Modulus-86 build thread

I noticed that it seems like nobody is using the gain resistor R14 for their builds.
Is it on purpose and am I missing something?
It's on purpose. You add R14 if you want gain higher than 20 dB. But 20 dB is plenty for the vast majority of systems and lower gain means lower noise. Some add a bit of gain to make the Modulus-86 match other amps.

I love the Tower of Power in @solhaga's build. Those are nice and compact amps.

I don’t post on this forum much, but had to come over once I did a test run on my Modulus 86 build. This is a fantastic amp! I’ve been on a tube kick for a while and even using vinyl as a source the background is black and the imaging is superb.

Currently setup with a Thorens TD-121 running and AT VM-95ML into a Hegeman Hapi 2 preamp with the Modulus 86 driving a pair of Yamaha NS-690’s.

Tom’s documentation was easy to follow and very helpful as well. Thanks for the great amp Tom!


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Thanks! The chassis came from Par Metal Products out of New Jersey, they sell on eBay as pimetalproducts. I’ve had a few different projects in the chassis.

I’d like to get a set of rack handles for it and install an indicator lamp on the front. Right now it just has a lighted switch on the back I scavenged from a dead Dynaco 410.

The Modulus drove my AR 303’s this morning and the heat sink got a little warm, but still not bad. They’re 4 ohm and 85db. I think my trusty Stereo 70 will be on the shelf for a while.


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Made progress on the project and now it’s complete! Checked for voltages and offset, everything checked out well. Currently playing this with my ELACs speakers.

Missing power button though. Front plate is thick at 8mm and switch I planned to use did not fit.
Looking for suggestions for a good replacement.


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I just received a couple of these boards to try out. I've used a number of Tom's other boards and modules in various projects.

There is no information regarding C27 in the printed BOM in the documentation and it does not seem to be included in the Mouser BOM. Is this part no longer being used?

EDIT: Never Mind - I figured out that it was the second line for Item 4 - 100nF.
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