Abomination! or Painting a Mustache on the Mona Lisa meets the Island of Dr. Moreau

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roender

roender

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Joined 2006
John,

The RMI-FC100 was designed as a high end amplifier, capable to drive very expensive speaker systems, where every shortcomings are well detected in listening tests.
I was able to detect a BIG sound improvement when I replaced the silly SamWha with MUSE KG capacitors, or input BJTs with JFETs or silly toroids with high quality R-Core transformers. Also, improvement was detected by replacing feedback capacitor with a MUSE NP
We are not able to detect sound changes related with topology/component changes if we don't have a high end speakers and source

Cheers,
Mihai
 
MJL21193

MJL21193

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Joined 2007
roender said:


Did you measured the power supply ripple rejection? How do you know is high enough? What about PSRR at HF?
Do not forget that all voltage references (LEDs) are powered directly from PSU and not trough current sources
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I can measure the rejection in the simulation. I may do that if I have time latter.
The point of my layout was to give the builder (me) the choice of a separate front end regulated supply (which I will try, as mentioned above) or a single supply.
 
MJL21193

MJL21193

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roender said:

We are not able to detect sound changes related with topology/component changes if we don't have a high end speakers and source
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Roender :whazzat:
What do you know of my speakers or sources for that matter? I don't make assumptions about the equipment you have.

Really, step back and take a look at the other DIY amps here and measure my changes to your amp by putting them in perspective.
I notice that you went ahead and made your own version of the Symasym, correct? Did MikeB give you a hard time over that?

I honour you by recognizing that your amp, apart from the layout, is the best available here. That I have made some changes to suit my tastes and to give any other potential builders a choice should be seen as a bonus. Mine uses cheaper and more common parts (not inferior) and has other benefits that you do not acknowledge.

Yours is the ultimate high end, mine is the low end Abomination!
:devilr:
 
roender

roender

Member
Joined 2006
MJL21193 said:


Roender :whazzat:
What do you know of my speakers or sources for that matter? I don't make assumptions about the equipment you have.
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I presume nothing. It is just common sense and a well known fact that isn't possible to detect changes we talking about without a high quality audio chain.
By the way, did you ever heard differences among various speaker cables? :devilr:
Please don't take it personally.
MJL21193 said:

Really, step back and take a look at the other DIY amps here and measure my changes to your amp by putting them in perspective.
I notice that you went ahead and made your own version of the Symasym, correct? Did MikeB give you a hard time over that?
Click to expand...
Hey, I don't understand why you take is so personally. I just want to help you.
If you know better than anyone how all the changes I proposed perform in real world, then go ahead and ignore me.

Regarding last question
Yes, and was a very good lesson :D
MJL21193 said:

Mine uses cheaper and more common parts (not inferior) and has other benefits that you do not acknowledge.
Click to expand...

Like LM394 ? :devilr:
 
MJL21193

MJL21193

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roender said:

Hey, I don't understand why you take is so personally. I just want to help you.
If you know better than anyone how all the changes I proposed perform in real world, then go ahead and ignore me.
Click to expand...

:whazzat:
Where does it seem that I'm taking it personally? Not me, you are reading something into what I'm saying that is not there.

I would love your help. Here's an example of NOT helping: "don't build that drek, build mine"
Anyone who has spent any time reading my words here will know that I don't have all the answers. I do have this answer though - this is a very good amp in every way. There are no compromises by selecting the components that I did.

I don't build high quality speakers to listen to the transistors or caps in my amps, I listen to the music. I recommend everyone does this - less stress. :)
 
MJL21193

MJL21193

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roender said:


By the way, did you ever heard differences among various speaker cables? :devilr:


Like LM394 ? :devilr:
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Speaker cables? No comment.

The LM394 I have, so I may as well use them. I bought those for another project but I will use them here, just to get rid of them. Waste not.
You do see on my schematic that the diff pair are BC550? These are, back to front, the same pin out as the LM394. Options are good.


roender said:

Do you think that I deliberately complicate the design for nothing?
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Yes. If you do not use the fets on input, the gurus will not approve...:)
 
MJL21193

MJL21193

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roender said:


Where did you see that statement in all my posts?
I just want to know that "your" version was tested by me in an earlier stage of FC100 design and was not better than standard symasym.
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Your general demeanor, I guess. Others would agree.

Why put "your" in quotes? It is MY version. Post your "old" version with the MPSA42/92 and the 2SA1381/3503 and the drivers - 2SA1837/4793. Oh, and the other changes I made.
"version" is not the same as "original design".

Well, the Symasym is highly regarded around here, so I can take that as a thumbs up. :)
I have not found this to be accurate though. I haven't built an actual Symasym, but I have extensively simmed it. It is not as good as this. Real performance seems to bear this out.
 
MJL21193

MJL21193

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MJL21193

MJL21193

Disabled Account
Joined 2007
roender said:
John,

Besides the fact that you have some mistakes in the schematic, the main two issues are related with highly asymmetrical clipping and headroom.

Cheers,
M

ps. Where did you get that input stage? Maybe AKSA?
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I put that together in 2 hours, so i expect there will be mistakes.

Hugh suggested the CFP input but "gave" me nothing. I researched it, in particular D. Self's book.
I'm not totally without a clue. :)
 
lineup

lineup

Member
Joined 2005
MJL21193 said:

Hi lineup,
My real supply is very stable at 72.6VDC - both rails. 20000uF of smoothing per rail. Not bad for a temporary supply.
Remember I simulate first, then I build a real amp to test and listen to.
:)

This amp is designed for an over sized power supply. Even though the supply will swing enough voltage for a power output of 250 watts into 8 ohms, it's input sensitivity (1.2Vrms) limits it to just 150 to 160 watts into 8 ohms. That allows room for transients without clipping. Rail sag will not be an issue and will not cause the problems that you assume. It should be fairly obvious that when the amp is operating at the point where the rails will sag significantly, the speakers will be producing enough db and distortion of their own to swamp any increased noise from the amp. Let's be sensible here.

An amp like this that has CCS and CM will have very good ripple rejection. That is the advantage of these mechanisms, as opposed to simple resistor loads or bootstrapping. Don't downplay their effectiveness in this.
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MJL21193.

I see. You have a very good stable and clean supply.
I did not know. Was supposing a more ordinary DIY transformer & power supply.

And yes, your amplifier has probably very good immunity against supply rails.

You have explained good this design, showing you know well what you are doing.
--------------------

My own design idea about power amplifiers (not preamplifier at lower currents) is:
that it is not difficult & a very small cost to add a small separate transformer+supply for the sensitive input/vas.

Else Good designers like e.g. Nelson Pass etc. is practising same less good one transformer power supplying.
:xeye: I can never understand those that do this.
I do not get the idea. The benefit :xeye: When there is a better option.
Because, separated supplies can only improve a good circuit. Never be of any whatever drawback :cool:


Lineup
 
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