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Author Topic: Anyone tackle the Sunn Beta Lead or similar?  (Read 3832 times)

tra

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Anyone tackle the Sunn Beta Lead or similar?
« on: March 06, 2014, 02:42:12 PM »
I've been trying to get my hands on a Sunn Beta Lead for years, but the few that pop-up on eBay are either in bad shape or priced way out of my pay grade.

Has anyone tackled a DIY version of the Beta Lead? Anything similiar? I really dig the very unique distortion that I haven't really found in another amp.

Loudthud

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Re: Anyone tackle the Sunn Beta Lead or similar?
« Reply #1 on: March 06, 2014, 03:58:05 PM »
I don't know of a DIY Beta preamp. There are one or two clones built into stompboxes that can be found. The biggest problem with the ones made by Sunn is that they need to be recapped. There are about a dozen 2uF non-polar electrolytics that need to be replaced to get the preamp running well.

If you can find one that is non-operational for a good price, buy it. The -15V regulator frequently fails and the amp goes completely silent, even the power amp stops working. There is a hard to find chip that manages the channel select and footswitch logic. The fix for that is a little piggyback module that will plug into the original PCB found here: http://sunnforum.ampage.org/index.php/topic,6864.msg29374.html#msg29374

Edit: The Channel select LEDs on the front of the amp will stop working in both cases above. Normally if you plug into a channel, that channel's LED will come on, both will come on if you plug into the Both input. When the channel select logic goes bad, the power amp will still work if you plug into the Master Effects Return on the back of the amp but the Channel LEDs on the front won't work properly. Sometimes one channel may still work. The power amp has internal fuses that will blow if the power amp goes bad. In that case nothing will work except the light in the power switch. This usually indicates blown transistors in the power amp.
« Last Edit: March 06, 2014, 05:10:34 PM by Loudthud »

tra

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Re: Anyone tackle the Sunn Beta Lead or similar?
« Reply #2 on: March 06, 2014, 04:01:37 PM »
Sweet!

Thank you!