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Old 18th November 2017, 03:42 PM   #221
xrk971 is offline xrk971  United States
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Is the 1.5% THD typical of a resistive current sink SE Class A amp? For my headphone amps, I do same thing and distortion is typically in the 0.1% or less but then it's 70mA bias and 120ohm loads.
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Old 18th November 2017, 04:11 PM   #222
needtubes is offline needtubes  United States
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The load impedance and the power you're putting into it (obviously) affect THD in a significant way. Plus, your headphone amp isn't a pure follower, is it?

Last edited by needtubes; 18th November 2017 at 04:15 PM.
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Old 18th November 2017, 04:33 PM   #223
xrk971 is offline xrk971  United States
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It's not a headphone amp - it's a preamp designed to drive higher impedance loads like power amp input stages. Schematic here:
Click the image to open in full size.

As far as load I am giving it standard 8ohms and 2.83vrms - standard setup for testing amps at 1watt with 8ohm speakers.
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Old 18th November 2017, 05:32 PM   #224
Ultima Thule is offline Ultima Thule  Europe
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Quote:
Originally Posted by JPS64 View Post
Here my first one, again, thank you Mr. Rothacher.

JP
Beutiful PCB JP, but it has unusually many vias, I am a bit curious when you order these types of PCB with so many vias how does it affect the cost?
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Old 18th November 2017, 05:44 PM   #225
Dennis Hui is offline Dennis Hui  Canada
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Quote:
Originally Posted by Michael Rothacher View Post
Starting to bag boards for the store. The first fifty pairs get a spiffy sticker.
Very nice Mike. Hope to see them in the store soon.

It's weird seeing an amp PCB with so few parts...almost like a chipamp.

Cheers,
Dennis
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Old 18th November 2017, 05:56 PM   #226
JPS64 is offline JPS64  Germany
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I thought so too but no extra cost!

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Old 18th November 2017, 07:02 PM   #227
Ultima Thule is offline Ultima Thule  Europe
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@JP

oh, I am surprised, especially to see the amount of vias in your example, thanks JP!

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Old 18th November 2017, 07:10 PM   #228
hifibluedevil is offline hifibluedevil  United States
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Originally Posted by Michael Rothacher View Post
Starting to bag boards for the store. The first fifty pairs get a spiffy sticker.
First come first serve?
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Old 18th November 2017, 07:21 PM   #229
xrk971 is offline xrk971  United States
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I'm not sure if 4 resistors, 2 caps, a pot and a mosfet needs a PCB? P2P is really just the perfect thing here.

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Last edited by xrk971; 18th November 2017 at 07:25 PM.
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Old 18th November 2017, 07:55 PM   #230
Michael Rothacher is offline Michael Rothacher  United States
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Quote:
Originally Posted by xrk971 View Post
I'm not sure if 4 resistors, 2 caps, a pot and a mosfet needs a PCB? P2P is really just the perfect thing here.
Perhaps, but there's large contingent of DIYers, who prefer to have a PCB. I'm trying lower the bar for beginners as much as possible. Also, many prefer the neatness of a board.

And it helps to support the forum we're using right now.
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Last edited by Michael Rothacher; 18th November 2017 at 07:58 PM.
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