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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control really)
BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control really)
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Old 1st April 2020, 09:15 PM   #891
Nikon1975 is offline Nikon1975  Austria
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Is the 64 step board available somewhere? I have the small one with 16 steps.

D
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Old 4th April 2020, 02:10 PM   #892
MrSlim is offline MrSlim  Canada
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I have Han's gerbers for the 64 step one, that would be pretty low cost to make a small batch (prototype) from jlcpcb.com. I've had good luck with them in the past.
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Old 4th April 2020, 02:19 PM   #893
Tfive is offline Tfive  Germany
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If you're interested in making the whole preamp board with 64 steps you could also use the one I did in kicad: VolCtrlDR - Balanced Stepped Volume Control

The PCB shown on the page was also done by JLCPCB. Had several different boards fabricated by them and they all turned out great.
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Old 4th April 2020, 09:25 PM   #894
alexcp is offline alexcp  United States
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BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control really)
I have no 64-step PCBs left, unfortunately - only 16-step and BPPBP. The link to Hans Polak's gerbers (and other documentation) is in the post #861. You can order three PCBs from OSHPark - they offer free shipping, and if you only need one, two, or three PCBs, they are a tad cheaper compared to any Chinese PCB maker if you count in shipping.
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Old 7th April 2020, 03:20 PM   #895
Nikon1975 is offline Nikon1975  Austria
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Dear All,

I built the circuit with the original board from eurocircuit that I got with the Linear Audio book.
I am having only the hot phase out. Strange that this affects both channels and both inputs in the same way I am kind of puzzled. I am trying to trace the signal.

At R7/R16 I see the two phases (My input has phases shifted 180 degrees).
When I get to R2/13, on one side I see the signal in opposite phases on the other side they have the same phase.

Not sure how this is possible.

Any hint ?

Thanks,

D.
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Old 7th April 2020, 03:56 PM   #896
Nikon1975 is offline Nikon1975  Austria
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I guess it is designed to work like this and I read the article, but I am not sure I fully understand. Let's go running, maybe I'll be enlighted.

D.
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Old 7th April 2020, 11:27 PM   #897
alexcp is offline alexcp  United States
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BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control really)
It is a common misconception that balanced output must have two anti-phase ground referenced signals on hot and cold wires, even though some balanced outputs do work like that. To quote the original article (page 3):
Quote:
Take-home messages
Differential transmission of audio doesn’t mean you need to make a symmetrical voltage.
An input that expects a symmetrical signal is not differential because it’s trying to involve a third node into the equation whereas voltages are only measured between two nodes.
The BPPBP circuit is not designed to drive both hot and cold outputs in anti phase - it should be clear from the schematic. You get one output signal between the hot and the cold wires, not two ground referenced signals in anti phase.
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Old 8th April 2020, 09:25 PM   #898
Nikon1975 is offline Nikon1975  Austria
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This is my plain vanilla implementation.
Partly done with scrap parts:
The chassis is from an old Russian multi channel analyzer
The transformer from a Japanese signal generator
The panels used to be a door

The only interesting bit is the mechanical demultiplier that I also took from the signal generator. I still have to produce a decent concentric knob, but basically when you turn the outer ring you act straight on the pot.
When you use the inner ring (where the knob is now connected) the pot turns very slowly. I hope that this device, together with a mechanical stopper (also to be done tomorrow), will make the system usable. I only made measurements so far, will listen tomorrow.

Regards,

Davide
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Old 8th April 2020, 09:37 PM   #899
MrSlim is offline MrSlim  Canada
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Davide, Great job with the Re-use!
The big question is: How does it sound?

John
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Old 8th April 2020, 10:10 PM   #900
Nikon1975 is offline Nikon1975  Austria
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Quote:
Originally Posted by MrSlim View Post
Davide, Great job with the Re-use!
The big question is: How does it sound?

John

Will know tomorrow.

D
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