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B1 Buffer Preamp
B1 Buffer Preamp
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Old 27th July 2008, 03:38 PM   #331
cadaverdog is offline cadaverdog  United States
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Default I am using this transistor.................

Phillips BF861B

This one is available from DIgikey. It seems to match the specs quoted in Nelson's article, it's cheap, and from the datasheets- it looks to have good performance.

I have attached my design of a pcb that I came up with in order to utilize the smd jfets.

I'll attach the other one without the ground plane on the next post.
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Old 27th July 2008, 03:54 PM   #332
cadaverdog is offline cadaverdog  United States
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Default Here's another one..............

This one is sans ground plane.

You would need two of these for stereo.

As you can see, the PSU is on board; the electrolytics I'm using are 2700uF Panasonic FM.

There are pads on the board for power in out, led, input, and the pot.

Also note that here is room enough for those big-honkin' coupling caps that we all like to use.

I wanted to purchase Mr. Pass's boards, but I didn't know if they would be configured for SMD devices.

Thank you for sharing your designs with us Mr. Pass, I've been waiting for a simple design like this for a while.
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Old 27th July 2008, 04:25 PM   #333
cadaverdog is offline cadaverdog  United States
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Default BTW..........................

I've been reading some of the posts about using a battery supply for this buffer, but in my opinion- the current draw in this circuit is so low- and the capacitance is so high that all you'd really have to do is perhaps use EMI filtering on the AC side- and refrain from using switching power supplies.

As far as the rectification in cheap "wall-warts" go, you could always opt for an AC "wall wart"- and use hexfreds on the board itself.
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Old 27th July 2008, 08:32 PM   #334
Tolu is offline Tolu  Germany
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Default square wave measurements

I just have read the article of NP in enjoythemusic.com. What surprised me a little bit was the figure of the 200kHz measurement of square waves.
The B1 was praised with high bandwith and low distortion. So, the square waves at fig. 5 were at first half more than sine waves. Yesterday I had a long conversation at a birthday party with M. Bayer of Omtec Audio (e.g. phono pre Antares) and he told me that his class A devices all have perfect measurement results up to 500 kHz. He always develops only with his measure equipment and not with his ears.
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Old 27th July 2008, 08:47 PM   #335
MRupp is offline MRupp  Germany
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Not sure what you are trying to say ? Are you shure you are not mixing up bandwidth response with the reproduction of sqare waves of a given frequency? From the article: "... Figure 5 below shows a 100 kHz square wave at 1 volt at the output. The bandwidth of the preamp is -3dB at about 700 kHz." Btw. it says 100 KHz in the text and 200 KHz in the accompanying chart.

P.S. ONLY developing with measurement equipment and not with his ears says a lot about Mr. Bayer.
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Old 27th July 2008, 10:10 PM   #336
Tolu is offline Tolu  Germany
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No, I am not mixing bandwith and freq. response. The square wave isn't square. It has a curve! Not more, not less!
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Old 28th July 2008, 12:30 PM   #337
Skorpio is offline Skorpio  Denmark
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I have nov finised a B1 version with 10uF BGF for coupling capacitors, 2sk163, 680K gate resistors and 820ohms for series in and output resistors (parts from the home stock).

Supply is 24V from capacitor multiplier and it sounds wonderfull and no hum/noise audible at all

One question:

I am planning a ICEpower poweramp with a 8k input resistance and 1.2V sensitivity. Will this match the B1?

Or is it possible to reduce the output series resistor to ex. 100-200 ohms?
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Old 28th July 2008, 04:43 PM   #338
Nelson Pass is offline Nelson Pass  United States
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B1 Buffer Preamp
I wouldn't worry about it, but you could probably go down to 221
ohms without problems.
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Old 28th July 2008, 05:02 PM   #339
Tolu is offline Tolu  Germany
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@NP

When will the PCBs for B1 be available?
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Old 28th July 2008, 05:11 PM   #340
Diomedian is offline Diomedian  Canada
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Quote:
Originally posted by Tolu
@NP

When will the PCBs for B1 be available?

"Soon". :-) Just relax, and use a perf board or a vector board if need be.

-d
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