Phonostage (WAD clone) and 12B4A Preamp Build - diyAudio
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Old 17th January 2012, 03:26 AM   #1
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Join Date: Mar 2005
Location: NY
Default Phonostage (WAD clone) and 12B4A Preamp Build

I had built a WAD phonostage clone and a 12B4A line driver in a wooden wine crate. The power supply was housed separately. The phonostage hummed a bit. The line driver seemed fine. So after a few years, I thought I'd better put it in a proper shielded box.

This set up was in the library with some 2A3 monoblocks and a Garrard 401. But the cartridge had an unfortunate accident, so I thought might as well get off my butt and get this done.

I put the new kit in the main system in the living room replacing my Linn Linto.

This is the WAD phonostage circuit. I don't show the step up and 10k loading resistor. (Or the 1st grid leak). The CCS on top of the 1st stage passes 0.9mA and the one under the CF 0.8mA.
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Here's the PS.
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Here's the 12B4A line driver. I used a Sowter preamp output transformer. Running 120V on the plate.
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Here the Pre's PS (don't hold me to that first cap value, I need to check it)
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Here's the first stage CCS
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Everything went together nicely. I did enjoy the prices at Digi-key over Radio Spares, now that i am in the US. And I used Sonic Cap for some caps.

I lined the box with copper. Here's the hard wired rat's net.

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I sprayed the box with semi-flat black.

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Here's the separate power supply.

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In it's new habitat.

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Obligatory glowing tube shot

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And my trusty and dusty WAD push pull.

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I'm no reviewer when it comes to writing about the sound. Just sounds really good. A bit different from the Linto. Lush and maybe not with as much attack as the Linto. But needs time to settle in.

Oh and extremely quiet the phonostage is. Scary quiet. At moderate levels, switching from CD to Phonostage just barely gives a tiny bit of noise. I was shocked. Of course, turn the dial to "10" and it is noticeable.

Funny thing is that the pre amp is giving me a warm dose of hum. I don't recall that before. I'll have to look into that. But later....

Last edited by lt_texan; 17th January 2012 at 03:34 AM.
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