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Old 31st May 2011, 01:05 PM   #41
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I saw this a couple of days ago and started to draw it up. Another entertaining design Elvee. When I looked again mickeymoose had offered to lay out a board.

Here's my stab at it, I've used a 4-way header for the connections to the heatsinked components. As per my usual practise I've filled the unused areas with groundplane, but with a generous clearance, to make for easy assembly if etching at home, but also to save on etchant. All tracks are 50 thou. The board is no particular size (4.45*2.6 in), just the size it came out, I could probably tweak it down a bit smaller, but why? There's a bit more clearance at the edges than is absolutely necessary.

circlophone2.jpg

I went with the packages my schematic tool had built in. The board is obviously single-sided, with half-a-dozen wire links. I've used capacitor pakckages that will accommodate 2 different sizes in the non-electrolytics, the electrolytics are all radial packages which should be big enough, but again I'd be re-checking this when I had the components in hand if I was doing the build myself.

circlophone1.jpg

Some component designations are changed from the original, and of course some errors may have crept in in transcription.

I won't be building one myself in the immediate future so if anybody does want to work from this layout you better scrutinize the board pretty closely for anything you object to and get back to me for modifications.

Graphicode's free GC-Prevue should pretty much swallow (import) the whole .zip file, it'll balk at a couple of places, the drill file, just keep going yes, OK.

circlophone - CADCAM.ZIP

w
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Old 31st May 2011, 01:52 PM   #42
Elvee is offline Elvee  Belgium
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Thanks for your work, Wakibaki,

I have spotted one or two small errors in the schematic, see below.

About the layout, I'm a bit unhappy with the daisy-chaining of the power tracks towards the decoupling capacitors.

It would be better to place C8 near D8, R12, J3-1 and C10 near D9, R24, R13, J3-3, and start from there to distribute the supplies to the low-power circuits.

I have highlighted in white the tracks in question.

Apart from that, everything looks OK.
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File Type: gif Waki1.GIF (105.4 KB, 1395 views)
File Type: gif Waki2.GIF (145.1 KB, 1372 views)
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Old 31st May 2011, 02:01 PM   #43
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OK, I'll sort that out shortly.

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Old 31st May 2011, 02:18 PM   #44
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OK, I'll sort that out shortly.

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Old 31st May 2011, 03:31 PM   #45
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Sorry about the double post, I inadvertently reloaded the page.

Revised circuit:

circlophone_fix.jpg

Positive power distribution:

pos_pwr.jpg

Negative power distribution:

neg_pwr.jpg

Gerber:

circlophone_fix_1 - CADCAM.ZIP


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Old 31st May 2011, 05:04 PM   #46
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Found some definite errors, missing links on the dual pin 1's of the dual size cap packages.

circlophone_fix_2.jpg

circlophone_fix_2 - CADCAM.ZIP


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Old 31st May 2011, 05:09 PM   #47
Elvee is offline Elvee  Belgium
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I see a possible improvement, if you don't mind:

The area enclosed by Q12, Q13, R21 and D9 makes me a bit nervous.

This can be avoided by placing R21 differently:


Edit:
I have just seen that Q10 & Q11 have their emitter and collector swapped.
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Last edited by Elvee; 31st May 2011 at 05:13 PM.
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Old 31st May 2011, 05:24 PM   #48
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Default I like it very much

Congratulations.

regards,

Carlos
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Old 31st May 2011, 05:29 PM   #49
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2N6259 very nice
these are some of the most robust transistors EVER made from GE/RCA. probably similar Ft's to the original 2N3055 but 4X the die size.
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Old 31st May 2011, 05:57 PM   #50
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by destroyer X View Post
Congratulations.
Thanks!
Quote:
2N6259 very nice
these are some of the most robust transistors EVER made from GE/RCA. probably similar Ft's to the original 2N3055 but 4X the die size.
Yeah, they are a bit on the slow side, but the SOAR is phenomenal.


I have made some tests to evaluate the actual necessity of an inductive Zobel.

I have tried increasing values of capacitance starting with 47nF, 100nF, ... up to 2.2µF, directly connected to the output through 25cm leads (10in).
Pure capacitance, no parallel or series damping resistor, test signal a 10KHz triangle of maximum amplitude.

There were no signs of instability, distortion, or anything else.

In conclusion, I think that such a network is not needed in 99.9% of the cases.
Exceptions might be a combination of very exotic speaker cables and exotic loudspeakers, not the kind of target for this simple amplifier.
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