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Old 14th August 2012, 12:37 PM   #61
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Bonsai maybe you ve done some measurements, dont you find higher order harmonics actually being higher relative to the total THD obtained when using Low feedback on your designs. I use mostly current feedback amps and did not look at this intently till now, but clearly the pattern as JLH predicts happens. Local vas feedback is not a good option with CFB amps though because of stability.
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Old 14th August 2012, 05:59 PM   #62
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The inner loops must be faster over outer loops e.g. a local nfb should have a -3dB higher than the encompassing loop, the global nfb. Using this, local feedback generally shouldn't be clashing with global feedback in my opinion.
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Old 14th August 2012, 09:40 PM   #63
a.wayne is offline a.wayne  United States
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Originally Posted by Bonsai View Post
Precisely because it allows me to experiment between lower loop gain, lower VAS stage local gain and the high loop gain options. High loop gain is not a prerequisite for success - I think the sound of both my amps attest to that.

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Old 14th August 2012, 11:59 PM   #64
Bonsai is offline Bonsai  Taiwan
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Bonsai maybe you ve done some measurements, dont you find higher order harmonics actually being higher relative to the total THD obtained when using Low feedback on your designs. I use mostly current feedback amps and did not look at this intently till now, but clearly the pattern as JLH predicts happens. Local vas feedback is not a good option with CFB amps though because of stability.
Yes, higher order harmonics are greater with low feedback. I do not want to get into a feedback debate because on hi feedback, low feedback, no feedback I am basically agnostic. For me what's important is that if I decide to in any of the directions, I can do it and get good results.

OT/ BTW I am just waiting for PCB's and parts for two new amps -sx and nx that will use CFB. But, these are very stripped down designs targeting simplicity. Still a few weeks of work, but I will blog it as I go along ok my website /end OT
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Old 15th August 2012, 12:00 AM   #65
Bonsai is offline Bonsai  Taiwan
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How would we know ...
Trust me

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Old 16th August 2012, 06:38 AM   #66
dadod is offline dadod  Croatia
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Ty.
Did you simulate this amp with your models? I would appreciate your comments.
dado
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Old 16th August 2012, 10:05 AM   #67
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Dadod I havent had time for proper inspection, so far I just changed all the semiconductors and looked at a quick sim, The figures were worse but Im using models made through private company and I find them more accurate than most others so I was expecting this anyway. Stability wise things looked good though, TMC puts the performance of this circuit on another level.
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Old 15th September 2012, 03:19 PM   #68
dadod is offline dadod  Croatia
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Default Low Power version

Here is low power version and very good to start with this amplifier.
Challenge, now, it to design good PCB according to discution we had in other thread starting somewere here: Has anyone seen this front-end before?
I know that here, in thst forum, are very skilled layout designers capable to do good job. I will tray to do my best also and suggestion and a layouts are wellcome.
dado
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Old 16th September 2012, 07:11 AM   #69
dadod is offline dadod  Croatia
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Default BOM

BOM is here.
dado
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Old 2nd October 2012, 08:34 PM   #70
dadod is offline dadod  Croatia
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Thanks to catalin a wonderfull sziklai here is a variation on the TCM. What do you think if it could work, simulation is OK? TCM capacitors and resistor could go lower.
dado
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