ART Power Plant preamp

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F_Ostrander
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Re: ART Power Plant preamp

Post by F_Ostrander » Sun Dec 02, 2018 3:29 am

I wasn’t completely without conveniences. I had figured out how to model circuits using spreadsheets and programs written in Microsoft basic. This circuit leant itself particularly well to such modeling. I also had access to an Audio Precision System One analyzer through my day job as a Project Engineer at Bogen Communications. I later used the same circuit topology to develop Loudspeaker-specific EQ at Renkus Heinz. I ended up doing quite a bit of crossover design (active and passive) and in the mid 1990s wrote two crossover design programs.

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Re: ART Power Plant preamp

Post by F_Ostrander » Sun Dec 02, 2018 4:04 pm

(I had tried posting a reply earlier, but I don't think it took. If it did, some of this will be redundant.)

The good thing was that Buck had nearly ten years' experience using the Power Plant (working with the likes of Al Dimeola and Jan Hammer), and had pretty-much perfected the EQ curves using outboard gear. That made my job was made easier, all I had to do was re-create his curves in hard-wired form.

I had a number of tools at my disposal. I was a Project Engineer at Bogen Communications when Buck approached me and I had access to an Audio Precision System One analyzer. This, of course, helped me immeasurably (no pun intended). I had also worked as an intern at IBM while an engineering student and they had taught me how to use spreadsheets - I had since learned how to use them for circuit development. For the Power Plant I had generated a program in Microsoft Basic that would give me component values for the EQ circuit based on gain, frequency and bandwidth parameters. I later used the same topology as an Engineer at Renkus Heinz designing loudspeaker-specific EQs.

I eventually wrote a pair of Windows applications called Filter Workshop and Active Filter Workshop that aided in the design of passive and active crossovers for loudspeakers. (These programs led to a job at JBL Professional!)

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Andy
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Re: ART Power Plant preamp

Post by Andy » Sun Dec 02, 2018 6:16 pm

Sometimes the forum software imposes that the moderators approve a post, I think that is just an anti spam measure and maybe why your post didn’t take as you say.

As were on a jvm forum , would any of the information you have given us , and your your endeavours in the analog audio world world be useful for JVMs?

thanks for sharing your interesting information !
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Casey_Butt
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Re: ART Power Plant preamp

Post by Casey_Butt » Tue Dec 04, 2018 12:23 am

This is bringing back some dormant memories. I remember running filter programs that calculated capacitance given resistance and 3dB point or something along those lines. In fact, I believe I wrote some simple programs like that as a student (though nothing on the level of complexity of commercial-ready software you're describing). In my engineering student days everything was C++ though, Fortran and Basic were a few years earlier (though the physics world long clung to Fortran). By the time I graduated engineering undergrad (2001), spice programs and Matlab/Simulink had replaced just about all that.

I'm in the process of simulating those Power Plant filters now... just have to check some components. Do you recall the op amp type? I'm getting some weird resonance with the generic model. Perhaps I'll have it figured out by the time you read this.

Andy, how about I come up with a JVM Power Plant mod? smilie=icon_lol.gif
_ JVM410H: "Blackface" Clean channel, "Plexi" Crunch channel, "Dual Rec" OD2 channel, 3rd stage bias pot with switchable 100nF bypass cap, switchable 470k/470pF "treble peaker", OD1/2 Orange and Red extra gain pot, signal boost into power amp, PI voltage set to 2203 levels, 5H choke w/ 50uF on screens, -ve feedback pot.
_ Marshall 2203/1959 clone - switchable (with FX loop, resonance control and -ve fb pot) built from a Peavey Windsor 'donor' head
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Re: ART Power Plant preamp

Post by F_Ostrander » Tue Dec 04, 2018 3:12 am

I believe that we used National LM833s. If you’ve opened a Power Plant you’ll notice that the supply rails were bypassed at every Op-Amp.

Regarding programming, I took courses in FORTRAN Turbo Pascal and assembly language, but the computer of choice in the Engineering department was the Radio Shack Color Computer! Later on I taught myself C. When I decided to write Windows apps I chose Visual Basic for Windows, beginning with version 3 and eventually moving to VB6.

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