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Old 18th March 2009, 11:38 PM   #251
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Dan,
Quote:
do you mean they are deteriorating in terms of the sound or the high freq roll off... ??
Both, these are directly correlated.
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Old 19th March 2009, 12:15 AM   #252
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I am not sure i understand why Lumba,

can you add some info for me ??

by my calculations the 68pF only come into play in the HF region
and the 2200pF is there for a similar reason HF stability,

I understand the stance on audio being affected my how the amp performs many octaves higher, but it measures out to the hundreds of kHz,

Perhaps you can shed some light - i am open to hear your thoughts on this ?

-Dan
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Old 19th March 2009, 01:06 AM   #253
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Dan,
missing bandwidth means distortion. Extending Cob to 70pF in a voltage amplification stage is devastating. These caps, even much smaller values, do a lot of damage sonically, please believe me.
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Old 19th March 2009, 01:35 AM   #254
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i get what you are saying.... it is a valid point,

the Cob is 55-65 for 2SC1096/2SA634... perhaps i can remove them due to the input filter (and the amp seems stable....

i guess if you look at it as 68pF + 65pF that is 133pF

using 1/(2PiFC) at 20kHz that is 59832.7Ohms..... Hmmm
at 20Hz 59.8327 MOhm.... so HF could be affected....??

Perhaps it is time for these caps to go.....

What is the resoning behind the 2200pF being a problem ?

(if i do remove them i will do before and after listening and measurement tests.)

-Dan
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Old 19th March 2009, 02:38 AM   #255
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Dan,
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if you look at it as 68pF + 65pF that is 133pF
Exactly, compare it to 1.6/1.8pF for 2SD756/2SB716.
Please be cautious when removing these caps, maybe you should wait. Firstly, the 2SC1096/2SA634 is obsolete having poor specifications. Would it be possible to use some type in TO-126 package?
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Old 19th March 2009, 03:50 AM   #256
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probably what i will do is keep the "Le class A" the same as it is currently because it was designed to "sound" a certain way and it does in fact sound very good in my opinion. I think the caps were added for stability and measured performance and listening is very good.

I think I will build another "Le monstre" with batteries this time.
Le class A is almost as good as Le monstre but there is somthing about this tiny power monstre amp that is special......

What (everyone) do you think about using newer devices - perhaps with better spec than the originals used in "Le monstre"

for example better JFETs with lower noise (if possible)
I would say the input devices in the Le monstre may be hard to better in terms of noise/Cob etc though

thoughts anyone?


-Dan
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Old 19th March 2009, 04:44 AM   #257
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probably what i will do is keep the "Le class A" the same as it is currently because it was designed to "sound" a certain way and it does in fact sound very good in my opinion.
It certainly does, but improvements are still possible.
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I think the caps were added for stability and measured performance and listening is very good.
For stability only.
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I think I will build another "Le monstre" with batteries this time.
A very good idea.
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Le class A is almost as good as Le monstre but there is somthing about this tiny power monstre amp that is special.....
That`s due to the superior, exceptionally clean topology and carefully chosen parts.
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What (everyone) do you think about using newer devices - perhaps with better spec than the originals used in "Le monstre" for example better JFETs with lower noise (if possible)
Newer, yes, but hardly better.
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I would say the input devices in the Le monstre may be hard to better in terms of noise/Cob etc though
True.
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Old 19th March 2009, 05:09 AM   #258
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Thanks for the detailed reply Lumba.

I agree with you on all comments with this one.

I did a search earlier today for readily available parts which have similar or better spec than the le monstre transistors.

not so easy to find...

-Dan
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Old 19th March 2009, 05:53 AM   #259
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Also, Le Monstre has an outstanding driving ability and stability under almost any type of load, without a single additional part. The current feedback mode is an important reason for that.
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Old 19th March 2009, 09:37 AM   #260
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I am glad you wish to make the battery version, that makes two of us

Before I print the PCBs I am trying to add the option to accept a precision trimmer for 1K too, in order to set the bias correctly. Audiomanics, if you could provide the pcb file it would be much easier than trying to edit the image.

A good and cheap option for the batteries if someone lives in Greece: http://www.eshops.gr/index.php?act=viewCat&catId=589
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