this to mine, but I dont imagine it would be all that hard to wire one in.

nickt

Re: ART MPA Gold - Starved Plate or Tube!!??
« Reply #7 on: November 13, 2008, 06:01:51 AM »
http://www.harmoniccycle.com/hc/images/sound/ART_MPA/ART-MPA-Gold-schematic.pdf

Interesting looking circuit. Current mirror plate loads feeding a current mirror.
As far as I can tell it's running at +150V.

But what does it mean?


Schemo was from this thread: http://music-electronics-forum.com/showthread.php?t=7971&highlight=ART+Gold



 

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