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Old 8th September 2010, 09:09 PM   #51
wahab is offline wahab  Algeria
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Quote:
Originally Posted by Rafael L View Post
The Leach amp is good project, but choices of transistors can impair performance (0,2%- 20KHz in site the Prof M.Leach). Advantage of this amplifier is speed (60 Vus) more suitable for powerful amplifiers.

What was the Bias of the output TR's in simulation?
About 70mA per pair, since i simmed with two pairs.

The leach amp is somewhat dated , prove is the triple
emitter follower ,typical of a time where you could
barely achieve a 2K Hfe using a double EF once the current
reached a pair of A...
True that his VAS has low Iq , rendering the triple EF mandatory,
but at the expense of stability...
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Old 8th September 2010, 09:26 PM   #52
wahab is offline wahab  Algeria
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In continuation to THD analysis, the second
batch is about clipping behaviour , step response
in resistive and capacitives loads.

First tries are for the AX2, Blame ES , Apex ultimate
and ESP P3A...
Attached Files
File Type: zip AMPS COMPARISONS 7.zip (166.2 KB, 272 views)
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Old 8th September 2010, 09:31 PM   #53
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by metal View Post
This will also give us some better ways to correlate what we see in simulations to what we listen to, also correlate what we see in simulations and what has been measured in the real world, it would be more interesting this way.
Yes , it would .....................


Quote:
Originally Posted by wahab View Post
In continuation to THD analysis, the second
batch is about clipping behaviour , step response
in resistive and capacitives loads.

First tries are for the AX2, Blame ES , Apex ultimate
and ESP P3A...
Thanks Wahab , Most interesting if accurate ..............
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Old 8th September 2010, 10:51 PM   #54
AKSA is offline AKSA  Australia
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Wahab is doing us a service. The more simulations we see of readily available DIY amps, the more correlation can be drawn between schematic and sound quality.

This also goes to the heart of the thd and the model debates, of course. Every year the models get better......

Hugh
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Old 9th September 2010, 12:37 AM   #55
lineup is offline lineup  Sweden
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Quote:
Originally Posted by AKSA View Post
Wahab is doing us a service. The more simulations we see of readily available DIY amps, the more correlation can be drawn between schematic and sound quality.

This also goes to the heart of the thd and the model debates, of course. Every year the models get better......

Hugh
Yes, I agree with AKSA.
Comparing amplifiers using some numbers is more productive
than some individuals discussing the sound they experience.
At least this is what I have found.

On the other hand we should not make 8 Ohm THD at 2 frequencies at one power level too important.
There are plenty of more numbers and other things that can make an amplifier we like.
----------------------------------------------
Some other things to weigh into:
- Bandwidth & Phase
- Can it cope with heavy loads
- How handle complex, capacitive, reactive loads/loudspeakers
- How behave at Clipping, Overdrive
- Safety, Current, power limiting
- DC Offset stability
- Noise and noise immunity
- What parts are used. Easy to find replacements.
- Power Supply sensitivity, PSRR, CMRR
-------------------------------

Generally speaking there IS OFTEN A CORRELATION
between low THD and a good amplifier.
With some few exceptions.

(Take for example some of Nelson Pass's amps.
We can not truthfully say they are very low in THD.
Still it would be totally unfair to say they are bad amplifiers.)
A designer that strive for low distortion is most often intrested in quality regarding most everything.

I applaude Wahab's topic & work.
Interesting and we have always something new to learn.


Regards Lineup
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Old 9th September 2010, 10:17 AM   #56
balaboo is offline balaboo  United States
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I agree with lineup - THD figures in isolation are meaningless.

I would rather see IM figures swept from idle to full-power and clipping behavior.
It would also be nice to see the THD spectra swept from idle to full-power to identify the designs that minimize the generation of 5th and higher-order harmonics.
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Old 9th September 2010, 10:29 AM   #57
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Quote:
Originally Posted by balaboo View Post
...It would also be nice to see the THD spectra swept from idle to full-power to identify the designs that minimize the generation of 5th and higher-order harmonics.
Wahab,
be the first who described and connected measurings and sound quality
maybe a manual?
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Old 9th September 2010, 11:01 AM   #58
wahab is offline wahab  Algeria
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Quote:
Originally Posted by balaboo View Post
I would rather see IM figures swept from idle to full-power and clipping behavior.
It would also be nice to see the THD spectra swept from idle to full-power to identify the designs that minimize the generation of 5th and higher-order harmonics.
This would require considerable time.
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Old 9th September 2010, 11:06 AM   #59
AndrewT is offline AndrewT  Scotland
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I thought Balaboo was volunteering to do that research for us.
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Old 9th September 2010, 11:36 AM   #60
wahab is offline wahab  Algeria
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Quote:
Originally Posted by smartx21 View Post
Hi, Wahab,
Long awaited comparisons.
As the model I built was DX Blame ST (not ES), I ask you to kindly try to simulate this amplifier against AX, Ultimate Fidelity, Symasym and/or any other one you think would be useful.
The reasons are:
1) I intend to built another different amplifier;
2) More than 50 guys are building DX Blame ST right now, and this would be an useful tool, also for learning purposes.
Thank you.
All the best,
Max.
Hi, Smartx

There should be no great difference between the two
designs you mentioned.
For comparison with Symasym, you can use the existing
graphs , since the scale is strictly the same..



Quote:
Originally Posted by fredlock View Post
Wahab, can you also do the comparison of ostripper's symasym and Leach amp? If you get a chance, just curious how it look.
Ostripper s AX work very well, set apart some minors
design rework needed.
In my tries, i did find his Symasym version no better
globaly than the AX.
The leach amp is not the better version of a symetrical
differential , as it is devices dependant in respect to
stability.

regards,

w
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