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Chip Amps Amplifiers based on integrated circuits

My_Ref Fremen Edition - Build thread and tutorial
My_Ref Fremen Edition - Build thread and tutorial
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Old 14th August 2019, 06:40 PM   #4171
Panelhead is offline Panelhead
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Do not know. I know it shows using a capacitor to block DC and set a high pass filter is not so bad.
I have a real EVO Rev A in the closet. Need to test it.
GeorgeK and Dario both said it is slightly cleaner than the Fremen due to layout differences. The measurements GeorgeK performed on a Fremen are SOTA. Very few commercial amps are even close.
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Old 17th August 2019, 04:21 PM   #4172
turion64 is online now turion64  United States
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Default Audiophile upgrades

Quote:
Originally Posted by Panelhead View Post
The Evo A Mod builds do respond to tweaking. But are fine with generic parts.
The original designer was a cheap part guy. DIP general purpose bridge rectifiers, zener regulated low voltage rails, low end MF resistors. His later projects evolved to better spec parts.
He felt circuit design, layout, and operating points were 99%.
So I took the plunge and installed the Z-foils at R10 & R12, the Amtrans at C12, 30 & 32 and the Cerafine at 9. I already had the Mundorfs at C13 and C101&201. It still sounds fantastic: excellent low end response, clarity and openness and wonderful resolution overall. However, the Mouser BOM build on the Evo A mod was just as wonderful (as I remember) and its really hard to say that doing the upgrades didnít bias me into thinking that I hear something better than how wowed I was before (with the original build). Iím driving both amps with a single 400VA 28+28 instead of making two monoblocks.

Has anyone actually done a side-by-side real time comparison of the basic build versus with the "audiophile" upgrades? Will dual toroidals bring me anything better? Is it advisable to finish the Z-foil upgrades at R7 & R37?

Thanks

Turion64
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Old 19th August 2019, 03:33 PM   #4173
lehmanhill is offline lehmanhill  United States
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Turion64,

A long time ago, on a different BOM, I did the single versus two toroids comparison. I couldn't hear any difference and didn't measure any significant difference in hum. If I recall correctly, the reason that two transformers were originally specified by Mauro was to increase the hum immunity. As for sound quality, having a big enough transformer is key to getting the best bass performance and you should be good at 400VA. The Mundorf power supply caps are also said to improve bass sound and are very low ESR which makes sense. In this case, I can't say personally because I have always built with the Mundorfs.

I have done many of the "audiophile" upgrades, but I did them in a different order and, sometimes, with too much time between evaluations to make a proper "back to back" evaluation. However, Dario has done a huge number of back to back evaluations and I have never gone wrong following his advice. The "audiophile" upgrades are based on those evaluations and are meant to offer improvements over the base BOM for those willing to spend the time and money. By the way, we really owe Dario for all his work on this project. You would be amazed at the hours and money Dario has spent working on the best BOMs.

As for Z-foils, others have done evaluations and said that each additional Z-foil in the signal chain offers improvement. The FE I am currently using has all Z-foils in the signal path and I changed them all at once (however, lots of other build variations). I can't say that a big sound difference jumped out immediately after the change, but in the weeks since the change I have been enjoying the amp immensely and it clearly sounds the best of any amps I have ever listened to.

In the end, if you like how your amp sounds with the current build, then enjoy it as is. As you said, the base BOM build sounds amazing. There will always be a tweak or two when you want to play again. Actually, when that time comes, I recommend having a second pair of boards so that you can play with tweaks on one pair and keep a build you like on the other pair.

Jac

Last edited by lehmanhill; 19th August 2019 at 03:35 PM.
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Old 19th August 2019, 04:40 PM   #4174
turion64 is online now turion64  United States
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Thank you much for that Jac!

Pete
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Old 20th August 2019, 10:31 AM   #4175
Panelhead is offline Panelhead
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I may have missed some of Mauro’s circuit boards, but all that I built were stereo and used one power transformer. He was very opinionated on stereo versus mono amplifiers.
He had some tricks used to minimize the current spikes with two channels sharing a power supply.
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Old 20th August 2019, 12:22 PM   #4176
turion64 is online now turion64  United States
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Thank you Panelhead... I'll have to search for thosr.

Pete
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Old 20th August 2019, 01:59 PM   #4177
lehmanhill is offline lehmanhill  United States
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Mauro's articles are sometimes hard to find. Here is one that overviews the my_ref project.

Dropbox - project_my_ref.pdf - Simplify your life

Jac
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Old 20th August 2019, 02:12 PM   #4178
Joseph K is offline Joseph K  Hungary
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Nice. To see again that document. That's my translation of the original, that was my little personal offer to the great work of Mauro...
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Old 20th August 2019, 04:38 PM   #4179
lehmanhill is offline lehmanhill  United States
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George,

Nice job. I know that Mauro's English was not great. Better than my Italian, of course. I knew that he had some help in the translation, but I never knew who did the translation. Very nice. Thank you.

Jac
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Old 20th August 2019, 06:48 PM   #4180
turion64 is online now turion64  United States
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Many thanks Jac. I have some reading to do.

Pete
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