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

Preamp Control - Volume, input, mute, remote
Preamp Control - Volume, input, mute, remote
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Old 18th August 2018, 05:01 AM   #11
viki_v2 is offline viki_v2  India
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Quote:
Originally Posted by johnhenryharris View Post
I forgot to attach the pics. Here they are. LEDs overwhelm the cell phone camera.
Very Nice. I will try using this design with a tube preamp if you can share the Gerber of revised and latest design.

What are the pcb sizes.
Thanks
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Old 20th August 2018, 10:53 AM   #12
Neutrality is offline Neutrality  Denmark
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From looking at your mainboard schematic, it looks like you might be missing some functionality that could end up being crucial.

Lets say 00000000 is maximum attenuation and 11111111 is no attenuation.

What happens if you are at 01111111 and you turn up the volume by 1 step?

Remember that realys do not make/break instantly.

Then if you were really unfortunate all relays could be ON for short(1ms or so) while and you would now temporarily end up with 11111111 which is no attenuation at all before you end up at 10000000. the same goes the other way, what if you start at 10000000 and want to turn the volume down by 1 step? you could go to 11111111 temporarily before you end up at 01111111.

I have,while developing my own design, tried it without anything to control the relay timing and it is not pretty, it sounds awful changing volume, with a lot of pops and clicks.

Something to think about.

Last edited by Neutrality; 20th August 2018 at 10:55 AM.
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Old 21st August 2018, 09:36 PM   #13
johnhenryharris is offline johnhenryharris  United States
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The volume goes up and down very smoothly, with 256 steps it is gradual. There is no clicking or popping in the audio. The slight sound of the relays isn't very audible.
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Old 21st August 2018, 09:41 PM   #14
johnhenryharris is offline johnhenryharris  United States
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The main board is 7"x12", the display board is 2.75"x6", the remote is 1.5"x 2".
I will try and attach the gerbers later.
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Old 22nd August 2018, 03:43 AM   #15
viki_v2 is offline viki_v2  India
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Quote:
Originally Posted by johnhenryharris View Post
The main board is 7"x12", the display board is 2.75"x6", the remote is 1.5"x 2".
I will try and attach the gerbers later.
I am starting to collect parts for my tube pre amp. Hope to get gerbers soon.
Thanks
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Old 22nd August 2018, 06:31 AM   #16
GASCo is offline GASCo  United States
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Preamp Control - Volume, input, mute, remote
Quote:
Originally Posted by johnhenryharris View Post
The main board is 7"x12", the display board is 2.75"x6", the remote is 1.5"x 2".
I will try and attach the gerbers later.


Reading from my phone I couldn’t open the BOM to see if the information is there but: what is the estimated cost in components?
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Old 22nd August 2018, 03:40 PM   #17
johnhenryharris is offline johnhenryharris  United States
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ok here are the GERBERS.
In three posts.
Display:
Attached Files
File Type: zip Display_Through_R2.zip (21.5 KB, 21 views)
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Old 22nd August 2018, 03:41 PM   #18
johnhenryharris is offline johnhenryharris  United States
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Main Board
Attached Files
File Type: zip PreAmp Main Board.zip (56.2 KB, 23 views)
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Old 22nd August 2018, 03:45 PM   #19
johnhenryharris is offline johnhenryharris  United States
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And the Remote Board.
Attached Files
File Type: zip Remote_Board_R2.zip (6.8 KB, 18 views)
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Old 22nd August 2018, 03:49 PM   #20
johnhenryharris is offline johnhenryharris  United States
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And of course when ordering the boards you need specs:
Materials:
FR4, overall thickness to be .062” (1.6 mm) +/-10%
Copper Foil to be 1.0 oz finished minimum.
All plated-through holes shall be plated with aminimum thickness of 0.001” copper.
Finish: All exposed copper areas not coveredwith solder mask shall be plated HASL.
Solder Mask: Apply green liquid to both sides ofthe board over bare copper.
Silkscreen: Shall be applied top side with whitenon-conductive permanent epoxy ink. There shall be no silkscreen on anysolderable component pad.
Tolerances:
Conductor widths and spacing shall be within +/-.002” of Gerber Data.
Remove all burrs and break sharp edges .012”max.
Test Requiements: The main board to beelectrical verification for continuity open and shorts.

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