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.
Face plates and knobs subject to change. It is an improvement over my BA-3 (ASM) Audio Society of Minnesota build 2 years ago.Attachments
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.
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.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.
This would overcome the common problem of introducing a ground loop when feeding a stereo (or dual mono) power amplifier.
Star ground
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.
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.
Gain
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.
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.
Parallel outputs
Hi Ryan, I do have a double pair of RCA connectors for the output. I plan to use the second set for a subwoofer amplifier. On my ASM build this worked fine although it depends largely on the input impedance and cable length. At one time I had dedicated left and right subs. My Maggie MG2.5R's are just a little to tough to match. At least with cheap ported subs. Just to slow. Thinking about a Rythmic F15HP sealed sub next time around. So yes if the input impedance is at least 50 K Ohms on both amps it should work OK. I detected no loss of fidelity or loading effects. Thanks for the question, Dave
Hi Torchwood; my BA3 pre is up and running all be it with a single transformer at the moment. I went with 220R for R13 as I don't think that I need 30db of gain.Sounding good so far but only a few hours of listening.
A link to some pics.
http://www.diyaudio.com/forums/pass-labs/258022-ba-3-preamp-build-guide-19.html#post4305050
A link to some pics.
http://www.diyaudio.com/forums/pass-labs/258022-ba-3-preamp-build-guide-19.html#post4305050
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.
Hi, can you share what board/kit are you using for the input selector?
Thanks!
Nice build
Hi Marra, Enjoyed the pictures. A very nice build. I have around 200-300 Hours now on mine. Just love it. P3 is centered. No plan to adjust this one. Love the pin point imaging on good recordings.
6 input stereo switch
Hi Jean, I used this one. Hope the link works.... Input Selector 6CH Kit (6-to-1 Way Stereo)_Input Selector_Accessories Kit_Analog Metric - DIY Audio Kit Got mine from them via the big auction site. You can also buy direct. It comes with a 5 VDC regulator on board. Needs +8 VDC. The circuit was perfect, I added 2 small Polypropylene capacitors at the electrolytic's. It comes with all the parts ready to assemble. My LED's are mounted at the front panel and I made a cable assembly. 4 inputs wasn't enough for me, 6 is perfect.
Hi Jean, I used this one. Hope the link works.... Input Selector 6CH Kit (6-to-1 Way Stereo)_Input Selector_Accessories Kit_Analog Metric - DIY Audio Kit Got mine from them via the big auction site. You can also buy direct. It comes with a 5 VDC regulator on board. Needs +8 VDC. The circuit was perfect, I added 2 small Polypropylene capacitors at the electrolytic's. It comes with all the parts ready to assemble. My LED's are mounted at the front panel and I made a cable assembly. 4 inputs wasn't enough for me, 6 is perfect.
Analog Metric
Hi jean, They offer a number of items. I have 2 of the TDA1541A D/A. Had to change the designs on that. Had a goofy reclocking scheme that doesn't work. Once you eliminate that, add a better I/V and filtering scheme (off board). Input receiver and digital filter. Sublime. The boards are very heavy, high quality items. The designs sometimes need work. So were possible study the circuits before purchase.
Hi jean, They offer a number of items. I have 2 of the TDA1541A D/A. Had to change the designs on that. Had a goofy reclocking scheme that doesn't work. Once you eliminate that, add a better I/V and filtering scheme (off board). Input receiver and digital filter. Sublime. The boards are very heavy, high quality items. The designs sometimes need work. So were possible study the circuits before purchase.
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