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B1 preamp build thread
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Old 12th March 2018, 06:47 PM   #411
Zen Mod is online now Zen Mod  Serbia
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B1 preamp build thread
it's OK , except no need to post in several threads

no need for 1M after balance pot

lower values of R104 and r204 to anything between 22R and 51R
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Old 12th March 2018, 07:56 PM   #412
Syl20m is offline Syl20m  Finland
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B1 preamp build thread
Thanks Zen mod,

not sure to understand why to lower R104/204, is it because of selected values for balance /attenuation?
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Old 12th March 2018, 08:03 PM   #413
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other reasons , to keep output impedance lowest possible
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Old 13th March 2018, 06:58 AM   #414
Syl20m is offline Syl20m  Finland
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B1 preamp build thread
Hi Zen,
i am mainly going to use the B1 with A FirstWatt M2 Clone, which has a imput impedance of 100K.
i was also reading ... you are going same direction than Papa, but 22-51R isn't that too low?
B1 Buffer Preamp

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Old 13th March 2018, 07:12 AM   #415
Zen Mod is online now Zen Mod  Serbia
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that's idiot proof part , Papa put there as protection , taking in account that B1 was commercial product , with all possible consequennces

however , when I'm making some gadget , I'm only idiot going to use it , so why not optimize it ......

you can omit that resistor completely , meaning - you can put short instead
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Old 13th March 2018, 06:01 PM   #416
Syl20m is offline Syl20m  Finland
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Thanks zen
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Old 14th March 2018, 04:30 PM   #417
Mixi is offline Mixi  Austria
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i'm currently gathering parts to build a B1 buffer. now i'm trying to find out which DPDT switch to order for input switching. NKK makes nice toggles. there's the normal version rated at 6A and the "fancy" one rated at 0.4VA with gold plated contacts. would it make any difference witch one i use for input switching?

here's the pdf with the NKK toggle switches: NKK Toggles
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Old 14th March 2018, 04:52 PM   #418
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Cool B1 selector switches

Characteristics to look for in a switch for line-level work include:

Silver plated contacts. Yes, gold is prettier and doesn't oxidize as quickly, however silver has always sounded a lot better than gold, and its' oxide is very soft and designed to be displaced by the action of the switch contacts.

Douglass Sax, of The Mastering Lab, says he can always hear a gold contact in an audio signal chain! I'm not sure I can, but Doug has done some really fine work in his day. It has always amused me to see all of the gold in use nowadays, just another example of manufacturers' fashion statements at work.

Secondly, switches should preferably be make-before-break, to avoid the possibility of a nasty pop occurring at the moment of switching. You can probably get away with break-before-make if your sources are free of any trace of DC on the outputs.

Last edited by jeffharr; 14th March 2018 at 04:54 PM. Reason: addition
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Old 14th March 2018, 05:03 PM   #419
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thanks!

so I guess the one with silver contacts would be better suited although with a rating of 6A @ 125V AC & 3A @ 250V AC it seems to be a power switch. but i guess it wouldn't matter if it switches much, much less than that, would it?
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Old 14th March 2018, 05:05 PM   #420
6L6 is offline 6L6  United States
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B1 preamp build thread
Use the smaller one. Don't worry about contact material. The smaller one will be easier to use, nicer to touch, and more appropriate for the teeny signals of sources.
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