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Old 1st April 2015, 11:19 PM   #1
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Location: Prior Lake, MN
Default New Dual Mono Super BA-3

Just sharing my latest build. It is a Nelson Pass BA-3 (Burning Amp 3). Features 6 stereo inputs. Goldpoint 24 position attenuator. Jung Didden Super regulators for each channel. Face plates and knobs subject to change. It is an improvement over my BA-3 (ASM) Audio Society of Minnesota build 2 years ago.
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Old 1st April 2015, 11:21 PM   #2
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Default Additional

The back side.
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Old 1st April 2015, 11:22 PM   #3
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Default Front

Will likely use a Maple front and change the knobs. It is big....
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Old 2nd April 2015, 02:51 AM   #4
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Default Clarify what I mean by dual mono

So each channel has it's own power supply independent of the other. No shared power transformer, regulator or raw supply. The channels share just a common star ground. The stereo input relay board has it's own power supply to operate the relays. I am using it in "stereo mode" as I am feeding it left and right signals. Should have excellent performance as far as cross talk goes.
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Old 2nd April 2015, 03:16 AM   #5
ammel68 is offline ammel68  United States
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Great work! I'm jealous.
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Old 4th April 2015, 07:36 AM   #6
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Torchwood421 View Post
So each channel has it's own power supply independent of the other. No shared power transformer, regulator or raw supply. The channels share just a common star ground. The stereo input relay board has it's own power supply to operate the relays. I am using it in "stereo mode" as I am feeding it left and right signals. Should have excellent performance as far as cross talk goes.
Might be worth investigating using separated audio grounds for the two channels, with a pair of separate Disconnecting Networks to connect each channel to the Chassis.

This would overcome the common problem of introducing a ground loop when feeding a stereo (or dual mono) power amplifier.
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Old 17th April 2015, 07:01 PM   #7
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Default Star ground

Quote:
Originally Posted by AndrewT View Post
Might be worth investigating using separated audio grounds for the two channels, with a pair of separate Disconnecting Networks to connect each channel to the Chassis.

This would overcome the common problem of introducing a ground loop when feeding a stereo (or dual mono) power amplifier.
Thanks for the comment. Actually that is a really great idea. I'll have to investigate what sort of network to use. So far it is dead quiet. I really enjoy the clarity and imaging on good recordings. The Goldpoint attenuator is superb.
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Old 19th April 2015, 09:14 AM   #8
Marra is offline Marra  United Kingdom
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That's lovely work Torchwood.

What db of gain did you opt for?

My board is on it's way and my build will be similar to yours with separate power supplies(Salas bib regs) but a common transformer which has four secondaries.
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Old 19th April 2015, 03:10 PM   #9
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Smile Gain

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Originally Posted by Marra View Post
That's lovely work Torchwood.

What db of gain did you opt for?

My board is on it's way and my build will be similar to yours with separate power supplies(Salas bib regs) but a common transformer which has four secondaries.
Hi Marra, This Nelson Pass BA-3 is built per his schematic. So I think that is 25 db gain. The devices "JFET's" are a matched quad and matched to 0.1 mA. They were also within Nelson's current specification for the design around 7 mA. If you can "get" well matched JFET's. I found no need for a balance control. I do have gain adjustments on the Class D amplifier, so I am covered just in case. You should get awesome results with the Salas regulators. The Antek power transformers I used are very cost effective so I decided to use separate transformers. Separate winding will be just as good. My regulated rails are at + and - 22.5 VDC. This design benefits from a good volume control. I find the Goldpoint to be very transparent. No real coloration. I have ordered a set of Curly Maple knobs and plan to leave the brushed Aluminum front plate. Please share your build and any thoughts on it I'd love to see it.
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Old 24th April 2015, 12:47 AM   #10
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The schematic says the gain is = 30 db.
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