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B1 Buffer Preamp
B1 Buffer Preamp
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Old 12th February 2018, 11:00 PM   #4411
rickmcinnis is offline rickmcinnis  United States
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That is what I needed.

While i am at it, I am using the 220K you specified in your LIGHTSPEED volume control.

Is that about as high as one should go?

Is there an ideal? Is this something that would vary with system? As I would expect ...

THANKS, ZM
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Old 21st February 2018, 08:31 AM   #4412
Mixi is offline Mixi  Europe
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I've been thinking about building a passive pre for quite some time and just now i read about the B1 buffer pre which looks like a very nice project. Of course I have a few questions for the people on here who know more about electronics than I do (probably most people :-).

1.) I was planing on building a super simple passive with just a volume control and a selector switch. (signal in --> selector switch --> pot --> signal out). Now as far as I know there wouldn't be an impedance issue between my phono pre, passive and power amp using a 20k pot. So here's the question: Assuming no buffering is actually needed, would there be any benefits (or drawbacks) in using a B1 over the mentioned "super simple" passive?

2.) people seem to use a variety of different caps for the B1. Will the caps actually affect the sound or is it just a matter of taste or a matter of what spares people have in their tool box :-) ?

3.) it seems the B1 uses linear pots instead of log pots. why is that?

4.) the input impedance is determined by the resistance of the pots used - but what's the output impedance of the B1?

Thanks,
Michi
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Old 21st February 2018, 07:23 PM   #4413
Decker is offline Decker  United States
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I have an answer to question 1 and maybe question 2. I have tried a simple passive, a B-1, and maybe a dozen preamps with gain over the years. In my system, the B-1 sounded "better" than the simple passive, and better than the preamps with gain. I use tube amps, generally with 50-100k ohm input resistance. If you are using a CD player, tuner or other source with more than 1 volt output, you might not need any more gain. As far as coupling caps are concerned, I tried different types and did not find a preference. None of them were $$$$, but I did try metalized polypropylene, film and foil, and paper in oil, and concluded that the differences were insignificant. As always, YMMV. I liked mine so much, I built one for my son's system.
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Old 21st February 2018, 09:28 PM   #4414
Mixi is offline Mixi  Europe
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hi decker. thanks for sharing your experience.
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Old 21st February 2018, 09:40 PM   #4415
Variac is offline Variac  Costa Rica
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B1 Buffer Preamp
Hi Mixi,

I’ve used “super simple, just a pot” instead of a preamp in the past because my components should work well together, but the sound was alway kind of wan and thin and just didn’t sound as great as I expected. Tried the buffer, and the system sounded a lot more solid. So it worked for me!
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Old 22nd February 2018, 07:54 AM   #4416
Mixi is offline Mixi  Europe
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Quote:
Originally Posted by Mixi View Post

3.) it seems the B1 uses linear pots instead of log pots. why is that?

4.) the input impedance is determined by the resistance of the pots used - but what's the output impedance of the B1?

Thanks,
Michi
Thanks a bunch! Anyone have answers to my other two questions :-) ?
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Old 22nd February 2018, 08:16 AM   #4417
mjf is offline mjf  Austria
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lin or log pot.........everybody has his personal preference (lin: more precisely, less abbreviation between the two channels;
log fits subjectively better to the "loudness properties" of the ears );

a buffer amp has a low output impedance, ideally near zero ohm.
in the B1 it is dertermined by R104/R204 = 1kOhm in the signal path......
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Old 23rd February 2018, 02:56 PM   #4418
Mixi is offline Mixi  Europe
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seems like some people use batteries to power the B1. are there any advantages or disadvantages (except the obvious like having to change the batteries) in using batteries instead of a mains connection? how long will the b1 run on say to 9V batteries in series?

regarding the vol pot. isn't it common practice to use log pots for audio use? any special considerations why one would use linear pots in the b1?
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Old 8th March 2018, 01:15 PM   #4419
trung224 is offline trung224
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I have few question about the original B1:

1. Can I omit the C100 and C200 input caps if my source (DAC) is direct-coupled?

2. If yes, do I need to change value of other components ?

Thanks,
Trung
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Old 8th March 2018, 01:37 PM   #4420
tborzic is offline tborzic  Croatia
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Hi, Would it be possible to increase R1 a bit in order to lower PSU voltage?
I will be using 20V PSU, so I was aiming towards recommended voltage, especially if BF862 would be in question.

If possible, is there a need for changing C1 also, since R1 and C1 are working/acting as noise filter?

Thanks
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