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Chip Amps Amplifiers based on integrated circuits

My new monobloc layout for Mauro Penasa's MyRef Rev. C
My new monobloc layout for Mauro Penasa's MyRef Rev. C
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Old 29th February 2020, 05:12 PM   #121
Panelhead is offline Panelhead
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Join Date: Dec 2002
Location: Houston
Quote:
Originally Posted by Naaling View Post
blackh0le has already stated that he is not interested in the Fremen edition.

By the way, I wasn't aware the Rev C had stability problems!

It does not as long as the input capacitor is sized to provide a low frequency filter. There was extensive testing done on the My_Ref prior to public release of the circuits.
The 0.22 ufd value was selected for this reason. The feedback changes in the Evo allows the safe use of a larger value coupling cap.
But I used a 1 ufd coupling cap in a Rev C for years and never heard any issues. It is signal level and frequency dependent.
I had an original My_Ref I modified to Rev C and a set of TP Rev C monoblocks. Build the TP monos like a poor manís ASR Emitter II. Four chassis.
It was excellent. But after building an Evo I retired the Rev C. The Evo drove my speakers better.
I later built a Fremen Evo and used three of the chassis from the TP Rev C. It sounds better to me than the real Evo Rev A. Tests better too.
But I think that can be fixed.
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Old 20th September 2020, 01:26 PM   #122
cgunawan23 is offline cgunawan23
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Join Date: Jun 2019
Hello,
Finally I have completed building Mauro's MyRef C. Not exactly following Russ's BOM.
After 2 days running, my impression for this amp, is a very good sounding. Almost similar, on par, with my HK-990. I use Marantz CD6005 cd player and JBL HP520 floor stander. The bass is very good, mid is good, but treble is a bit wee harsh to my liking. I use a cheap MKP for C13 input cap at 1 uF. I don't use black gate at C9 220 uF. I use also usual metallics resistors.
If I would like to tame the harness a little bit, what parts should I upgrade?

Thanks.

Note: I double posted this to original Mauro's thread, it is much more quiet than this thread. My apology for that.
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Old 20th September 2020, 05:53 PM   #123
Joseph K is offline Joseph K  Hungary
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Location: gran sasso
You have written.. Marantz CD6005..?
I think we found the "resistor" which is causing the problems..

Hey just joking.. That is.. Half joking..
I know that it is a very dirty game to blame the problems on some poor other guys..
But still, that Marantz offers itself so eagerly..

May I suggest something? Do you have access to some analog record player setup? Or a tape recorder, anything..
That could give a different 'point of view' on the amp behaviour.

I am saying this, because it has happened to me constantly.. Adjusting something in the amp, and it starts to 'squeel'.. But later it surfaces that the source was not up to task, and the more revealing amplifier "do not forgive".

Then, apart from this, there are many little faults to be attacked in the Ref-C. I do not know about the topology, have never had the Russ design. But it is different either from the original both the FE design.
The original Ref-C is using a less forgiving compensation. It is using a less performant opamp PS regulation scheme. It id using the LM318, which has quite less power supply rejection capability, than the more evoluted opamps we use in the latest versions..

I think all this together, and maybe, but lastly, some resistors quality could result in what you hear..
For example, the power resistor in the Howland current pump feedback (0.5ohm) -- can be nasty, if not taken care. (like a cemented wire resistor, original BOM).
Also the 12kohm, 390 ohm feedback resistors to be chosen carefully.

I think less than top quality capacitors are rather only sucking out life, rendering things "duller", instead of bringing agressivity..

But before that, make sure about the source.
A. Marantz. CD player.. . . I know that sound...

Ciao, George
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Old 22nd September 2020, 03:23 AM   #124
cgunawan23 is offline cgunawan23
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Join Date: Jun 2019
Thanks for the comment George. Unfortunately I don't have the analogue sources.
I will rebuild again the amp with audio grade resistors and capacitors, and see where it will lead me.

Thanks
Chandra
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Old 26th September 2020, 01:02 PM   #125
cgunawan23 is offline cgunawan23
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Another newbie question please. I happened to install 1N5349B Zener 12V, at 5 Wattage rating for the LM318M shunt regulator. Will the high wattage (5W vs 1W recommended) affect the sound? Thank you in advance.
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Old 27th September 2020, 02:38 AM   #126
madisonears is offline madisonears  United States
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The first component to change is C13. It determines the character of the sound of the MyRef more than any other part. I have built many MyRef's, and experimented with many different capacitors at C13 and all the other parts in the amp. C13 makes the most difference to the sound. It is an excellent amplifier, whether in the original configuration or the Fremen edition.

Every part you improve will make the amp sound slightly better, but C13 should be the first and will transform the sound, especially the high frequencies.

You can use high grade Nichicon such as FG at C9 and get excellent sound. Do not use Elna Silmic because it will muffle high frequencies.

Peace,
Tom E
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Old 27th September 2020, 02:38 PM   #127
cgunawan23 is offline cgunawan23
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Hello Tom,
Thanks for the suggestion and will do that. In fact, I am relocating C13 near the RCA port input for ease of future swaps.
For C9, I use Nichicon Muse FW.

Would you happen to know the question about my Zener replacement with 5W rating?

Thanks in advance.
Kind regards

Chandra
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Old 27th September 2020, 02:49 PM   #128
Joseph K is offline Joseph K  Hungary
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I can not say for sure, but as a firsthand opinion, it should be similar noise wise.. One point could be the dynamic impedance of the diode, at the target current.
It could be higher, for the higher power diode.
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Old 28th September 2020, 12:11 AM   #129
Panelhead is offline Panelhead
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This is apples and oranges but I replaced 1 watt zeners in another circuit with 5 watt and the sound was “grittier” with audible increase in high frequency noise.
They were different brands, same voltage. Changed back to 1 watt. Some zeners are relatively noisey for setting a Vref.
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Old 28th September 2020, 12:20 AM   #130
Joseph K is offline Joseph K  Hungary
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Thank You. I did not try it directly like that.
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