SA2022 - Modular High End Analog Precision Preamp (with headphone amp, digital controlled relay volume, monitor output, IR remote, SE and bal. I/O)

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#41
Have 3 Rohde & Schwarz UPL in restauration. This will soon improve my measurement capabilities.

In fact the preamp is far better as I have thought it could be. The baseboard design which mostly makes cableing obsolete due to very low impedance balanced interconnects is a direct hit.
Also the new developed headphone amp which is able to drive even a 8 R load is a highlight.
Soon 2 new input modules will be presented. A MM (with a MC preamp extension as daughter board) phono stage (D. Self design) and a own design USB dac with PCM1794A powered by Amanero Combo384 module to connect a PC, Laptop or even a Raspberry Pi et al on the fly for outstanding sound quality. The controller firmware will get extended features to control the DAC and the phono stage
 
#43
PCB sets are available for interested users. Maybe some day commercial but for now I would send it for mostly the price I have payed for + packing + shipping. Just PM me.
I haven't thought about complete kits ... it depends on the crowds interest... 😉

BR, Toni
 
#44
Today got the 1mm lightblue acryl to cnc machine the knobs background.
 

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#47
The base kit was a sainsmart 3018. Have done a complete redesign of the Z-axis and replaced the T-nut profile. Using better spindle 12000RPM 400W with frequency controlled 3 phase motor. Control PC is a raspberry pi running opensuse tumbleweed and the CNC software is bCNC.

BR, Toni
 
#49
theoretically yes if you have internal balanced connections. otherwise you need to change the input buffer design. maybe possible by adapting values...
The base frequency can of course be changed. D. Self has detailed calculation information in his book.

BR, Toni
 
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#50
this is really a very nice project and a lot of thought and planning went in to this, wow.

i want to use the tone boards for a balanced salas dcg3 build with variable gain.
I am also looking for a variable loudness controll board, for the easy listerning moments.
I will look in to how to change the base frequenty.
I really like the use of rotary switches a lot.

just let me know when and how to buy boards from you!!

regards,
John
 
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#53
What a coincidence. I'm currently evaluating relays. I don't like the "Z" types, because they contain nickel. Might do THD. According to the Omron data sheet, they do not contain nickel, but silver and gold. Of course, it could be that the information is incomplete and the core is also made of nickel. Good measurements would be necessary here. Unfortunately I don't have the opportunity at the moment.
 
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#55
I read it somewhere (Self?) that nickel is not supposed to be good. I can't find the paper now. With my modest measuring equipment I could not find anything now (3V, 2k load). All good so far.
 

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#58
Afaik all small signal relay have the possibility to "fail" after years of usage. "Fail" is defined as increasing contact resistance if the minimum load can't be guaranteed. It depends also on the humidity environment where there are used. I see no problems here for normal usage for several years. Think we get problems with lytics years before any relay "fails".

BR, Toni
 
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