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Simple Symetrical Amplifier
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Old 9th August 2011, 01:28 PM   #111
Lazy Cat is offline Lazy Cat  Slovenia
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Quote:
Originally Posted by Nico Ras View Post
After building a spider web mock-up, my first impressions were that it sounded very good, but after a while it fatigued me a little (listen on headphones HD800s, which is the easiest way to get irritable). Subjectively I would say that the odd order harmonics may be responsible as it sounds too crisp/detailed for my liking. Transients are excellent bass is very tight and probably due to the high bandwidth.

Lazy Cat, I made a few modifications to the circuit and I now appreciate your design much more. The mods evened out the harmonic artifact and the subjective sonic results are excellent (no measurements has been made this is subjective only)

I do not want to corrupt this thread with modifications as I have asked you not to and would like to ask if you would start a new thread calling for Simple Symmetrical Amplifier Updates, and I will post my stuff there.

Kind regards

Nico
So first listening test took place, nice.

Nico I would really like to go on with this thread since it started as not fixed project but the project with evolving possibilities to come to the best solution around the basic core of the circuit and ready made PCB at the end. So any differences made are welcome and there is no need to start new thread, cause that would only bring a confusion. Let this thread finish the design started as a common DIY project, with your strong contribution. I hope you'll agree.
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Old 9th August 2011, 01:30 PM   #112
Nico Ras is offline Nico Ras  South Africa
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AJ, popular wisdom?
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Old 9th August 2011, 01:49 PM   #113
Lazy Cat is offline Lazy Cat  Slovenia
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Quote:
Originally Posted by Stormrider View Post
Per popular wisdom, your grounding is wrong. The main filter cap gnd should not be connected through the star point. They should have their own connection straight across, preferably with solid copper or aluminum bar, and then the center point of that goes to the star. Minor difference in your drawing, but it can be make a big difference to how a PS is wired or laid out on a PCB.
OK thanks AJ, corrected.
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Old 9th August 2011, 02:29 PM   #114
Nico Ras is offline Nico Ras  South Africa
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Thanks Lazy Cat, attached please find my contribution in this regard. As I said the results at this point remains subjective and I will post the simulated results as reference.
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File Type: pdf Lazy Cat Refined.pdf (42.1 KB, 902 views)
File Type: pdf Lazy Cat Refined time.pdf (34.7 KB, 420 views)
File Type: pdf Lazy Cat Refined Ferq.pdf (9.9 KB, 318 views)
File Type: pdf Lazy Cat Refined THD 1kHz 1 watt.pdf (16.8 KB, 385 views)
File Type: pdf Lazy Cat Refined THD 1kHz 40 watt.pdf (16.7 KB, 481 views)
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Old 9th August 2011, 03:19 PM   #115
Lazy Cat is offline Lazy Cat  Slovenia
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Hehehe, I am happy to hear that your listening impressions and simulated results are good. I experienced the same excellent musical enjoyments as you did, only with my BIGBT outputs present.

As I already stated before, clasical current feedback amplifier topology obviously needs buffer at the output and performs an order of magnitude worse if this one is missing.

Your SCH is fixed or it is discussable about some minor changes? Let's say about biasing regulation possibility, for someone to determine the level of quiescent current by himself.

Last edited by Lazy Cat; 9th August 2011 at 03:23 PM.
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Old 9th August 2011, 03:25 PM   #116
Nico Ras is offline Nico Ras  South Africa
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Of course it is open for discussion, it is after all your circuit
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Old 9th August 2011, 03:31 PM   #117
Lazy Cat is offline Lazy Cat  Slovenia
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OK so we are on line both.

Look, few comments:
- I would certainly omit cap at input
- bias regulation from A/B to A class
- feedback loop from the output, to better control load conditions
- maybe mosfet as I/V conversion and BJT as buffer

For now enough, please comment.
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Old 9th August 2011, 03:40 PM   #118
Nico Ras is offline Nico Ras  South Africa
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I have looked at no input capacitor, problem is if input has dc off-set then the offset is transferred to output. Maybe all ancillary equipment is either capacitive coupled or has near zero off-set.

Yes I agree one could bias it class A, but AndrewT mention that it is very heat intensive and maybe needs a few parallel devices for output.

FB loop from output - of course this was a mistake when I drew it neatly, I will fix it. Simulation is correctly terminated.

Last point I do not understand what you mean.
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Old 9th August 2011, 03:45 PM   #119
Nico Ras is offline Nico Ras  South Africa
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Default Lazy Cat Refined Rev01

Have a look.
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Old 9th August 2011, 04:05 PM   #120
Lazy Cat is offline Lazy Cat  Slovenia
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Yes I know that perfectly, I want that the amp is DC coupled overall, maybe someone would use it for turntable DC motor or DC servo motor control, both direction linear regulation.

So no signal bypass caps.

I really didn't mean to put it in full power A class, but it certainly should have bias regulation, cause people found out that at certain bias level amplifier sounds the best, it somehow tracks Gauss distribution curve where you have quiescent current on X axis and pleasure factor on Y axis.

So bias regulation is mandatory.

FB loop from the output settled.

In my last request I meant to have mosfet transistor located as driver and powerful BJT as output device, vice versa as it is in your sch.

I think that mosfet by its nature belongs to this position as we can choose medium power mosfet driver having low Cgs, high forward transconductance, low drive energy for previous stage. BJT as the output device will perform excellent. Also this combination suits my BIGBT philosophy.

Last edited by Lazy Cat; 9th August 2011 at 04:15 PM.
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