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Old 11th December 2012, 12:35 PM   #81
AndrewT is online now AndrewT  Scotland
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don't use bitmap. They are enormous file without compression.
You originally used jpeg.
Go into your software and adjust the jpeg compression to give good clarity.
I use Irfanview, there are many others.
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Old 11th December 2012, 02:52 PM   #82
Vostro is offline Vostro  South Africa
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I've explained the best I can.\
but to much off topic
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Old 11th December 2012, 04:56 PM   #83
AndrewT is online now AndrewT  Scotland
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where's the answer to my restating the same question?
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Old 11th December 2012, 05:58 PM   #84
jaycee is offline jaycee  United Kingdom
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the clarity had nothing to do with jpeg quality though.. it was simply at too low a resolution. If it had not been single colour the software may have dithered it.

PNG is good if you can use it, a 256-colour grayscale image compresses well with that.
Personally im happy to scroll a large, clear schematic
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Old 12th December 2012, 06:46 AM   #85
AndrewT is online now AndrewT  Scotland
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Quote:
Why are R41 & R42 different value?
1600wide and 170kB

compare to post76 @ 213kB
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Last edited by AndrewT; 12th December 2012 at 06:50 AM.
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Old 13th December 2012, 05:03 PM   #86
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Vostro, what improvement did you notice by replacing Q21 fron 2N5551 to MPSA42 ??
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Old 13th December 2012, 05:11 PM   #87
Vostro is offline Vostro  South Africa
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The MPSA42 has nicer stats,
But in honesty either works well.
This circuit is a evolution and changes constantly, used for me to learn more.

I don't have instruments to measure THD/distortion,
So to answer your question, the choice to replace the 2n5551 was purely based on datasheets.
I can't notice any difference, on scope and on listening, they the same to me.

What I have not done yet, is check by how much i can lower CDOM,
But I think this will be the last time I use Miller compensation.

Keeping Q23/24 MJE340/350 is also the same

Regards

Last edited by Vostro; 13th December 2012 at 05:14 PM.
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Old 20th December 2012, 11:41 AM   #88
Vostro is offline Vostro  South Africa
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Quote:
Originally Posted by AndrewT View Post
Why are R41 & R42 different value?
They don't need to be different values, they were originally the same value then I increased R42 for already mentioned reason, but there was no 'need' to increase R41, and I was happy with stability at current value, so I didnt change R41 to same value as R42,
This is not symmetric VAS circuit so I don't mind them not being same value.

I've not had any chance to work on the amplifier, and sadly wont till January.

@AndrewT, sorry for not answering sooner, for some reason I didn't see the question on the resistors, guess I was just focusing on trying to export jpg in a better way.

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Old 15th November 2013, 05:30 PM   #89
Vostro is offline Vostro  South Africa
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Ok after getting the previous circuit working, but not confident on the cascode of enhanced Vas and Vas current source I've decided to change it again.

I'm hoping after this revision that it will be my final, and finally will see a permanent enclosure and a place in my sitting room.

I'm awaiting components from store to arrive in next week or so.
Here is the PCB's etched with toner transfer.
Have not drilled the pcb yet
The PCB is hopefully final version but allows me to tweak it still.

I'll be trying TMC but left space to revert to miller cap if needed.
With TMC phase margin is 58deg.

Q1,2,13,14,11,22 2N5401/2N5551 can be substituted with rotated BC550/BC560.

Regards
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File Type: jpg Final CCT.jpg (253.7 KB, 106 views)
File Type: jpg Final PCB Layout.jpg (362.9 KB, 101 views)
File Type: jpg Final PCB Tracks.jpg (304.5 KB, 97 views)

Last edited by Vostro; 15th November 2013 at 05:38 PM.
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Old 15th November 2013, 05:57 PM   #90
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You've done well with the toner transfer, which paper were you using ?
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