music, guitars & other obsessions

Valveking to Vintage Modern, or VK to VM In A Few Simple Steps

I was thinking about modifying the VK212 when I first got the amplifier a few months ago, and came up with some potential modifications. But at the end, I abandoned the idea and went with a near-scratch build – I took out all the PCB’s, and put in a Marshall 2446 Vintage Modern clone in their place instead. This worked out great, since the chasiss has quite large so I had ample room to work with. Of course, I re-used the PT and OPT which were perfectly fine. I also saved the PCB’s from the VK in case if I ever want to put them back (which I doubt seriously). The only tricky bit was to modify the heater supply, since the VM uses one extra 12AX7 tube than the Vk212.

I don’t really like the series heater arrangement in the VK, however the PT came that way, and I did not want add another filament transformer to the chassis, so it would have to do. Of course, the disavantage is if one of the tubes go bad, the whole amp will be out of commission. Since it is just for home use, it is not a really big deal, but I would not want to take it on the road.

Instead of the 6L6’s that came with the amplifier, the output tubes have been changed to the 5881’s that I have laying around, so the output power was lowered to about 75W. I also took the opportunity to add a bias adjustment board, which is the small board mounted above the power tubes that you see in the photo. It came from a scrap’d hi-fi amplifier. With the board, each of the output tubes could be biased individually, which was sorely missing from the original VK212.

With the existing VK speakers, the amp sounded a bit bright to me, then again, I haven’t spend much time with it…

Here are some photos from the build:

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2 responses

  1. On your valvking to VM switch, did you copy the entire preamp circuit? I had a problem with some switching. As I was not going to attempt making a PCB, I wonder if you had a modified schematic I could get a look at? I have modified mine using a few ideas from various forums and while it plays and feels much better, I have been wanting to try that very same Marshall build.

    December 2, 2015 at 4:54 am

    • jazzbo8

      Sorry for the late reply… I did copied the Marshall preamp circuit, of course not the reverb section, which was kept the same as the Peavey design but built on a separate area on the protoboard. Hope this helps.

      I think the Peavey speakers could be better, so there are still some room for improvement to bring the sound to Marshall VM level, just had a listen to Robin Trower’s CDs, the tone just seemed much fuller…

      December 29, 2015 at 7:28 pm

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