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Old 24th February 2013, 04:42 AM   #581
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by sonidos View Post
Here is something sold by one of the vendors on this site that might work for equalization -

miniDSP

It looks like just the thing to do auto EQ of headphones. Very good price, too.
Thx-RNMarsh
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Old 25th February 2013, 07:28 AM   #582
Telstar is offline Telstar  Italy
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Hi Ryan,

I have already available a +-15V regulated PSU, would this voltage be allright for your amp (I have the semiconductors kit from Jackinnj) or should I reduce it?
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"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
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Old 1st March 2013, 10:47 PM   #583
RNMarsh is offline RNMarsh  United States
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Unofficially, yes. I run my little guy at +/- 15v. But the devices would be safer operated at +/-12v.

Thx-RNMarsh
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Old 1st March 2013, 11:42 PM   #584
Telstar is offline Telstar  Italy
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Did you compare the distortion at both voltages?
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Old 3rd March 2013, 04:50 PM   #585
RNMarsh is offline RNMarsh  United States
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I used a bench supply at 12v during development and it was just fine there.
I only use 15v for finished amp because it was the easiest to find a high quality regulator circuit pre built. But it stresses the output devices near there max limits and so I wouldnt recommend it to others.

Having said that, try it if you want to. I have not had a failure yet. Just I would be more conservative when recommending to others. The amp doesnt seem to be supply sensitive when it comes to distortion -- whether 12 or 15volts.

-RNMarsh

Last edited by RNMarsh; 3rd March 2013 at 04:57 PM.
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Old 3rd March 2013, 07:11 PM   #586
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I've used 2SB649AC/2SD669AC for the output devices at higher voltages without failure. The SAO is about the same @15VDC, but ft and gain are higher.
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Old 3rd March 2013, 10:33 PM   #587
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New layout guys, what do you think?
Different approach this time. Following previous advice, it began with small changes and ended with quite a different shape.
I also added optional bypass capacitors, filter cap on the input (220pF), big electrolytic across the rails, and higher bias if needed.
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File Type: png Marsh_headamp_rev5B__bottom_layer.png (42.8 KB, 354 views)
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Old 3rd March 2013, 11:53 PM   #588
RNMarsh is offline RNMarsh  United States
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Cool. Can you give the ground to trace a little bit more space?

-RNM
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Old 4th March 2013, 09:39 PM   #589
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OK, I increased a bit the clearance on the supply rails side, but I prefer not to on the signal side, as it would split the ground plane too much. Do you have any reason that you want to widen it more? The clearance is 16mil, which is quite conservative and should not pose any problem for manufacturing.

I renumbered the parts, and added information on the silkscreen.


I will soon send the files to manufacturer for a quote.
Anybody interested can shoot me a PM. Cost for one board should be no more than $6-8 each, possibly lower if several people join in.
If there is enough interest, we could go for high quality 2oz copper PCBs, possibly gold plated.
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Last edited by CaféNoir; 4th March 2013 at 09:46 PM.
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Old 4th March 2013, 09:53 PM   #590
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Originally Posted by CaféNoir View Post
If there is enough interest, we could go for high quality 2oz copper PCBs, possibly gold plated.
My advice -- tinned boards are much easier to work with than gold
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