Second attempt at Building my own amp from scratch - Page 9

AndrewT · 11th December 2012, 12:35 PM

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.

Vostro · 11th December 2012, 02:52 PM

I've explained the best I can.\
but to much off topic

AndrewT · 11th December 2012, 04:56 PM

where's the answer to my restating the same question?

jaycee · 11th December 2012, 05:58 PM

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

AndrewT · 06:50 AM

Quote:

Why are R41 & R42 different value?

1600wide and 170kB

compare to post76 @ 213kB

canonnica · 13th December 2012, 05:03 PM

Vostro, what improvement did you notice by replacing Q21 fron 2N5551 to MPSA42 ??

Vostro · 05:14 PM

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

Vostro · 20th December 2012, 11:41 AM

Quote:

Originally Posted by AndrewT

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.

Regards

13th December 2012, 05:11 PM	#87
Vostro diyAudio Member Join Date: May 2012 Location: Other side of the fence	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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11th December 2012, 12:35 PM	#81
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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.

11th December 2012, 04:56 PM	#83
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	where's the answer to my restating the same question?

11th December 2012, 05:58 PM	#84
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	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

13th December 2012, 05:03 PM	#86
canonnica diyAudio Member Join Date: May 2011 Location: Quebec	Vostro, what improvement did you notice by replacing Q21 fron 2N5551 to MPSA42 ??