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Old 27th October 2005, 08:50 PM   #11
Mad_K is offline Mad_K  Norway
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Marius, the zener at the input is there to prevent any static discharge from destroying the mosfet, and can be omitted if you are careful when connecting the preamp (touch RCA gound to power amp chassis before plugging it in). As always, there are no zener in my amp
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Old 28th October 2005, 06:34 PM   #12
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Thanks for answering mads, i was still writing when Nelson posted.

-marius
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Old 28th October 2005, 06:42 PM   #13
moe29 is offline moe29  United States
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Quote:
As always, there are no zener in my amp
You must be a Fearless DIYer to walk in the Class A amplifier woods!
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Old 28th October 2005, 07:00 PM   #14
steenoe is offline steenoe  Denmark
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Quote:
You must be a Fearless DIYer to walk in the Class A amplifier woods!
Just right, Moe I always prefer to have the zener input protection onboard You never know when someone starts fiddling with your system, do you???
The resident ("Female") is one possibility!!! Some other freak might also be tempted to do some "reorganisation"
You are doomed, whatsoever. I kind of hate that ****, resoldering for the fourth time the ZVP3310 on my Zen amp
BTW I am glad you take look at this forum, Marius

Steen

I nearly forgot the most important thing: Great work Mads
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Old 28th October 2005, 07:24 PM   #15
Mad_K is offline Mad_K  Norway
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Thanks for the comments guys!

Moe, I've reason to be fearless: No matter how careless I have been , I've yet to blow something up. Usually, I'm quite concentrated when fiddling with my stereo And, the female never does anything but
play music on my system

I've made a pcb layout, and will submit it for production over the weekend toghether with a MM-pre and preamp of the same (but common source) topology; essentially a Pacific and a BOZ).

Here's a screen dump of the pcb layout in case anyone is curious:
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File Type: jpg sewa-ra-layout-dump.jpg (96.3 KB, 7557 views)
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Old 28th October 2005, 07:38 PM   #16
steenoe is offline steenoe  Denmark
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Quote:
Here's a screen dump of the pcb layout in case anyone is curious
Yep, we are curios allright What does the preamps look like?

Steen
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Old 28th October 2005, 07:49 PM   #17
Mad_K is offline Mad_K  Norway
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They are called Atlantic (MM Phono, two stage JFET passive eq, like Pearl, only much simpler) and Moschatus (Pre, one IRF510 in common source mode, like BOZ). I will link up the schematics in the projects section on my webpage as soon as they're ready
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Old 28th October 2005, 07:57 PM   #18
steenoe is offline steenoe  Denmark
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On a second look, that is one qute, little board you made there!

Steen
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Old 28th October 2005, 10:20 PM   #19
Mad_K is offline Mad_K  Norway
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Thanks. It was a very easy layout. Not really necessary with a pcb, but I like to design them
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Old 29th October 2005, 11:53 AM   #20
djk is offline djk
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For those of you that would like to use a zener, I would suggest adding a 1N4148 type diode in series with it.

The zener acts like a non-linear capacitor with changes in the input signal. A 100 ohm resistor in series with it (as Nelson suggested) helps, and so does an extra series diode. The extra diode allows the zener capacitance to charge, but as the signal changes the extra diode holds the charge so as not to discharge back into the input node.

I think both 47K resistors could be increased by an order of magnitude, to 470K, making the input impedance much higher. This may be of help for peoples using a tube preamp, or an input transformer (for voltage gain), or a transformer volume control (some of which can have voltage gain too).
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