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Old 30th November 2008, 10:52 AM   #1
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Default Another thread regarding CCS vs BOOTSTRAP

Similar threads may have appeared here touching the subject of CCS versus Bootstrap configurations and I have simulated and build two identical amplifiers one using a CCS and the other a Bootstrap.

Interestingly enough the amplifiers overall performance is very similar, identical output, band width and overall THD.

However they sound remarkably different the amplifier using a bootstrap has a warmer and friendlier sound while the one with CCS has a more clinical and harsh sound.

Following is the amplifier with CCS, its band width and harmonic distortion at 1kHz, 10 kHz and 100 kHz.

Then follows the amplifier using a bootstrap with its associated illustrations.

The front ends on both amps are identical, current through the VAS, output swing and bias through the output devices are identical.

One can see the difference in sound by observing the harmonics, the one using the CCS reveals higher odd order products.

Yesterday after some of my buddies and I watched England getting thrashed by the All Blacks, we auditioned both amps and seven out of nine preferred the sound of the bootstrap.

Interesting.......
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Old 30th November 2008, 10:54 AM   #2
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Default Amp with CCS

Attached is the simple amp using CCS
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File Type: gif ccs.gif (5.4 KB, 994 views)
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Old 30th November 2008, 10:56 AM   #3
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Here is the same amp using a bootstrap.
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File Type: gif bootstrap.gif (5.0 KB, 963 views)
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Old 30th November 2008, 11:04 AM   #4
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Default CCS Performance Graphs

Attached are the CCS performance graphs

http://digisec.co.za/ras/music/CCS%20Perf.pdf
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Old 30th November 2008, 11:10 AM   #5
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Attached are the bootstrap performance graphs.

http://digisec.co.za/ras/music/BOOTSTRAP_Perf.pdf
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Old 30th November 2008, 11:57 AM   #6
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Hi Nico. These kind of reports is what makes DIY-boards such a great place to visit. Hypothesis - experiment - report. I find this last and very important part missing far to often.
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Old 30th November 2008, 01:56 PM   #7
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HI Nico,

What about CLG and OLG from each ?

Thanks.

-Ed
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Old 30th November 2008, 01:57 PM   #8
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Hi Nico

Good work, distortion figures like these could also be seen at the patchwork thread. I have one question, did the bootstrap circuit sound as detailed as the ccs one, by detail I mean for example fingers sliding accross guitar strings, that type of detail, not necessarily based on high frequencies? Ive never used bootstrap circuit before, maybe I should try one sometime.

England smashed by All blacks again, I ll drink to that.
. I still have a case of Castle I brought with me from SA, for the special occasions. I ll be in London next week again so Ill have plenty to at the pubs.

Nico, are you maybe familiar with a SA audio designer in the early 90s based in I think it was Meyerton or Vereeniging??. They had some tube, mosfet and speaker designs.
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Old 30th November 2008, 02:04 PM   #9
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Good research Nico,
I was given a hard time in my Patchwork project for choosing the bootstrap. Reasons being better PSRR for the CCS - proved not to be an issue at all for the amp, and reduced linearity at low frequency - as demonstrated to be overblown. I did a little experiment here that compares the performance of the actual bootstrap to the simulated one. While this is not directly related to the CCS vs bootstrap argument, the results do show the shortcomings of the bootstrap to be exaggerated.
I have not had the opportunity to compare identical amps using CCS and bootstrap, as all of the (working ) amps I've built have a bootstrapped VAS. I'm not sure that I would hear a difference.
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Old 30th November 2008, 03:24 PM   #10
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Hi Homemodder,

Detail in that respect is the same, but when I say more clinical means a little sharper, 'S' sound is more pronounced. This is a direct attribute to the higher level of the 5th and 7th harmonic.

Higher up in the spectrum this does not matter that much since we cannot hear 50 or 70 kHz, but it is particularly noticed where our ears are more sensitive.

Anyway, I will not conclude that either is better, but the difference is very noticeable on all kinds of music. I think it is a matter of preference as one will notice that the typical specification as one may put it is very much alike.

John,

I will post THD at 100 Hz for both in a moment. Sorry I should have run these as well but I normally optimize where the ear is most sensitive.

Kindest regards

Nico

P.S. if some one feels like building either of these amps I will post the component values, but I did not think at the time that it was important, it is not intended as a project.
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