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-   -   X-Calibre : Hot Rodding Mauro Penasa's LM3886 design (http://www.diyaudio.com/forums/chip-amps/69167-x-calibre-hot-rodding-mauro-penasas-lm3886-design.html)

rudi 5th December 2005 12:57 PM

X-Calibre : Hot Rodding Mauro Penasa's LM3886 design
 
X-Calibre: Hot Rodding Mauro Penasa's LM3886 design

Mauro Penasa designed a very "different" LM3886 amp
http://www.diyaudio.com/forums/showt...threadid=54571
This is a really great sounding amplifier and tweaking it is allot of fun

There has been allot of speculation as to "tweaking" this design and unfortunately it has been shot down several times.

Here is a tweakers board, you can try allot of different configurations on it even build the original design on it, if you want, Minus the bridge rectifier

I will be doing a bit more documentation on it and how to build it,

My design uses
2 x 550VA transformers
8 x 10 000 Sprague 40v caps
16-x MUR 860
And all other caps are Rubycons

Regards
Rudi

rudi 5th December 2005 12:58 PM

PCB
 
2 Attachment(s)
PCD - component side

rudi 5th December 2005 01:00 PM

2 Attachment(s)
Front view

rudi 5th December 2005 01:01 PM

2 Attachment(s)
Back view

Dr.H 6th December 2005 05:26 AM

Hoe klink die blerry ding?!
 
Rudi, that's what we all want to know!
For the chaps in outer Mongolia to decide to build this after they built Rev C, they need to know that this outperforms previous designs. Also some specs perhaps?

rudi 6th December 2005 06:12 AM

Hi Dr.H

I do not want to give Mauro the idea that I am being disrespectful to his intellectual property. But he will have to give us something new because this one (for me at least) is much better. There is no way that I am going back to the old design - this one beat it hands down. in one word CLEAN

Sound staging is wide, while keeping a pinpoint accurate focussing
It has a depth that i did not pick on the original.
The entire sound spectrum cleaned up, bass is tight well defined. mids are sweet and very clean and tops are just spectacular,

The basic specs are the same as the original. i have just changed board features

* Possibility for larger input caps. The big boxy ones normally sound better
* Bipolar feedback cap configuration
* Parallel main caps. - You can get the advantages of more expensive caps by doubling up two caps
* snubber - if you want that. I tried it and it worked well, gave some life back to the amp
* Series or shunt regulation for the LM318 or even both if you want.
* Discrete diodes for the bridge rectifier MUR 860

for the rest. It is exactly the same as the ref C, the main reason for me making this board available is that I thought that you can really make this amp sing. And that is where Mauro had the vision and I just want to give it the drive, as you can see in essence it still Mauro layout and 90% of his design. I just added the BLING

rudi 6th December 2005 08:06 AM

2 Attachment(s)
just realised that we are missing the components

Dr.H 6th December 2005 11:25 AM

In the spirit of DIY, thanks to Mauro
 
I've listened to Rudi's X-amp. It is very very good. We are all here to DIY and in that sense I think that Rudi has taken a great design and gotten even more performance out of it.

The sound of X:

Most noticeable was the quietness/blackness of the background, with no noise/hash present.

Extended, detailed and airy highs-lovely to listen to, no hint of grain. This is a real strong point in the amps performance, giving a real sense of musical timing, especially in acoustic jazz feauring cymbal work.

Mids were wonderfully detailed and present in the performance. In one instance, for the first time, I heard voice vibrato on a well-known piece by a female vocalist.

Bass was fundamental, i.e. not rolled off, but deep and powerful. The body of an acoustic/upright bass takes on more flesh/realness than previously.

Staging and presence were reference class.

Shortcomings? The amp needs a good pre to show its best. We started the listening session with a passive ALPS, but the pot tended to some warmth/bloom in the lower mids/upper bass. Replacing with a passive NOBLE cured the problem.

Bottom line is that I was intending to build REVC to replace my 3875-based design. I will now be building X-Calibre, the jump in performance is compelling!

Nordic 6th December 2005 11:46 AM

Yeah been talking to Rudi on the phone, actualy had to nag him to post the amp, seeing how there are so many people who are quick to dismiss anything.

I realy like what he did to the amp, although it is certainly no longer a low cost one. Will be one of those multiple month projects for me.

I was in two minds about adding that much capacitance, but Rudi was so convinced and compelling after actualy hearing his amp, there was no containing him.

I look forward to ordering my boards

First we gave you the heart transplant operation, now the x-calibre... proudly souf efrican

carlosfm 6th December 2005 04:43 PM

Quote:

Originally posted by rudi
* Possibility for larger input caps. The big boxy ones normally sound better
* Bipolar feedback cap configuration
* Parallel main caps. - You can get the advantages of more expensive caps by doubling up two caps
* snubber - if you want that. I tried it and it worked well, gave some life back to the amp
* Series or shunt regulation for the LM318 or even both if you want.
* Discrete diodes for the bridge rectifier MUR 860

Hi Rudy,

You are obviously in the right direction, and you start to solve some of the issues that made me have absolutely no interest about this amp, it would not perform to the levels I'm used to with my LM3886.
This is not any critics to Mauro, which I respect, but I see this amp since the beginning as an exercise.
There are lots of things to improve there (and still are), but I stepped out of the discussion because:

1. I find the design unappealing. You can do better with less parts.
2. There was some 'animosity' on the other thread against whatever I (and others) said about the design, even if it was a suggestion to help improving it.

Yes, you have better results by snubberizing those big caps.
Yes, you have better results with discrete diodes, and the MUR860s are very good. This was reported years ago by Peter Daniel.
What are you guys doing, sleeping?
We are discussing this for years, working hard and sharing it here and you guys go all the way back and make the same mistakes all over again and then 're-discover' the ways to improve the amp, while this is old story for us that have extensive experience with these chips.

PS: Ryan, listen to the amp with the AD815 pre. ;)


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