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N00b alert: My first amp design
N00b alert: My first amp design
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Old 22nd January 2009, 10:27 PM   #1
HighTower is offline HighTower  Netherlands
diyAudio Member
Join Date: Jul 2008
Default N00b alert: My first amp design

This newbie has been struggling on his own amp design for a while which was supposed to become "top notch". Off course, all isn't as simple as it looks and by now I've realised that my learning process will stretch for years to come, only to find out that there's even more to learn

Anyway, instead of j@rking around by myself with limited knowledge and lack of experience I thought I'd share my "work" with those people that know best, hoping to get some critics I can work with.

Click the image to open in full size.

The schematic I used for spice, I've left out the obvious that have little or no effect on the spice sims like rail decoupling caps and the input filter network.

Click the image to open in full size.

FFT simulated at moderate output power, 2 Ohm load. Is the noisefloor somewhat high or is this to be expected IRL?

Click the image to open in full size.

Simulated freq. response with the schematic as shown.

Now, the onemilliondollarquestion is: Should I start over from scratch ore could the design be polished to a decent performing amp?

For those critics that want to ask; "Have you built it?" Yes, I have, albeit in a somewhat earlier version. The "MKI" version I've built was slightly different with Sanken output devices and a few changes in schematics. The MKI has a bandwith of 500 KHz and is stable with a resistive load no matter what input signal.
Afterwards I discovered flaws on the MKI design so I never got to serious testing and listening.

There are multiple points in the design that I'm having second thoughts about but I'll keep that to myself for know as not to poison your minds with prejudices.

Hoping to learn from your replies - be gentile!!
"If you can't convince them, confuse them." - Harry Truman
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Old 22nd January 2009, 11:36 PM   #2
ostripper is offline ostripper  United States
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Join Date: May 2008
Location: Smoky Mountains , Tennessee
Good job , Hightower , real close .. just a little refinement
possible. You need some type of "dominent pole" compensation,
or you will oscillate. (see below-C4/5) The input is a little too simple,
you need some compensation there ,too. the 100pf at Nfb
is way too much and would throw your phase margin way off.
The vas runs a little hot 20-30Ma..

Just look below , simulate it.. and you will see..
To be simple, what is below is .. I saved it as "babyleach.asc"..
I'd be happy to answer any questions..
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File Type: gif babyleach.gif (21.4 KB, 140 views)
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